Conference Agenda

The primary objectives of the International Subcommission on Cretaceous Stratigraphy are to establish a standard global stratigraphic subdivision and nomenclature for the Cretaceous, and to produce a stratigraphic table displaying agreed subdivision to stage and substage level, with boundaries that are defined by a Global boundary Stratotype Section and Point (GSSP). The Cretaceous Period is the longest of the Phanerozoic with12 stages. In 2000, none of the stage boundaries of the Cretaceous System was defined using a GSSP, a concept initiated in 1977. Increasingly rapid progress has been made since the ratification of the Maastrichtian Stage in 2001, now under revision, with 5 GSSPs ratified over the last 6 years. These stratotypes will be reviewed to illustrate the requirements for formal recognition of stage and substage boundaries, with only the former requiring ratification by the ICS. Out of 12, only two stages, the Berriasian and Aptian, remain to be defined. No substages have yet been formalised. A range of criteria are being used as primary markers to define stage boundaries including macrofossils (ammonites, inoceramids), microfossils (planktonic foraminifera), a magnetic reversal, and a carbon isotope event. Additional secondary markers are essential to enable the wider placement of stage boundaries. Nonetheless, no single section will ever include the complete range of potential markers to define a stage boundary. Standard Auxiliary Boundary Stratotype (SABS) sections, approved by the IUGS in 2023, provide a basis to extend the correlative potential of a GSSP between continents, biogeographic provinces, climate zones, depositional facies and preservation states.

While the effects of OAEs are well known for the pelagic successions of the Tethys Ocean, little is known about their impact on the Peri-Tethyan shallow-water carbonate systems. We present the preliminary results of a study related to the realisation of the Geological Map of Italy (CARG Project), focussed on the identification and description of the perturbation induced in the Lower Cretaceous shallow-water carbonate succession of the Latium-Abruzzi Carbonate Platform by the well-known Early Cretaceous OAEs. Two stratigraphic sections were studied in the Ernici Mts. (central Apennines, Italy) "calcari ciclotemici a gasteropodi" fm. (CCG - Berriasian p.p. - lower Aptian p.p.). A layer of black dolostone, about ten centimetres thick, has been observed in several outcrops of the dolomitic lithofacies (CCGa) of CCG. SEM images, along with EDS and WDS analysis indicated the presence of siderite and pyrite aggregates starting from the basal part of the blackish dolostone and gently decrease towards the upper part of the study interval. TOC and sulphates show similar trends. In situ analyses using the LA-ICP-MS facility at Roma Tre University shows a significant increase in elemental concentration of redox-sensitive elements as well as in the Fe/Al ratio in the blackish dolostones. Biostratigraphic calibration performed on the collected samples has established a Hauterivian p.p. age. A preliminary attempt for U-Pb dating of the CCGa black dolostone was carried out through LA-ICP-MS investigations providing a lower intercept age of 125.7± 1.8 Ma. These promising results suggest that the perturbations were induced by the Faraoni OAE.

Mudurnu-Göynük basin, Central Pontides (NW Turkey) and Central Taurides (S Turkey) and Arabian Platform include records of Cretaceous oceanic anoxic events in Mid-Barremian, Aptian, Albian, Cenomanian-Turonian, Campanian intervals of the Cretaceous successions as presence of black shale intervals and or their representatives respectively.

The Mid-Barremian black shales (MBE) have been recorded within pelagic succession in central Sakarya zone of Pontides after the drowning of the platform. The carbon isotope curve displays a 2 ‰ shifts. Eu, Ce, V, Cu, Zn, Fe, Ba, P, and S values display a relative enrichment. The Aptian black shales (OAE1a) are recorded in pelagic carbonates in central and north of Sakarya zone negative carbon shift of 2 ‰, and TOC around 2%. In Sakarya zone of Pontides, OAE2 is recorded in pelagic carbonates with more than 1 ‰ carbon positive shift and >2 % TOC. This interval is relatively rich in S, Mo, Ba, Cd, Ni, V, Zn, Pb, Cr, Co. Another OAE2 wasrecorded in Antalya Nappes of Taurides without carbon isotope curve but TOC >20%.

Mid-Late Campanian OAE is recorded in Pontides and Arabian Platform. It displays relative enrichment of S, Mo, Cd, Fe, Ni, V, Zn, Cr, Co, U.

The OAE1a and OAE2 levels recorded in Turkey are correlated with European examples controlled by sealevel and tectonics in large-scale and climate and oceanographic changes in small-scale. The most extensive OAE records in Turkey belong to OAE1a and OAE2, and display potential for source rocks for hydrocarbon and sedimentary strategic element exploration.

A carbon cycle disturbance occurred in the mid Cretaceous, within the upper Albian-lower Cenomanian interval, described as the Albian-Cenomanian Boundary Event (ACBE). This anoxic event is seen as a global one, being identified in both Tethyan and Boreal realms. For pointing out changes related to the ACBE, we investigated two successions of the Tethyan Realm: (i) Lepşa section, Eastern Carpathians, placed at 34°N palaeolatitude during mid Cretaceous times and (ii) Youxia section, S Tibet, situated at 21°S palaeolatitude. Both successions contain nannofossil events characterizing the Albian-Cenomanian Boundary Interval, i.e., the successive LO (last occurrence) of Crucicribrum anglicum and Hayesites albiensis, followed by the successive FO (first occurrence) of Gartnerago chiasta, Calculites anfractus, and Corollithion kennedyi, spanning the UC0 and UC1 zones. In the Youxia section, a few nannofossils confined to high palaeolatitudes were identified in the UC0a subzone. In both sections four successive peaks (A, B, C and D) of d¹³C isotope were observed, where A, B, and C are late Albian in age and peak C is early Cenomanian. The boundary between the Albian and Cenomanian falls, as globally identified, between peaks C and D, just above the FO of Calculites anfractus. Additionally, the lower part of Youxia section (UC0a subzone) shows increased values of d¹⁸O, accompanied by increased productivity of the nannofossils, possibly linked to temperature decrease in the surface waters. These changes might reflect ocean circulation modifications in the Southern Hemisphere, resulting from the enhanced connection among different oceanic basins during the mid Cretaceous times.

The Early Cretaceous of the Umbria-Marche Basin is marked by three Oceanic Anoxic Events (OAEs) within the Marne a Fucoidi Formation, which is composed of multicolour marlstones and marly limestones interbedded with organic-rich black shale layers. These events are associated to the development of anoxic conditions at the sea floor. Some of these occurred on a global scale—such as the early Aptian OAE1a—while others were regional, such as the early Albian OAE1b. In the present study, the microfloristic content from the Fiume Bosso, Roccaccia, and Bottaccione sections was analysed for the first time, along with data from the Poggio le Guaine section. The palynological assemblage of OAE1b is characterized by sporomorphs as Cyathidites spp. and Afropollis spp., and dinocysts as Florentinia mantellii. The dinoflagellate cyst species Litosphaeridium conispinum was recorded in all studied sections. Its first occurrence marks the late Albian in the Tethyan domain. The occurrence of Elaterosporites klaszii and E. verrucatus—typical of the Albian to Cenomanian—was also recorded. These taxa were found in association with L. conispinum in the Fiume Bosso section, and below its first occurrence in the Bottaccione section. The distribution of dinoflagellate cysts provides valuable insights into the palaeobiogeographic dynamics of the Tethyan realm during the Early Cretaceous, highlighting patterns of ecological response to regional and global anoxic events and reinforcing their utility as biostratigraphical and palaeoenvironmental markers.

This study provides data from a 15-meter-thick section located within the outermost thrust sheet of the Eastern Carpathians. The lower part contains deep-sea black shales, silts, and black radiolarites, whereas the upper section consists of cm-thick radiolarites-green shale couplets, and rarely, thin sandstones, clastic radiolarites and black shales. Based on calcareous nannofossil biostratigraphy, the analyzed sequence corresponds to the UC3 and UC4a zones/subzones. The succession of the nannofossil event is the LO (last occurrence) of Gartnerago theta (base of the UC3b subzone), followed by the LO of Staurolithes gausorhethium (base of the UC3c) and the LO of Corollithion kennedyi (base of UC3d). The youngest event recorded in the studied succession is the FO (first occurrence) of Cylindralithus biarcus which marks the base of the UC4 biozone. As Lithraphidites acutus and Cretarhabdus striatus are present from the base to the top of the succession, we consider that the youngest nannofossil subzone is UC4a.In the base of the sequence, two peaks of the isotope δ¹³C_org were identified: i) the oldest reaches the value of -23.7‰, being accompanied by the highest values of TOC (total organic carbon) in the studied section (5.9%), and (ii) the youngest, up to -23.9‰, keeping high TOC values, i.e., up to 1.8%. These peaks, positioned in the UC3a nannofossil zone, likely represent the distinct characteristics of the Mid-Cenomanian Event (MCE), with the oldest significant positive excursion attributed to MCE Ia while the youngest to MCE Ib.

Since the Permian/Triassic boundary, significant atmospheric and oceanic carbon cycle perturbations repeatedly occurred in the Mesozoic. One well-documented perturbation is Oceanic Anoxic Event 2, which occurred at the Cenomanian/Turonian boundary. Integrated Ocean Drilling Program, Expedition 342 recovered a relatively expanded Cretaceous sequence, including the Cenomanian/Turonian boundary interval in the northwestern Atlantic, off Newfoundland. We examined planktic foraminiferal assemblages, planktic foraminiferal mass accumulation rate (PFAR), and organic carbon isotope stratigraphy across the Cenomanian/Turonian boundary sequence from Site U1407. At around 269 mCCSF. a distinctive and typical organic carbon isotope excursion is identified within an approximately 40 cm-thick black shale layer. The development of this black shale indicates that the subsurface and/or deep-water column became anoxic in this interval. On the other hand, the coarse fraction and planktic foraminiferal accumulation rates began to decrease at 270 mCCSF and returned to the pre-event level at approximately 267 mCCSF. The carbonate production rate was depressed for a 3 m-thick interval, which is significantly thicker/longer than the thickness of the black shale. If we assume that the decline in PFAR represents surface-ocean acidification, this acidification, hence an increase in pCO₂, started significantly earlier than the observed water-column anoxia.

The Late Jurassic to Early Cretaceous period is a crucial stage of dramatic climatic and environmental transition in the late Mesozoic. However, our understanding for the climate pattern and its dynamics are still unclear. This contribution presents a data set of magnetostratigraphy age of 151.3 Ma -129.96 Ma for the strata (1061 meters thick) on the Hongliugou Section in the northern Qaidam Basin (East Asia), and the high-resolution environmental magnetism (χ_lf, χ_ARM, χ_fd/HIRM, χ-T, Loop), chromaticity (L*, a*, Redness%, Hm/(Hm+Gt)) and TOC of the fluvial-lacustrine sediments along the Section. The depositional environments on the section from bottom to top are interpreted as shore-shallow lake facies, delta facies and meandering river facies, exhibiting an overall coarsening sequence upward. The variation of proxies depends on the lithology and environmental facies. This indicates their variation can be linked to the climate change. Hence the climate condition recorded by the proxies can be divided into four stages: warm and humid (151.3 Ma -147.5 Ma), hot and arid (147.5 Ma ~ 145 Ma), warm and arid (145 Ma ~ 136.4 Ma), and warm semi-arid (136.4 Ma ~ 129.96 Ma). The trends of the first to third stage are in accordance with variation of global temperature curves, and the transition from second to third stage may be linked to the Jurassic-Cretaceous boundary events. Those reveal that the climate changes in this region were influenced by global change. While the fourth phase, unlike the earlier stages, might have been affected by the paleogeomorphology in the interior Asia.

The carbonate reservoirs of the Brazilian Pre-salt are made up of lacustrine deposits formed in an evaporative and alkaline lake with high concentrations of silica and magnesium. The typical inland lake facies comprises spherulites, shrubs, and magnesian clays. At the marginal regions of the lake, reworked facies, such as grainstones and packstones, indicate an energetic and fluctuating coastline. Based on the analysis of drill cores and thin sections (Santos Basin), diagnostic features of paleosols were identified and described (horizons, structures, bioturbation, colours, dissolution, cementation, neoformation, and illuviation of clay minerals), allowing us to classify them as well-drained paleosols (WDP) and poorly drained (PDP). From an environmental perspective, well-drained paleosols (WDP) are rich in dolomite, overlying areas with karst porosity, indicating a drop in lake level and prolonged periods of subaerial exposure. In turn, poorly drained paleosols (PDP) are rich in organic matter, greenish-grey colours and minerals formed under reducing conditions. Such characteristics indicate palustrine regions (backshore) under the influence of saline waters rich in Mg, where the dolomitization of carbonates occurred due to high evaporation rates. A model of Aptian landscape evolution in the Santos Basin is proposed here, incorporating both tectonic and climatic aspects. The first and fourth authors thank the Brazilian National Council for Scientific and Technological Development (CNPq) for the productivity grants (process 310734/2020–7 and 311491/2019–7, respectively.

Initiation of the transition from Early to Late Cretaceous and Cretaceous Thermal Maximum, coincided with major, global hydrologic cycle changes. Within western North America, an increased storm strength and dominance of eddy diffusion fractionation over advection-based fractionation within atmospheric processes controlled the dispersal of oxygen isotopes (δ18O) over the continent. The resulting pattern from this dispersal process can be observed within the δ18O isotopic landscape (isoscape) of meteoric water over the North American continent during the Albian to Cenomanian Ages. As observed in the δ18O isoscape, latitudinal effects have a dominant control over the dispersal pattern and subsequently of a shallow δ18O gradient from equator to the poles. The favored direction of water movement was from the south near the equator northward, dispersing oxygen-18 along the way. Locally, we examine the effects of the climatic conditions and effects on the oxygen isotopic composition of vertebrates within low versus high latitude sites. We examined the Albian-Cenomanian vertebrate assemblages within the higher latitude upper Cloverly Formation of Wyoming and Montana and two assemblages within the low-latitude upper Antlers Formation and Woodbine Formation in Texas and Oklahoma. Within these sites and assemblages, water δ18O isotopic values are calculated from the mineralic isotopic composition combined with the reconstructed latitudinal location and timing of deposition by utilizing the ‘palaeoverse’ package in R in conjunction with GPlates. Values predicted by the δ18O isoscape as well as predicted by a derived 3^rd order isotopic gradient are compared to the assemblage and site averages.

The late Early Cretaceous (121.4 to 100.5 Ma) was characterized by a gradual warming trend superimposed on an already warm greenhouse climate. Whereas the evolution of ocean temperatures during this time interval is relatively well constrained, information on the climatic response of continental interiors is limited. Here we report new paleotemperature estimates based on brGDGT distributions, bacterial membrane lipids used as temperature proxy, from two different sites located within the Choir-Nyalga Basin of central Mongolia including the Shivee Ovoo (SVO) and Tevshiin Govi (TSG) opencast lignite mines. Both sites include lignite-rich continental successions assigned to the Khukhteeg Formation, well known for its exceptionally well-preserved fossil flora. The lignites from both sites exhibit low thermal maturity, as indicated by huminite reflectance, pointing to minimal post-depositional alteration. To reconstruct peat-forming conditions, we combined coal petrology and palynology, with geochemical analyses (TOC, TS, δ¹³C_org) and brGDGT-based paleothermometry. The brGDGT analysis yielded mean annual air temperatures estimates for both sites of approximately 12 ± 3°C at SVO and 10 ± 3°C at TSG. These results represent some of the oldest brGDGT-based paleotemperatures to date and support previous estimates for relatively cool paleotemperatures in Asia during the late Early Cretaceous. The data will be compared with climate model outputs to better constrain boundary conditions for intracontinental climates during greenhouse phases.

North America contains abundant Cretaceous continental strata that hosts potential archives of paleoclimate records. While detailed work has been done in Late Cretaceous strata which not only contains archives for stable isotope proxies, but also leaf physiognomic data, less study has occurred in the Early Cretaceous which lack angiosperm-dominated floras. Here we present new paleotemperature estimates from multiple stable isotope proxies including δ¹⁸O of pedogenic carbonates, clumped isotope paleothermometry, and paired stable isotopes of aquatic and semi-aquatic taxa. The southern-most data originate from the Hensel Formation of South Texas. Clumped isotope paleothermometry of pedogenic carbonates result in temperature estimates between 35°C and 42°C. Clumped isotope paleothermometry of lake and palustrine carbonates from the Cedar Mountain Formation range from 15°C and 31°C for lake carbonates and 20°C to 44°C for palustrine carbonates. Farther north in Wyoming, we utilize the oxygen isotope value of semi aquatic taxa such as crocodilians and turtles to provide a proxy for water and utilize the oxygen isotope value of fish scales and teeth to estimate temperature at 26°C though with significant error. Preliminary clumped isotope paleothermometry provides a temperature of 25°C. The farthest north locality, the Kootenai Formation contains lacustrine, palustrine, and pedogenic carbonates. Utilizing a previous empirically-derived latitudinal gradient of meteoric water, carbonate δ¹⁸O values were used to estimate a temperature range for the Kootenai Formation between 13°C and 28°C. These values provide a temperature gradient for the Aptian-Albian over the mid latitudes of North America of ~-1°C/degree of latitude.

After the mid-Cretaceous hothouse, the Earth cooled severely by more than 10°C in the late Cretaceous largely under ice-free conditions. Causes of the cooling are still poorly constrained, mainly considered as result of reduced lithospheric outgassing after the climax of LIP-related volcanism or effects of ophiolite weathering. Possible interactions with changes in chemical weathering intensity based on changes in paleo-landscape and the terrestrial biosphere, instead, received little attention so far. Here, we present a new chalk-derived Li-isotope record for the Late Cretaceous and discuss its baseline and multi-million year-scale variability in terms of plate tectonic reorganization and paleo-landscape change. Rising and high δ⁷Li values in the Turonian-Santonian and the Maastrichtian contrast with lower δ⁷Li values in the Campanian. The pattern of the δ⁷Li record matches with results of paleo-landscape modelling showing an overall decrease in erosion rates together with variable fluxes of dissolved weathering solutes in the tropics and warm temperate zones based on budgets of sediment erosion and deposition. Rising δ⁷Li values in the Turonian-Coniacian and latest Campanian-Maastrichtian correspond to prominent cooling phases in concert with sea-level falls and the reorganization of fluvial catchments indicating rather incomplete weathering reactions by increased formation of clay minerals. We suggest that plate tectonic reorganization supported the conversion of terrestrial habitats and ecosystems through the spread and evolution of angiosperms. The higher productivity of flowering plants in terms of water usage together with the increased activity of ectomycorrhizal fungi intensified chemical weathering and contributed to the ongoing reduction of atmospheric CO₂.

This research focuses on Late Jurassic–Early Cretaceous high-resolution carbon isotope stratigraphies derived from DSDP Site 534A located in the central Atlantic Ocean. We present both δ¹³Ccarbonate and δ¹³Corganic data (combined with published datasets) in order to evaluate whether a consistent pattern in carbon isotope variation can be established, particularly with respect to the Jurassic–Cretaceous boundary. We observe positive values in the Late Callovian followed by a decrease is δ¹³Ccarbonate through the Late Jurassic and across the Jurassic-Cretaceous boundary, consistent with carbon isotope stratigraphies of Tethys. Biostratigraphic and magnetostratigraphic data allow us to accurately place the low point seen in the carbon isotope curve within these schemes. The δ¹³Ccarbonate minimum appears within magneto zones M14-M12 and nannofossil zones NK-2B - NK3A. The Valanginian positive excursion (Weissert event) is clearly seen. The δ¹³Corganic data although more scattered, also show positive values in the Late Callovian followed by a decrease in values through the Late Jurassic and across the Jurassic-Cretaceous boundary. The Valanginian (Weissert event) is also evident in our δ¹³Corganic data suggesting organic carbon and dissolved inorganic carbon were coupled during this time. In contrast to some high-latitude δ¹³Corganic records, a marked Tithonian (~middle Volgian) VOICE negative excursion is not observed. Our data leads us to conclude that curiously there was latitudinal decoupling between the Arctic and Atlantic/Tethyan seas.

Studying the Jurassic-Cretaceous transition is never easy: the interval is plagued by faunal endemism and hiatuses. In the Netherlands, the Cimmerian rift phase was in full swing during the Jurassic-Cretaceous transition, resulting in non-marine facies and unconformities. In some areas however, e.g. the offshore Terschelling and Dutch Central Graben basins, subsidence continued uninterruptedly allowing marine sediments to accumulate during the Jurassic-Cretaceous transition. In a published record¹ from cored intervals ammonites were retrieved, alongside with dinoflagellate cysts and pollen and spores, allowing calibration of the dinoflagellate cysts events to ammonite zones. In the neighboring Dutch Central Graben, the sediments across the at the Jurassic-Cretaceous boundary are coarse-grained and display intra-formational reworking. Surprisingly, the palynological assemblages, even the reworked specimens, are well preserved. The reworked specimens are probably derived from lithic clasts floating in the sandy matrix. Because of the excellent preservation, it was difficult to distinguish between reworked and in situ specimens. High resolution and detailed taxonomic analyses made it possible to constrain the Jurassic-Cretaceous transition biostratigraphically. In terms of paleoenvironment, the boundary interval is also very interesting, high dominance/low diversity dinoflagellate cyst assemblages reflect restricted marine conditions. The common occurrence of genera such as Mendicodinium, Senoniasphaera and Muderongia points to low salinity environments related to freshwater input. Also interesting are the recurrent peak abundances of extremely large and thick-walled specimens of Cribroperidinium hanseni, although a cause for this phenomenon could not be established.

The studied basins included the Tucano and Jatobá sedimentary basins and the comparison with chronocorrelated Brazilian basins. The biostratigraphy of these basins has been established through the identification of fossil ostracods, with species from this group serving as guide for local stratigraphic stages of Lower Cretaceous. This biostratigraphic framework based on ostracods covers the Tithonian–Aptian ages and is applied to both Brazilian onshore and offshore basins. Focusing on providing updates for the Tithonian–Barremian interval, this study involved field visits to mapped localities within these basins to collect material for analysis and species identification, aiming also to recognize potential index taxa. In total, 91 outcrop samples were collected and processed in the laboratory for the recovery the calcareous microfossils. Representatives of the non-marine genera Theriosynoecum, Cypridea, Candona, Brasacypris, Paracypridea, Salvadoriella, Reconcavona, Rhinocypris, Darwinula, Alicenula, and Tucanocypris were identified, supporting the fluvial and lacustrine paleoenvironment described for these geological interval. The main dating species recovered were Theriosynoecum pricei, present in several basins and indicative of the Tithonian; Candona? condensa (Berriasian–Valanginian); Paracypridea elegans elegans (Valanginian–Hauterivian); Cypridea (Morinina) bibullata bibullata (Hauterivian–Barremian); and Cypridea semilunaris (Barremian). The first occurrences of Candona? condensa and the genus Brasacypris were recorded in the Jatobá Basin, and the identification of morphotypes corresponding to potential new species highlights both the need to deepen our understanding of the biogeographical distribution of these taxa and the considerable diversity of the group in these intervals that remains to be fully explored.

The present work refines and updates the taxonomy of a species belonging to the genus Cypridea (Ostracoda: Cypridocopina: Cyprideidae), while also inferring its population age-structure and paleoenvironment in which its specimens were preserved. An ostracod-rich sample, containing several specimens of Cypridea opifera from the Candeias Formation of the Recôncavo Basin (Lower Cretaceous, Berriasian–Valanginian), was collected in the Praia de Plataforma outcrop, a well-known fossil locality from the City of Salvador, Northeast of Brazil. Other than thirty-six closed carapaces of Cypridea opifera, we also recovered a single carapace specimen of Cypridea dromedarius (this was considered, however, an autochthonous contamination, due to its isolate character). Additionally, a remark on chronobiostratigraphic approach of this occurrence, a well-marked succession of subzones seems to suggest that the biostratigraphic position would include Cypridea salvadorensis nodifer (RT-004.1) and Reconcavona? polita (RT-004.2) subzones. According to the current chronobiostratigraphic framework, it would be covering the lower Valanginian interval. The studied locality is also the type-locality for Mawsonia gigas Mawson & Woodard, 1907, a fossil fish with occurrences in the Gondwana realm.

Keywords: Lower Cretaceous, Candeias Formation, taxonomy, paleoecology.

Coquinas strata are significant reservoirs in Cretaceous Brazilian marginal basins, including the pre-salt area. Outcropping in southwestern Sergipe-Alagoas Basin, northeastern Brazil, at the Atol Quarry, this coquina sequence—the Morro do Chaves Formation—is a relevant coexisting analog for subsurface coquinas reservoirs of the Campos, Santos, and Espirito Santo basins.

Subsurface and outcrop samples from the quarry section yielded varying concentrations of well-preserved spores, pollen grains, and rare dinoflagellate cysts. Most samples correspond to black shale interbeds within a predominantly coquinoidal sequence, including bivalve banks and siliciclastic sand, with hummocky cross-stratification. The palynomorph taxa represented in the assemblage comprise 15 species of spores distributed among eight genera, 20 species of pollen grains (12 genera), and one dinoflagellate cyst.

Gymnospermous pollen grains (Classopollis, Equisetosporites, Araucariacites, Eucommiidites, Gnetaceaepollenites, Inaperturopollenites, Dicheiropollis) dominated the assemblage, together with lesser amounts of trilete spores. Angiosperm pollen grains are minor components. Dinoflagellate cysts are scarce and indicate the oldest evidence of marine influence in the Brazilian Lower Cretaceous strata. The co-occurrence of Dicheiropollis etruscus, Aequitriradites spinulosus, and Transitoripollis crisopolensis define the Dicheiropollis etruscus palynozone, which is dated as Barremian (= Lower Jiquiá, Brazilian local stage). The abundance of palynomorphs, dispersed cuticles, woody tissue, and other terrestrial plant remains, allied with the rare presence of marine microplankton elements in the palynoflora, suggest a predominantly continental depositional environment with weak marine influence for the section. The macrofossils recorded, including invertebrates, tetrapods, and several fish taxa such as Semionotidae, Elopomorpha, Paraclupeidae, Gonorynchiformes, Salmoniformes, and Mawsoniidae, collectively corroborate the palynological data.

松辽盆地是白垩纪发育的亚洲最大的大陆盆地之一。松辽盆地的 ostracoda 化石非常丰富，在地层相关性、古生态和古环境重建中发挥着重要作用。对 ostracoda funa 的简要回顾是我们的。松辽盆地共鉴定出 30 属 241 种。这些 ostracoda 动物群以 Cypridea、Strumosia、Lycopterocypris、Triangulicypris、Limnocypridea、Talicypridea 等属为代表。综上所述，在松辽盆地已鉴定出 17 种介形鲸类组合。组合 1 可以追溯到白垩纪早期 （Aptian） 时期，组合 2 到 16 属于白垩纪晚期（Cenomanian - Maastrichtian）时期，组合 17 来自马斯特里奇晚期 - 早期丹尼安时期。来自松辽盆地的白垩纪国际大陆科学钻探项目岩芯 SK1 提供了一个难得的机会，可以在一个漫长的、连续记录的时间间隔内研究晚白垩纪的非海洋排斥虫。SK1 包含青山口（.Triangulicypris torsuosus-Triangulicypris torsuosus var. nota）、姚家（Cypridea exornata-Lycopterocypris retractilis）、嫩江（Cypridea gunsulinensis-Cypridea ardua）、四方台（Talicypridea amoena-Paracandona qiananensis）和明水（Ilyocypris bisulcata-Candona declivis）组。在从上坤头组到明水组的沉积序列中已鉴定出 20 个介形粒组合。最初的生物地层相关性表明，组合 1 到 19 涵盖了 Cenomanian 到 Maastrichtian 阶段，而组合区 20 可能从最新的马斯特里赫时期延伸到最早的 Danian。

关键词：松辽盆地， Cenomanian-Danian， Ostracoda 动物群

Famed for its Upper Jurassic dinosaurs, Utah’s Cretaceous dinosaur record has exploded from 7 named genera at 3 faunal levels to 36 Upper Cretaceous taxa and 55 Lower Cretaceous taxa in 21 faunal levels in the last 30 years. Local subsidence due to salt tectonics in eastern Utah resulted in the preservation of 6–8 basal Cretaceous dinosaur faunas known nowhere else in North America, subsequent to the extinction of many North American Jurassic dinosaur clades. These basal Cretaceous faunas document waning paleobiogeographic connections with Europe across the proto-North Atlantic. The more medial Aptian-Albian Cretaceous strata in central Utah, preserves unique dinosaur assemblages on an isolated North America. The basal Upper Cretaceous strata record the first immigration of Asian dinosaurs into North America and the last occurrences of a number of endemic North American dinosaur lineages. Through the Late Cretaceous, extensive, fossiliferous floodplain deposits are exposed in the high plateaus of southern Utah on the western side of the Late Cretaceous Western Interior Seaway. Research on microvertebrate sites has resulted in a diverse record of vertebrate life substage by substage through most of the Upper Cretaceous sequence. Particularly, rich dinosaur-bearing beds through the Campanian have resulted in the discovery of many new dinosaur species distinct from the coeval dinosaur-bearing beds farther north along the western coast of the seaway in Montana and Alberta. The further development of Utah’s rich dinosaur assemblages will provide the basis for considerable research in the future.

The stratotype section of the Quiricó Formation (Minas Gerais State, Brazil) provides a unique opportunity to understand the early Aptian paleoenvironmental dynamics in the São Francisco basin. Based on the biostratigraphic framework of ostracods, this section records two units: the Alicenula longiformis Zone (Barremian) and the Harbinia spp. Zone (lower Aptian). The present study integrates ostracod assemblage data from this section with a recent publication dealing with brief marine incursions, also identified in the stratotype section. The lower beds are barren, while the middle portion hosts the highest species richness. The upper beds are dominated by Harbinia spp., indicating hypersaline lacustrine conditions, consistent with abundant evaporites, desert roses, and mud cracks. These features support a scenario of increasing aridity and basin restriction during the early Aptian. Based on this recent publication that reports palynomorphs and other marine microfossils in the Harbinia spp. Zone, it is suggested that the marine influence may have reached the basin margin during early Aptian. These occurrences highlight the importance of integrating micropaleontological and sedimentological data to evaluate basin connectivity during the early Aptian. Such links may reflect the establishment of a drainage system, facilitating faunal dispersal and episodic marine ingressions during a time of tectonic reorganization and climatic aridification. This integrated approach refines the paleoenvironmental and biostratigraphic framework of the Quiricó Formation, illustrating how limnic ostracods record might contribute to approach the basin evolution and transient marine influence during the Early Cretaceous in the Gondwanaland hinterlands.

The Quiricó Formation, São Francisco basin (Minas Gerais State, Brazil), preserves a lacustrine and fluvial-lacustrine sequence deposited during the Early Cretaceous. This study reconstructs the paleoenvironmental evolution and terrestrial ecosystem dynamics of the basin based on the stratigraphic distribution of ostracod assemblages, sedimentological data, and paleogeographic frameworks. The objective is to assess how paleoclimate, drainage evolution, and basin paleogeography influenced continental lacustrine systems during the breakup of central Gondwana. Stratigraphic sections from three key outcrops yielded 21 ostracod species attributed to multiple genera. Their vertical distribution was analyzed in relation to sedimentary facies and paleogeographic reconstructions, indicating that the basin was positioned near 20–25ºS paleolatitude, within tropical to subtropical climatic belts. Two major paleoenvironmental phases were recognized. The lower interval (Berriasian–Barremian?) was deposited in a humid fluvio-lacustrine environment, with moderate ostracod diversity and limited faunal exchange. In contrast, the upper interval (Aptian) shows increased lacustrine restriction and aridification, yet a notable rise in ostracod diversity. This pattern suggests that, despite drier climatic conditions, the establishment of a fluvial system related to the origin of the São Francisco river enhanced hydrological connectivity, facilitating faunal dispersal among isolated basins. It may also reflect brief marine influences recorded in the Aptian, contributing to environmental instability and salinity shifts. Biostratigraphic units were interpreted based on species distribution and paleoenvironmental shifts. Ostracods, as sensitive indicators of salinity, hydrology, and climate, provide critical evidence of ecosystem responses during major continental reorganization. These results contribute to a detailed approach on Early Cretaceous paleoenvironments on Gondwanaland.

Southern Morocco provides extensive exposures of a fluvial-coastal-shallow marine succession developed between the Albian? and the Early Turonian. The so-called Kem Kem beds represent the lower portion of this succession and are characterized by fluvio-deltaic sandstones at the base (Ifezouane/Gara Sbaa formations) passing upward into coastal mudstones and marls (Aoufous/Douira formations). A robust chronological constraint is available only for the uppermost part of the succession, the Akrabou Formation, which records the establishment of a carbonate platform during the late Cenomanian–Early Turonian. Besides the poor chronostratigraphic constrain there is a broad consensus to place in the Albian the onset of the lower-mid portion of the studied succession, known for its varied vertebrata fossil content including dinosaurs, crocodiles, turtles, and freshwater fishes. This study aims at providing stratigraphic and sedimentological lines of evidence to frame the Kem Kem palaeobiota into a novel depositional model. The fluvial-coastal strata, exposed from the Kem Kem region to the south up to the southern front of the Central High Atlas to the north, are correlated outlining a stratigraphic architecture made of unconformity-bounded sub-units. Facies associations recognized in this succession suggest a temporal variation of the depositional processes in the fluvial-coastal systems. While the lower part of the Ifezouane/Gara Sbaa formations testify a fluvial environment hinting to a moister seasonality along with a deep hydrographic network reorganization, its upper part and the Aoufous/Douira formations, show facies indicating a fluvial environment evolving into a coastal plain with evaporites and fine-grained intercalated deposits hinting to a drier seasonality.

Ilyocypris riograndensis is a limnic microcrustacean species with a bivalved carapace, belonging to the Class Ostracoda. Originally, based on outcrop in Argentine, it was described from occurrences at the Plottier, Bajo de la Carpa, and Anacleto members (Santonian to Maastrichtian), currently elevated to formation status. Subsequent occurrences have also been recorded from the Allen Formation (Argentina), as well as the Araçatuba and Adamantina formations of the Bauru Group (Brazil, Campanian to Maastrichtian). These occurrences are related to a chronostratigraphic interval from Santonian to Maastrichtian. Recently, in São Geraldo District, São Francisco basin, it was identified occurrences of this species in outcrops previously considered as Lower Cretaceous. Based on chronostratigraphic distribution in Argentine and Bauru Group, it might be suggested that the outcrops in São Geraldo District are at least Campanian to Maastrichtian in age, and chronocorrelate with strata from the Neuquén Basin in Argentina and the Bauru Group in the Paraná Basin, Brazil. These Cretaceous outcrops in the region of São Geraldo District, Municipality of Coração de Jesus, northern Minas Gerais State, Brazil, represent a remarkable record of paleontological data that has drawn scientific interest, particularly regarding its dinossaurs and ostracod fauna. The chronostratigraphic and lithostratigraphic significance of these occurrences as contribution for a more detailed chronobiostratigraphic position of strata previously attributed to Areado Group are herein suggested as Urucuia Group. The studied outcrops consist of interbedded fine-grained sedimentary rocks (siltstone and sandstone), displaying whitish to reddish hues, which are characteristic of the region.

Constrained Optimization (CONOP) is a widely used quantitative stratigraphic method for high-dimensional, automated stratigraphic correlation. Based on fossil co-occurrence relationships, it can integrate and extend incomplete local observations of taxa across multiple sections to form an optimal composite sequence that represents a regional or global estimation of true stratigraphic ranges of taxa, which can be used to decipher the evolutionary history of life in the deep time.

We used OneStratigraphy Database to compile and manage stratigraphic and paleontological data. Rigorous quality control was applied, including spelling corrections, taxonomic consistency, and removal of low-resolution sections. After data cleaning, 76 ostracod-containing sections/cores remained, which show good connectivity by network analysis. Chronological constraints were established using fourteen age-control points, including those from zircon U-Pb dating, magnetic stratigraphy and astronomical tuning. We arranged these points in chronological order and created a weighted virtual section to improve computational efficiency. During the CONOP calculation, we tested different optimization parameters to balance efficiency and optimization. Finally, over 100 results were generated, of which 30 with nearly the highest computational times showed consistent diversity patterns throughout. The best result was then calibrated to the Geological Time Scale 2020 and used for subsequent analysis. To test the influence of sampling bias, we used Classic Rarefaction (CR) and Shareholder Quorum Sampling (SQS) to validate the results' robustness. Ultimately, we obtained an ostracod richness curve with a unique temporal resolution of ~0.079 Myr, providing insights into the evolutionary history of terrestrial life during the Late Cretaceous and even the Cretaceous-Paleogene extinction.

The end of the Cretaceous Normal Superchron (ECNS), recently ratified as the Global Boundary Stratotype Section and Point for the Santonian/Campanian boundary (SCB), marks a critical transition in Earth’s geomagnetic behavior, yet its precise timing remains debated. The International Continental Scientific Drilling Project SK-2 borehole in the Songliao Basin recovered an exceptionally preserved upper Santonian to lower Campanian terrestrial succession of the Nenjiang Formation. A detailed magnetostraigraphic framework have precisely positioned the ECNS within the Member 2 of the Nenjiang Formation. The presence of multiple datable bentonite layers in this interval provides a unique opportunity to apply high-precision geochronology to precisely constrain the ages of the ECNS and associated paleoenvironmental events. Here we present high-precision U-Pb zircon geochronology by chemical abrasion isotope dilution thermal-ionization mass spectrometry (CA-ID-TIMS) method from four bentonite layers in the lower Nenjiang Formation of the SK-2 borehole, integrated with Bayesian age-depth modeling, to establish a robust chronostratigraphic framework. Our Bayesian Bchron age-depth model and the combined Astro+Bchron age-depth model constrain the end of CNS at ~83 Ma. Further, the onset of the marine incursion event occurred during the deposition of the Nenjiang Formation is constrained to ~84.8 Ma, which provides robust temporal basis for further regional and global correlation to investigate their driving mechnisms.

The Dongning Basin, located in NE China along the Sino-Russian border, is adjacent to the Suifen Basin in the South Primorye region of Russia. In this study, 16 genera and 30 species of plant fossils were identified from the Lower Cretaceous Dongning Formation in the Dongning Basin. The flora is dominated by Bennettitales and Filicopsida, which exhibit high diversity, though the number of Filicopsida specimens is less abundant than those of Bennettitales. In addition to previously reported distinctive taxa such as Nathorstia pectinata, Sagenopteris suifenensis and Dictyozamites cordatus, several new taxa were discovered, including Chiaohoella dongningensis sp. nov. , Podozamites reinii, and Neozamites denticulatus. The genus Chiaohoella was previously reported from the Early Cretaceous Aptian Stage in the Jiaohe area of Jilin Province. Podozamites reinii was first documented in the Kuwajima Formation (Valanginian Stage) of Ishikawa Prefecture, Japan, and is commonly found in the Didao Formation of the Jixi area in China. The genus Neozamites ranges from the Berriasian-Valanginian stages in Japan to the Albian Stage in the South Primorye region of Russia. These fossil taxa, reported for the first time in the Dongning Formation, highlight the unique characteristics of the Dongning flora compared to contemporaneous Early Cretaceous floras in northern China, while also exhibiting features of southern flora. This discovery not only enriches the composition of the Dongning flora but also confirms that during the Early Cretaceous, the Dongning area (Northeast China), South Primorye (Russia), and Japan formed a transitional paleofloristic region influenced by shared paleoclimatic and paleogeographic conditions.

Spinicaudata, commonly known as clam shrimp, are freshwater brachiopod crustaceans with a rich fossil record dating back to the Devonian period. Their unique bivalved carapace, which undergoes partial molting, retains ontogenetic growth records and has made them significant paleoenvironmental indicators and biostratigraphic markers. Despite their ecological and evolutionary importance, discrepancies exist between the habitats of extant and fossil Spinicaudata, particularly regarding interpretations of ancient water bodies.

This study investigates the ecological and evolutionary puzzles surrounding Spinicaudata, focusing on their decline in diversity and abundance post-Mesozoic. By analyzing shell microstructure, growth patterns, and composition, the research compares fossil Spinicaudata from the Early Cretaceous Sihetun paleolake with extant species from diverse habitats. Additionally, external factors such as temperature and predator pressure are evaluated to disentangle the drivers of their Cenozoic decline. The findings provide new insights into the potential role of shell microstructure adaptations in ecological and evolutionary shifts, offering a deeper understanding of pre-Cenozoic limnological dynamics and the broader implications for lake community transitions.

High-resolution paleoclimatic reconstructions require precise temporal correlations, a goal that remains unachieved at orbital timescales in the Mesozoic. In this study, we aim to establish orbitally-paced correlations across 3 geographically distant basins spanning the Valanginian Stage (Early Cretaceous). This interval is characterized by large-amplitude organic carbon isotope excursions concomitant with a neritic carbonate production crisis. A total of 350 samples were analyzed for organic-carbon δ¹³C from 3 sites: DSDP Site 534 (western Atlantic Ocean), Vergol-Morénas in the Vocontian Basin (GSSP of the Valanginian Stage; SE France), and Cerro La Parva (western Argentina). The values of δ¹³C_org values range from -30.1‰ to -23.8‰ in DSDP Site 534, -29.7‰ to -27.1‰ in the Vergol-Morénas section and -24.4‰ to -21.5‰ in Cerro La Parva. The trends in the δ¹³C_org show common features in between the different sites and several negative peaks within the Weissert Event, identified in the Somanakamura group in Japan (Tomura et al., 2025), are also observed in the Vocontian and Neuquén basins (Moreau-Ledegen et al., 2025). The correlation of the different sites using these common features show a pacing of the δ¹³C_org by the 405-ka eccentricity cycle. This highlights the potential of δ¹³C_org as a reliable proxy for recording orbital forcing and demonstrates it as a robust tool for chemostratigraphic correlation at a global scale in order to align paleoclimatic signals at an unpreceded time resolution for the Early Cretaceous.

References:

Moreau Ledegen et al., 2025. French Association of Sedimentologists Publications 84, 139-143. https://doi.org/10.70665/EXDU8024.

Tomaru et al., 2025 Newsletters on Stratigraphy. https://doi.org/10.1127/nos/2025/0868.

The mid-Cretaceous Period experienced significant disruptions in the global carbon cycle, leading to widespread oceanic and climatic perturbations that influenced marine ecosystems and sedimentation patterns. This study focuses on the Aptian–Albian interval, aiming to refine the timing and underlying mechanisms of these perturbations through high-resolution cyclostratigraphic analysis.​ We analyzed sediment cores from Deep Sea Drilling Project (DSDP) Site 511, located on the Falkland Plateau in the southern South Atlantic, which offers a rare, nearly continuous stratigraphic record from southern high latitudes. Multiproxy datasets—including carbonate carbon (δ¹³C), oxygen (δ¹⁸O) isotopes, and gamma-ray (GR) measurements—were utilized to identify Milankovitch-band cyclicities. Time-series analysis revealed prominent ~405 kyr long-eccentricity cycles within δ¹³C, δ¹⁸O, and GR profiles.​ Astronomical tuning, employing low-pass filtering of eccentricity cycles and alignment with the La2004 g₂–g₅ target curve, facilitated the construction of a floating Astronomical Time Scale (ATS) for the Aptian–Albian interval. This approach enabled refined age estimates for the onset and duration of the observed oceanic perturbations and proposed a cyclostratigraphic framework for the Aptian–Albian boundary.​ Our findings enhance the chronostratigraphic resolution of mid-Cretaceous oceanic events in the South Atlantic realm and underscore the role of astronomical forcing in modulating paleoceanographic and climatic conditions. This study contributes to a more precise understanding of the pacing and global synchroneity of Cretaceous climate perturbations.

Carbon cycle perturbations dramatically affected the ocean-climate system during the Aptian-Albian transition. This interval is notably associated with Oceanic Anoxic Events (OAEs), characterized by enhanced burial of organic carbon and widespread anoxia in marine environments. Despite its significance, the timing and duration of these events—particularly in the South Atlantic Ocean—remain highly debated. In this study, we provide a comprehensive astronomical calibration of key biostratigraphic events, including the appearances of planktic foraminifera such as Microhedbergella renilaevis and Ticinella primula, as well as calcareous nannofossils like Praediscosphaera columnata. These events are recorded in a continuous marine sedimentary succession from Core SER-03, drilled in the Sergipe-Alagoas Basin, South Atlantic, spanning from the latest Aptian to the middle Albian.

The Core SER-03 astrochronology is constructed using a high-resolution natural gamma ray (NGR) record, which is paced by the long eccentricity (405 kyr) orbital cycle, and integrated with high-resolution paleomagnetic data. This record spans the interval from approximately 114.7 to 109.5 million years ago, within magnetochron C34n. Age estimates for key biostratigraphic markers align within one long eccentricity cycle with previously published ages. Additionally, stable carbon isotope data and elemental ratios (e.g., V/Al, Cr/Al, and Ni/Al) from Core SER-03 suggest a local expression of Oceanic Anoxic Event 1b (OAE 1b), helping to fill a gap in low-latitude areas.

In the last years, several astrochronological frameworks have been published on the Aptian Stage and yield scattered duration of this stage, ranging from 7.2 to 9.6 Ma (Leandro et al., 2022; Charbonnier et al., 2023). Here, I reassess the time scale of the Aptian by using several datasets published from Spain, France and Italy (Beil et al., 2020; Leandro et al., 2022; Charbonnier et al., 2023; Rodriguez-Martinez et al., 2024) to provide a consistent time scale between these basins. The 405-ka eccentricity is recorded and can be correlated thanks to biostratigraphy and chemostratigraphy between these basins. A provision duration of the Aptian Stage falls in between 8 and 9 Ma, with a preferred duration of 8.3 Ma, starting 121.15 Ma and ending 112.9 Ma. Importantly the duration of the OAE1a is assessed at 1.2 Ma. According to the timescale I propose here, he OAE1a started 119.9 Ma and ended 118.7 Ma, in a good agreement with recently published U-Pb from Japan (Li et al., 2024). Altogether, these data point toward a converging astrochronology for the Aptian Stage from multiple sites.

References:

Beil, S., et al., 2020. Climate of the Past 16, 757–782. https://doi.org/10.5194/cp-16-757-2020.

Charbonnier, G., et al., 2023. Earth and Planetary Science Letters 610, 118104. https://doi.org/10.1016/j.epsl.2023.118104.

Leandro, C.G., et al., 2022. Nature Communications 13, 2941. https://doi.org/10.1038/s41467-022-30075-3.

Li, Y., et al., 2024. Science Advances 10, eadn8365. https://doi.org/10.1126/sciadv.adn8365.

Martinez-Rodriguez, R., et al., 2024. Global and Planetary Change 233, 104361. https://doi.org/10.1016/j.gloplacha.2024.104361.

The Late Albian–Turonian Judea Group is a lithologically diverse sequence of shallow-water carbonates deposited across the Israel-Sinai sub-plate.

Boreholes CT2 and CT8 in the Carmel area penetrate the Isfiye (dolomitised chalk), Tavasim Tuff, and Arqan (micritic carbonates, chalk with chert nodules) formations. Rich nannofossil assemblages indicate that the Isfiye Fm. is Late Albian and the Arqan Fm. is Late Albian–Middle Cenomanian). The Tavasim Volcanics (V2) is Late Albian (CT2) or Late Albian–Early Cenomanian (CT8).

In the Judea Mts, the Kefira, Soreq, Moza, Kefar Shaul and Bina Fms (limestones, marls, clayey marls) have been dated based on nannofossil assemblages: the Aptian–Campanian Kefira Fm., the Albian–Maastrichtian age Soreq Fm., the Early–early Middle Cenomanian age Moza Fm., the Late Cenomanian Kefar Shaul Fm., and rare nannofossils of the Bina Fm. broadly indicate its Albian–Maastrichtian age.

In the Northern Negev (boreholes Massada-1 and Kohal-1), the Hazera Fm. (Hevyon, En-Yorqeam, Zafit and Avnon members) consists of limestones, dolomitic limestones, marls and clayey marls. Rare and poorly preserved nannofossils and ostracods indicate the Early Cenomanian age in Massada-1 and Late Albian – Early Cenomanian in Kohal-1 for the Hevyon member. Nannofossils provide the Early to Late Cenomanian age for the En-Yorqeam member, which is further restricted to the Late Cenomanian by ostracods. The Zafit member is the Middle–Late Cenomanian in both boreholes. In Kohal-1, nannofossils from the Avnon member indicate its Middle–Late Cenomanian age.

Biostratigraphy remains the key practical tool for correlation and age calibration. If we wish to demonstrate the synchronous nature of events in the rock record (e.g. sea-level change), it is necessary to be able to correlate rocks between regions and between depositional settings. However, despite decades of research, fundamental uncertainties exist in how bioevents and zonation schemes of different fossil groups relate to one another, and how they relate to the standard chronostratigraphic subdivisions. Here we have collated and attempted to calibrate what we consider to be important Cenomanian fossil bioevents from across a number of fossil groups. Some fossil groups are relatively well-known and calibrated. Others such as microcrinoids are relative newcomers to the biostratigraphic scene. For some groups (e.g. the larger benthic foraminifera) definition of bioevents and creation of a calibrated biozonation scheme is a work in progress.

For almost all Cenomanian fossil groups, creation of a bioevents/biozonation scheme is challenged by issues surrounding identity of the fossils (common agreement of what is meant by a taxonomic name) and by precise age calibration of the known occurrences of those fossils. Loose approaches to taxonomy and age calibration can result in over-extended “smeared” ranges. Fortunately, facies-independent techniques such as carbon and strontium isotope stratigraphy are beginning to form the basis for a Rosetta Stone to interpolate between fossil groups.

Our synthesis is ongoing, and we welcome comments from experts to improve our understanding.

The uppermost Turonian – lower Campanian Chalk succession at Seaford Head, southern England, has been proposed as a global reference section for the Coniacian–Santonian and Santonian–Campanian stage boundaries, and has recently been designated an auxiliary GSSP boundary stratotype for the Campanian Stage. The section is described and the placement of stage and substage boundaries defined. New micropalaeontological data are presented for 99 samples spanning the full exposed section. Samples yield abundant well-preserved diverse microfossil assemblages. The stratigraphic distributions of 39 stratigraphically important foraminifera species of Gavelinella, Stensioeina, Protostensioeina, Bolivina, Bolivinoides, Pyramidina, Pseudouvigerina and planktonic foraminifera (Contusotruncana, Dicarinella, Globotruncana, Marginotruncana) are presented. Foraminifera records are placed within a framework provided by an integrated stratigraphy that includes lithostratigraphy, macrofossil, microcrinoid and calcareous nannofossil biostratigraphy, and a high-resolution carbon-isotope (δ¹³C_carb) chemostratigraphy comprising 30 named CIEs of regional to global significance. The succession comprises benthic foraminifera zones UKB.11 Reusella kelleri IZ – UKB.16 Bolivinoides culverensis IZ. Four new species, Gavelinella praestelligera, G. praethalmanni, G. praetumida, and Protostensioeina ukrainica, and three informal species of Pyramidina are recognised. Evolutionary lineages of foraminifera genera provide the basis for a refined biostratigraphy that is successfully correlated to Salzgitter-Salder, Germany and Dubivtsi, Ukraine. Records are compared to literature data and benthic foraminifera zonations across northern Europe. However, differing taxonomic concepts of authors hamper comparison with literature data. This precludes rigorous assessment of diachronism of marker species, although regional stratigraphic differences in the distribution of the first stensioeinids and representatives of the Gavelinella clementiana group in Europe are apparent.

Seaford Head is a 3 km long sea cliff section on the south coast of England, between Brighton and Eastbourne in the county of Sussex. The succession comprises upper Turonian – lower Campanian white nannofossil chalk and represents a key reference section for the Upper Cretaceous of NW Europe. This study aims to revise the calcareous nannofossil biostratigraphy of the upper Turonian – lower Campanian interval and calibrate it to a new high-resolution carbonate δ¹³C record spanning the upper Turonian– middle Santonian. The calcareous nannofossil assemblages are investigated in terms of both semi-quantitative and quantitative abundances. This approach allows an accurate description of the abundance pattern for each observed taxon and the application of several types of biohorizons: LO (Lowest Occurrence) and HO (Highest Occurrence), LCO (Lowest Consistent Occurrence) and HCO (Highest Consistent Occurrence), Base acme and Top acme. The available calcareous nannofossil biozonations for the Late Cretaceous (CC, NC*, UC and Boreal UCizones) are applied and each biohorizon detected is evaluated both for its local reproducibility and regional to supra-regional reliability. Several zonal and subzonal markers show a high reliability: the LO of M. staurophora; the Top acme of H. trabeculatus; the HO of L. septenarius; the LO of A. parcus parcus; and the LO of A. parcus constrictus. Secondary nannofossil events have been identified and proven to be highly reliable events. The new calcareous nannofossil biostratigraphy and δ¹³C chemostratigraphy of the Seaford Head section is correlated with the GSSPs record of Salzgitter-Salder (Germany), Olazagutia (Spain) and Bottaccione (Italy).

Seaford Head (southern England) offers an accessible and complete succession of exposed uppermost Turonian to lower Campanian chalk. It is an important regional reference section for the base of the Santonian and is an auxiliary GSSP for the Campanian Stage. Microfossil assemblages were studied in 99 samples spanning the 162 m thick succession. Samples yielded abundant, well-preserved and diverse microfossil assemblages dominated by benthic foraminifera. Ostracod recovery was relatively poor from the nodular chalk-rich beds of the lower–middle Coniacian but improved considerably across the Coniacian–Santonian boundary, with more consistent occurrences, and increased numbers and diversity upward through the section.

The first detailed ostracod records from the English Coniacian–Campanian are presented. Forty ostracod taxa were identified. Ostracod records are placed within a framework provided by an integrated stratigraphy that includes lithostratigraphy, macrofossil, microcrinoid, benthic foraminifera, calcareous nannofossil biostratigraphy, and a high-resolution carbon-isotope (δ¹³C_carb) chemostratigraphy comprising 30 named CIEs of regional to global significance. Five new ostracod interval biozones are proposed, defined by the lowest occurrences of the index species: Cytherelloidea granulosa, Neocythere (Physocythere) virginea, Limburgina senonensis, Phacorhabdotus lonsdaleianus and Pterygocythere laticristata. The ostracod taxa used for zonation are discussed, and their stratigraphic ranges are placed in the context of previous work on the English Cenomanian – basal Coniacian Chalk. The occurrences of biostratigraphically important ostracod species at Seaford Head are compared to their distributions reported in published studies of Upper Cretaceous strata from continental Europe – Spain, France, Belgium, Netherlands, Denmark, Germany, the Czech Republic and Poland.

An expanded Campanian–Maastrichtian boundary succession is well accessible in the composite Middle Vistula River section, Central Poland. The studied succession, approximately 80 m thick, represented by opoka facies with a distinct three-fold lithofacies subdivision, spans an interval from the base of the Nostoceras hyatti ammonite Zone of the Upper Campanian through the lower part of the range of the ammonite Pachydiscus neubergicus in the lowermost Maastrichtian.

The Tercis-based lower boundary of the Maastrichtian cannot be precisely located; however, its approximate position is indicated by several taxa listed in the boundary definition: ammonites (FO of P. neubergicus), inoceramids (FO of Endocostea typica), and dinoflagellates (LOs of Raetiaedinium truncigerum and R. evittigratia, and LOs of Samlandia mayi and S. carnavonensis); and other taxa, not listed in current definition, with high chronostratigraphic potential: belemnites (FO of Belemnella vistulensis), benthic foraminifers (FO of Neoflabellina reticulata), planktic foraminifers (FOs of Rugoglobigerina pennyi, R. hexacamerata, and R. milamensis), and nannofossils (LO of Eiffelithus eximius, LO of Uniplanarius trifidus, FO of Arkhangelskiella cymbiformis var. N, and LO of Zeugrhabdotus praesigmoides).

All biostratigraphic markers correspond well with the isotopic signal, suggesting the base of the Maastrichtian lies close to the top of the CMBE-2 (Campanian–Maastrichtian Boundary Event) of the carbon curve, and with the magnetostratigraphic signal placing the boundary within the C32n2n Polarity Chron.

The geographic location, along with the bio-, chemo-, and magnetostratigraphic signals, makes the Middle Vistula section a valuable source of chronostratigraphic information for the ongoing work on redefining the base of the Maastrichtian Stage.

Climate reconstructions are vastly supported by unconsolidated sedimentary deposits that contain unaltered, carbonate-rich microfossils. These deposits have routinely been targeted for ocean science research and proven to be valuable archives. Specifically, these ocean drill sediments have allowed scientists to reconstruct past global temperature changes, polar ice sheet variations, and global carbon cycle dynamics over varying time scales, for the last 66 million years of Earth’s history. As we go deeper in time, into the Late Cretaceous (~ 66 to 84 million years ago), these sediments are less abundant and often more challenging to recover. Here we present our latest efforts to define a global geochronological reference for the Late Cretaceous from soft sediments recovered at Shatsky Rise (Pacific Ocean). X-ray fluorescence core scanning data and bulk carbonate stable carbon and oxygen isotope records were integrated to assemble a composite record spanning the entire Campanian and Maastrichtian at unprecedented resolution. Our goal is to establish an astronomically tuned global geochronological reference for the Campanian Stage, possibly serving as a guide for addressing questions regarding the timing and phasing of global climate warming events during the Late Cretaceous.

The GSSP for the base of the Maastrichtian Stage at Tercis-les-Bains (SW France), ratified in 2001, earned some criticism over the years, mainly because of diachroneities among macrofossils, the poor definition of lowest (LO) and highest (HO) occurrences of planktonic foraminifera and calcareous nannofossils, and the lack of magnetostratigraphy. Thereby, the main concern is the missing definition of a primary boundary marker mandatory for a GSSP. In March 2023, some members of the new Maastrichtian Working group resampled Tercis for calcareous nannofossils, planktonic and benthic foraminifera, inoceramids, palynomorphs and petrography. First results prove the preservation of foraminifera as very poor preventing the development of a reliable definition of bioevents. Results of organic-walled palynomorphs revealed relatively rich and diverse dinoflagellate cyst assemblages and the HOs of Raetiaedinium evittigratia and of R. truncigerum are useful boundary markers. The recognition of significant species among calcareous nannofossils also proves difficult. Biostratigraphic index species such as Reinhardtites levis or Monomarginatus quaternarius occur only in a few samples, Broinsonia parca constricta is consistent, but B. parca parca is very rare. Uniplanarius gothicus and U. trifidus do not occur in every sample. Their proven HO is better resolved now and lies within the uncertainty range of previous studies. A new highly resolved carbon isotope stratigraphy allows a more precise definition of the CMBE carbon isotope events, with the HO of U. trifidus to occur within CMBE-4, and its correlation to orbital chronologies of other Maastrichtian sites in the Bay of Biscay area.

A Campanian–Maastrichtian boundary succession is well exposed in a series of outcrops along the banks of the Vistula River, forming a composite Middle Vistula River section, located approximately 100 km south of Warsaw, Poland. This 80-m-thick succession, composed of opoka facies, spans an interval from the base of the Nostoceras hyatti ammonite Zone of the Upper Campanian to the lower part of the Pachydiscus neubergicus ammonite range in the lowermost Maastrichtian.

Calcareous nannofossils are continuously present throughout the entire succession. Despite their poor preservation, low abundance and diversity, the nannofossil assemblage appears to adequately reflect patterns recognized in other regions. Among the biostratigraphically significant nannofossils characteristic of the Campanian–Maastrichtian boundary interval in the Boreal Realm, most key taxa have been identified, including Eiffellithus eximius, Arkhangelskiella cymbiformis var. N, Zeugrhabdotus praesigmoides, Broinsonia parca constricta, Tranolithus orionatus, Reinhardtites levis, Zeugrhabdotus bicrescenticus, and Calculites obscurus. Uniplanarius trifidus, another key boundary marker whose last occurrence approximates the Campanian–Maastrichtian boundary in the Tethyan Realm, was also recorded in the studied material.

In addition, the following bioevents were recognized: the last occurrence (LO) of E. eximius, the first occurrence (FO) of A. cymbiformis var. N, the LO of Z. praesigmoides, and the LO of U. trifidus. Their succession, as identified in the Middle Vistula River section, is successfully compared – via carbon isotope curves – with equivalent successions in the Danish and North German basins.

The Maastrichtian oil shales of Jordan, deposited along the southern Tethyan margin of the north Arabian Plate, represent one of the most organic-rich Late Cretaceous successions in the region. Formed under the influence of a sustained coastal upwelling system, these deposits provide a sensitive archive of orbitally paced climate variability. The total organic carbon (TOC) content is
consistently high throughout the studied interval, with values reaching up to 20 wt.% in the lower part of the Muwakkir Chalk Member (MCM). A pronounced cyclic pattern in TOC and lithology is observed across all studied cores, terminating with a sharp decline in TOC to below 0.5 wt.% at the transition to the overlying chalk. This study integrates high-resolution calcareous nannofossil, dinoflagellate cyst, and bulk carbonate carbon isotope stratigraphy from four cores to investigate the timing, duration, and orbital control on organic matter accumulation and paleoenvironmental change. Integrated stratigraphic data constrain the age of the oil shale-rich interval to the Early Maastrichtian (71.6–69.85 Ma), representing a depositional duration of approximately 1.85 million years and an estimated sedimentation rate of ~2.4 cm/kyr. Spectral and cyclostratigraphic analyses reveal a dominant precession signal throughout the Early Maastrichtian interval, reflecting strong insolation forcing on productivity and monsoonal upwelling intensity. A significant shift to obliquity-dominated cyclicity occurs following the Middle Maastrichtian Climatic Event (MMCE), likely related to changes in paleogeography and ocean circulation that enhanced high-latitude climate sensitivity and intermediate water ventilation. These findings highlight a strong astronomical imprint on sedimentation, organic matter preservation, and redox conditions.

The Maastrichtian marks a cool greenhouse period after the long-lasting late Cretaceous temperature decline. Our understanding of climate and carbon cycle dynamics is still limited in pre-Cenozoic times. The lack of highly resolved stratigraphy introduces severe uncertainties in the quality and interpretation of global correlation. Here we present new achievements in the development of an astrochronology for the Maastrichtian stage that integrates sedimentary cyclicity, carbon isotopes and magnetostratigraphy in combination with calcareous nannofossils from the combined record of the Basque-Cantabrian sections at Zumaia, Sopela, Bidart and the GSSP locality Tercis-les-Bains. The sedimentary successions of Zumaia, Sopela and Bidart show a distinct orbital cyclicity, less distinctly expressed at Tercis. Particularly, bedding cycles of Bidart and Sopela surprisingly match on a bed-by-bed scale, thus allowing the transfer of precession cycle numbers from Zumaia and Sopela to Bidart. Further, new high-resolution δ¹³C data from Bidart and Tercis enable a precise correlation of both sections, roughly consistent to nannofossil events. With some accuracy, we can tie the Campanian-Maastrichtian Boundary Carbon Isotope Excursions CMBE 1-4 into the Basque-Cantabrian astrochronology showing the CMBEs to be forced by long-eccentricity. This approach yields a strong potential for a calibration of existing carbon isotope stratigraphies from the boreal chalk and the Pacific Ocean along a common orbital Maastrichtian timescale. Thereby, diachroneities in the first and last occurrences of nannofossil index taxa occur, mainly in the context of habitat stability and biogeographic provincialism between low and higher latitudes, but also because of poor preservation.

Palinostratigraphic analysis of sequences from the Codó Formation in the Parnaíba Basin identified the unmistakable occurrence of the Subtilisphaera Ecozone — a phytoplanktonic assemblage dominated by dinoflagellate cysts of this genus. The recognition of this ecozone in the Parnaíba Basin reinforces the hypothesis of marine ingressions into the Araripe Basin through the São Luís and Parnaíba Basins. This record is especially prominent in the middle and upper portions of the Codó section, corresponding to the upper Aptian, and marks the onset of the basin’s first marine incursion more clearly. The Subtilisphaera record becomes increasingly significant throughout the sedimentary succession, with several dinoflagellate peaks identified at 10–20% frequencies. In addition to these moderate peaks, levels of greater dinoflagellate richness were also identified, characterized by the monospecific dominance of the Subtilisphaera group, which becomes the prevailing component of the association. These levels are distinctly observed in the 9-PCR-1-MA well at a depth of 13.20 m and in the 9-PCR-3-MA well at 10.50 m, reaching peaks of 90% and 60% of Subtilisphaera, respectively. High frequencies of Subtilisphaera are sometimes accompanied by an increased presence of continental palynomorphs, supporting interpretations of shallow, coastal, and low-salinity marine environments. This bioevent likely reflects the opportunistic nature of Subtilisphaera, capable of tolerating salinity fluctuations. The ecozone was identified in the upper Aptian, aligning with numerous records from other Brazilian Cretaceous basins. The consistent presence throughout the section of the guide species Sergipea variverrucata and Equisetosporites maculosus further supports the early Aptian age attribution.

During the Cretaceous, the carbonate platform of the Jandaíra Formation, Potiguar Basin (Northeastern Brazil), recorded an important episode of phosphogenesis associated with oceanic upwelling. This phenomenon, common in other regions of the globe during the same period, provided nutrient input to the water column, intensifying biological productivity and promoting significant changes in marine paleoenvironments. In this study, micropaleontological samples from well FD-BP-003 were analyzed based on biostratigraphic observations and paleoenvironmental inferences from ostracods and foraminifera present in the phosphatic interval. A significant proliferation of ostracods such as Cytherella, Leguminocythereis, Soudanella, and Bairdoppilata genera, as well as the marked presence of planktic (Rugoglobigerina macrocephala and Rugoglobigerina rugosa) and benthic foraminifera (Gavelinella spp. and Afrobolivina afra), indicated neritic shallow to neritic deep conditions. The results demonstrate that phosphate deposition was associated with a significant increase in the abundance and diversity of these microfossils. The biostratigraphic distribution allowed the identification of two intervals: Interval I, attributed to the Quinqueloculina spp.–Gavelinella spp. zone (Upper Campanian), and Interval II, corresponding to the Globotruncana aegyptiaca–Gansserina gansseri zone (Upper Campanian to Lower Maastrichtian). This study highlights the role of microfossils as indicators of paleoenvironmental dynamics during global changes in the Late Cretaceous.

The Lower Cretaceous deposits of the Sanfranciscana Basin in southeast Brazil were traditionally viewed as products of a continental Gondwanan environment. However, marine microfossils have been identified in these deposits, prompting further investigation into their depositional evolution. This study analyzes samples from five sections of the Quiricó and Três Barras formations from the Sanfranciscana Basin to reconstruct the paleoenvironmental conditions during episodes of marine incursion. Microfossil assemblages include continental (non-marine ostracods and palynomorphs) and marine microfossils (benthic and planktic foraminifera, radiolarians, ascidian spicules). Lithologically, the alternation of claystone and quartz-rich biogenic chert layers suggests the presence of radiolarites. Key index microfossils, including the radiolarian Turbocapsula spp., Holocryptocapsa fallax, the planktic foraminifera Leopoldina sp., hedbergellids and the palynomorph Tucanopollis crisopolensis, permit the interval to be dated as Aptian. Based on lithological and paleontological evidence, the interval is interpreted as a continental setting that experienced episodic short-lived marine incursions. Three successive paleoenvironmental scenarios are proposed: an initial lacustrine (lake) depositional environment with exclusively non-marine biota; a subsequent phase marked by episodic marine influence, evidenced by the presence of marine microfossils; and a return to continental conditions, evidenced by aeolian (wind-blown) deposits. These marine incursions were episodic and short-lived, indicating that the interior of Gondwana was intermittently connected to marine waters during this time, influencing sedimentation and paleoenvironmental conditions. These scenarios reflect the early stages of the South Atlantic Ocean, highlighting the dynamic interplay between continental and marine influences in the basin during the Aptian. [Acknowledgements: Mar Interior Project]

The Sergipe-Alagoas Basin, located in the Brazilian northeast, contains stratigraphic sections that are essential for the understanding of the opening of the South Atlantic Ocean. There are divergences in the literature regarding the age in which this process took place, the paleoceanographic conditions related to the first marine incursions, and the establishment of this ocean. In this context, here we present a biostratigraphical and paleoenvironmental study based on calcareous nannofossils, foraminifera, and ostracods, aiming to contribute for the understanding of the evolution and opening of the South Atlantic Ocean. We analyzed 32 samples from quarry São José (SJ-2-Lago), Sergipe state, Brazil, which is a 25 m section composed of carbonate rocks (mudstones/marlstones). Calcareous nannofossils were recovered, with the recurring presence of genera Nannoconus, Cervisiella, and Zeugrhabdotus. In addition, the presence of Micrantholithus hoschulzi and Radiolithus planus suggests the upper Aptian age. For foraminifera, primarily benthic taxa were recovered, with a predominance of agglutinated forms (e.g., Ammobaculites sp.) and some calcareous ones (e.g., Lenticulinas sp.). Planktonic foraminifera were recovered mainly microhedbergellids and favusellids, suggesting upper Aptian–early Albian transition. Ostracods were frequent throughout the section, with an abundance of marine, continental platform species such as Paracypris eniotmetos, Sergipella viviersae, Praebythoceratina deltalata, P. amsittenensis, P. trinodosa, and Aracajuia benderi. As such, the microfossil assemblages of the SJ-2-Lago Quarry suggests the presence of marine incursions from the South Atlantic Ocean at the upper Aptian, with the establishment of a shallow marine environment in the region. [Acknowledgements: CNPq project 405679/2022-0]

This study integrates palynological, palynofacies, and organic geochemical (TOC and Rock-Eval pyrolysis) analyses of the Late Cretaceous Urucutuca Formation (Almada Basin, eastern Brazil). Fifty-six core samples from onshore wells SST-02 and SST-03 were examined. The palynofloristic assemblage comprises 11 pollen grains, eight spores, 14 dinoflagellate species, and rare freshwater and marine forms. The recognition of the Palaeocystodinium lidiae, Dinogymnium acuminatum, Tricornites elongatus, Cricotriporites almadensis, and Crassitricolporites brasiliensis species enabled the recognition of the Tricornites elongatus palynozone, placing the interval within the Upper Maastrichtian. Two distinct palynofacies were identified: Palynofacies 1, dominated by phytoclasts (67% and 73%) with lesser AOM (28% and 25%) and palynomorphs (2% and 5%) in both wells, respectively. Palynofacies 2, characterized by AOM dominance (64% and 67%) over phytoclasts (31% and 30%) palynomorphs (5% and 2%) on average for SST-02 and SST-03, respectively. TOC values range between 0.32–1.42% (SST-02) and 0.11–1.37% (SST-03). Rock-Eval pyrolysis results indicate poor hydrocarbon potential and predominantly Type IV organic matter. The depositional environment evolved from a dysoxic-anoxic marginal setting to a suboxic-anoxic, restricted marine basin under tropical to subtropical conditions inferred from peridinioid dinoflagellate assemblages. This integrated approach refines the biostratigraphic framework and paleoenvironmental interpretation of the Almada Basin.

Global marine ostracod databases have great potential for use in paleogeographic studies of the Cretaceous, but they have been scarce so far. In this study, the relationship between different ostracod assemblages is analyzed and discussed for the Albian and Cenomanian. The distribution of 168 genera for the Albian and 174 for the Cenomanian was used for quantitative paleobiogeographical analysis. The affinity between different ostracod assemblages from different regions allowed for the delineation of 30 operational geographic units (OGUs) for the Albian and 32 OGUs for the Cenomanian, grouped in three paleobiogeographic units (PBUs; Megatethys, Persia, Austral) and one sub-unit (PBSU; Maghreb associated to the Megatethys). The relationship among the OGUs grouped in each PBU is related to different factors, like eustatic sea level events, similar climatic zones, and marine current circulation patterns. A relationship was observed between the Gabon and Nigeria OGUs with the Persia PBU, which suggests a direct east-west connection between them during the Cenomanian. The affinity observed in the Austral PBU between the South American, South African, and Australian regions during the Albian can be explained by their relative geographic isolation due to the Walvis Ridge barrier. The eventual flooding of this barrier led to the relationship observed between the SE Brazilian and Bolivian regions with the Austral PBU. Finally, the data also suggested that the separation of the Indian subcontinent from the Austral PBU took place during the Cenomanian.

Early to Middle Campanian to Danian planktic foraminiferal and calcareous nannofossils assemblages provide new information on age and paleo-environments of the Ultrahelvetic Zone of Upper Austria. Tectonic windows within Penninic Zone deposits give access to up to 200 m thick stacks of mainly gray but also red coloured marlstones. A c. 80 m thick nearly continuously exposed section in the Hochhub area and several single samples from nearby outcrops were analysed. The measured section ranges from late Maastrichtian to middle Danian, including a Cretaceous – Paleogene transition. The nearly uniform sediments (marlstones and clayey marlstones) and the absence of turbidites points to continuous sedimentation processes. Preliminary quantitative analyses of Late Cretaceous planktic foraminifera show that deposition took place at bathyal paleo-water depths of about 1,000 m or even at greater depths but above the carbonate compensation depth (CCD). Living conditions were generally stable and oligotrophic. Some exceptional assemblages point to increased mixed layer paleo-productivity indicated by reduced equilibrium species contents and increased contents of species with opportunistic reproductive strategy. Danian strata contain abundant calcareous nannofossils with less reworking from Cretaceous pointing to stable marine conditions with normal salinity and well stratified water column.

The Upper Cretaceous in the Central Balkan Mts is represented by the carbonate deposits of the Bazov Dyal, Darmantsi, Kunino and Mezdra formations, which have previously been assigned to the upper Campanian–lower Maastrichtian based on rare, poorly-preserved macrofauna. We have studied seven sections in an attempt to better characterise these lithostratigraphic units by means of calcareous nannofossils, foraminifera and macrofauna. Nannofossil preservation has largely been thwarted by facies and diagenetic factors, particularly in the Bazov Dyal Formation. In one section, benthic foraminifera (Nonionella austinana, Idalina cf. antiqua, Cibicidoides velascoensis, Stomatorbina binkhorsti) from the middle part of the latter unit indicate Campanian age, whereas the uppermost part yielded late Maastrichtian nannofossils Lithraphidites quadratus and Micula murus. Nannofloras from the Darmantsi Formation indicate late Campanian–early Maastrichtian age. The lower part of the Kunino Formation in most sections contains moderately-diverse nannofossil assemblages that indicate early Maastrichtian age, which is further supported by rare finds of Pachydsiscus spp. (ammonites) and Endocostea typica (inoceramid). In one section, in the upper part of the same unit, single specimens of Paleogene taxa (Sphenolithus cf. S. primus, Neochiastozygus cf. N. perfectus, Coccolithus pelagicus) were observed. The Mezdra Formation is largely barren of nannofossils, except for one section, where lower Maastrichtian taxa were noted. These data show that the stratigraphic extents of the studied lithostratigraphic units are highly variable between each section and much wider than previously thought, reaching up to the Paleogene.

Acknowledgements. This study was funded by the Bulgarian National Science Fund, Grant KP-06-N74/3.

The calcareous nannofossil group Aspidolithus parcus (Broinsonia parca of former authors and Nannotax3) including the forms traditionally classified as Aspidolithus parcus constrictus, Aspidolithus parcus parcus, and Aspidolithus parcus expansus, plays a crucial role in Upper Cretaceous biostratigraphy, yet its taxonomy remains unresolved. This study integrates high-resolution morphometric analysis, bulk carbonate δ¹³C stratigraphy, and palaeoecological indices from the Niobrara Formation (Western Interior Basin, USA), with data from two Tethyan localities (Loibichl and Postalm, Austria) to assess evolutionary versus environmental control on coccolith morphology. A total of 2440 specimens were measured for coccolith length (L) and the central area-to-rim ratio (b/a). Finite mixture models revealed three statistically significant morphogroups based on b/a ratio and two for coccolith length. A consistent threshold at ~8.5 µm distinguishes Aspidolithus enormis from A. parcus, supporting its biostratigraphic utility across palaeogeographic settings. However, b/a-based subspecies assignments were not robust, indicating a morphometric continuum likely shaped by surface water temperature, as supported by strong correlations with the Nannofossil Temperature Index (NTI). The δ¹³C profile aligns with known Santonian–Campanian isotope events and enables refined chronostratigraphic placement. Morphometric trends across the studied sections suggest an evolutionary turnover near the base of Chron C33r but also emphasize ecophenotypic plasticity. This study proposes a revised, statistically supported morphometric framework for Aspidolithus and highlights the need to standardize size-based criteria for improved global correlation and taxonomic consistency.

Planktic foraminifera are preserved abundantly within the stratigraphic succession of Core SER-03, drilled in the Sergipe-Alagoas Basin. Assemblages are composed of typical post-extinction taxa that diversified after the Aptian-Albian boundary. The recovered planktic foraminiferal families and genera are HEDBERGELLIDAE (Microhedbergella and Muricohedbergella), ROTALIPORIDAE (Ticinella) and FAVUSELLINIDAE (Favusella). Acnes of Favusella were associated with sea level falls, and slight increases of HEDBERGELLIDAE and ROTALIPORIDAE taxa with rising sea level. We identified four zones at Core SER-03: The base of the Microhedbergella renilaevis Interval Zone was defined by the first occurrence of M. renilaevis (at 171.55 m), and its top by the first occurrence (FO) of Microhedbergella rischi (at 168.14 m); The M. rischi Interval Zone has its base defined by the FO of M. rischi (at 168.14 m), and its top by the FO of Ticinella madecassiana (at 122.57 m). The base of the Ticinella madecassiana Interval Zone is defined by the FO of T. madecassiana (at 122.57 m), and its top is defined by the FO of Ticinella primula (at 117.51 m). The T. primula Interval Zone was identified between 117.57 and 6.26 m, with its base defined by the FO of T. primula and extending up to the top of the studied succession. Changes of planktic foraminiferal distributions and abundances at Core SER-03 suggest a link with sea level changes.

This study presents new micropaleontological data on benthic and planktonic foraminiferal assemblages from the Aptian–Cenomanian ammonite-bearing succession of Kotraža (Central Serbia), focusing on palaeoecological dynamics and biostratigraphy in relation to global oceanic anoxic events (OAEs). In contrast to the fine-grained, organic-rich sediments typical of the Atlantic domain, the Kotraža succession, linked to the Tethys realm, is dominated by coarse-grained deposits.

The studied section includes four ammonite-bearing sedimentary units (A–D). Analysis of 22 thin sections revealed distinct foraminiferal responses to OAE1b and OAE1d intervals. Unit A (Late Aptian) is characterized by agglutinated benthic foraminifera indicating low-oxygen bathyal environments. Unit B (Aptian/Albian transition) records a shift to small, thin-walled planktonic forms (Microhedbergella spp.), reflecting stressed conditions linked to OAE1b, with associated Douvilleiceras mammillatum Superzone ammonites.

Units C and D (uppermost Albian–lowermost Cenomanian) document increasing planktonic diversity (Parathalmanninella appenninica, Planomalina cf. buxtorfi, Praeglobotruncana delrioensis) alongside typical ammonite fauna (Phylloceras velledae, Kossmatella agassiziana, Puzosia mayoriana, Stoliczkaia dispar). Significant faunal changes during OAE1d include a rise in infaunal agglutinated and calcareous benthic taxa (Bulbobaculites problematicus, Gaudryina sp., Pleurostomella sp.) and a decline in epifaunal species, reflecting a shift from dysoxic to suboxic conditions.

This study integrates planktonic and benthic biostratigraphy, correlating local foraminiferal and ammonite assemblages with global mid-Cretaceous oceanographic and climatic perturbations.

The Early Cretaceous section of the Espírito Santo Basin covers a set of rocks from its active petroleum system. However, detailed studies are needed to characterize the Albian-Aptian section, particularly in its emerged area - the shallow portion of the São Mateus Platform. This work presents analyses of two continuously cored wells (PEI-12 and PEI-3) containing strata deposited above the salt section in this area belonging to the São Mateus Formation, deposited on the edge of the basin, comprising a succession with alternating sandy and carbonate layers, integrating palynostratigraphic and palynofacies data. The palynozones Sergipea variverrucata and Complicatisaccus cearenses were recognized to correspond to those established by Regali & Santos (1999) for the Sergipe-Alagoas Basin. The presence of Sergipea variverrucata, Equisetosporites maculosus, Trisectoris reticulatus, and Spiriferites chebka species assures the occurrence of the Sergipea variverrucata palynozone (P-270). Its upper limit is the species' extinction level that gives the palynozone name, as shown in the species distribution in well PEI-3. The Complicatisaccus cearenses (P-280) palynozone was better identified in well PEI-12, where the extinction of the Sergipea variverrucata species and the occurrence of Equisetosporites maculosus immediately above marks its lower limit. Based on the characterization of the palynozones, the Upper Aptian age is signed for the section crossed by both wells. The strata analyzed show a constant post-salt palynoflora dominated by spores, pollen grains, and woody organic residue of continental origin, co-occurring with essentially marine forms, such as dinoflagellates and foraminiferal linings evidenced deposition in shallow and coastal areas.

Cretaceous reefs that record coral growth under mesophotic conditions apparently are very rare. Hereunder we present a middle-upper Coniacian to lower Santonian reef composed mainly of coral platestone that is located within the synorogenic wedge-top succession of the Eastern Alps (Gosau Group, Turonian to Ypresian) near Strobl am Wolfgangsee (Salzburg, Austria). In the studied reef, an exposed 15-18 m of coral platestone is overlain by a few meters of domestone-mixstone and bioclastic limestones. The platestones display a dense, continuous, interlocked fabric with a matrix of wackestone with planktic foraminifera and calcareous nannoplankton. Bioencrustation of coralla and boring traces are scarce. Hippuritids and radiolitids settled on the corals, but only few developed into adults. The dome/mixstones comprise massive and branched corals, show a packed fabric, and contain intercalated singles and clusters of rudists. In the reefal interval, one helioporid octocoral and 25 colonial scleractinian species (25 % pennular species) were identified. The top bioclastic limestones contain dasycladaleans, Miliolina, Textulariina and rare Rotaliina. The vertical succession from coral platestones to bioclastic limestones indicates shoaling. The platyfoliaceous shapes and packing of coralla in the platestones, and the scarce encrustation suggest constratal to low-superstratal growth under mesophotic conditions. In the dome/mixstones, toppled corals and rudists indicate episodic disturbance. In Jurassic seas mesophotic reefs were widespread, yet the studied reef is the first Upper Cretaceous example. This contrast in reef style may be attributable to: (1) intensified production and dispersal of chalk; (2) extinction/emigration of Jurassic microsolenids; and, (3) implicit description of Cretaceous mesophotic reefs.

Conical agglutinated larger benthic foraminifera (Orbitolinidae, Coskinolinidae) are an integral part of the Cenomanian megadiversity within the preserved biota of Neotethyan carbonate platforms. Three subfamilies (Orbitolininae, Dictyoconinae, Dictyorbitolininae) are present with varying numbers of taxa that fluctuate through the duration of the stage. Understanding the Cenomanian diversity and abundance of the group also requires a critical assessment of the relevant assemblages of the previous stage, the Albian, allowing assessment of taxa unique to each stage, boundary crossers and generic newcomers. With 27 Cenomanian species considered to be taxonomically valid, orbitolinids are present in almost equal numbers by comparison to the other important group of mid-Cretaceous larger benthic foraminifera, the porcelaneous Alveolinoidea. In contrast to the assemblages reported from the peri-Mediterranean carbonate platforms (e.g., Italy), Orbitolinidae are reported from the late Cenomanian of the Arabian Plate, co-occurring with Cisalveolina fraasi but becoming extinct prior to the Alveolinoidea. After a stratigraphic gap of roughly 5.7 mya, representatives of the Orbitolinidae reappear (but with different genera) during the early Coniacian. A comparable order of magnitude for recovery (again with different genera) is also observed for the second large-scale extinction of the Orbitolinidae at the K-Pg boundary.

Calcareous nannofossil assemblages of Cretaceous strata provide valuable information on surface water temperature (SST), as some taxa are considered typical of warm or cool waters. Several temperature indices (TI, NTI) have been reported for different time intervals (e.g., Thibault et al., 2016), involving multiple warm- and cool-water taxa. The main warm-water taxon used as numerator is Watznaueria, especially W. barnesiae, a long-ranging, conservative species dominating low-latitude assemblages from the Early to the Late Cretaceous. In contrast, the denominators typically include several different cooler-water taxa, selected based on their restricted stratigraphic ranges. M. staurophora, which first appears in the Coniacian, is often used as part of the cool-water taxa (e.g., Jain et al., 2022; Granero et al., 2024), and occurs generally in low percentages in Coniacian-Campanian Tethyan assemblages (Švábenická et al., 2002). Across the carbon-isotope Campanian–Maastrichtian Boundary Event we observe a sudden and consistent shift in western Tethyan (Austria, Turkey) and Peri-Tethyan (northern Bulgaria) assemblages, from Watznaueria-dominated (>25%) to Micula-dominated (>50%). This shift, also reported from other areas (e.g. Doeven et al., 1983), defines an acme of Micula spp., here proposed as the Micula–Watznaueria Event (MWE). The MWE likely reflects palaeoceanographic changes associated with the peak of long-term Campanian–Maastrichtian cooling (Linnert et al., 2013), and may serve as a valuable biostratigraphic and palaeoenvironmental marker.

Doeven, 1983, Geol. Surv. Canada, Bull. 356.

Granero et al., 2024, doi:10.1016/j.cretres.2024.105954.

Jain et al., 2022, doi:10.1016/j.jafrearsci.2022.104474.

Linnert et al., 2013, doi:10.1038/ncomms5194.

Švábenická et al., 2002, VEDA Publ., Bratislava.

Thibault et al., 2016, doi:10.5194/cp-12-429-2016.

Extant Nautilus and Allonautilus hatch at large size and immediately begin a nektobenthic existence tied to the bottom and never move in the water column either as adult or juveniles, based on new ultrasonic tracking data presented here. Since all post-Triassic nautiloids except Aturia hatched at approximately similar, large size and morphology, the observed distribution of nautiloids can provide clues for paleobiogeography and terrane study. Here, a highly diverse (11 species in four genera) assemblage of previously unstudied, endemic Nautilus, Allonautilus (the first recognized in the fossil record) and Eutrephoceras from the Turonian to Paleogene Nanaimo Group of British Columbia, Canada, provide important clues to the tectonic assembly of Cordilleran North America during the Cretaceous. Here, new oxygen isotope analyses of nautiloids, ammonites, gastropods and bivalve fossils including inoceramids and rudistids from Mainland North America show no systematic temperature change from the Coniacian through Campanian, and only a minor temperature reduction in the Maastrichtian, whereas the same groups from the Nanaimo Group demonstrate a systematic reduction in temperatures of shelf temperatures of ~ 25-30^oC in the Santonian to around 10^oC in the latest Campanian, over the same time intervals. This combination of data is consistent with the Baja British Columbia Hypothesis of Cowan et al, 1997, that the Insular Terrane now making up much of coastal British Columba and southern Alaska migrated northward from a mid-Cretaceous latitude of current Baja California. The nautiloid evidence suggests that it did so, while at least 100km offshore of the Western North coastline.

In the upper part of the medium-bedded turbidites of the Ropianka Formation within the Bystrica Zone of the Magura Nappe, a distinct horizon of variegated mudstones, designated as the Farony Shale, has been recognized. This unit potentially serves as a valuable correlation marker, extending at least to the Lubomierz–Limanowa region. It was deposited during the late Campanian to early Maastrichtian in a deep-water environment of the Magura Basin.

The foraminiferal assemblages are characterized by low to very low taxonomic diversity and abundance. In the samples, certain foraminiferal species predominate. In some samples, excluding fragments of tubular specimens, the genus Caudammina - particularly Caudammina ovula (Grzybowski) and Caudammina gigantea Geroch - comprises up to 70% of the foraminiferal assemblage. In others, Placentammina placenta (Grzybowski) and Saccammina grzybowskii (Schubert) collectively represent between several percent and 50% of the specimens. These assemblages display characteristics of an acme. The Caudammina gigantea-ovula acme and Saccammina-Placentammina acme assemblages developed concurrently across the Magura Basin.

The Caudammina gigantea-ovula acme is associated with red or green, homogeneous, and very fine-grained mudstones rich in clay minerals, deposited in low-energy environments. Conversely, the Saccammina-Placentammina acme is found in coarser-grained grey mudstones deposited under conditions of increased clastic input and elevated delivery of organic matter. Placentammina placenta (Grzybowski) exhibits considerable variability in test size and surface granulation. Two morphological types are distinguished: smaller forms (approximately 0.3–0.6 mm in diameter) with a distinct short neck, and larger forms, attaining 0.8 mm or greater in diameter, provisionally referred to as var. gigantea.

The primitive deep-water agglutinated genus Arthrodendron Ulrich, 1904 is one of the largest foraminifera known from deep water environments. It is characterized by chambers arranged in uniserial or occasionally horizontally branching sequences. Arthrodendron is known for inhabiting benthic environments in bathyal to abyssal settings and is generally considered to display a single terminal aperture presented on a small neck, or at most two apertures in the case of specimens that display branching.

A taxon commonly reported from the Tethyan realm is Arthrodendron grandis (Grzybowski), and for the first time, this study documents the presence of multiple apertures in this species. We observed two to seven apertures arranged on small necks, that are commonly organised a circular or subcircular pattern on the terminal chamber.

Material was recovered from three localities: two in the Polish Outer Carpathians (Siekierczyna and Żurawnica sections) and one in the Italian Umbria-Marche Basin (Contessa section). The sediments represent outer bathyal to abyssal depositional environments, with low-diversity agglutinated assemblages indicating low-oxygen conditions in the Carpathians, and normal oxygenation in Contessa.

As the majority of specimens observed document only the isolated terminal chambers, thus, limiting interpretations of growth patterns. The occurrence of multiple apertures may indicate intraspecific variability within the genus, potentially linked to environmental adaptation. They occur rarely, together with chambers or sequences of several chambers from the middle part of the chain, as well as with terminal chambers with a single aperture. These findings add to the known morphological variability in Arthrodendron

This poster showcases the ChaSE (Chalk Sea Ecosystems) project. As an economically important resource, the UK Chalk Group has been studied and quarried for >200 years and a detailed stratigraphic framework is available. The sequence is abundantly fossiliferous, recording every marine trophic level from phytoplankton to apex predators. Key events recorded in the Chalk include peak Cretaceous warming and biodiversity crises across the Cenomanian – Turonian boundary (Oceanic Anoxic Event 2), the highest global sea-levels of the last 250 million years, and the coldest temperatures of the Late Cretaceous.

The Natural History Museum, London (NHM) contains >50,000 UK Chalk Group macrofossil specimens, including rare taxa and material from now inaccessible localities. Only a fraction of these have been published or are available in public datasets. Many specimens contain limited metadata, and ages or stratigraphic position are poorly constrained. To unlock these 'dark data' we are re-dating >1,500 macrofossil specimens using calcareous nannofossil biostratigraphy. Combining these with data from new fieldwork, we are conducting the first whole-ecosystem study of the functional diversity and ecology of the Chalk Sea. These data will provide an unprecedented record of the effects of global Cretaceous climate change at a variety of temporal and spatial scales, within the same depositional system.

The Cretaceous Period is a vital time interval in deciphering the evolutionary history of the Neo-Tethys Ocean and the convergence of different plates and blocks across the Qinghai-Tibetan Plateau. Here, the Cretaceous stratigraphy, biota, paleogeography, and major geological events in the Qinghai-Tibetan Plateau are analyzed to establish an integrative stratigraphic framework, reconstruct the paleogeography during the Cretaceous Period, and decode the history of the major geological events. The Indus-Yarlung Tsangpo Suture Zone was responsible for the deposition of deep marine sediments. To the south, the Tethys Himalayas and Indus Basin received marine sediments; to the north, the Xigaze and Ladakh forearc basins are also filled with marine sediments, the Lhasa Block, Karakorum Block, western Tarim Basin, and West Burma block consist of shallow marine, interbedded marine-terrestrial, and terrestrial sediments, while he Qiangtang Basin and other areas are dominated by terrestrial sedimentation. The Cretaceous strata of the Qinghai-Tibetan Plateau and its surrounding areas are widely distributed and diversified, with abundant foraminifera, calcareous nannofossils, radiolarians, ammonites, bivalves, and palynomorphs. On the basis of integrated lithostratigraphic, biostratigraphic, geochronologic, and chemostratigraphic analyses, we proposed herein a comprehensive stratigraphic framework for the Cretaceous Period of the eastern Neo-Tethys. By analyzing the Cretaceous biota of different biogeographic zones from eastern Neo-Tethys and its surrounding areas, we reconstructed the paleobiogeography of different periods of eastern NeoTethys. The eastern Neo-Tethys and its surrounding areas experienced a series of major geological events, including the formation of the large igneous province, oceanic anoxia events, and mass extinction during Cretaceous.

The Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE 2, ca. 94 Ma) is characterized by a marked positive carbon isotope excursion (CIE), linked to increased organic carbon (OC) burial driven by high productivity and widespread deoxygenation. To date, however, the precise pattern of changes in the burial rate of organic matter has not been well constrained. In this work, we present a compilation of data from 42 globally distributed OAE 2 sites, as well as organic carbon isotope (¹³C_org), total organic carbon (TOC), and trace element concentration data from a new OAE 2 interval in southern Tibet, China. In southern Tibet, the absence of redox-sensitive trace element enrichment through OAE 2 indicates prevailing oxic conditions. Organic carbon (OC) mass accumulation rate (MAR) at this site decreased from the lower part of the CIE to the upper part, in contrast to an approximate doubling of organic carbon MAR in the upper part observed globally. This result, coupled with detailed analysis of the compilation, shows that redox was a key factor controlling organic burial rates during OAE 2, with OC MAR scaling positively with increasing deoxygenation. Leveraging a biogeochemical model to simulate these data suggets that 5-20% of the seafloor became anoxic during OAE 2, and that this deoxygenation was accompanied by 100% to 200% increase in global seawater P concentration. Our findings indicate that during OAE 2, elevated nutrient levels may have resulted from enhanced recycling from sediments under reducing conditions, sustaining intensified primary production and subsequent organic carbon export and burial.

Intensified frequency and scale of wildfires due to global warming has been increasingly recorded in recent years. Studies of wildfire activity during deep time greenhouse climate states are crucial for evaluating their likely impacts on the global environment and ecosystems in the future. Oceanic anoxic event 2 (OAE 2), which was characterized by extremely high global temperature and a reduced equator-pole temperature gradient, could provide insights into our understanding of present-day global change processes. Here we provide data on polycyclic aromatic hydrocarbon (PAH) abundance from the Qiangdong section in the Tethyan Himalaya of southern Tibet to investigate wildfire behavior and its impact on the environment during OAE 2. Our results indicate a significant increase in the frequency of wildfires during the early part of OAE 2, followed by a rapid weakening. The change of PAH composition through OAE 2 in Qiangdong shares a similar trend to that previously found in the Western Interior Seaway, indicating potentially globally elevated wildfire frequency during the early part of OAE 2. We also document a rapid increase in chemical index of alteration values in Qiangdong. These data, coupled with other proxies for weathering intensity through OAE 2, suggest that increased weathering during OAE 2 can be attributed at least in part to the effects of vegetation loss caused by wildfire. As such, we suggest that frequent wildfires during OAE 2 promoted the flux of nutrients to the oceans, thereby stimulating productivity that, in turn, increased the area of oceanic anoxia and organic carbon burial.

Oceanic Anoxic Event 2 (OAE 2) across the Cenomanian/Turonian boundary (93.9 Ma) is characterized by a synchronous positive δ¹³C excursion in both carbonates and organic matter that likely resulted from burial of large amounts of organic carbon in deep-sea and hemipelagic settings. According to several studies, causes for OAE 2 are massive submarine volcanic activity that emitted greenhouse gases and provided biolimiting metals in marine ecosystems, leading to the onset of the Cenomanian-Turonian Thermal Maximum and to the enhancement of ocean fertility. Ocean temperature, sea-surface stratification, nutrient availability, carbonate ion saturation and continental weathering were subject to significant variations during OAE 2 that resulted in fluctuations in diversity, abundance and calcification of marine species.

We analysed the record of the main biocalcifiers of pelagic-hemipelagic settings (planktonic foraminifera and calcareous nannofossils) and of low-latitude carbonate platforms (larger benthic foraminifera and rudist bivalves) by looking at well-dated sections. Using carbon isotope stratigraphy, we performed precise correlation from shallow to deep water and tied the biotic response to the record of geochemical proxies of paleoenvironmental changes. The main extinction event, severely affecting the shallow-water benthic biocalcifiers and to a minor extent the calcareous plankton, occurred within the so-called Plenus Cold Event. High surface seawater temperature and extreme fluctuations over geologically short time intervals were probably the main cause of extinction, with concurrent contributions from decreased seawater carbonate saturation and disruption of ocean stratification. Overall, calcareous plankton fared much better, showing a greater resilience than carbonate-platform biocalcifiers to paleoenvironmental perturbations across the OAE 2.

Oceanic Anoxic Event 2 (OAE2, ~94 Ma) occurred near the Cenomanian-Turonian boundary and marks a major perturbation to global marine environment in the middle Cretaceous. Increased nutrient input into oceans are thought to have stimulated primary productivity and triggered OAE2. Both large igneous province (LIP) - related submarine volcanism and enhanced continental weathering can deliver abundant trace elements including iron in oceans. Because iron is micro-nutrient and its isotopes can fingerprint these processes across OAE2, here we present a high-resolution whole-rock Fe isotope record (δ⁵⁶Fe_T) and Fe_T/Al data of Gongzha section in southern Tibet, an OAE2 reference section in eastern Tethys where redox states and detrital inputs were stable, to investigate the relative roles of enhanced submarine volcanism and continental weathering in triggering OAE2. The iron isotope results show three notable negative shifts at ~94.8 Ma, ~94.5 Ma, and ~94.3 Ma corresponding well to episodes of intensified volcanism as documented by the osmium isotope data indicative of hydrothermally sourced iron inputs. In particular, the most prominent negative δ⁵⁶Fe_T shift by ~0.4‰ occurred at the onset of OAE2 around 94.5 Ma and was followed by a prolonged positive δ⁵⁶Fe_T excursion coeval with the positive δ¹³C shift of OAE2 in the persistent presence of hydrothermally sourced iron. Similar δ⁵⁶Fe_T variation patterns occur in other OAE2 sections worldwide, implying LIP-related submarine volcanism as the driving force for initiating OAE2. Enhanced continental weathering in the middle Cretaceous may have played an increasingly important role in terminating OAE2.

The Coniacian-Santonian is the time of deposition youngest Cretaceous episode of anoxia namely the oceanic anoxic event 3 (OAE3). The OAE3 was confined to the equatorial Atlantic Ocean and adjacent basins rather than being global in scale.

We focused on nannofossil paleoceanography of the late Turonian to early Campanian time interval and applied quantitative analyses to assess the response of calcareous nannoplankton to paleoenvironmental changes across OAE3. The study was conducted on sites from the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) situated in the Atlantic Ocean and the Indian Ocean.

A detailed, revised, and high-resolution nannofossil biostratigraphy of the selected sites enabled correlations at a supra-regional scale. Quantitative analyses allowed us to characterize paleotemperature and nutrient changes before, during, and after OAE3.

We identified relatively large fluctuations in abundance (“acmes”) of the genera Micula and Marthasterites, across OAE3. The onset of OAE3 coincides with a major increase in abundance (and local dominance) of M. furcatus, suggesting the rapid establishment of new and peculiar paleoceanographic conditions at a widespread to global scale. The most altered paleoceanographic conditions occurred during the core of OAE3 as characterized by the synchronous maximum abundance (climax) of M.staurophora on a global scale. In addition to their value for paleoenvironmental reconstructions, the Micula and Marthasterites “acmes” are useful for the biostratigraphic characterization of the Turonian/Coniacian, Coniacian/Santonian, and Santonian/Campanian boundaries and might be introduced as additional events in future nannofossil zonations for the Late Cretaceous. This research was funded through MUR for ECORD-IODP Italia.

The scarcity of reliable sea surface temperature (SST) records from the eastern Tethys during the Cretaceous is a critical knowledge gap in paleoclimate studies. Cretaceous shallow marine sequences in the Tibetan Himalaya offer exceptional archives for reconstructing Tethyan SSTs. However, conventional paleothermometers – particularly carbonate oxygen isotope systems – suffer substantial diagenetic overprinting associated with Himalayan orogenesis. This study presents oxygen isotope values of bioapatite to estimate the SST during the Albian-early Campanian in the Tibetan Himalaya. Nineteen limestone samples were collected from the Albian-early Campanian in Nirang section and processed to obtain fish remains. In-situ oxygen isotope measurements were conducted using secondary ion mass spectrometry (SIMS), and elemental compositions were analyzed with SEM-EDS and LA-ICP-MS. Results show that fish teeth are composed mainly of bioapatite, with some samples partially replaced by silicon-bearing minerals. Oxygen isotope values (δ¹⁸O) of better preserved fish teeth indicate an average SST ranging from ~21°C to ~32°C (averaging 26.3°C ± 2.4°C). The SST evolution through time reveals a cooler climate during the Albian, with a warming trend through the Cenomanian to early Coniacian, followed by a rapid cooling in the early Campanian. This trend is consistence with previously published TEX₈₆ data compilation, confirming that southeastern Tethyan SST variations predominantly tracked global climatic forcings.

The Cretaceous was a prolonged greenhouse period characterized by relatively cool early (Berriasian to Aptian) and late (Campanian to Maastrichtian) phases separated by the “Cretaceous super greenhouse” (Albian to Santonian). Extensive research has focused on the evolution of Cretaceous paleoclimate conditions; however, questions remain regarding the nature of extreme climate conditions during the Cretaceous (e.g., glacial and hyperthermal conditions). To address these questions, we employ updated, proxy-based global maps of mean annual temperature (MAT), warmest mean monthly temperature, and mean annual precipitation from nine Cretaceous time slices in order to 1) better constrain the occurrence of glacial conditions; 2) estimate maximum and minimum ice volumes and areas; and 3) describe the occurrence of excess mean annual and summer temperatures. Our preliminary analyses of proxy-based winter temperatures and three precipitation seasonality scenarios suggest that even during the coldest periods of the Cretaceous, high-latitude snowpack build-up was less than 1 meter water equivalent and no snow survived the melt season at elevations <2000 meters above sea level (masl). However, our results leave open the possibility that alpine glaciers could have accumulated at high latitudes on isolated peaks at minimum elevations ranging from 2000 masl during the Hauterivian-Barremian to 3500 masl during the Turonian. Additionally, our results suggest excess temperatures were commonplace during the summer months in the tropics during the middle Cretaceous supergreenhouse, and that MAT >35 °C may even have occurred in restricted areas. The strategies that plants employed to survive these high temperature conditions is a ripe field for future research.

The Tianjialou Formation of the Dasheng Group, situated within the Yishu Fault Zone in East China, exhibits the development of dolomite and gypsum, which serve as records of a notable warming event. The existing K-Ar isotope ages of the andesite in the Tianjialou Formation is 95 Ma, which constrain the depositional time of the Tianjialou Formation to the Cenomanian Stage during the Late Cretaceous, hinting that the warming event documented by the dolomite and gypsum may be associated with Oceanic Anoxic Event 2 (OAE2). Carbonate carbon-oxygen isotope and organic carbon isotope analyses were further conducted, revealing that, in contrast to carbonate carbon isotopes, organic carbon isotopes can be correlated with the carbon isotope curves related to OAE2, whereas the deviation in carbonate carbon isotopes is influenced by the degree of closure of inland salt lakes. Our research reveals that terrestrial geological events can be correlated with OAE2 through the perspective of concurrent significant warmth. The global warming associated with OAE2 exerts a more prominent impact on terrestrial systems, due to the lesser thermal buffering capacity of land in comparison to the ocean. Of course, organic carbon isotope comparison is essential.

The Oceanic Anoxic Events (OAEs) caused by volcanic activity during the Cretaceous period, which was a super-greenhouse period, had a major impact on marine ecosystems. On the other hand, there has been limited research on the impact on terrestrial ecosystems (e.g. Heimhofer et al., 2018). In the present study, we analyzed biomarkers in the sediments deposited across the Cenomanian/Turonian boundary (CTB) from California, USA to reconstruct terrestrial ecosystem changes during environmental disturbance event.

We analyzed sedimentary rocks across the CTB in the Budden Canyon Formation, Great Valley Sequence (GVS), were collected from the North Fork Cottonwood Creek sections in northern California, USA. The OAE2 interval (1st build-up, Trough, 2nd build-up, Plateau, and Recovery phases) was determined by δ¹³C and osmium isotope stratigraphy (Vivier et al., 2015). For the biomarker analysis, the extractions of crashed sediments were fractionated using silica-gel column and analyzed by GC-MS.

The aromatic terpenoid-based angiosperm/gymnosperm index (ar-AGI) values fluctuated wildly in the early stages (1st build-up to 2nd build-up), and then stabilized in the middle stage (Plateau). The Higher Plant Parameter (HPP), which indicates the contribution of conifers, increased rapidly at the last stage (Recovery phase) and remained high after OAE2. These results suggest that the abrupt climate changes caused by OAE2 had a significant impact on the terrestrial ecosystem of the western North American continental margin at that time, and that it shifted to a different environment before and after the OAE2.

Palaeobotany has long provided estimates of terrestrial climate in deep time. Most quantitative estimates come from leaf physiognomy, with wood anatomy providing more qualitative data. An exceptional wood flora from the Upper Campanian Jose Creek Member, McRae Formation (76 to >72 ma), Western Interior of North America, provides both qualitative and quantitative evidence for megathermal (tropical) temperatures and minimal seasonality at ~40 degrees paleolatitude. The wood flora comprises abundant conifers, >38 species of dicots, and 5–8 types of palms. Over 90% of the dicot species and specimens representing three major groups of conifers, show the absence of growth rings, indicating low seasonality and above-freezing Cold Month Mean Temperature (CMMT). This is corroborated by diverse palms. For dicots, patterns of vessel diameter and density are most like those of modern tropical woods from moist to wet climates. Transfer functions based on a subset of 10 anatomical traits for dicots estimate Mean Annual Temperature (MAT) of 21–28°C, CMMT of 16–24°C, abundant precipitation, and no dry season. MAT estimates fall within the range of other palaeobotanical and geochemical proxies, while moisture estimates are compatible with Jose Creek paleosols. The Jose Creek climate is most comparable to that of moist to wet, submontane to lowland tropical forest using the Holdridge system of climate classification, comparable to Af, or perhaps warm Cfa climate, in the Koeppen system.

The Deccan Traps (DT) Large Igneous Province (LIP) erupted during the Cretaceous-Paleogene (K-Pg) boundary interval (67–65 Ma), fundamentally transforming the global terrestrial environment. However, mechanisms coupling volcanic gas emissions to hydroclimatic shifts remain poorly constrained. Here, we present the first continuous high-resolution terrestrial precipitation record from East Asia (Songliao Basin), reconstructed using paleosol organic carbon isotopes (δ¹³C_SOM) spanning the critical DT eruptive sequence. Our results reveal three hydrologic regimes: (1) an early humid phase (66.5–66.3 Ma) coinciding with CO₂-driven equatorial Pacific warming; (2) an abrupt arid shift (66.3–66.1 Ma) aligned with sulfur-rich eruptions and enhanced basalt weathering; and (3) a post-boundary return to humid conditions (65.9-65.7 Ma) linked to CO₂-induced amplification of land-sea thermal contrasts. Pre-boundary aridity—potentially driven by combined volcanic forcing (e.g., sulfur aerosols, weathering feedbacks)—may have exacerbated ecological pressures, while post-boundary warm-humid conditions provided a foothold for forest ecosystem recovery in mid-latitude regions, as evidenced from North America. This study establishes a terrestrial hydrological framework and advances our understanding of LIP-climate linkages during the biotic upheavals.

Base of the Calpionella alpina Subzone, or Calpionella alpina Ecoevent is being applied for years as a provisional marker of the Jurassic/Cretaceous boundary. The event is characterized by a decline of large species of Calpionella (= C. grandalpina Nagy), the disappearance of C. elliptalpina Nagy, the last occurrence of Crassicollaria brevis Remane and Cr. massutiniana (Colom), and increase in abundance of small (or medium-sized) spherical forms of Calpionella alpina Lorenz. The problem is that multiple conditions mentioned above are not always met together within a single studied section, and decision must be made which one is crucial. Some calpionellid specialists put more weight to the bloom of small spherical C. alpina, while for other the LO events are decisive. Visual identification of C. alpina bloom is difficult using standard range-charts, since C. alpina is usually presented as a single taxon, therefore the base of C. alpina Subzone falls somewhere in the middle of its total range. Furthermore, the taxonomy of Calpionella is inconsistent: some of the numerous species distinguished by Nagy are used (C. grandalpina, C. elliptalpina), as well as informal subdivisions into small, spherical, medium, etc. forms. The range-charts are rarely accompanied by quantitative or semi-quantitative graphs, which would be helpful to reveal an internal structure and dynamics of the C. alpina Ecoevent. Additionally, a division of underlying Crassicollaria Zone is not standardized, and it seems that Cr. colomi Subzone sometimes overlaps with abundance increase of small spherical C. alpina, leading to confusing stratigraphical interpretations and biased long-distance correlations.

The VOICE is a negative carbon isotopic excursion initially identified in organic carbon at high latitudes (Hammer et al., 2012) and recently documented in the Neuquén Basin, western Argentina (Pellenard et al., 2022; Weger et al., 2023). The global correlations of the carbon isotope curves show discrepancies in the trends, making its record unreadable at global scale. We propose an integrated radio-astrochronology of the VOICE anchored on calcareous nannofossil and Andean ammonite biostratigraphy on the Las Alcantarillas and Las Loicas sections. Five new CA-ID-TIMS U-Pb ages are introduced together with 532 datapoints of δ¹³C_org. Palynofacies analyses demonstrate the organic matter is mainly marine with no apparent source changes. The δ¹³C_org values decrease from -25 ‰ PDB to -30 ‰ PDB from the P. zitteli to the C. alternans/S. koeneni Andean ammonite zones before returning to -27 ‰ PDB in the latest Tithonian. The U-Pb ages indicate that the VOICE started around 146.18 Ma. They also show a pacing of the δ¹³C_org by the 405-ka eccentricity cycle. Anchoring these cycles to the U-Pb ages, we determine that the VOICE ended 142.44 Ma and lasted for ~4Ma. This new integrated chronostratigraphic framework provides with a reference for further global correlations of the carbon isotopic curves.

References:

Hammer, Ø., et al., 2012. Norwegian Journal of Geology 92, 103–112.

Pellenard, P., et al., 2022. 11th International Congress on the Jurassic System, 29 August – 2 September 2022, Budapest, Hungary, p. 88. https://jurassic2022.hu/download/JURA2022_AbstractBook_web.pdf

Weger, R.J., et al., 2023. GSA Bulletin 135, 2107–2120. https://doi.org/10.1130/B36405.1.

This research presents the results of cyclostratigraphic investigations performed in the Tithonian–lower Berriasian carbonates of the Torre de’ Busi and Lókút sections. A precise bio- and magnetostratigraphic control provided a temporal framework for this research; it allowed also to take an account on increasing sedimentation rates calculated for the Tithonian of both successions. Although studied sections are characterized by decreasing lithogenic influx, MS (Torre de’ Busi, Lókút) and ARM (Lókút) series indicate relatively well expressed 100-kyr short eccentricity cycles. Their number within given magnetozones correlates between the studied sections and corresponds with their durations estimated from the geomagnetic polarity time scale (GPTS). Long eccentricity cycles are poorly expressed and only within the lower/upper Tithonian transition interval a reliable 405-kyr cycles can be interpreted; consequently, most of long eccentricity cycles were interpolated through successive counting of 100-kyr cycles. The reliability of provided interpretation is additionally strengthened by correlation with the Jebel Meloussi (Tunisia), which manifests a similar record of the latest Tithonian–earliest Berriasian orbital forcing. Ultimately, the results of this study point to diachronic character of the base of the Alpina calpionellid Subzone, which may be shifted for at least 300-kyr, either due to inconsistent definition or a diachronic nature of the ‘Alpina event’ itself. Diachronism can be inferred also in case of some calcareous nannofossil zones and subzones, such as NJT17 and NC0.

Magnetostratigraphy, calibrated to chemo- and biostratigraphy, offers a reliable tool for creating high-resolution stratigraphic frameworks and can therefore be employed in selecting the Jurassic/Cretaceous (J/K) boundary stratotype. The Bosso Valley section, co-proposed with Torre de Busi for the J/K stratotype, was studied alongside others by Houša et al. (2004), which included magnetostratigraphy. Houša et al. identified five normal and five reverse polarity zones, including the subzones M20n.1r (Kysuca) and M19n.1r (Brodno). Their data were, however, accompanied by rock-magnetic analyses of only two samples. Rock-magnetic analyses can provide essential information on the origin of the carriers of the remanent magnetization, deciphering the correct applicability of the paleomagnetic record for magnetostratigraphy. Ten selected samples (one from each individual polarity zone) from the original Houša et al. sample collection will be used for additional rock-magnetic analyses. These analyses will include stepwise acquisition and demagnetization of isothermal remanent magnetization and a three-axial Lowrie (1990) test, which will allow further verification of the previous polarity zone interpretation and thus support the stratotype proposal. Furthermore, the position of Kysuca and Brodno subzones is very well defined by the large number of samples. Our re-evaluation of the paleomagnetic data and subsequent correlations revealed the mean directions of the Brodno subzone (Declination = 100.5°; Inclination = −41.5°) and the Kysuca subzone (Declination = 116.6°; Inclination = −30.1°). These are in good agreement with Houša et al.'s Early Berriasian (Declination = 100.1°; Inclination = −39.0°) and Late Tithonian (Declination = 107.0°; Inclination = −32.3°) reverse polarity mean directions, respectively.

A Berriasian age (145–142 Ma) for the base of the lower Yellow Cat Mbr. (YC) of the Cedar Mountain Fm. (CM) in Utah is indicated by microfossils, chemostratigraphy, and U-Pb dating of paleosols, with the onset of deposition near the beginning of Cretaceous. Euroamerican Morrison “style” dinosaur faunas dominated by diverse sauropods (mostly diplodocids), stegosaurs, small to medium ornithopods, large theropods (ceratosaurs, megalosaurids, and allosaurids), and uncommon coelurosaurs persisted during last 10 myr of the Jurassic. By contrast, the first 25 myr of the Early Cretaceous had Wealden “style” dinosaur faunas dominated by a low diversity of turiasaur and titanosauriform sauropods, polacanthid ankylosaurs, large ornithopods, large megalosauroid spinosaurids (exclusive to Europe), allosauroid carcharodontosaurid theropods, and an increased abundance of larger coelurosaurs reflecting a profound J-K dinosaur faunal turnover. The paleosol sequence at the base of the YC, laterally equivalent to the fluvial Buckhorn Conglomerate of the CM, consists of basal ferruginous paleosols (gleysols) overlain by silicified peat (histosols), which are then overlain by calcareous paleosols (vertisols and aridosols). A kaolinite bed (oxisol) has been identified at the J-K unconformity locally. Based on these paleosols, Utah’s earliest Cretaceous is characterized by an interval of unusually wet paleoclimates bracketed by drier paleoclimates during the Late Jurassic and remainder of the Early Cretaceous. Potential drivers close to the J-K boundary for this climatic excursion and faunal turnover include a mega-shield volcano(s) at Shatsky Rise in the western Pacific, and less significantly South Africa’s Morokweng impact. Was the Cretaceous bookmarked by asteroid impacts?

The Berriasian Bückeberg Group accumulated in the Lower Saxony Basin and comprises fluvial,
lacustrine and marine deposits of a late regression to early transgression. The geothermal reservoir
potential of the nearshore and terrestrial sandstone deposits have recently drawn economic interest.
A comprehensive facies-based paleodepositional interpretation of potential reservoir rocks and
implications for sequence stratigraphic surfaces are presented based on core analysis.
Facies are identified based on sedimentological and ichnological expression, e.g., sediment texture,
sedimentary structures, lithological accessories, bioturbation index (BI) and trace fossil assemblage.
Facies are grouped into facies associations. Potential sequence stratigraphic surfaces are proposed
based on vertical juxtaposition of facies associations.
Six facies associations are identified: (1) basin deposits below fair-weather wave base, (2) lagoon
deposits, and (3) floodplain accumulations are predominantly mudstone dominated. Mudstone to
sandstone dominated deposits are found in (4) crevasse-splays and (5) marine wave- and storm-
dominated deltaic deposits. Sandstone-dominated intervals are associated with crevasse splay
channels, proximal crevasse splays and deltafront deposits.
Basal contacts of the Bückeberg Group are preserved in two cores and support the interpretation of
deposition on a sequence boundary, possibly with conformable transgressive surface. Juxtaposition
of basin mudstone on deltaic deposits in two cores across the Lower Saxony Basin imply a
transgressive surface. Several other flooding surfaces identified in core are interpreted as autogenic.
The study refines the depositional model of the Bückeberg Group and permits a review of previously
proposed sequence stratigraphic surfaces. Concise interpretations of paleodepositional
environments and their responses to base level assist prediction of potential geothermal reservoirs.

Normandy, in north-western France, has yielded a fairly large number of dinosaur remains since the 18th century. Most of them come from Jurassic rocks. However, several important dinosaur specimens have been collected from Cretaceous formations cropping out in the cliffs along the coast of the English Channel. The first record is an isolated caudal vertebra from the Albian of Bléville (Le Havre, Seine-Maritime), which was in the collection of the local palaeontologist Bucaille as early as 1877. It was identified as belonging to a sauropod in 1988 and later referred to Normanniasaurus genceyi Le Loeuff, Suteethorn & Buffetaut, 2013, a titanosaurian sauropod taxon based on vertebrae and pelvic elements from the same area and geological horizon. Caletodraco cottardi Buffetaut, Tong, Girard, Hoyez & Párraga, 2024 is a furileusaurian abelisaurid theropod described on the basis of a tooth, sacral and caudal vertebrae and ilia from the lower Cenomanian Chalk at Saint-Jouin-Bruneval (Seine-Maritime). To this scanty record can probably be added a bone found in the Cenomanian Chalk of Villers-sur-mer (Calvados) and referred to a bird on the basis of histological characters by Hupier in 1933 ; no detailed description was published and the whereabouts of the specimen are unknown. All these specimens come from marine deposits and the dinosaurs in question probably lived on emergent areas of the Armorican Massif, some 100 km to the west. Although scanty, this Cretaceous record from Normandy provides useful information about the dinosaur faunas which inhabited north-western Europe during the middle part of the Cretaceous.

A combination of sectioning and microscopy techniques, along with the application of finite-difference-time-domain modeling on a fossil feather, results in the novel estimation of the range of iridescent colors from the fossilized melanosome type and organization preserved in the elongate head crest feathers of a new Cretaceous enantiornithine bird. The densely packed rod-like melanosomes are estimated to have yielded from red to deep blue iridescent coloration of the head feathers. The shape and density of these melanosomes also may have further increased the feather’s structural strength. This occurrence on a likely male individual is highly suggestive of both a signaling function of the iridescent crest, and a potential behavioral role in adjusting the angle of light incidence to control the display of this iridescent structural coloration.

This study results from the first complete survey of vertebrate fossils (N > 4200) from the Lower Cretaceous terrestrial deposits of southeastern Australia. These materials, some of the richest samples of polar vertebrate fossils known anywhere in the Mesozoic, derive from two layers separated by ~10 my: the upper Barremian-lower Aptian upper Strzelecki Group and the lower Albian Eumeralla Formation. Both were deposited in rift-basin fluvial systems during the separation of Australia from Antarctica.

Most fossils are well-preserved, suggesting they were neither exposed to extensive surface weathering nor transported far from their initial burial sites, and thus likely retain information about their original source ecosystems. However, secondary deposition in high-energy river systems likely affected both small and large-bodied forms. The presence of rare elements from large theropod and ornithopod dinosaurs suggests that the absence of sauropods in both strata is genuine; conversely, the lack of small lepidosaurs and lissamphibians may be due to winnowing and needs to be further investigated.

Faunal profiles show high abundances of bony fishes and turtles—i.e. aquatic and semi-aquatic taxa—followed by dinosaurs (ornithopods being the most common), many of which show potentially close relationships with non-polar forms. Relictual giant temnospondyls in the upper Strzelecki gave way to much smaller crocodilians in the Eumeralla. Yet despite some important distinctions, these vertebrate communities seem to be polar ‘variants’ of non-polar ecosystems elsewhere in Gondwana.

Dinosaur nests and their associated site fidelity are usually discovered in low-energy alluvial plains. However, the Gojeong-ri dinosaur egg site in Korea reveals an unusual nesting strategy and evidence of site fidelity, preserving numerous sauropod egg assemblages within high-energy braided river conglomerates. This includes an in-situ clutch of faveoloolithid eggs from a mid-channel bar deposit, with 127 out of 175 eggs in the study area preserved in high-energy conglomerates—suggesting periodic destruction of nesting colonies. All egg assemblages were categorized into three taphofacies based on the textural differences between the egg interiors and surrounding materials, a key taphonomic criterion: 1) in-situ clutches (Taphofacies I), 2) parautochthonous clutches (Taphofacies II), and 3) allochthonous clusters (Taphofacies III). Synthesizing insights from modern bird and turtle nesting behaviors with taphonomic analyses and interpretations, we propose that sauropods at Gojeong-ri utilized surrounding streams as natural moats to minimize predation risks and protect their nests. The sauropod’s ability to balance the risks and benefits for reproductive success indicates their highly sophisticated egg-laying behavior.

Mesozoic teleost fossils are globally widespread. However, larval fish fossils with preserved soft tissues remain rare in the geological history, thereby constraining our understanding of the early evolution and life history traits of teleost. Here, we describe a group of incompletely ossified teleost larvae fossils from the Lower Cretaceous in northwest China, exhibiting clear soft tissue preservation in the eyes, trunk and dorsum of the abdominal cavity, with ultrastructural features consistent with melanosomes. The consistent presence of similar pigment patterns across distinct developmental stages provides a foundation for the identification of incompletely preserved larval fish fossils. Notably, the pigment pattern observed in the dorsum of the abdominal cavity is commonly found in extant teleost larvae fishes. Ancestral state reconstruction based on peritoneum pigmentation distribution patterns in 470 existing fish species reveals teleost fishes usually present a row of melanophores in the upper abdominal cavity in the early stage of their evolutionary history. This pigmentation pattern may represent a primitive trait of teleosts, providing photo-protective function against ultraviolet radiation for hematopoietic tissues during larval development. It is worth noting that most species that differentiated in the late Mesozoic were generally covered with melanophores in the abdominal cavity. This shift in pigmentation may correlate with Mesozoic environmental stressors.

Keywords: teleost, Early Cretaceous, larval fish fossil, peritoneum

This work is supported by the National Natural Science Foundation of China (42372006 and 42272029), the Fundamental Research Funds for the Central Universities (lzujbky-2022-ey18) and the Gansu Province Postgraduate Innovation Star Program (2025CXZX-090).

The Balve site is an Early Cretaceous Karstic (Barremian to Aptian) fissure fill within Devonian limestone situated in Northwestern Germany. The deposits most likely represent a cave infill in an upland environment, which was situated at least 100 m above sea level. Hence, this locality offers valuable insights into a Cretaceous hinterland ecosystem. Annual excavations at the site are being carried out by the LWL Museum of Natural History Münster since the year 2000 and have yielded remains of a diverse vertebrate fauna. This faunal assemblage includes osteichthyes, chondrichthyes, amphibians, multiple mammal taxa, crocodilians, pterosaurs and dinosaurs. Among the latter are numerous teeth and isolated bones referrable to Theropoda. Based on an analysis of the former, a previous report has already indicated the presence of Tyrannosauroidea among the fossil material. The results of our morphometric analysis of an isolated, partial quadrate suggests strong affinities with the British Eotyrannus, supporting the presence of tyrannosauroids. An as of yet indeterminate taxon of large theropod dinosaur is represented by an additional, larger and almost complete quadrate bone. Another, recent addition to the theropod fauna present at the Balve locality is ornithomimosaurs, represented so far by a manual ungual and a distal third metatarsal fragment. Ongoing analyses of the material potentially indicate the presence of further groups at the site, contributing to our growing understanding of this Early Cretaceous upland ecosystem.

We have conducted a comprehensive study of calcareous nannofossils in numerous Cretaceous successions located at low and middle latitudes, including both land and oceanic sections. Through a rigorous review of existing literature and the incorporation of new findings, we have significantly revised previous zonal schemes. The proposed biozonation include the intercalibration of nannofossil events with planktonic foraminiferal biozones, magnetostratigraphy and chemostratigraphy. This enhancement includes a critical assessment of the reproducibility and reliability of individual nannofossil events, as well as a reevaluation of their ages in light of recent advancements in defining Cretaceous stage boundaries. Moreover, the new nannofossil biozonation is specifically applied to the characterization of oceanic anoxic events.

The Valanginian stage of the Early Cretaceous (~137.05–131.29 Ma) witnesses important geological, climatic, and biological events and is a key interval for global stratigraphic correlation. As precise radio-isotopic ages were scarce until recently, the chronology of events remained poorly understood, and comparing the Andean and Tethyan domains has been challenging due to differing depositional environments and tectonic settings.

Data on ammonoid biostratigraphy, calcareous nannofossil bioevents, astrochronology, and chemostratigraphy have significantly improved their temporal alignment. A pivotal event aiding correlation is the Valanginian carbon isotope excursion (Weissert CIE), a globally recognized positive δ¹³C shift, interpreted as linked to increased volcanic activity and carbon cycle perturbation. This excursion is recorded in both Andean and Tethyan sedimentary sequences, serving as a reliable chemostratigraphic marker.

The Vergol-Morénas (Vocontian Basin, France) and the Cerro La Parva (Neuquén Basin, Argentina) sections were studied recently. They are geographically remote, were deposited in different environments, and encompass the lower-upper Valanginian boundary. In both cases, the δ¹³ Corg correlates with the 405-ka eccentricity cycle, and both sections can be correlated based on these cycles with a precision in time of ca. 100 ka. This study adds the Cañada de Leiva section (Neuquén Basin), which spans the entire Valanginian with a precise ammonoid and nannofossil biostratigraphy.

By integrating fossil evidence provided by ammonites and calcareous nannofossils with astrochronological and chemostratigraphic data, it has been possible to strengthen the correlation between the Andes and Tethys during the Valanginian, clarifying global paleoenvironmental changes and refining the Early Cretaceous timescale.

The Lower Cretaceous (Barremian - Albian) interval is marked by complex stratigraphic correlations between the Boreal Realm and the Tethys, often hindered by biostratigraphic inconsistencies and regional variation. We present stable and radiogenic isotope data (δ¹³Ccarb, δ¹⁸O, ⁸⁷Sr/⁸⁶Sr) for the Lower Cretaceous (Barremian - Albian) based on new findings from northern Germany, contributing to a refined chemostratigraphic framework.

1) Geochemical analyses of eight well-preserved macrofossils (corals, oysters, gastropods, ammonites, belemnites), from a single level dated to the earliest Albian reveal notable variability. The δ¹³Ccarb values vary by up to 5‰, indicating organism-specific food sources and subsequent biofractionation. Due to diagenetic effects the ⁸⁷Sr/⁸⁶Sr signals also differ significantly among taxa by 0.000225, with belemnites providing the most reliable data. They are in closest agreement with existing Early Cretaceous Sr-isotope reference curves, and are thus considered the most stratigraphically reliable ones.

2) The belemnite-based Sr-isotope data enable correlation between the Boreal Realm and the Tethys independent of biostratigraphy. This chemostratigraphic approach addresses long-standing discrepancies within the Lower Cretaceous biostratigraphic framework. Several offsets in the current biostratigraphic scheme, are re-evalutated. The mid-Barremian warming event is mirrored by the highest Sr-isotope values recorded int the entire Early Cretaceous, which we link to intensified continental weathering and increased run-off. These environmental conditions likely contributed to the deposition of black shales in restricted Boreal basins.

Our data offer an independent temporal framework to support regional and interregional stratigraphic alignment, providing new insights on Early Cretaceous paleoceanography and climate dynamics.

The Aptian Working Group (AWG) of the International Commission on Stratigraphy (ICS), led by Elisabetta Erba and Helmut Weissert, has been working on the definition of the base of the Aptian stage over the last three decades. After considering the base of magnetic chron M0r, following research on ammonite biostratigraphy triggered further discussion and the need for another primary marker. Consequently, in 2024 the AWG decided to shift the base of the Aptian upwards into C34n and for the first time in Mesozoic stratigraphy, a chemostratigraphic event was selected as primary marker. A prominent “negative spike” in the C_org- and C_carb- isotope records was first identified by Menegatti et al. (1998) in Northern Italy (Cismon section) and later recognized in various land and marine sites across different paleolatitudes and settings (Erba et al., 2015; Leandro et al., 2022).

This distinctive C isotope negative spike was, therefore, selected by the AWG as the new marker for defining the base of the Aptian. Two potential sites were chosen for the final vote as candidate Global Boundary Stratotype Section (GSSP): Cismon (Italy) and Cau (Spain). The majority of AWG members favored the expanded hemipelagic shelf section at Cau for the Aptian GSSP.

This communication presents a review of available data for the Barremian/Aptian boundary interval at the proposed Cau locality in Spain, characterized both in an outcrop section and in a continuous core (Castro et al., 2021).

This study investigates relative paleointensity (RPI) variations during the Aptian–Albian using high-resolution sedimentary records from the Sergipe-Alagoas Basin (SER-03, Brazil) and the Umbria-Marche Basin (PLG, Italy). Advanced paleomagnetic and rock magnetic techniques were applied, including NRM normalization using ARM, IRM, and magnetic susceptibility, as well as the pseudo-Thellier method. In PLG, ARM 20 mT proved to be a reliable proxy, with magnetite as the primary remanence carrier. Variations in mineralogy and coercivity were observed, notably with hematite and goethite in upper layers. In SER-03, ARM 15 mT was identified as the most sensitive proxy, with PSD-dominated magnetite/titanomagnetite mineralogy. RPI curves from both sites show good agreement with global data, revealing secular variations even within the Cretaceous Normal Superchron (CNS). A marked decline in RPI is observed prior to the M0r reversal, followed by low intensity during the ISEA event (~117 Ma) and subsequent recovery. These results refine the magnetostratigraphic framework for the Aptian–Albian and contribute new data from underrepresented Southern Hemisphere sites, supporting interpretations of core dynamo behavior and improving global geomagnetic models.

The Albian was a major turning point for palaeoenvironmental change in the Cretaceous, with the opening of the Equatorial Atlantic Gateway leading to a reorganisation of surface and deep circulation, frequent occurrence of Oceanic Anoxic Events and significant increases in surface and deep water temperatures. Therefore, a radioisotopic-based age model for the Albian period is important, but has yet to be realized, because silicic tuffs are rarely interbedded in the representative Albian strata in Europe. The Yezo Group, Hokkaido, Japan, comprises forearc basin sequences accumulated on the active continental margin of the Eurasian continent in the northwestern Pacific Ocean. The strata yield abundant age-diagnostic macro and microfossils, and intercalate numerous silicic tuffs. We have compiled microfossil-, macrofossil- and carbon isotope stratigraphy for the Albian section of the Yezo Group, and obtained U-Pb zircon ages of tuffs from several stratigraphic levels. On the basis of integrated stratigraphic correlation with the sequence of the Vocontian Basin, we identified the levels of the Leenhardt of OAE1b, OAE1c, OAE1d and A/CB in the Yezo Group. U-Pb zircon ages of silicic tuffs intercalated in these levels, are 110.00 ± 0.60 (Leenhardt), 103.71 ± 0.82 Ma (OAE1c), 101.67 ± 0.81 Ma (OAE1d) and 100.74 ± 0.10 Ma (A/CB). The former three ages were obtained by LA-ICP-MS, the latter by ID-TIMS, so there is room for improvement. Further dating of the Yezo Group silicic tuffs is expected to make a significant contribution to improving the accuracy and precision of the global Albian age model.

New biostratigraphic and paleobiogeographic data on Valanginian ammonites from the states of Coahuila and Zacatecas have been produced as part of the Ph.D. thesis of one of the authors (JROF), with a significant portion published in 2024. This new information, combined with previously published data, is integrated and re-evaluated alongside ongoing data collection. This comprehensive dataset confirms that the Lower Valanginian ammonoid record of northern Mexico can be biostratigraphically analyzed using the Standard Mediterranean Ammonite Zonation (SMAZ). However, a few endemic species appear in the uppermost part of the Lower Valanginian. Thus, this strong Lower Valanginian Mediterranean affinity shifts abruptly at the onset of the Upper Valanginian, which is characterized by a significant increase in endemic ammonoids and the absence of SMAZ index species, thus requiring the development of a distinct Mexican biozonation. A publication currently in preparation, based on four stratigraphic sections in the Taraises area (Coahuila), will propose two new Upper Valanginian zones: the Saynoceras americanum and the Oosterella gaudryi zones. Two additional stratigraphic sections in the state of Nuevo León, Entronque San Roberto 1 and 2, have yielded an abundant ammonite assemblage from the uppermost Lower and Upper Valanginian and are under active investigation. Although the abundance of endemic ammonites has slowed down research progress, data from these two stratigraphic sections will be crucial for establishing a robust Upper Valanginian zonation for Mexico. The re-evaluation of the Upper Valanginian ammonoid record from Cuencamé, in Durango State, will also contribute to this Upper Valanginian Mexican zonation.

New taxonomic, biostratigraphic, and paleobiogeographic data on ammonites from the San Isidro Formation in Santiago Huauclilla, southern Mexico, spanning from the Hauterivian to the Barremian stages, are presented. Sampling at five new localities yielded 730 specimens, leading to the identification of 21 taxa. Bed-by-bed sampling in four stratigraphic sections from four localities enabled the identification of eight ammonite zones: six correlate with the Standard Mediterranean Ammonite Zonation (SMAZ), and two with the Austral zonation of the Neuquén Basin (Argentina). The Upper Hauterivian exhibits a transitional pattern, with the two lower zones correlating with the Austral scheme and the two upper zones with the Mediterranean scheme. In the Barremian, the four recognized ammonite zones correspond to the SMAZ. The paleobiogeographic turnover between Austral and Mediterranean ammonite assemblages within the middle part of the Upper Hauterivian is initially gradual, with the Mediterranean index species Subsaynella sayni appearing in the lower half of the Upper Hauterivian. However, this transition ends abruptly, as Austral ammonites are entirely absent in the subsequent SMAZ zones. Three-dimensional models of key ammonites are being produced for biostratigraphic purposes as part of this ongoing study, and preliminary paleobiogeographic analyses support the integration of both zonal schemes. During the Barremian, Mexican ammonoids show a broad distribution of Holcodiscidae and Pulchelliidae. Notably, while Holcodiscidae are well represented in the studied area of Mexico, both in terms of specimen abundance and taxonomic diversity, they are extremely scarce in the Pacific domain (e.g., Colombia) and in the Austral province.

A profuse late Albian magmatism and hydrothermalism related to lithospheric hyperextension affected the thick marine sediments in the centre of the Basque-Cantabrian basin.

In the locality of Sopela, the uppermost Albian deep marine 50 m-thick succession shows basaltic pillow and tabular bodies with intervening pyroclastic deposits developed in a siliciclastic muddy depositional area. Ammonoids indicate a Mortoniceras (M.) fallax Zone to M. (M.) rostratum and perinflatum Zones upwards.

Ammonoids in the mudstones are flattened and scarce, but in the pyroclastics they occur abundantly and well preserved. Grain size varies from fine to coarse ash and lapilli. Scoria grains with bubble structures, irregular basalt and recrystallized limestone clasts with calcitic borders, among others, and a common parallel lamination suggest the deposit of hot water-logged dense high-energy flows formed after a submarine volcanic explosion.

Ammonoids show the shell replaced by calcite and chlorite. All the ontogenetic stages are preserved, being juveniles and smaller forms more abundant than large (cm-sized) adults.

Spheroidal structures 0.3 to 0.7 mm diameter with a very thin calcitic wall, are found in association with ammonitellas of similar size; although the shell is not identified inside these spheroids, some of them may correspond to eggs or very early hatchlings.

A rich community of planktic and benthic forams, ostracods, gastropods, bivalves and small crinoids occurs with the ammonoids.

The origin of the flows and the presence of this rich fossil community suggest a likely ammonoid spawning area affected by catastrophic magmatism leading to intermittent mass-mortality events in the sea-water column.

The evolution of soft-bodied squids, which provide a significant part of the biomass in modern oceans globally, is poorly understood due to their patchy fossil record. We provide a comprehensive evolutionary history of squids through “digital fossil-mining” techniques, revealing a new Lagerstätte (Ikegami et al., in press, 2025; the origin and radiation of squids revealed by digital fossil-mining, Science). The more than 250 fossil beaks of 40 species show that squids originated and rapidly radiated by 100 million years ago. Our new data suggest that the radical shift from heavily shelled, slowly moving cephalopods to soft-bodied forms did not result from the end-Cretaceous mass extinction (66 Ma). Early squids had already formed large populations and their biomass exceeded that of ammonites and fishes. They pioneered the modern-type marine ecosystem as intelligent, fast swimmers.

Sepioids are an evolutionarily successful group of modern ten-armed cephalopods (Decapodiformes) of high biodiversity, which provide a large amount of biomass in present-day oceans. They include the internal-shelled order Sepiida (cuttlefish) and the soft-bodied order Sepiolida (bobtail squid). The phylogenetic position and evolutionary history of these two orders are, however, so far poorly understood due to the patchy fossil record of Decapodiformes. Here we report a new genus and species from the upper Campanian to upper Maastrichtian (~74–67 Ma, Upper Cretaceous), South Dakota, which shows an intermediate morphology between Sepiida and Sepiolida. This is the first study in which an AI (artificial intelligence) model led to the discovery of a new fossil taxon. This new species demonstrates a close relationship between the two sepioid orders, which has previously been interpreted controversially. Our findings indicate that sepioids experienced an early phase of radiation in the later part of the Late Cretaceous.

The world’s largest ammonite, Parapuzosia (P.) seppenradensis (Landois, 1895), has fascinated the world ever since the discovery in 1895 of a specimen measuring 1.74 metres (m) in diameter near Seppenrade in Westfalia, Germany. Its co-fauna was describedin detail The species was also found in sections in Mexico and southern England. The high-resolution integrated stratigraphy allows for precise trans-Atlantic correlation of these occurrences, and the Tepeyac section in Mexico has become Associated Stratotype Section and Point for the base of the Campanian (Gale et al. 2023). It yields giant ammonites in original deposition context (Ifrim et al., 2021) together with a rich macrofossil assemblage (Ifrim and Stinnesbeck, 2021) which is correlated to other parts of the world by ammonoid and inoceramid stratigraphy and the stable carbon isotope curve. The ammonoids in the co-fauna of P.(P.) seppenradensis in Germany and Mexico show common and endemic species. They allow for the interpretation of partially unexpected paleobiogeographic relations.

References

Gale, A., Batenburg, S., et al. 2023. The Global Boundary Stratotype Section and Point (GSSP) of the Campanian Stage at Bottaccione (Gubbio, Italy) and its Auxiliary Sections: Seaford Head (UK), Bocieniec (Poland), Postalm (Austria), Smoky Hill, Kansas (U.S.A), Tepayac (Mexico). Episodes. doi: 10.18814/epiiugs/2022/022048.

Ifrim, C., Gale, et al. 2021. Ontogeny, Evolution and palaeobiogeographic distribution of Parapuzosia (P.) seppenradensis, the world's largest ammonite. PLoS ONE 16, e0258510. doi: 10.1371/journal.pone.0258510.

Ifrim, C., Stinnesbeck, W., 2021. Ammonoids and their biozonation across the Santonian-Campanian boundary in north-eastern Coahuila, Mexico. Paleontologia Electronica 24.3.a34. doi: https://doi.org/10.26879/1046.

Radioisotopic dating using single crystal U-Pb zircon and ⁴⁰Ar/³⁹Ar sanidine methods since publication of Geologic Time Scale 2020 (GTS2020) continues to improve the Cretaceous time scale and more firmly establish the ages and uncertainties associated with several stage boundaries and key phenomena. Examples here aim to highlight some of these recent contributions. Bayesian age-depth modeling of 19 U-Pb dates of tuffs in the Yezo Group, Hokkaido, Japan where Leupoldina cabri fossils occur above nearly synchronous carbon and osmium isotope excursions indicate that OAE1a began at 119.55 +0.072/−0.079 Ma and had a duration of 1116 +87/−93 kyr. These findings imply that Ontong Java volcanism is a probable driver of OAE1a. Collective U-Pb and ⁴⁰Ar/³⁹Ar dating of tuffs in Quingshan Group, Jiaolai Basin, China constrain the onset of magnetic chron M0r, and thus the Barremian-Aptian boundary, to 120.287 ± 0.088 Ma (±2s full external uncertainty) which is >1 myr younger, and nearly an order of magnitude more precise than in GTS2020. U-Pb and ⁴⁰Ar/³⁹Ar dates from 11 tuffs in 5 sections of the Yezo Group, Hokkaido, Japan have yielded an age for the Albian-Cenomanian boundary of 100.74 ± 0.10 Ma. This age, which exceeds that in GTS2020 by 240 kyr, relies on correlating distinctive positive δ¹³C excursions of OAE1d from the GSSP near Mt. Risou, France to those identified within Yezo Group strata where a first appearance of Thalmanninella globotruncanoides has been documented. A slight osmium isotope excursion in these mudstones suggests a role for Kerguelan LIP volcanism in driving OAE1d.

The linkage between silicate weathering as a sink for atmospheric CO₂ and the late Cretaceous climate cooling is not well constrained so far. The lithium isotopic composition (δ⁷Li) of marine carbonates is a proxy for the chemical weathering intensity of silicate rocks, and thus provides information about the role of silicate weathering as Earth’s thermostat.

Here, we present a 20 Myr δ⁷Li record (86.3–66.0 Ma) using chalk from Northern Germany as an archive to evaluate the role of weathering as a sink for atmospheric CO₂ during the Late Cretaceous. The late Santonian to Maastrichtian record shows an overall increase of ~4.5‰ with superimposed increases in the late Santonian, early Campanian and across the Campanian–Maastrichtian transition and a decrease in the mid- to late Campanian. The overall increase in δ⁷Li corresponds to the Late Cretaceous change in radiogenic seawater strontium isotopes (⁸⁷Sr/⁸⁶Sr), which is also a tracer for continental weathering, indicating an increase in continental weathering. Furthermore, a correlation between δ⁷Li and the benthic foraminiferal δ¹⁸O curve occurs, indicating a close link between weathering flux, lowered atmospheric pCO₂ and climate cooling on a multi-million-year time scale.

For the Late Cretaceous, we suggest that an enhanced formation of clay minerals in lowlands – which were increasingly exposed during the long-term sea level falls in the Late Cretaceous – promoted more incongruent weathering and stronger lithium isotope fractionation.

Sea surface temperature (SST) is a key parameter for reconstructing past climate conditions. Most Cretaceous SST estimates rely on molecular biomarkers or on oxygen isotopes from foraminifera and belemnites, both being affected by habitat depth and seasonal biases. SST reconstructions for the Cretaceous remain rare, especially for lower paleolatitudes during the Albian stage, which presents a critical 4-million-year gap in available data. Additionally, there is very limited data on seasonality during the Cretaceous. This study addresses that gap by reconstructing precise seasonal SSTs for the middle Albian (~110–106 Ma) using exceptionally well-preserved oyster shells from the Kazhdumi Formation in Iran. Three large specimens were cleaned, thin-sectioned, and screened for preservation using transmitted light and semi-quantitative trace element mapping via micro-X-ray fluorescence (µXRF). Their ages were constrained through chemo-and strontium isotope stratigraphy. To capture full seasonal cycles, annual growth increments were micro-sampled along the maximum growth axis for δ¹⁸O and δ¹³C analyses. Resulting δ¹⁸O profiles provide sclerochronological estimates of mean, minimum, and maximum SSTs. To account for flawed knowledge of δ¹⁸O_seawater values, Mg/Ca ratios were also measured using high-resolution (25 µm) µXRF line scanning, validating SST trends. Assuming a δ¹⁸O_seawater value of 0‰ near the paleoequator, the oysters record average SSTs of 36.8 °C, ranging from 31 to 43 °C. Mg/Ca variations confirm these cyclic seasonal patterns. These preliminary findings highlight the strong potential of oyster shells as reliable archives for reconstructing Cretaceous SSTs and seasonality in equatorial regions, where other climate proxies are limited, absent, or poorly preserved.

The late Cretaceous period encountered a long-term climatic cooling, along with a decrease in pCO₂ hinting to the involvement of processes driving the long-term carbon cycle (Royer et al., 2012). This interval coincides with major tectonic uplifts of part of the south African and south American continents (ex. Raab et al., 2005), that may have impacted climate through atmospheric CO₂ consumption by silicate weathering reactions. Our work explores the response of erosion and weathering to these tectonic uplifts occurring in different climatic belts using a combination of clay mineralogy and isotopic composition. Importantly, this approach allows to capture the evolution of chemical weathering of silicate rocks at the catchment scale (Bayon et al., 2016) and thus to identify regions affected by enhanced silicate weathering during the late Cretaceous, an information required to constrain geochemical-climate models able to quantify associated CO₂ consumption.

A compilation of published clay Hf-Nd isotopic data along with new clay mineralogical and isotopic data from DSDP site 369 offshore Spanish Sahara and from southern African (Cape Basin) highlight an increase in weathering occurring at all analyzed sites along west Africa and eastern South America. The onset of this increase differs between the sites, highlighting the complexity in tectonic-climate-weathering links and the importance of local climatic and geodynamic contexts. Overall, data show that enhanced chemical weathering is most pronounced during the Campanian-Maastrichtian interval but initiated as early as the Turonian at some sites, suggesting a potentially important role of tectonic uplift in the late Cretaceous cooling.

Spatiotemporal distributions of Cretaceous rocks, namely, plutonic, volcanic, sedimentary rocks, and accretionary complexes along the Japanese Archipelago are compiled, using the Seamless Digital Geological Map of Japan (1: 200,000), as well as a large amount of published geological research. The distributions of these rocks were delineated on reconstructed palaeogeographical maps of the Southwest (SW) and Northeast (NE) Japan arc masses prior to the opening of the Japan Sea (25 Ma). Their zonal arrangements can be broadly recognized throughout both arcs: 1) mostly non-marine sedimentary rocks in intra-/inter-arc and backarc basins; 2) granitic and volcanic rocks in the magmatic arc; 3) mainly marine and subordinate fluvial sedimentary rocks in forearc basins; and 4) sedimentary rocks of turbidite and mélange facies in accretionary complexes. A total of 71 Cretaceous sedimentary successions in backarc, intra-/inter-arc, and forearc basins from Kyushu to Hokkaido, including a southern Sakhalin succession and two eastern Hokkaido (Kuril arc) successions, are correlated on three stratigraphic charts. Stratigraphic ranges and major sedimentary facies are generally similar between the SW and NE Japan arcs, except for the pre-Aptian Lower Cretaceous in Hokkaido of NE Japan, suggesting continuity throughout the two arcs during the Cretaceous. Although Cretaceous strata are sporadically exposed in northern Honshu, NE Japan, interpretation of seismic sections suggests that Cretaceous forearc strata measuring several tens of kilometres laterally are developed offshore beneath the present Pacific forearc. In contrast, Cretaceous forearc strata in SW Japan are distributed along two narrow belts that may have been deformed by post-Early Miocene tectonism.

Alkenones, biomarkers of haptophyte algae, allow for the reconstruction of past SST based on the ratio of di-unsaturated and tri-unsaturated alkenones with a carbon chain length of 37. Consequently, they are widely used in Quaternary paleoceanography. Meanwhile, Hasegawa & Goto (2024 Organic Geochemistry) advanced research on the OAE2 horizon and discovered C_40:2Et, a diunsaturated alkenone, in the high latitude of the Southern Hemisphere, as well as C_40:3Et, a triunsaturated alkenone, marking the first such finding from the Cretaceous. It has significantly expanded the potential application of alkenone paleothermometry to Cretaceous research. The authors also noted the presence of an isomer of C_40:2Et that co-eluted with C_40:3Et in gas chromatography; however, as its abundance was relatively low compared to the exclusively trans-configured C_40:2Et, they deemed it negligible in their discussion.

Alkenones were extracted from the upper Cenomanian underlying OAE2, and their relative abundances were preliminarily compared using selected ion monitoring (SIM) mode on a GCMS for three molecular species: C_40:2Et (all-trans), C_40:2Et (cis isomer), and C_40:3Et. The results revealed that variations in the abundance of C_40:2Et (cis isomer) were similar to those of C_40:3Et, suggesting that C_40:2Et (cis isomer) may also exhibit temperature dependence, akin to C_40:3Et. Furthermore, even in stratigraphic intervals where the abundance of C_40:3Et decreased—presumed to correspond to relatively higher temperatures—C_40:2Et (cis isomer) was still detectable. This finding indicates the potential to develop a novel tool for paleotemperature reconstruction, enabling temperature estimations in high-temperature intervals where the conventional UK′40 index, based on C_40:3Et, is not applicable.

The mid-Cretaceous period is characterized by high atmospheric pCO₂ and frequent occurrences of Ocean Anoxic Events (OAEs); however, the response of terrestrial environments to OAEs remains uncertain. There is only a limited number of studies assessing changes in continental vegetation during OAEs based on palynological analysis, such as the OAE2 interval in southern France (Heimhofer et al., 2018), and the OAE1a interval in northern China (Lu et al., 2025).

In this study, we investigated Lower Aptian lacustrine deposits located in southeastern Mongolia, which has recently been considered to potentially cover the OAE1a interval. The material used in this study has been collected from the CSH01 and CSH02 research cores (Hasegawa et al., 2018, 2022). To quantitatively reconstruct changes in land plant-derived organic matter input, we attempted to establish a palynofacies analysis method utilizing an AI-based image recognition system developed by Itaki et al. (2020).

Initially, we analyzed a total of 40 samples from the CSH01 core. The results reveal a clear correlation between lithofacies and palynofacies. Abundant pollen and plant fragments are observed in layers reflecting high lake-levels, while abundant charcoal is observed in deposits representing low lake-levels.

In a next step, analysis of ~200 samples from the CSH02 core covering the OAE1a period revealed a significant increase in pollen and plant debris, accompanied by an overall decrease in charcoal, in the interval considered to represent the onset of OAE1a. This finding is consistent with a scenario of increased humidity occurring during the onset of OAE1a.

While it has been suggested that increased terrestrial chemical weathering and enhanced oceanic surface productivity during OAE1a, direct evidence of terrestrial environmental changes is limited. We are currently investigating the Aptian lacustrine deposits (Shinekhudag Formation) in Mongolia to reconstructing the terrestrial environmental changes during OAE1a. In this presentation, we report the high-resolution carbon isotope stratigraphy of the Shinekhudag Formation. The Shinekhudag Formation is lacustrine deposits possibly covering OAE1a interval and is characterized by the preservation of distinct annual laminations of 50-120 μm thick (Hasegawa et al., 2018, 2022). Compared to marine sediments used in previous OAE studies, the sedimentation rate is much faster (about 10 cm/ky), and it is expected to reconstruct changes in the terrestrial environment with high temporal resolution. The organic carbon in the lake sediments is a mixture of that formed by freshwater algae and that derived from higher plant sources that enter from the surroundings. Since the isotopic composition of the organic carbon varies greatly depending on their mixing ratio, C/N was used to evaluate the ratio. Carbon isotope ratios are gradually decrease to -30‰ in the middle part of the formation, and then increase to -22‰ toward the top, possibly reflecting the negative to positive excursion of the OAE1a event. In order to correlate with the OAE1a event, reconstruction of a high-resolution carbon isotope ratio stratigraphy is ongoing.

The Cenomanian–Turonian Oceanic Anoxic Event 2 (OAE2) is known for the widespread oceanic anoxia. Recent studies focus on the significant environmental changes in southern high latitude, especially the paleo-Indian Ocean. However, due to the hiatus and low carbonate and low organic content, geochemical records from this region remain limited.

This study examines the geochemical characteristics of ODP Sites 763 and 766, located on the Exmouth Plateau in northwestern Australia, where limited organic geochemical data for the OAE2 period have been previously reported. The aim is to capture environmental changes in the marine ecosystem during OAE2 in the high-latitude Southern Hemisphere. Analyses of stable carbon isotope ratios, organic carbon content, carbonate content, and biomarkers as environmental proxies were conducted.

The results confirm positive shifts in carbonate carbon isotope values (δ¹³C_carb) during the early OAE2 at both sites. At Site 763, however, these values were unobtainable above the black mudstone layer due to reduced carbonate content, while Site 766 showed lower δ¹³C_carb values, likely influenced by diagenesis, highlighting the need to re-evaluate methods and interpretations. Biomarker analysis at Site 763 indicates well-preserved organic matter, including C₄₀ alkenones, allowing reconstruction of surface ocean changes. In contrast, no alkenones were detected at Site 766, suggesting organic decomposition during early diagenesis. However, isorenieratene derivatives which are indicatives of photic zone euxinia were observed, implying that OAE2 impacted even the photic zone on the Exmouth Plateau.

The Albian-Cenomanian collection studied comprises 33 taxa of Tetragonitidae, Kossmaticeratidae, Hoplitidae and Cleoniceratidae. Phylogenetic lineages appearing in the Albian continued their development into the latest Cenomanian. The early Albian temperature maximum (12.5-21.6˚C) is reflected in a diversity increase and the emergence of cosmopolitan forms. In the Albian, connections between the Pacific palaeobiogeographical realm and Tethys were still preserved, and ammonite migration thus continued. However, starting from the Albian-Cenomanian boundary, these links were severed as a result of a relatively short-term regressive episode and active tectonic rearrangements. Albian-Cenomanian ammonite faunas everywhere differ from both precursors and successors not only in taxonomic composition, but also in some morphological aspects. Important changes seem to have occurred across the Aptian-Albian and Cenomanian-Turonian boundaries. Both of these mark important bioevents also for numerous other marine biota. Some evolutionary aspects recorded in sections across the globe have often been discussed within a threefold division of the Cretaceous, and variations noted for the Middle Cretaceous could well refer to the Albian-Cenomanian interval. Naturally, for a formal threefold division of the Cretaceous, data would need to include information on significant groups such as ammonites, inoceramids, micro- and nannofossils, as well as results of magnetic, event- and sequence-stratigraphical studies. Our research confirms that the Albian-Cenomanian interval did differ from older and younger time slices with respect to the evolution of Pacific ammonites. Thus, this is an argument favouring the distinction of a Middle Cretaceous Series. Who’s in favour, who’s against? Let the discussion commence …

The Coniacian–Maastrichtian succession of the Belqa Group in western Jordan records a diverse array of marine lithofacies—including chalk, sandstone, chert, phosphorite, oyster mounds, and organic-rich marls—deposited along the passive southern margin of the Neo-Tethys Ocean. Exceptional outcrop exposures along deeply incised wadis allow to reconstruct the stratigraphic architecture along a ~300 km N-S transect. In contrast to equivalent successions on the southern and eastern side of the Arabian Plate margin (e.g. Oman, Iran), the succession in western Jordan was only locally affected by structural deformation which makes it a prime candidate for the Arabian Plate during this time period.

This study integrates a recently published high-resolution chronostratigraphic framework with a newly developed high-resolution sequence stratigraphic model. Preliminary results reveal four major depositional sequences: Sequence I (Upper Coniacian–Santonian, ~4 My) comprises a transgressive chalk at the base, overlain by prograding siliciclastics with a distal transition to the first phosphorite-chert facies and oyster mounds; Sequence II (Lower Campanian, ~5 My) also has transgressive chalk at the base transitioning into aggrading shallow-marine chert-rich marls and limestones containing thin phosphorites and oyster coquinas; Sequence III (Upper Campanian, ~5 My), is characterized by transgressive chalk at the base overlain by shallow-marine phosphorites transitioning laterally to decametric thick oyster mounds; and Sequence IV (Maastrichtian–Paleocene), represents an abrupt shift to organic-rich pelagic marls.

These sequences can be correlated to the neighbouring countries. Together they allow to map out the gradual installation and migration of a long-lived upwelling system along the Levant margin.

Long-term Barremian-Aptian-Albian oceanic-atmospheric-biogeochemical megacycles span from deep-water, siliciclastic, locally organic-rich deposits to carbonate-rich shelf deposits. New research documents two cycles in the Aptian, and two in the Albian. The basal Aptian megacycle begins with the Deshayesites oglanlensis Zone overlying the ~124.8-124.5 Ma unconformity, and grades up into deeper facies in the Deshayesites forbesi Zone of chemozone OAE 1a.

The second deepening megacycle is at base of the upper-lower Aptian Dufrenoyia furcata Zone at the ~119.9-119.8 Ma unconformity and extends into uppermost Aptian. This interval spans a variably long hiatus beginning in the upper Aptian Epicheloniceras martini Zone during the “cold snap”. The third megacycle begins with mud-rich, multiple organic deposits comprising OAE1b and warming in the “Hypacanthoplites” jacobi Zone spanning the Aptian-Albian transition. The fourth megacycle overlies the lower-upper Albian Dipoloceras cristatum Zone at the widespread subaerial unconformity ~104.8-104.6 Ma at base of Pervinquieria/Mortoniceras pricei Zone. This megacycle is overlain by the unconformity in the uppermost Albian Arrhaphoceras briacensis Zone ~101.2-100.5 Ma. This contact in Texas records subaerial exposure, drowning and widespread oceanic paleoecological change into the Cenomanian.

These events on the Arabian Platform, in the Vocontian Basin and in cratonic basins surrounding the Gulf of Mexico were numerically dated in a chronstratigraphic database of 108 localities and more than 2700 biostratigraphic and chemostratigraphic events and polarity chrons integrated with radioisotopic dates. These sea-level changes appear to be coeval among the three sites suggesting eustatic processes associated with ocean-basin tectonics, LIPs, volcanism, and possible polar glaciation, which were modulated by local tectonics.

Integrated chemo-, bio-, event and sequence stratigraphic calibration of upper Cenomanian sections in several sedimentary basins around the Mid-European Island (Münsterland, Lower Saxony, Subhercynian, Saxonian and Danubian Cretaceous basins) reveal a conspicuous geslinianum- and juddii-zonal cyclicity reflecting high-frequency sea-level changes potentially paced by the long- and short-eccentricity cycles of the Milankovitch band. Resting on a conspicuous mid-late Cenomanian 3rd-order sequence boundary (SB Ce 5), the following depositional sequence DS Ce-Tu 1 consists of three high-frequency sequences of inferred ~405 kyr up to its capping unconformity SB Tu 1 (lower–middle Turonian boundary interval). The lower long-eccentricity cycle ranges from SB Ce 5 up to the Cenomanian–Turonian boundary (CTB) and consists in stratigraphically complete basinal successions of four shallowing-upward cycles (~100 kyr each); the lowermost short-eccentricity cycle is commonly absent in sections located towards the basin margins, reflecting the lack of accommodation associated with the sea-level fall and lowstand across SB Ce 5. A major marine onlap started with the second short-eccentricity cycle that is associated with the inter-regional plenus Event. Up-section, two additional shallowing-upward cycles up to the CTB reflect the infilling of the accommodation generated by the plenus Transgression. A moderate unconformity at the top of the uppermost short-eccentricity cycle terminates the latest Cenomanian high-frequency sequence, the stacking pattern of which reflects a long-eccentricity with four superimposed short-eccentricity cycles (405 vs. 100 kyr). Another major transgressive pulse at the base of the following high-frequency sequence culminated in a global earliest Turonian maximum flooding interval at ca. 93.8 Ma.

The Aruma Formation was deposited over the Arabian platform during a tectonically active period with sealevel fluctuations, posing challenges to regional correlations. In this study, we measured a North-South transect of the Aruma outcrops in Central Saudi Arabia to define the Campanian/Maastrichtian boundary using foraminiferal, sedimentological, and isotopic data. The Khanasir Member is a 45 m thick, bioturbated wackestone with abundant dasyclad algae and rare micro- and megalospheric forms of Pseudedomia complanata interpreted to be of Campanian age. It is capped by layers of large radiolitid rudists in the northern Argouba section and transitions to meter-scale low-angle cross-bedded wackestones interpreted as shallow channels in the southern sections (Buwaibiyat and Al-Kharj). It is overlain by an undated shale unit followed by the carbonate dominated Hajajah Member with dasyclads and foraminiferal floatstones including Orbitoides sp., Lepidorbitoides sp., and the Maastrichtian Omphalocyclus macroporus. Carbon isotope measurements show a positive CIE in the Kanasir Member, followed by negative values in the overlying clays and carbonates of the Hajajah Member, interpreted as the Campanian/Maastrichtian Boundary Event (CMBE).

This study positions the Campanian/Maastrichtian boundary around a sequence boundary that has been recognized in the region (Iran, Jordan), and suggests a relative sea level component. Therefore, the paleoenvironment for the Aruma outcrops evolved from a Campanian carbonate platform with rudist reefs to a terrestrially influenced shale dominated flat ramp with poor fauna at the CMBE. Sea level rise during The Maastrichtian restarted the carbonate factory resulting in a widespread distribution of larger benthic foraminifera and rudists.

We present new chronostratigraphic data from Hauterivian–Aptian coastal marine successions of the Lusitanian Basin (Portugal), based on ⁸⁷Sr/⁸⁶Sr measurements from twenty-five diagenetically screened bivalve shells. These successions record rich fossil assemblages, including exceptionally preserved early angiosperm pollen, and feature multiple transgressive-regressive cycles linked to relative sea-level fluctuations. Shallow-marine environments such as these are ideally suited for capturing the dynamics of shoreline migration; yet their chronostratigraphic resolution often remains poor, hindering regional and global correlations.
To address this, we apply a Bayesian approach to strontium isotope stratigraphy (SIS), enabling probabilistic age modeling and integration of stratigraphic priors, and thereby overcoming the limitations of traditional look-up table methods. The resulting age model refines the timing of key stratigraphic discontinuities, improves alignment with global sea-level trends, and highlights the local expression of relative sea-level fall and carbonate platform turnover coeval with OAE 1a. These findings shed light on how Hauterivian–Aptian eustatic and environmental changes influenced marginal marine sedimentation across the western Tethys, and contribute to broader efforts to constrain the timing, magnitude, and drivers of Early Cretaceous sea-level change.

The reconstruction of paleo-elevation serves a dual purpose to enhance our comprehension of geodynamic processes affecting terrestrial landforms and to contribute significantly to the interpretation of atmospheric circulation and biodiversity. The oxygen (δ18Ow) and deuterium (δDw) isotopes in atmospheric precipitation are systematically depleted with the increase of altitude, which are typical and widely applicated paleo-altimeters. The utilization of hydrogen isotope of hydrous silicate minerals within the shear zone system, volcanic glass, and plant leaf wax alkanes offers valuable insights for addressing evaporation and diagenesis. we review the principle, application conditions, and influencing factors of the hydrogen isotope paleo-altimeter. In addition, we discuss the feasibility of utilizing this technique for quantitatively estimating the paleo-elevation of the southeastern Tibetan Plateau, where multiple shear zones extend over hundred kilometers parallel to the topographic gradient.

The Dakota Formation (Albian-Cenomanian) in Kansas contains abundant paleosols that are preserved in outcrop exposures and core materials, providing the opportunity to explore the paleoclimate and greenhouse conditions thought to have persisted during the Cretaceous. Paleosol morphology varies throughout the study area, but many contain features including abundant sphareosiderite that is consistent with high and/or fluctuating water tables and a humid climate. By analyzing the mineralogical, stable isotopic, and major element composition of clay minerals that crystalize in the paleosols, details about the Cretaceous climate, including temperature and precipitation patterns, can be evaluated. The data also provide the unique opportunity to compare samples collected from outcrop and core to evaluate possible influence from modern weathering effects on mineralogical and stable isotopic composition. This study presents new oxygen and hydrogen stable isotope data from isolated pedogenic phyllosilicate samples collected from the Dakota Fm. Stable hydrogen isotope values of paleosol pedogenic phyllosilicates range from -86‰ to -72‰ and stable oxygen isotopes range from 17.1‰ to 19.5‰. The stable isotopic composition of the pedogenic phyllosilicates used in conjunction with their respective mineral and chemical compositions produced in-situ soil crystallization temperature estimates ranging from 14 ± 3 ℃ to 28 ± 3 ℃. Samples collected from the lower Dakota Fm. reveal an average temperature of 19 ℃ versus the upper Dakota Fm. which averages 24 ℃, indicating a possible warming event. These results confirm warm and humid paleoclimatic conditions along the eastern margin of the Western Interior Seaway, consistent with a pervasive greenhouse climate.

The Cretaceous Period is recognized as a distinctive episode in Earth's history, being the last epoch in geological interval during which the planet experienced globally uniform warmind. This unique condition resulted from a series of geological events that triggered particular climatic conditions during the Cretaceous. Hasegawa et al. (2012) suggest a poleward expansion of the subtropical high-pressure belt during the Early and Late Cretaceous, and an equatorward shift of this belt during the mid-Cretaceous (Barremian–Turonian) “supergreenhouse” period, associated with a significant weakening of the Hadley cell. Chumakov et al. (1995) also propose the absence of a humid equatorial zone from the Berrasian to the Aptian. In this context, it is important highlighting that most paleoclimatic studies have predominantly focused on the northern hemisphere, with a notable gap of data from the southern hemisphere. Recently, Santos et al. (2022) reported the establishment of a humid equatorial belt in Late Aptian, challenging the prevailing conception of a predominantly arid Equatorial Gondwana before the Albian, as similarly suggested by Burgener et al. (2023). In this context, it becomes pertinent to question the extent to which data limitations influence our understanding of southern hemisphere paleoclimates, and how many other climate interpretations remain obscured by a predominantly northern hemisphere-centered gaze?.[Acknowledgements: PaleoClima Project].

The influence of orbital forcing, particularly precession cycles, on the δ¹³C and δ¹⁸O compositions is a key to understanding the Late Cretaceous climate variability. In Haymana Basin, Turkey, high-resolution δ¹³C and δ¹⁸O isotopic records from planktonic and benthic foraminifera reveal precession-driven climate cyclicity, with supplementary insights from mineralogical and trace element data. Spectral analyses highlight that precessional forcing strongly influenced oceanic δ¹³C and δ¹⁸O dynamics in the Haymana Basin, with minima (high insolation) driving arid conditions, elevated salinity, and deep-water convection that triggered ocean mixing and diminished surface-to-deep isotopic gradients. Conversely, precession maxima (low insolation) promoted wetter conditions, enhanced stratification, and intensified organic matter remineralization. Trace element analysis shows increased volcanic activity during the uppermost Maastrichtian, evidenced by tellurium (Te) proxy. In addition, a notable iridium (Ir) peak at the K-Pg boundary, with concentrations up to 3.57 ppb further confirms the Chicxulub impact. Our study provides new insights into the role of orbital forcing in steering stable isotope records and environmental shifts in the Earth’s history. Our findings not only highlight the role of orbital forcing in shaping Late Cretaceous ocean-climate dynamics, but also imply a complex interplay between astronomical cycles, volcanic activity—likely linked to Deccan Traps eruptions—and the cascading environmental stressors that culminated in the end-Cretaceous mass extinction.

During the warm Cretaceous period, extensive carbonate platforms were established, particularly at subtropical and equatorial latitudes. However, the development of these carbonate platforms was punctuated by several crises. One of these occurred during the late Early Aptian period, known as the Oceanic Anoxic Event OAE1a, and is characterised by the global demise of carbonate platforms and the accumulation of black shale in deeper environments.

Prior to the definitive drowning of the Urgonian carbonate platform during the OAE1a, some precursor episodes occurred during the Barremian-Aptian transition, during which marls strongly enriched in orbitolinids were deposited. The orbitolinids are generally associated with mesotrophic conditions and high nutrient inputs. This episode, known as the “Lower Orbitolina Beds”, suggests a significant climatic change, characterised by wetter and warmer conditions, leading to an increase in detritism and a change in carbonate production. These changes may have been triggered by an increase in volcanic activity associated with the onset of the Ontong Java plateau.To confirm the relationship between volcanism and the deposition of the Lower Orbitolina Beds, mercury measurements (used as volcanic marker) were conducted in several sections of the Urgonian carbonate platform in the Vercors area. The Ecouges section, along with the Gorges du Nan and the Gorges du Frou sections, show significant mercury anomalies in the Lower Orbitolina Beds intervals.

These data suggest the relationship beween the onset of the Ontong Java Plateau and the eutrophication of the Urgonian Carbonate Platform as a precursor to Oceanic Anoxic Event 1a in shallow marine environments.

Large-scale tsunamis are mainly caused by dramatic submarine/coastal crustal shifts and asteroid impacts. They destroy coastal areas and rapidly transport huge amounts of plants and other debris over long distances. However, due to their poor preservation potential and the lack of unequivocal identifying features, tsunami deposits are rarely recognized in the geological record except for geologically young Holocene coastal deposits. This study focuses on pelagic settings as potential archives of large-scale paleo-tsunami events. Here we describe extraordinarily rich amber concentrations in Early Cretaceous deep sea deposits. The amber is distinctively deformed in a manner comparable to typical soft sediment deformation structures such as flame structures. As resin exposed to the air hardens quickly in weeks, the flame deformation of the resin suggests that it reached pelagic seafloors without significant subaerial exposure. This new observation of amber as a soft-sediment unveils the whole sedimentary process from erosion to burial, a view neglected by previous sedimentological studies that focused on clastic and carbonate sediments. The most plausible cause for the presence of this enigmatic amber in a deep-sea setting is large-scale tsunamis, which are supported by the mode of occurrence of amber, associated sedimentary structures, and a massive coinstantaneous landslide.

Marine phytoplankton has a wide diversity of microorganisms, including calcareous nannofossils, which respond to changes in the water column, particularly to nutrients increases (such as P and Fe), which result from sediment input. However, the ecology of these organisms remains a topic of considerable debate, especially regarding volcanic events effects on the composition and distribution of this fossil group. In this context, were studied samples from DSDP Leg 39 – Site 356, focusing on the presence of volcanic ashes and the results on calcareous nannofossils assemblage. The samples were processed for biostratigraphic, geochemical (XRF and Hg content), paleoecological, and morphometric analyses of Watznaueria barnesiae and Eiffelithus spp., as well as biogeochemical analyses using Synchrotron Light for μXRF measurements. The presence of Lithastrinus grillii and L. septenarius enabled the determination of a Coniacian–Santonian interval. The ash layer shows low abundance of calcareous nannofossils, high concentrations of Fe, Hg, and Mn, along with decreased of Ca and Al content. Morphometric analyses of W. barnesiae revealed abundance and size decreasing during ashes depositions, and more circular shapes. Morphometric analyses of Eiffelithus spp. showed high variation in size and ellipticity during the volcanic event. The geochemical results provided a better understanding of the volcanic event’s influence on the assemblage, revealing a small coccoliths associated to biogeochemical processes marked by increased Fe and Zn levels during ashes deposition.

Acknowledgements: Mar interior Project

Nickel (Ni) isotopes, recognized as a promising tracer for understanding ocean biogeochemistry, are now being applied to investigate the ancient oceans. Modern seawater Ni isotopes (d⁶⁰Ni_sw) are heavy relative to the global input d⁶⁰Ni (d⁶⁰Ni_input), driven by the preferential sorption of light Ni to Mn oxide that leads to an isotopically light sedimentary sink. Modern organic-rich sediments from upwelling margins are unfractionated relative to the global seawater reservoir, potentially providing an archive of the past oceanic dissolved pool, and thus the history of deep ocean oxygenation. Here, we present an extensive record of trace metal abundances and Ni isotopes for organic-rich sediments, covering three oceanic anoxic events, OAE1 (Aptian-Albian), OAE2 (Cenomanian-Turonian) and OAE3 (Coniacian-Santonian), and through the Cenozoic, to track the biogeochemical and redox evolution of the ocean since the Cretaceous.

The contemporaneous d⁶⁰Ni_sw recorded by authigenic Ni isotopes in organic-rich, open ocean sediments since the Cretaceous reveals two prominent features: 1) d⁶⁰Ni_sw increased to the modern value of around +1.3‰ only in the early Cenozoic, suggesting that the deep ocean has not been fully oxygenated until then, later than has previously been suggested; 2) d⁶⁰Ni_sw remained relatively constant across each OAE, but at lower than modern seawater. Coupled Ni and Mo mass balance models suggest that d⁶⁰Ni_input under the Cretaceous greenhouse warming was most likely lower than modern, and that the areal fraction of the euxinic sink during the OAEs increased by up to a few percent.

The lower Cretaceous (Valanginian ‒ Aptian) is characterized by several significant environmental perturbations, accompanied by black shale depositions. Faunal and floral changes go along with significant excursions of the carbon isotope record, marked by Oceanic Anoxic Events (OAEs). These OAEs are well reported from the western Tethys and elsewhere with few reports from the central Tethys. Here a 722 m thick interval of Valanginian ‒ Aptian sediments, lithostratigraphically assigned to the Garau Formation, is investigated with regard to its calcareous nannofossils and stable isotopes. The Garau Formation mainly consists of black marly shales with intercalations of marls, marly limestones, one of the major source rocks of oil.

The lowermost OAE that is recorded from the Garau Formation is the Valanginian Weissert Event. This event is marked by two positive excursions of the carbon isotope data (2.8‰ and 2.4‰) that are separated by a negative carbon isotope excursion (CIE), recorded from the middle part of nannofossil zone NK3a to the middle part of the NK3b-NC4a subzones. The next OAE is the Faraoni Event in the late Hauterivian, which is marked by a negative and a subsequent positive CIE from NC5a to the middle part of the NC5b nannofossil subzone. The early Aptian OAE1a is marked by a negative and a subsequent positive CIE, accompanied by the nannoconid crisis and the FO of Eprolithus floralis. Our data clearly document the various OAE signals of the early Creatceous (Weissert, Faraoni, and OAE 1a) from the central Tethys.

Oceanic Anoxic Events (OAEs) represent significant perturbations in the global carbon cycle, marked by the deposition of organic matter-rich horizons in various oceanic basins during the mid-Cretaceous. This study applies a multiproxy approach, integrating calcareous nannofossil biostratigraphy and paleoecology, carbon and oxygen isotopes, and organic/inorganic geochemistry to identify the Albian OAEs (OAE 1b, OAE 1c, and OAE 1d) in the South Atlantic Ocean and assess their effects on nannoplankton assemblages. Here, we analyzed samples from DSDP Hole 363 (Walvis Ridge) and DSDP Hole 327A (Falkland Plateau) to identify the OAE 1b; DSDP Hole 363, DSDP Hole 356 (São Paulo Plateau), and DSDP Hole 364 (Kwanza Basin) to OAE 1c; and DSDP Hole 363 and ODP Hole 962D (Ivorian Basin) to OAE 1d. The results show that these Albian OAEs lack evidence of volcanic activity, indicated by low mercury concentrations. OAE 1b and OAE 1d are marked by increased input of continental sediments, high Total Organic Carbon (TOC), low oxygenation, and high abundance of eutrophic/mesotrophic species of calcareous nannofossils, suggesting elevated primary productivity mainly driven by terrigenous nutrient input. During OAE 1c, despite high TOC, low oxygenation, and increased continental input, no significant changes are observed in the calcareous nannofossils assemblage. Our results suggest that the high primary productivity during OAE 1b and OAE 1d was primarily influenced by nutrient input. In contrast, OAE 1c appears to have had minimal impact on nannoplankton assemblages. Acknowledgements: CNPq/405679/2022-0; CNPq/402804/2022-8; CNPq/308087/2019-4; IODP/CAPES/88887.091703/2014-01; IGCP/609; INCT Atlântico CNPq/FAPERGS/CAPES #406898/2022-7; e CAPES-PVE/88881.062157/2014-01.

This study integrates high-resolution multi-proxy data from the Romualdo Formation (Aptian –Albian), in the Araripe Basin (NE Brazil), to reconstruct palaeoenvironmental changes during the early stages of the South Atlantic Ocean opening and the Oceanic Anoxic Event 1b (OAE-1b). Records from Sobradinho section, including sedimentological, geochemical, micropaleontological, and stable isotope data reveal a complex depositional history influenced by transgressive-regressive cycles, fluctuating oxygenation, and nutrient dynamics. Data from the ~100 m thick section show that dysoxic to anoxic bottom water conditions (V/Cr > 4.25) prevailed, leading to the enhanced preservation of organic matter (up to ~7% total organic carbon - TOC) and diverse fossil assemblages. Stratigraphic and isotopic correlations suggest that the lower black shale interval, containing remarkable fossil-rich carbonate concretions, was deposited during the Kilian sub-event of Oceanic Anoxic Event 1b (OAE-1b; ~113 Ma). The peak of negative carbon isotope excursion coincides with high C/N ratios, increased fluvial input, and extended oxygen minimum zones, favoring carbon burial and exceptional fossil preservation. Ostracod and foraminiferal records, combined with Sr/Ba and S/TOC ratios, indicate episodic changes in salinity and marine incursions during periods of maximum flooding. Magnetic susceptibility and log(Zr/Rb) data further support variable terrigenous input and energy conditions across depositional system tracts. Our results demonstrate that low-latitude epicontinental seas played a key role in global biogeochemical cycles during mid-Cretaceous climate perturbations. The Romualdo Formation provides a unique Southern Hemisphere record for understanding the interplay between sea-level change, redox dynamics, and carbon cycling during OAE-1b.

This study is focused on the upper Cenomanian - lower Turonian depositional interval, located in the outer skinned-thrusted nappes of the Eastern Carpathians. Two sections spanning this interval have been studied. The southernmost one, 19.8 m-thick (situated in the S Eastern Carpathians) is characterized by hemipelagic deposits, i.e., green and grey marlstones. This succession has been sampled in detail for pointing out calcareous nannofossil and geochemical fluctuations. Based to the calcareous nannofossils, the succession spans the upper Cenomanian – lower Turonian interval, covered by the biozones UC3d up to UC7. The values of d¹³C are increased by 1.83‰, showing four distinctive peaks attributed to the OAE2. The northern studied succession from the Eastern Carpathians, 10.2 m-thick, is mainly made by pelagic and hemipelagic deposits grading up into turbidites, i.e., grey-dark shales, marlstones and carbonate sandstones, with red and green shales in the upper part. The values of d¹³C_org fluctuates between -27.3‰ and -24.4‰, showing three peaks in the Cenomanian and one peak in the lower Turonian, where the base is marked by the successive FOs (first occurrence) of nannofossils Eprolithus moratus, E. octopetalus, and Quadrum gartneri. In both studied sections, the fluctuation pattern of the δ¹³C isotope led to the identification of several intervals related to the OAE2 setting, such as the first build-up, trough, second build-up and plateau.

The Oceanic Anoxic Event 2 (OAE 2) at the Cenomanian-Turonian Boundary (CTB) marks a major perturbation in Earth’s carbon cycle, characterized by widespread deposition of organic matter (OM)-rich sediments. While globally recorded mechanisms relating to enhanced productivity and reduced oxygenation are well established, significant local variations in the timing of OM-rich sediment deposition and total organic carbon (TOC) values occur on the Levant Platform at the CTB. Such variations suggest additional, more localized environmental controls on OM deposition and preservation.

To resolve these spatiotemporal patterns, this study presents preliminary results from a basin-scale investigation of the CTB interval in the Jordanian Ajlun Group, covering a ~124 km transect within an inner platform setting. Detailed sedimentological, geochemical (elemental proxies, RockEval pyrolysis), and micropaleontological observations suggest that locally restricted deposition of high-TOC facies (≤9.5%) was seemingly driven by elevated nutrient input, while suboxic conditions likely developed due to increased oxygen consumption. Reduced carbonate sedimentation rates in these sections suggest a relative lack of carbonate dilution of TOC accumulation, while a detrital surge preceding high-TOC facies and paleo-productivity markers could imply a continental nutrient source.

A broader regional synthesis (Levant Platform-scale), integrating new data and published records, demonstrates a general trend of increasing TOC values from the platform margin (present-day Mediterranean coastline) towards the inner platform setting (Jordan) at the CTB. We discuss differing nutrient sources (upwelling and continental sources) and the role of basin-morphology. These findings underscore the complex interplay between global drivers and local/regional controls on OM deposition during OAE 2.

The Bahloul Formation of northern Atlas Tunisia comprises deep water deposits rich in organic matter representing Oceanic Anoxic Event (OAE) 2 across the Cenomanian-Turonian boundary interval. Black shale and marlstone samples from a 38m thick section at Oued Kharroub section have been studied for their organic matter (TOC) and carbonate content, field magnetic susceptibility (FMS) cyclostratigraphy, and microfossil content. Biostratigraphy is based on planktic foraminifera and nannofossils. From bottom to top the Rotalipora cushmani zone (Dicarinella algeriana subzone), the Whiteinella archaeocretacea zone, and the Helvetoglobotruncana helvetica Zone could be distinguished, and the nannofossil zones UC4, UC5 and UC6 (first occurrence FO Quadrum gartneri). The positive carbon isotope excursion lasts from the last occurrence (LO) of R. cushmani (peak A) until the FO of H. helvetica (plateau phase with peak D). Two radiolarian acme intervals occur. TOC ranges up to 3-5%, carbonate contents from 20 - 80%. Spectral analysis of FMS indicates eccentricity, obliquity and precession signals, with the 100 ky signal as the most robust cyclicity. The tuned model finds 12.5 100 ky eccentricity cycles, resulting in an approximate duration of the studied section of 1250 ky (between ~1187 ky and 1500 ky, sediment accumulation rate of 3cm/yr). The palaeoenvironments during OAE2 can be reconstructed as highly stressed, with eutrophication and continuously oxygen-deficient waters.

Abstract

The Late Cenomanian–Early Turonian Oceanic Anoxic Event (OAE 2) represents one of the most significant anoxic episodes of the Mesozoic, recognized across the NeoTethys and marked by the widespread deposition of organic-rich black shales and finely laminated limestones. In Tunisia, this event is recorded in the Bahloul Formation, which is divided into three distinct lithological units. This study investigates the Bahloul Formation based on well-time-constrained outcrop and well sections, providing insights into its petrography, geochemistry, and unconventional reservoir potential.

Petrographic analysis of thin section and SEM imagery shows that the Bahloul Formation is composed of various carbonate facies, including finely laminated packstone to grainstone, mud-rich packstone to wackestone, and mudstone. These facies are enriched with planktonic foraminifera, radiolarians, and other microfossils, with a matrix dominated by coccoliths, kaolinite, quartz, and framboidal pyrite.

Rock-Eval pyrolysis indicates total organic carbon (TOC) values ranging from 2 to 7 wt%, with high petroleum potential (above 10 mg HC/g rock) and a hydrogen index (HI) averaging around 600 mg HC/g TOC. This suggests good to excellent oil-prone Type I/II organic matter, deposited under anoxic, stratified conditions.

X-ray diffraction (XRD) analysis confirms a consistent mineral composition dominated by carbonates, quartz, and clays, with minor plagioclase and pyrite. These results suggest that the Bahloul Formation in Tunisia contains well-preserved organic-rich facies developed during specific anoxic conditions, highlighting its potential as an unconventional calcareous mudstone shale reservoir, particularly where it is sufficiently buried in near onshore basins.

The Crato Formation (Aptian, Araripe Basin, northeastern Brazil) preserves mineralized radiolarian microfossils characterized by calcite- and manganese oxide-filled casts. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and synchrotron-based micro-X-ray fluorescence (µXRF) analyses reveal a predominantly calcium-rich composition, with trace amounts of Mn, Zn, Cr, and Fe. Micro-Raman spectroscopy confirms the presence of mixed-valence manganese oxides (Mn³⁺, Mn⁴⁺), possibly including biogenically influenced phases such as todorokite. Granular and nodular Mn-oxide precipitates, along with micrometric fossil biofilms, support a microbial role in fossilization under low-oxygen conditions. Chemostratigraphic data from the same interval show a negative δ¹³C excursion (~2‰), coinciding with a mercury enrichment peak (Hg/Al ~130 ppb), indicating volcanic influence and redox instability in the depositional environment. These results support a model of early diagenetic fossil preservation in a redox-stratified basin, possibly linked to regional volcanism and transient environmental disturbances during the Early Aptian. Geochemical signatures, including a high Zr/Rb ratio, suggest limited continental chemical weathering, consistent with an arid to semi-arid paleoclimate. The replacement of original siliceous structures by carbonates and metal oxides likely reflects silica instability in alkaline, calcium-rich waters, typical of confined lacustrine systems. The presence of chromium, associated with detrital input or reducing conditions, further underscores the complexity of the diagenetic environment. The integration of morphological, mineralogical, and geochemical evidence supports a fossilization model driven by the interplay of biological activity, volcanic influence, and unique diagenetic processes, with microbial mediation playing a key role in the preservation pathway. [Acknowledgements: Mar Interior project and CNPEM]

At the Aptian–Albian boundary (~113.2 Ma) widespread expansion of oxygen-depleted waters in the global ocean resulted in the development of the so-called Oceanic Anoxic Event (OAE) 1b. A major driving factor for this event was enhanced continental weathering and nutrient runoff, which stimulated high primary productivity and led to the widespread deposition of organic-rich sediments under anoxic conditions. In northeastern Brazil, the Araripe Basin preserves records of OAE1b within a transitional depositional context. To investigate OM characteristics under such conditions, we applied a multiproxy geochemical approach to the Sobradinho and Estiva sections, representing areas closer to the Atlantic Ocean and farther inland, respectively. OM-rich shales at both sites were deposited under stratified water columns with intermittent marine influence. TOC contents reach ~14% at Sobradinho and ~12% at Estiva), with kerogen types I–III and hydrogen indices (HI) below 1000 mg HC/g TOC in both sections. This contrast likely reflects differential, indicating differing OM preservation mechanisms. Redox-sensitive trace elements show U, V, Ni, Cr, and Co enrichment at Sobradinho, while Estiva exhibits elevated Zn, Cu, Cr, As, V, U, and Mo. Volcanic signals inferred from Hg/TOC; Hg/Fe₂O₃; Hg/Al₂O₃ peaks appear twice at Sobradinho and once at Estiva, coinciding with the Kilian subevent. Principal Component Analysis highlights better OM preservation and geochemical consistency at Sobradinho, while Estiva displays greater heterogeneity, influenced by carbonate input and redox variability. These results underscore the role of local and regional environmental factors in shaping OAE1b records in transitional settings.

The Valanginian Weissert Event is the earliest and perhaps the most puzzling Cretaceous carbon cycle perturbation. Unlike other OAEs, this event lacks a negative CIE and is characterized solely by a positive CIE, but is not associated with widespread black shales. However, studies of the Weissert Event are more limited compared to other OAEs, hindering the characterization of global to local responses. Here we report preliminary results from the newly excavated Rend-kő section and compare them with two previously studied localities nearby in the Transdanubian Range. Both the HK-12 and HÉK sections yielded ammonites only up to the Verrucosum Zone, but nannoplankton biostratigraphy revealed the presence of zones NK1 to NC5. Carbon isotope stratigraphy allows excellent correlation as pre-event d¹³C_carb values are consistently in the range of 1.2–1.4‰ and peak values of the Weissert CIE between 2.7–2.9‰. Differences exist at the onset of the CIE as HK-12 displays a jump of >1‰ at an ammonite-rich condensed bed marking a hiatus, whereas the rising limb of the CIE in the HÉK section is two-stepped, possibly also revealing arrested carbonate deposition. New data from Rend-kő suggest that this section is the most extended and least condensed at the onset of the event. More dense sampling is underway and is expected to yield a high-resolution carbon isotope curve. We will develop an astrochronology to constrain the duration of different phases of the Weissert CIE. Additional geochemical studies are planned to better understand the paleoenvironmental changes during the Weissert Event.

The Crato Formation, northeastern Brazil, is one of the most renowned Cretaceous sedimentary sequences due to its exceptional fossil preservation from Aptian–Albian. Although marine incursions have been recorded, their paleogeographic extent remains poorly understood. This study is based on a multi-proxy approach applied to core PTI-01, drilled at the Três Irmãos Quarry,, involving ichnology, palynology, palynofacies, microbiofacies, magnetostratigraphy and X-ray diffraction analyses. The punctual occurrence of Sergipea variverrucata suggests an Upper Aptian age for the upper part of the section. Palynofacies analysis reveals predominance of continental palynomorphs (pollen grains, bio-structured phytoclasts, banded, striped, opaque, and cuticles). Ichnodiversity was low throughout the section (Palaeophycus isp. and Skolithos isp.), indicating a bioturbation index of 1-2. The magnetostratigraphy exhibits a mean inclination of -21.5º, consistent with the expected geomagnetic field inclination for the region. Magnetic remanence is carried by (Ti-)magnetite and hematite. No polarity reversals are observed in the record, supporting the interpretation that rocks record a time interval within the Cretaceous Normal Polarity Superchron (CNPS),. However, the results identified several indicators, which suggest localized evidence of paleosalinity : (i) benthonic foraminifera (textularids) and levels with calcium carbonate concretions at the lower part of the section, (ii) calcareous dinoflagellates (e.g., Colomisphaera heliosphaera) at the middle part of the section, and (iii) Subtilisphaera sp, associated with the most bioturbated interval (bioturbated texture), and higher levels of calcite at the top of the section. Our data suggests deposition in coastal lagoonal setting influenced by incursions marine waters during the late Aptian. [Acknowledgements: Magneto Project]

Deep-marine turbiditic systems rely on the supply of terrigenous material and are typically shaped by autocyclic processes, often interacting with tectonic activity and episodic erosion. In this study, we present evidence for allocyclic (orbital) control on deep-marine sedimentation in the Proto-Silesian Basin (part of the Severin-Moldavidic Basin system in the Outer Western Carpathians) based on a detailed analysis of the Krzyworzeka river section. The Outer Western Carpathians of Poland have played a pivotal role in global sedimentological research, particularly in the study of turbidity currents. Nevertheless, several stratigraphic units remain understudied. Recent advancements in numerical methods now offer powerful tools to explore the influence of orbital forcing on sedimentary processes. At the studied site, the Valanginian-age Upper Cieszyn Beds and Hradištĕ Beds are exposed as an undivided unit due to limited lithological contrast. Five facies types (F1–F5) were identified and analysed using a suite of time-series techniques to evaluate the presence of deterministic controls on facies distribution and bed thickness. The results reveal distinct periodicities in sedimentation, including phases of intensified terrigenous influx, evidenced by the occurrence of facies F3, F4, and F5, and intervals marked by rusty layers (facies F2), indicative of episodic iron oxidation. These patterns point to orbitally paced environmental changes regulating sediment supply and diagenetic conditions in this deep-marine setting. The detected periodicities were linked to Milankovitch cyclicities. Sideritic bed occurrences are most favourably linked to the cycles of precession and obliquity, while the intensification of terrigenous material supply may also be related to eccentricity.

Recently, a series of studies has brought an attention to some important palaeoenvironmental turnovers which took place during the Jurassic/Cretaceous boundary. Among them, the most characteristic are the so-called VOICE (Volgian Isotopic Carbon Excursion), cool and arid climate mode during the late Tithonian–early Berriasian, as well as climate humidification at the early/late Berriasian transition. However, so far none of those events has been evidenced as manifesting a truly global scope. This study aims to compare paleoclimate and paleoceanographic signals documented via gamma-ray spectroscopy (GRS) in the Tithonian–Berriasian of the Neuquén Basin (Las Alcantarillas and Las Loicas sections, Argentina) with palaeoenvironmental records from coeval successions of the western Tethyan domain. Stratigraphic correlations are ensured by integration of magneto-, chemo- and biostratigraphic tools. Studied sections indicate suboxic/anoxic conditions during the early Tithonian and later on during the late Tithonian–early Berriasian. A stepwise increase in lithogenic influx (Th content) is characteristic of the Berriasian; besides, a sudden increase in Th/K ratio at the lower/upper Berriasian transition is suggestive of climate humidification. Such record, in particular oxygen deficit at the seafloor during the Tithonian/Berriasian transition and climate humidification during the early/late Berriasian corresponds with recent findings in the Transdanubian Range (Hungary), Slovenian Basin and the Vocontian Basin (SE France). This, in turn, may evidence the global scope of those latest Jurassic–earliest Cretaceous environmental processes.

The Cenomanian-Turonian OAE 2 represents significant climatic perturbation associated with global shifts in carbon isotopes and widespread development of black shales. While extensively studied in oceanic environments, its expression in continental environments is still not well understood. This research focuses on the Mayo-Figuil section located within the Babouri-Figuil Basin in Cameroon, using mineralogy, organic matter, phosphorus, mercury, major and trace element contents, chemostratigraphy, and preliminary palynological biostratigraphy, to constrain the depositional age and decipher environmental changes. Although the carbon isotope record lacks a distinct shift, the initial palynomorph dataset, including Classopollis sp., Araucariacites sp., Cicatricosisporites cuneiformis, Tricolpites sp., Ephedrepites sp., Cretacaeiporites sp and Triorites africaensis, suggests a late Cenomanian to early Turonian age, aligning with other basins in West Africa. These findings help defining the Triorites africaensis Zone (II; late Cenomanian), and Cretacaeiporites scabratus Zone (III; early Turonian). During the OAE 2, OM is primarily made up of Type II and I kerogens, consistent with a marine incursion via the Tran-Saharan Seaway. Enrichment in redox and productivity-sensitive trace elements coupled with high C_org/P_tot ratios and TOC contents, suggest that a larger part of P was remobilized and integrated with sediments during this period of fluctuating suboxic to anoxic conditions in the deposition process. During this timeframe, it clearly appears that TOC and P fluctuations have been driven by detrital input and consequently by climate. This study offers for the first time evidence of the OAE 2 in a Cameroonian rift basin, and providing valuable insights into ancient equatorial environmental conditions.

The Cretaceous-Paleogene (K/Pg) boundary marks one of the most significant mass extinctions in Earth's history, associated with meteorite impact and major environmental changes. Understanding the geochemical, sedimentological, and biogenic signatures of this transition is essential to reconstruct paleoenvironmental conditions and biogeochemical responses after global events. While deep-sea K/Pg boundary deposits have received extensive attention, the shallow-marine sedimentary record remains less explored. The K/Pg transition is recorded in the shallow water carbonates of the Adriatic-Dinaric Carbonate Platform on the Karst Plateau but is often poorly exposed. An 80 m-long core was drilled in Padriciano (Trieste) in an attempt to retrieve a continuous rock record, under the auspices of the Interreg Italy-Slovenia Kras-Carso II project. This effort seeks to enhance the geological heritage of the region by fostering cross-border research collaborations and promoting sustainable development. Detailed analyses on the core will help to enhance knowledge of the K/Pg which is recognized as one of the key geosites in the area. The Padriciano core comprises shallow-water carbonates, predominantly wackestones and packstones, exhibiting variable textural features. The succession includes intraclast-rich horizons, laminated intervals, brecciated layers, and karstified surfaces, reflecting a complex depositional and diagenetic history characterized by episodes of subaerial exposure and subsequent post-depositional alterations. Facies analyses, biostratigraphic investigations, and geochemical analyses (XRF, gamma-ray spectrometry, δ¹³C and δ¹⁸O) were carried out on the core. The integration of these data enhances the stratigraphic resolution of the K/Pg boundary in shallow-marine environments and provides new insights into environmental changes that occurred across the K/Pg transition.

The OAE1d is one of the oceanic anoxic events that punctuate the Cretaceous and represent Earth system-wide changes prominently captured by carbon isotope excursions (CIE). Although the positive CIE near the Albian-Cenomanian boundary (ACB) is known from multiple localities, many of these records disagree in the shape of the δ¹³C curve. Interpretations of the OAE1d and a broader ACB Event remain ambiguous, and their duration is insufficiently constrained. Here we present new analyses on high-resolution samples from Core Jásd-42. The >450 m thick Pénzeskút Marl Fm. provides an expanded record across the ACB. We generated elemental and stable isotope geochemical data and used these time series for cyclostratigraphic analyses. The derived astrochronologic age model establishes a depositional duration of 3 Myr and is integrated with ammonite and plankton foraminiferal biostratigraphy updated from previous works. Our high-resolution chemostratigraphy provides a new, calibrated record of OAE1d and the ACB Event that we correlate with other key reference sections, including the GSSP. The combined duration of the rising limb and the peak-to-peak culmination of the positive CIE, equated here with OAE1d, is estimated as 0.78 Myr. With an additional 0.58 Myr of the falling limb, a minimum estimate for the total duration of the ACB Event is 1.36 Myr. The δ¹³C record through the OAE1d appears orbitally controlled, where the positive peaks are paced by short eccentricity. Considering the differences between seasonality extremes, we suggest a model for depositional cyclicity in a synorogenic basin with a high sedimentation rate of 15-16 cm/kyr.

The highest southern latitude onshore record of the Cretaceous-Paleogene (K-Pg) mass extinction is found on Seymour Island, Antarctica. The boundary occurs within the upper levels of the abundantly fossiliferous and expanded (sedimentation rates of 0.2 cm/yr) López de Bertodano Formation. Previous studies based on species richness data have led to persistent debate as to the timing of the K-Pg mass extinction in Antarctica, but little quantitative work exists examining ecological or environmental change across the boundary at high latitudes. During early 2024 we conducted a detailed study of the K-Pg interval on Seymour Island, measuring multiple sections and making quantitative macrofossil collections across the K-Pg along strike for ~2.5 km. New faunal data indicate that existing macrofossil collections from Seymour Island provide an accurate picture of species richness, but do not adequately capture the ecological composition of the marine ecosystem in either the pre- or post-boundary intervals. Shifts in dominance and abundance of certain taxa occur within the final ~1 million years of the Maastrichtian, but the only significant ecological change occurs at the K-Pg itself, with an impoverished early Danian community dominated by the infaunal bivalve Lahillia larseni. Preliminary geochemical data from organic biomarkers suggest minimal temperature change across the boundary. New observations extend the stratigraphic ranges of several taxa closer to, and in one case across, the K-Pg boundary. These data confirm a single extinction event at the K-Pg boundary in Antarctica. Early disappearances of taxa are likely a result of insufficient sampling and poor taxonomic resolution.

High-resolution analysis of outcrops, cores, and logs from central Kansas provide new insights into the evolution of the Greenhorn marine cycle in Central, KS. This sequence, comprising the upper Dakota Fm., Graneros Shale, and Greenhorn Limestone, records the transition from non-marine to marine clastic, and carbonate depositional systems that resulted from eastward transgression of the WIS shoreline. This study refines previously outlined stratigraphic frameworks by combining modern chronostratigraphic techniques including U-Pb radiometric age dating and carbon stable isotope analyses with sequence-stratigraphic characterization.

Multiple orders of framework surfaces and major carbon isotope excursions are identified and correlated using absolute age control and relative markers. The lower package comprises a thick succession of coastal plain paleosols and fluvial deposits. An abrupt erosional transition is overlain by a conformable succession of tidally influenced sandstones and argillaceous mudstones that record the transgression of the WIS. The sandstones are overlain by 10m of argillaceous mudstone that comprises at least six parasequences and records successive drowning of the margin. The highstand succession records a transition from detrital (Graneros Shale) to carbonate-dominated marine sedimentation (Greenhorn Limestone). A high confidence regionally correlative ash bed previously hypothesized to be the 95.53 ± 0.36 Ma “X-Bentonite” in the upper Graneros Shale is used to date the maximum flooding surface. Our new ICP-MS and CA-TIMS analyses have produced significantly younger ages, shifting previously interpreted biostratigraphic and stable carbon isotope chemostratigraphic correlations along the eastern margin of the WIS.

The Opole Basin (southwestern Poland) preserves an expanded, fossiliferous Turonian to Coniacian succession, exposed through numerous cement quarries in the immediate vicinity of Opole. It serves as an important composite reference section for this interval in Europe, in part due to a rich record of many representative macrofossil and microfossil groups. Furthermore, it is situated near the nexus of the Bohemian Cretaceous Basin and the Central European Basin, providing unique opportunities for inter-correlation.

Here, we present a revised, high-resolution, integrated stratigraphic scheme of the accessible succession. A new inoceramid biozonation places the succession between the Inoceramus apicalis Zone (lower middle Turonian) and the Cremnoceramus deformis–C. crassus Zone (upper Lower Coniacian). Although the middle Coniacian is not presently exposed, it is observed further to the west in the subsurface. Ammonites are particularly well-represented in the Turonian, including enormous representatives of the genera Lewsiceras and Pachydesmoceras. The succession yields a rich and representative record of both planktonic (Dicarinella, Helvetoglobotruncana, Marginotruncana, and Falsotruncana) and benthic (Gavelinella, Globorotalites, Eponides, Lingulogavelinella, and Protostensioeina) foraminiferal lineages, providing a rare opportunity for the direct correlation of both groups in central Europe. Other invertebrate groups are well-represented, including ostracods (including the stratigraphically important genera Neocythere, Imhotepia, Bythoceratina, and Cytherelloidea), dinoflagellates, echinoids, and sponges. An independent chronostratigraphic framework is provided by a new carbon isotope chemostratigraphic record. This detailed integrated framework may help to better delineate the biotic and correlative significance of this keystone succession.

We present high-resolution (10–25 cm interval) carbonate carbon- and oxygen-isotope records (δ¹³C_carb, δ¹⁸O_carb) for the 162 m thick Chalk section exposed in the cliffs at Seaford Head, southern England. This reference section for the Upper Cretaceous of NW Europe has been proposed as a global reference for the Coniacian–Santonian and Santonian–Campanian stage boundaries and is designated an auxiliary GSSP boundary stratotype for the Campanian Stage. Carbon isotope stratigraphy, comprising 30 named carbon-isotope events (CIEs), supported by lithostratigraphy, macrofossil, microcrinoid, microfossil and calcareous nannofossil biostratigraphy, allows for precise correlation to other key European sections. CIEs provide the means of placing the Coniacian (top Navigation CIE) and Campanian (top Late Santonian Event) stage boundaries, while the lowest occurrence of Cladoceramus undulatoplicatus defines the base Santonian. Our holostratigraphic approach allows for intercalibration of biozonation schemes and chemostratigraphy. Spectral analysis of carbon and oxygen isotope profiles at Seaford Head demonstrates a clear expression of 405 kyr orbital cycles, offering the basis for orbital tuning of the isotope time series. Correlation of the Seaford Head orbital time scale to geochronological ages of bentonites from the US Western Interior Basin permits anchoring of the isotope records to various astronomical solutions. We favour a tuning approach to the La04 sinusoidal eccentricity solution along with a tie of 405 kyr minima to existing Laskar/Zeebe solutions for age calibration of biostratigraphic datum levels. Our results provide a basis for improved correlation and age calibration of Coniacian to Campanian successions at a regional to global scale.

The recent definition of the Santonian/Campanian boundary based on magnetostratigraphy (the C34N-C33R magnetic reversal boundary) by Gale et al, 2023, marks an important advance in attempting to correctly correlate the Santonian and Campanian Stages and their substages far from the European stratotypes. Unfortunately, the Gale et al, 2023 contribution made a fundamental error in the placement of this boundary in the Northeast Pacific (British Columbia, California, and Baja California), the Northwest Pacific (Japan and Sakhalin), and Antarctica. Data will be presented demonstrating that the C34N/C33R reversal most closely aligns with the base of the Canadoceras yokoyamai Zone in North America, Japan, and Sakhalin, and with the base of the newly defined, Anapachydiscus naumanni Zone (lowest Campanian) in Antarctica, allowing direct correlation to Japan and Sakhalin. Based on this error, the diachroneity between the stage boundary stratotype in Italy, and each of these regions, is estimated at one to three million years. In this talk, the state of magnetostratigraphy for the Santonian through Maastrichtian will be summarized with reference to both new magnetostratigraphic results and how chron boundaries in this vast "Pacific Basin" correlate to ammonite and inoceramid biostratigraphy in North America, Japan, Sakhalin and Antarctica. Proposals for new, stage boundary, auxiliary stratotype sections will be presented, as well a new proposal for a three substage Campanian and two substage Maastrichtian defined by ammonite biostratigraphy integrated with magnetostratigraphy. The timing of the first occurrences of globally cosmopolitan, Campanian Stage Baculites species will also be presented in support of a three substage Campanian.

The Oslen-Krivodol section is situated in the western Fore-Balkan Mountains, in a Peritethyan palaeogeographic position. The lower part of the studied 7m section is composed of green to greenish glauconitic limestones (Darmantsi Formation), overlain by thin- to medium bedded limestones, clayey and nodular limestones (Kunino Formation). A complete nannofossil zonal succession could be established, from the uppermost Campanian to the lowermost Maastrichtian, with subzones UC15c^TP, UC15de^TP, UC16a^TP and UC16b^TP. The nannofossil bioevent for the base of the Maastrichtian, the LO of Uniplanarius trifidus, is at 3.25m in the section. Strontium isotope stratigraphy indicates the C-M-boundary around 0.707736±5. Additional nannofossil bioevents include the FO and LO of Microrhabdulinus ambiguus below those two inferred CMB levels, and the decrease of warm-water nannofossil indicators like Watznaueria spp. indicating cooling along the Campanian Maastrichtian Boundary carbon isotope event. Two dinocyst zones have been recognized in the section: the upper Campanian Areoligera coronata and the lower Maastrichtian Cerodinium diebelii Zone. Their boundary is marked by the last occurrence of typical Campanian taxa (Odontochitina, C. robusta, C.horridum, A. fenestra) and the appearance of Maastrichtian forms (C. diebelii, M. carpentierae, Glaphyrocysta). inoceramid bivalves were collected from one level in the upper part of the Kunino Formation, represented mainly by the genus Cataceramus, but Endocostea is also present: Endocostea typica Whitfield, 1880; Cataceramus pallisieri (Douglas, 1942); Cataceramus subcircularis (Meek, 1876) and Cataceramus barabini (Morton, 1834). Based on the presence of E. typica we can indicate the upper part of eponymous inoceramid zone at the base of the Maastrichtian.

Certain doubts regarding the definition of the Global Boundary Stratotype Section and Point (GSSP) for the base of the Maastrichtian Stage (Tercis-les-Bains in southwest France) have led the Subcommission on Cretaceous Stratigraphy to establish a new Maastrichtian Working Group. The main tasks undertaken by the group include verifying the validity of the highest (HOs) and lowest (LOs) occurrences of micro- and macrofossil taxa that were used to define the Campanian–Maastrichtian transition and, if necessary, proposing new boundary indicators, including a primary boundary marker. Three of the twelve currently valid boundary criteria are dinoflagellate cyst (dinocyst) events, but only one of them (the HOs of Raetiaedinium evittigratia and R. truncigerum) has shown real biostratigraphic value. Other formal dinocyst boundary markers either disappear high above the GSSP level (Samlandia carnarvonensis, S. mayi) or has a limited geographical distribution (Corradinisphaeridium horridum). Potential candidates for new dinocyst boundary markers include the HOs of Callaiosphaeridium asymmetricum, Coronifera oceanica, Odontochitina costata, Xenascus ceratioides, and the LOs of Cladopyxidium saeptum, C. verrucosum, Florentinia mayi, Glaphyrocysta expansa, and G. pala. Although Callaiosphaeridium asymmetricum and Florentinia mayi have not yet been found in Tercis (the latter occurs in the geographically nearby Zumaia in northern Spain), all the above-mentioned bioevents have been shown to be geographically widespread, indicating their potential biostratigraphic importance. Understanding the actual relevance of the mentioned dinocyst events requires refined and highly-resolved studies at the GSSP site, including comparison with other Campanian–Maastrichtian dinocyst records precisely tied to the chronostratigraphic framework.

In this paper, results of an integrated stratigraphic analysis and seismic mapping project (TNO-EBN DeVli Project) are presented. The area of interest comprises the Broad Fourteens and the West Netherlands basins that occupy a large part of the southern Dutch on- and offshore. The stratigraphic interval of interest is the predominantly non-marine Upper Jurassic Schieland Group and the marine Lower Cretaceous Rijnland Group. The Mesozoic basins were affected by the late Cimmerian rift, resulting in complex stratal relationships within rapidly changing paleo-depositional environments and a plethora of lithostratigraphic units that required a sequence stratigraphic perspective. The integrated seismic and stratigraphic approach made it possible to fit the pieces of the lithostratigraphic puzzle into a tectonostratigraphic framework. Seismic sections, time structure maps and time-thickness maps were compiled to better understand the complex evolution of these two basins. One of the most interesting findings is the presence of massive sandstone units, that were previously assigned to different stratigraphic units but are in fact time equivalent and belong to the same tectonostratigraphic mega-sequence. This basin wide event occurs at the transition from the Ryazanian to the Valanginian and reflects erosion of the rift shoulders and redeposition in the rift. In the West Netherlands Basin, this event is embodied in the Delft Sandstone Member, which is the most important targets for geothermal energy in the region. The high level of detail in both the seismic and stratigraphic analysis allowed to propose an alternative depositional model for the unit, in contrast with existing models.

The sedimentary record of the Sverdrup Basin in the Canadian Arctic encompasses all stages of the Cretaceous. Owing to a brief history of research (from 1952) and a limited number of publications (<100) it is manageable to database the entire Cretaceous fossil record of the basin. We completed this task for macrofossils, and have made major progress regarding microfossils and palynomorphs. At present, the database contains more than 3700 entries of two types: 1) approximately 1900 entries pertain to specimens collected by CASP, with each specimen receiving its own entry; 2) approximately 1800 entries document literature data, with each entry corresponding to one species at one locality. All entries are georeferenced and dated to stage level, and can be displayed and interrogated in GIS. Sample coverage of Cretaceous outcrop area is governed by accessibility, both with regard to exposure and logistics, but is reasonably dense, given the often challenging fieldwork conditions. The relevance of the dataset extends beyond the Sverdrup Basin limits given that marine connections via Baffin Bay, North Greenland and the Western Interior existed at times during the Cretaceous, and many species are common to other parts of the Boreal realm. Notable macrofossil records of regional significance include the Berriasian and Valanginian ammonite and bivalve faunas of the Deer Bay Formation, sporadic Albian to Santonian ammonite occurrences, and a Sphenoceramus community from the Santonian–Coniacian boundary interval. Microfossils and palynomorphs are recorded from all stages, and were mostly employed for biostratigraphy, but also hold great palaeoecological potential.

The Mesozoic in Greenland is an almost exclusively siliciclastic sedimentary succession. The Cretaceous is dominated by dark-grey, silty mudstones low in organic carbon and fossils – and has thus been considered boring and of little interest.

We present three Early Cretaceous exceptions with “carbonate” deposition.

1) Vividly-coloured, fauna- and flora-rich Ryazanian–Valanginian mudstone deposits on structural highs. They were considered ‘the first representative of limestone deposition’ since the Late Permian in Greenland, when first described by the early mapping geologist in the 1930-40’ies. However, the amount of carbonate, originating from calcareous nannofossils (CN), only qualify the unit as calcareous mudstones. Calcareous nanofossils as well as various ammonites, belemnites and brachiopods are partly of Tethyan origin and reflect major palaeoceanographic changes.

2) The re-discovery of the mid-1930’ies fauna-rich Hühnerbjerg locality represent pure carbonates that largely originate from inoceramid prisms. The setting was an isolated basement horst submerged in earliest Cretaceous (Valanginian–Hauterivian) and constituted a seamount, protected from siliciclastic input and hosted a rich fauna: brachiopods, in particular, ammonites, nautiloids, belemnites, bivalves, gastropods, crinoids, echinoids, serpulids, corals and crustaceans – and barren of calcareous nannofossils. The mount top carbonates were swept of the sides of the mount and transported in debris flows down the flanks and deposited as packstones and grainstones.

3) Imbedded in dark Barremian mudstones are methane seep carbonates. The seep mounds attracted a rich and diverse fauna and provide a rare preservation window to the otherwise almost barren Barremian marine succession.

In northern Germany the Berriasian stage is represented by an overall brackish sedimentary sequence which was deposited in the landlocked, continuously subsiding Lower Saxony Basin (LSB). The brackish inland sea of the LSB extended for 400 km from west to east and ca. 100 km from south to north. It formed the southernmost extension of the North Sea Basin. The Berriasian deposits are lithologically attributed to the Purbeck and Wealden type facies, with the upper part of the Münder Formation dominated by carbonates and evaporites, and the overlying Bückeberg Group (= German Wealden) by siliciclastics.

This study improves our understanding of the parameters controlling the sedimentation patterns of the German Wealden, which accumulated up to 700 m of siliciclastics in the basin center. An integrated bio- and lithostratigraphic approach helps to reconstruct the spatial distribution and relationship between the different sandstone bodies in the Deister-Hils Embayment of the southeastern margin of the LSB. We provide new micropaleontological data from cores and outcrops, recalibrating the stratigraphic position of the sandstones. We further present an updated biostratigraphic range chart of the well established ostracod zonation. Several intercalated brackish–marine ingressions are documented from the central basin and the coarser grained siliciclastics of the margin, which allow a sequence stratigraphic interpretation. We propose a sequence stratigraphic model, which can also be applied to other parts of the LSB. This model will help to better understand the facies distribution for geothermal and hydrocarbon exploration as well as for potential CO2 storage.

The Lower Cretaceous Tuxen and Sola formations in the Danish Central Graben (North Sea) constitute one of the oldest chalk successions recorded globally. Forming a regionally extensive succession in the Central Graben with similar, age-equivalent units widespread across the southern Boreal Realm, it comprises a heterogeneous mixed carbonate–siliciclastic stratigraphy of predominantly bioturbated pelagic chalks and hemipelagic marlstones and mudstones, which straddle the global early Aptian Oceanic Anoxic Event 1a (OAE-1a). Despite testifying to a dynamic basin-filling history influenced by relative sea-level changes of both eustatic and intra-basinal tectonic origin, the Lower Cretaceous pelagic carbonates are relatively overlooked compared to their Upper Cretaceous – Danian counterparts of the Chalk Group characterized by more homogeneous, clean white chalk. Consequently, the timing, magnitude and depositional controls on these basin events remain to be fully understood.

We present herein an updated depositional and sequence stratigraphic model of the Tuxen and Sola formations in the Danish Central Graben, based on high-resolution sedimentological analysis combined with a new integrated stratigraphic framework from biostratigraphic and well-log data. The succession records c. 20 Myr of transgressive–regressive cycles, superimposed by numerous lower-order events controlled by local, global and (potentially) orbital forcings. The study thereby serves as a benchmark for deciphering sequence stratigraphic controls at multiple scales in pelagic successions, where this distinction is typically challenging.

Opoka is a carbonate-siliceous rock that forms thick Campanian-Maastrichtian successions in Poland, Ukraine, and Russia, and has also been documented in Western Europe (France, Germany, and the Nederlands). Its mineralogical composition has only recently been thoroughly examinated, and studies have revealed that the main component of the insoluble residue (remaining after calcium dissolution) is opal-CT. This silica polymorph forms a siliceous rock network composed of adjoining lepispheres. Opoka is usually characterized by a low content of terrigenous material and contains intercalated horizons of marls and cherts. The latter can be distinguished from flints by their different mineralogical composition—namely, the presence of primary opal-CT, which differs from the nano-α-quartz typical of flints. A common feature of opoka the presence of siliceous sponge fossils, often preserved only as voids resulting from spicule dissolution.

The recognition of opoka mineralogical composition and the origin of its components has helped constrain the Si cycle during pre-Eocene times. This also opens the discussion about the abiotic sources of Si in porewater, and the role of siliceous sponges in delivering Si into sediments, and subsequently contributing to chert formation. Proper mineralogical verification of rock types identified within the Late Cretaceous epicontinental European Basin also sheds new light on existing bathymetric models of chalk and opoka facies distribution.

Pygopide brachiopods – Antinomia, Pygope, and Pygites – were sessile benthic organisms with different paleobiogeographic origins, and from their first occurrence in the late Oxfordian until their final demise in the late Barremian, they were an emblematic group of Tethyan fossils. Their quick diversification during the early Tithonian is linked to their successful adaptation to limited food supply in the colonized thalassobathyal environment, that turned out disadvantageous in abundant food supply. They coudn’t inhabitate low oxygenated water masses, and they might be able to proceed long–distance dispersal only during their larval stage. Stepwise assemblage changes, migration patterns and extinction of Pygopides can be linked to intervals of environmental perturbations with dysoxic conditions, and controlled by the paleocurrent systems and sea level changes. The Weissert Event was a turning point: Antinomia got extinct, Pygites invaded new territorries, while Pygope was withdrawn from the Tethys and only documented from East Greenland. After a prolonged 2-5My lag, Pygope re-appeared in the Tethys as a Lazarus taxon. Our results further support the northward migration of Tethyan assemblages during the Berriasian–early Valanginian, but after the early late Valanginian, southbound dispersal from the north Boreal was not straightforward. It might be possible via the proto–North Atlantic and the Polish Trough as well, therefore a complete oceanic circulation cell could have existed between the western Tethys–Boreal–Arctic–Laurasian continental shelf regions. The middle Valangianian and middle Hauterivian transgression facilitated the backward dispersal of pygopides. Irrevocable extinction of pygopide brachiopods is linked to the latest Barremian–early Aptian global environmental perturbations.

The early Aptian Oceanic Anoxic Event (OAE 1a) represents one of the most important hyperthermal episodes in Earth’s history, associated with a massive light-carbon input from volcanogenic (Ontong-Java Plateau) and/or methanogenic sources. Its onset is marked by a disruption of the global carbon cycle, expressed as a pronounced negative carbon isotope excursion. This event is associated with global temperature increase, anoxia in ocean bottom waters, and widespread deposition of organic-rich sediments. Complex biotic and environmental perturbations are associated to this event, with their global expression being influenced by local factors.

In this study, we investigate the biotic and environmental perturbations associated with the OAE 1a in three sections from the Southern Iberian Palaeomargin (western Tethys): La Frontera, Carbonero and Cau sections, by the combination of biomarker analysis, elemental geochemistry, and total organic carbon (TOC) measurements. These sections comprise hemipelagic (Cau) and pelagic (Carbonero and La Frontera) sediments. We present high-resolution C-isotope records, used as a basis for a precise stratigraphic correlation (C-isotope segments C2/Ap2 to C7/Ap7).

Our results highlight that major biotic and environmental perturbations took place during segment C4/Ap4, marked by changes in both organic and inorganic proxies across all three sections. This coincides with widespread deposition of organic-rich sediments in all major ocean basins. Other episodes of environmental and biotic perturbations occurred at the top of segment C2/Ap2 and at the C5/Ap5-C6/Ap6 transition, though these are not recorded in all sections. The variable expression of the OAE 1a effects can be related with differences in local palaeogeographic conditions.

A comprehensive sedimentological and sequence stratigraphic study in Tunisia provides robust evidence for a significant climatic shift in the early late Aptian, expressed by a sharp facies change from a carbonate and evaporite dominated system, to shallow marine siliciclastics rich in plant material. It coincides with a high magnitude sea-level drop of about 60m, observed in Tunisia and other locations around the NeoTethys.

Based on over 20 wells and 10 outcrop sections, this study offers a well-constrained Aptian sequence stratigraphic framework along the southern Tethys margin. Two large scale sequences are defined, the first one covers the early and early late Aptian, and is dominated by marine and tidal-influenced carbonates, marls and gypsum, deposited under arid conditions. The second sequence is of late Aptian/earlies Albian age and is dominated by siliciclastic deposits. It comprises a lowstand wedge of sands and ooliths, during the transgression an incised valley system was backfilled with large-scale crossbedded tidal deposits, and in the shallow marin domain prograding deltaic sediments are remarkably enriched in plant material (leaf and wood fragments). In the most proximal settings mamal and dinosaur fossil remains were found. The climate at this time is interpreted as humid.

The wider implication of these results are that the Equatorial Humid Belt extended into Tunisia, and that this occurred during the late Aptian, instead of during the Albian. This timing corroborates recent work from Brazil, and may have its bearings on the understanding of the conditions that triggered the rise of the angiosperms.

We present a high-resolution record of long-term changes in detrital input, chemical weathering, freshwater influx, and palaeoproductivity across the late Aptian to late Cenomanian (~25 Myr), based on quantitative elemental data from the Umbria-Marche Basin (central Italy, western Tethys). This interval captures a major environmental transition, from multicolored marlstone and black shale-dominated sediments of the Marne a Fucoidi Formation to the widespread chalk deposition of the Scaglia Bianca Formation.

During the late Aptian "cold snap" surface water were oligotrophic and stratified while bottom waters were oxygenated although subject to cyclic redox shifts evidenced by the deposition of reddish and greenish marlstones and marly limestones. The Aptian cooling was followed by significant warming across the Aptian-Albian boundary characterized by a dissolution phase and the onset of seafloor deoxygenation cycles that persisted throughout most of the Albian. The early–middle Albian was characterized by intensified weathering and nutrient supply supporting meso–eutrophic conditions and favoring black shale deposition under stratified surface waters. A major shift occurred in the late Albian, with the onset of stable arid conditions that reduced runoff and chemical weathering associated to oligotrophic surface waters and a stable thermocline that persisted until the onset of Oceanic Anoxic Event 2 in the latest Cenomanian.

Geochemical data confirm a shift from an unstable palaeoclimatic/palaeoceanographic mode in the Aptian-Albian to stable circulation in the late Albian-Cenomanian. The Western Tethys recorded large-scale climatic-oceanic changes, but its peculiar palaeogeographic position also allowed recording regional variations in weathering/runoff, productivity, and redox conditions at the seafloor.

The Oceanic Anoxic Event 2 (OAE 2; ~94 Ma) was driven by volcanic activity, triggering global warming and ocean chemistry changes. Here, we focus on Eprolithus floralis size to improve our understanding of OAE 2’s impact on nannoplankton. Unlike previously studied coccolith taxa (Biscutum constans, Discorhabdus ignotus, Zeugrhabdotus erectus, Watznaueria barnesiae) linked to fertility changes, E. floralis is a heavily calcified nannolith associated with cooler waters. We measured total and inner diameters, and the diaphragm, on Eastbourne (UK), Clot Chevalier (France), and Novara di Sicilia (Italy) for morphometry.

Results show that E. floralis experienced size variations across OAE 2, with consistent patterns at all sites: total and inner diameters started to decrease just before the event, reaching minima values around peak B, followed by recovery. In contrast, diaphragm size increased during OAE 2 and decreased afterward. Two E. floralis morphotypes were identified: spiky and rounded. The rounded, on average smaller than the spiky one, dominates during OAE 2 (>80%), and strongly influencing average size. The main size trends of E. floralis partly mirror those of other coccoliths, with all species showing reduced sizes during OAE 2 and minima around peak B. Size reduction and subsequent recovery align with volcanism onset and end, with no clear link to temperature. This suggests E. floralis and other small coccoliths adopted similar strategies to cope with elevated CO₂ and/or toxic metals, and rounded morphotype may have been better adapted to these conditions.

Acknowledgements: Projects: CNPq/402804/2022-8, EU PRIN Missione-4/Componente-1 2022WEZR44, and Dipartimenti di Eccellenza-2023–27.

The ultimate cause of the end-Cretaceous mass extinction remains debated. While multiple environmental disturbances are recognized, their cumulative effects on environmental instability and species turnover remain unclear. Here, we reconstruct a quantitative record of global environmental variability (EV) across the Cretaceous-Paleogene transition by compiling multi-proxy paleoclimate data, including records of temperature, oxygen isotopes, carbon isotopes, atmospheric pCO₂, and chemical weathering from 31 globally distributed sites, spanning 69-63 Ma. Our analysis reveals a significant increase in EV starting at 66.9 Ma, followed by two distinct phases of escalation. The second phase, coinciding with the onset of Deccan Traps volcanism, peaks around 60 kyr before the Cretaceous-Paleogene boundary, aligning with the maximum eruption rate. By integrating these EV trends with global elasmobranchs and bivalve fossil records, we find a significant positive correlation between species extinction rates and EV. We conclude that the rapid escalation of environmental instability, primarily driven by Deccan volcanism, played a critical role in exacerbating the end-Cretaceous extinction.

An integrated study was developed to characterize the spatial patterns of facies distribution in Maastrichtian age Garzan Formation which is one of the most prolific reservoirs in the southeast of Turkey. The sedimentary architecture of depositional environment and the diagenetic history of this carbonate succession were built by the use of sedimentological analysis of well cuttings and cores, well logs, and three-dimensional seismic data in oilfields A, B, C, and D. A total of twenty wells were examined in detail to construct a 3D carbonate depositional model. The vertical and horizontal facies changes in shallow marine carbonate deposits of the Garzan Formation suggested that the rudist-dominated carbonate successions were built-up in distally-steepened carbonate ramp. The heterogeneity of the Garzan carbonate rocks is greatly influenced by diagenesis which overprints the sedimentary facies and impacts the reservoir properties. The main diagenetic properties defined in petrographic analysis are micritization, neomorphism, dissolution, cementation, compaction, and partial dolomitization. Seismic attribute maps allow estimating different geological properties of the subsurface and determining the stratigraphic heterogeneity. Spectral decomposition is a functional seismic interpretation method providing seismic facies map with distinctive colors. This study provides the correlation of the sedimentological facies to the seismic facies. Another aspect of this study is to reveal the possible mechanisms responsible for the formation of the channels identified on top of the Garzan Formation on the spectral decomposition map. Integration of the seismic data interpretation and sedimentological analysis suggested that these were the tidal channels influenced by bottom currents.

Early concepts of inversion tectonics relied on a model of half-graben bounded by deeply rooted listric fault that is subsequently reactivated as reverse fault, and as a result half-graben infill is uplifted and eroded. However, this model explains inversion of relatively small depocenters associated with uplift of relatively small crustal blocks, and it doesn’t include syn-inversion flexural subsidence of basin’s flanks, important during inversion of large sedimentary basins and uplift of large crustal block. Flexure of flanks of inverted basin implies specific thickness and facies distribution of syn-inversion strata, similar to foreland basin depositional system, with regional thickening of inversion-related succession towards the inversion axis, and presence of coarse-grained deposits in vicinity of basement blocks uplifted during inversion. The Late Cretaceous evolution of the Polish Basin provides excellent example of such flexural inverted basin. Its most subsiding axial part, the Mid-Polish Trough, was in Late Cretaceous transferred into the Mid-Polish Anticlinorium – major anticlinal structure that extends for approximately 1000 km from SW Baltic Sea towards the SE Poland and W Ukraine. Due to the large size of this structure, loading along the flanks of inverted basin axial part led to a regional flexure of its footwall. As a result, Upper Cretaceous syn-inversion succession is characterized by regional thickening towards the Mid-Polish Anticlinorium. Seismic data imaged Upper Cretaceous progradational wedges, localized thickness reductions, local unconformities and contourites that developed along the edges of crustal blocks uplifted during inversion.

This study was supported by NCN grants 2017/27/B/ST10/02316 and 2018/29/B/ST10/02947.

The study area lies in the central part of the Carpathian Foreland in southern Poland. The interval encompasses mixed carbonate-clastic facies of the Upper Cretaceous and the topmost part of the Lower Cretaceous –Upper Jurassic complex. The motivation for the research was to reconstruct the spatial orientation of faults concerning the major tectonic processes that took place in the area and to find the temporal and spatial relation with the sedimentation process. For this purpose, the novel interpretation tools of the colour-processing technique were applied for processing 3D seismic data. The idea behind the technique is to transfer the data into a new coordinate system that respects individual colour saturation. This result enables a new level of detail for structural interpretation, highlighting lineations within the seismic cube. Further validation of the proposed structural model was compared with the results of paleoenvironmental analysis, which is the result of the chronostratigraphic image and Wheeler diagram analysis. The techniques applied to the high resolution seismic data enabled better insight into the paleoenvironmental studies of the Late Cretaceous sedimentary basin in the research area. The resulting paleoenvironmental model is built based on seismic sequence stratigraphy, seismic attribute analysis and tectonostratigraphic analysis. The methodology allowed validation and modification of the previous tectonic model and allowed tracing of faults that continue into the Cenozoic formations. The work is founded by National Science Center Recognition of the depositional architecture of the Upper Cretaceous sedimentary basin in the central part of the Carpathian Foreland, 2021/43/D/ST10/02728.

Northern Central Europe is a key area for the Late Cretaceous intraplate deformation that is characterized by a tectonic inversion phase with the transformation of former extensional features into contractional structures. This inversion was distinct along the northern and southern margin of the Central European Basin System e.g., at WNW-ESE striking structures like the Sorgenfrei-Tornquist Zone, the northern Harz boundary fault and the Osning thrust. It is remarkable that so far, the best evidence for neotectonic activity in northern Central Europe and Denmark comes from these areas. It has also been shown that historic earthquakes, which were observed over the last 1200 years cluster at Late Cretaceous reverse faults like the Osning thrust, the Halle fault, the Haldensleben fault or the Gardelegen fault. These structures have in common that they penetrate large parts of the crust, partly down to the Moho. Therefore, they represent stress-sensitive, first-order lithospheric features, where past, present, and potentially future seismic events are manifested. Repeated reactivation of these structures might have caused large-scale fatigue processes that have weakened the faults and made them prone to stress release and neotectonic movements and enhance the potential for a reactivation due to glacial isostatic adjustment (GIA) related stress field changes. This has implications for the seismic hazard assessment of northern Central Europe.

The clumped isotope (Δ₄₇) composition of the fossil calcite and aragonite provides direct information about past seawater temperatures. Its greatest benefits include the independence of the Δ₄₇ thermometry from the oxygen isotope composition of the seawater. A limitation of this proxy is its susceptibility to diagenesis and solid-state reordering caused by the elevated temperatures during sediment burial, altering the original Δ₄₇ signal. Laboratory heating experiments show different Δ₄₇ resetting kinetics for various carbonate components, which are necessary to evaluate in order to choose optimal carbonate archives for paleoclimate reconstructions.

We present clumped and stable isotope data from Cenomanian-Campanian rudists, extinct bivalves widely used for Late Jurassic-Cretaceous paleoclimate studies. The fossils come from regions with different burial temperature histories, the Friuli-Venezia Giulia region (FVG; Italy) and Istria (Croatia). Although the rudist δ¹⁸O values from both regions are not significantly different, the Δ₄₇ temperatures in FVG reach as much as 71-101 °C, suggesting Δ₄₇ signal resetting, while Δ₄₇ temperatures in Istria specimens are much lower. We evaluate the clumped isotope resetting of rudist fossils using two models, which, however, do not conclusively reveal what reordering kinetics pattern rudists follow. This merits caution when using rudist calcite as an archive for past temperatures. The well-preserved Δ₄₇ composition of Istrian rudists indicates temperatures of 34-41 °C, aligning with the higher end of Late Cretaceous paleotemperature reconstructions. Combining Δ₄₇ and δ¹⁸O results yields δ¹⁸O_seawater values of -0.1 to 1.4 ‰, differing from the value of -1 ‰ assumed for ice-free Late Cretaceous oceans.

In this study the stable and clumped isotopes of belemnites are presented from the Albian and Campanian - Maastrichtian interval derived from the chalks of Norfolk, UK. These chalk sediments were deposited on the North Atlantic shelf, part of an extensive relatively shallow epicontinental sea that covered most of northern Europe and beyond. Cathodoluminescence and elemental geochemistry of the belemnites reveals that most of the rostra were well preserved. If interpreted in terms of temperature (using an assumption regarding the δ¹⁸O of seawater), our oxygen isotope record reveals relatively warm temperatures for the Albian, warm temperatures during the Campanian with maximum mean temperatures of ~24 °C, followed by cooling to ~21 °C during Maastrichtian. Clumped isotope palaeothermometry is a method that provides a temperature constraint that is independent of the isotopic composition of the water in which the carbonate formed. Our clumped data also show relatively warm temperatures for the Albian and Campanian - Maastrichtian cooling (from 26 to 20 °C). These clumped isotope data compare favourably with published TEX₈₆ temperatures. Significantly, our data are similar or higher than modelled temperatures, modelled with relatively high CO₂ concentrations.

A large part of the African continent has experienced a significant uplift throughout the Late Cretaceous. This event coincides with a decline of CO2 level, and a global climate cooling. Evidences of this uplift include quantification of sediment volumes in oceanic basins, thermochronological dating, and inland geomorphological observations. In addition, new geochemical data from sediment cores, including clay mineralogy and combined Hf and Nd isotopic composition for which data acquisition is still ongoing, indicates a contrasted and asynchronous response of continental weathering systems to this uplift.
Here we used the modelling framework GEOCLIM to simulate the response of continental weathering and global geochemical cycles to the Cretaceous African uplift. We developed an uplift scenario based on marine sedimentary data around the African continent, and reconstruction of paleo elevation and lithology. This scenario is used as input by GEOCLIM, that computes weathering fluxes (including silicates, petrogenic organic carbon and phosphorus), and the evolution of global carbon cycle (both organic and inorganic part). This framework allows us to quantify pCO2 drawdown and the associated global cooling that may have resulted from this tectonic event.

The Western Interior Seaway (WIS) was a vast epicontinental sea that inundated North America in a series of transgressive-regressive marine cycles from the Early to Late Cretaceous. The WIS has been studied as a classic shallow Cretaceous seaway with a complex stratigraphic record of the interplay between tectonics, climate, sea level, basin evolution, and faunal evolution. However, fundamental questions remain unresolved regarding the WIS, including how seawater temperatures and oxygen isotope compositions (δ¹⁸O_w) varied latitudinally and through time. A robust record of latitudinal temperature gradients (LTGs) could help explain paleoceanography and faunal evolution in the WIS. Previous WIS paleotemperature reconstructions have yielded improbably warm temperatures from poorly constrained δ¹⁸O_w values or focused on specific time intervals or regions. Here, we report carbonate clumped isotopes (𝚫₄₇) measurements from 94 Cretaceous oysters obtained from the Smithsonian’s Cobban collection and the University of Michigan Museum of Paleontology to obtain LTGs from the Aptian to Maastrichtian Stages. This study approximately triples the 𝚫₄₇-derived WIS temperatures and δ¹⁸O_w values published to date. Our measurements yield average seawater temperatures ranging from 23-31 °C and indicate LTGs were minimal from the Aptian to Campanian and increased in the Maastrichtian. Values of Cretaceous δ¹⁸O_w, traditionally assumed to be -1.0‰ Standard Mean Ocean Water (SMOW), varied between -1.0‰ and +0.4‰ SMOW through time. We interpret changes in mean temperatures and LTG as responses to global climate drivers and regional influences, offering insights on basin evolution resulting from sea level fluctuations, tectonics, and paleoceanographic circulation patterns in the WIS.

Past seawater osmium isotopic record (¹⁸⁷Os/¹⁸⁸Os) is a useful chemostratigraphic tool. The Os isotopic composition of seawater reflects the balance between radiogenic Os from continental sources and less radiogenic Os from the mantle and extraterrestrial materials. Because the residence time of Os in seawater (~10⁴ years) is longer than the typical ocean circulation timescale (~10³ years), its isotopic composition is relatively homogeneous throughout the ocean. Osmium isotope ratios in seawater have varied over geological time, and these signatures are preserved in sediments. Therefore, the past-seawater Os isotopic variations recorded in the sedimentary rocks are useful for the stratigraphic correlations.

Although Cenozoic seawater Os isotopic records have been compiled over the past 30 years, Cretaceous Os isotopic data have been limited to the major oceanic anoxic events (e.g., OAE1a and OAE2) and the Cretaceous–Paleogene boundary, which is insufficient to establish a complete Os isotope stratigraphy during the Cretaceous. However, in recent years, an increasing number of Os isotopic datasets have been assembled, enabling the development of reference curves for the entire Cretaceous. In this presentation, I integrate previously published Os isotopic data with newly obtained data to provide an updated Os isotopic stratigraphy for the Cretaceous. Furthermore, I explain key Os isotopic variations and their possible causes.

The Valanginian is characterized by a period during the Cretaceous when the earliest carbon cycle perturbation event (the Weissert Event) as well as the earliest on-land LIP emplacement took place. In recent years, the GSSPs for the Valanginian and Hauterivian stages have been ratified, and stratigraphic and palaeoenvironmental studies of the Valanginian are becoming more active. On the other hand, there is little paleoceanographic information on the Valanginian Panthalassa, the largest ocean at the time. In Northeast Japan, Berriasian-Hauterivian marine sequences, accumulated in the northwest of the Panthalassa on the northeastern margin of Eurasia, are exposed sporadically. These sequences have not been chronologically well constrained in detail due to a scarcity of age-diagnostic fossils. We have attempted detailed international stratigraphic correlation based on zircon U-Pb ages of tuff as well as carbon isotopic stratigraphy for the Berriasian-Hauterivian sequences (Karakuwa, Oshima and Somanakamura groups) exposed in Northeast Japan. As a result, the Berriasian/Valanginian boundary and the Weissert Event were successfully identified. In addition, an approximate stratigraphic level for the Valanginian/Hauterivian boundary was recognized, although it was not conclusive. On the basis of TOC and DOP analyses for the studied sequences, the Weissert Event was dominated by an oxic environment in NW Panthalassa, while transient dysoxia occurred sporadically.

The Upper Cretaceous Kuji Group (300-400 m thick) distributed along the Pacific coast of north Tohoku region, Northeast Japan are examined through sedimentary facies and sequence stratigraphic analyses, and U-Pb age dating of detrital zircon from intercalated tuff layers. Identified twenty-six sedimentary facies and seven sedimentary facies associations show that the group is composed of terrestrial to shallow-marine sandstone-dominated siliciclastic deposits. The Tamagawa (1), Kunitan (2), and Sawayama (3) formations in ascending order are represented by talus, flood plain, gravelly river, sandy meandering river, and inner bay-estuary (1), shoreface to inner shelf (2), and meandering river (3) depositional systems, respectively. Their stratigraphical and geographical distributions indicate five depositional sequences with ten forth-order sequences, reflecting five third-order relative sea-level changes with some local tectonic influence along the north-south trending western margin of the Yezo forearc basin. The U-Pb age data including those of a previous research range 92.6 to 79.1 Ma, showing the middle Turonian to middle Campanian age. Our results provide valuable information on paleo- and sedimentary environments for reconstructing Late Cretaceous biota including terrestrial and marine vertebrates such as dinosaur and shark, etc., benthic molluscs, and sporophyte, gymnosperm, and angiosperm fossils.

Understanding the climate variability and stability during past ‘hothouse’ periods is essential for predicting future climate under ongoing global warming. However, information on millennial-scale (and shorter) climate variability during such periods is extremely limited due to the lack of appropriate high-resolution, deep-time archives. We have been conducting research to elucidate decadal- to orbital-scale continental climate variability from a Lower Aptian lacustrine varve record located in southeastern Mongolia (Hasegawa et al., 2022). The material used in this study is the CSH02 research core, which we consider now to cover the OAE1a interval based on new analyses.

We performed ultra-high-resolution elemental composition analysis (6-yr resolution) using an XRF core scanner (Itrax), mineral composition analysis of 1282 samples, carbonate δ¹⁸O and δ¹³C analysis of 822 samples, and organic matter δ¹³C measurements combined with palynofacies analysis of ~200 samples. The results indicate a decrease in the K/Al ratio, an increase in kaolinite, a shift in carbonate δ¹⁸O and δ¹³C towards more negative values, and a gradual increase in pollen and plant fragments near the stratigraphic level presumed to mark the onset of OAE1a, suggesting increased humidity and enhanced chemical weathering.

Furthermore, the Ca/Ti ratio (evaporation/precipitation proxy) shows that, during a 20 kyr-lasting interval prior to the estimated onset of OAE1a, centennial-scale variations were predominant, whereas during the 20 kyr following the onset of OAE1a, pronounced millennial-scale (~1,000–2,000 years) variations are observed. Our findings suggest that the state dependence of the millennial-scale climate instability also existed at the transitional phase toward the “hothouse” climate state.

The Early Cretaceous Jehol Biota that is best known for producing exceptionally complete fossils such as birds, dinosaurs, pterosaurs, mammals, insects, and flowering plants, is preserved in lacustrine deposits interbedded with volcanic ashes. The fossil-bearing beds are from bottom up referred to the Huajiying, Yixian and Jiufotang formations respectively, in rift basins in northern Hebei, western Liaoning provinces in northeastern China. Geochronologic studies have not only constrained the ages of the fossil-bearing beds but also revealed a diachronous distribution pattern of the rift basins, i.e., they progressively migrated eastward. The diachronous development of the rift basins led to the lateral variations of stratigraphic sequences and depositional environments, which in turn influenced the spatiotemporal evolution of the Jehol Biota, i.e., the first stage of the Jehol Biota is restricted to northern Hebei Province and represented by the appearance of basal member of numerous vertebrate lineages, and the second and third stages of the Jehol Biota began in western Liaoning Province and then expanded to a wider area and are represented by a greater vertebrate species diversity. The diachronous development of the rift basins in the Early Cretaceous of northeastern China is controlled by the eastward retreat of the subducting paleo-Pacific plate along the northern margin of the North China Craton and accompanied by other local tectonic and volcanic activities.

The Mesozoic non-marine formations traditionally known as the so called ‘Grès Supérieurs’ cover vast areas in SW Cambodia. Although macroflora and palynomorphs were reported from the Kampot-Bokor area in the 1970s, other fossils are scanty. A fibula of a titanisauriform dinosaur, reminiscent of Euhelopodidae has recently been described from Koh Paur Island, Koh Kong Province, suggesting an Early Cretaceous age for the fossil-bearing deposits. Subsequent field surveys led to discovery of new fossil sites, with remains of plants, invertebrates and vertebrates.

Turtle shell fragments have been collected from Koh Moul Island in Koh Kong Province, along with abundant fossil wood. The outer surface of the shell is covered with ornamentation, consisting of vermiculated ridges and bulges. The carapace length is estimated at about 80 cm. The morphology of the wide diamond-shaped entoplastron is reminiscent of large basal trionychoid turtles known from the Khorat Goup in NE Thailand, such as Basilochelys macrobios from the Phu Kradung Formation.

Large basal trionychoid turtles are known from the top pf the Phu Kradung Formation and the Sao Khua Formation, as well as equivalent strata in eastern Thailand. They were also reported from Kut Island, Thailand, some 50 km NW of Koh Moul. The discovery of large basal trionychoids in SW Cambodia suggests that the fossil bearing deposits of Koh Moul are Early Cretaceous in age.

Characterizing paleoenvironments provides input for geological modeling of the Lower Cretaceous from the Santos Basin, thereby reducing the risks and uncertainties with exploration and production processes. Reconstructing and visualising the spatial distribution of paleoenvironments during the Buracica-Alagoas ages contributes to the understanding of the sedimentary and stratigraphic evolution of the basin. In this scenario, the ecological preferences of non-marine ostracods were used to reconstruct the Lower Cretaceous Pre-Salt paleoenvironments of the basin. This reconstruction was based on interpretations of ostracod abundance and diversity values. Three paleoenvironmental lacustrine conditions were recognized: (i) Deep Zone (anoxic conditions); (ii) Open Water Zone (Intermediate Lake); (iii) Littoral Zone (poor preservation in high energy areas). The ostracod rates made it possible to observe conditions in the Deep and Open Water Zones during the Buracica and early Jiquiá ages. In the upper portion of the Jiquiá, there was a high frequency of alternation between lake conditions. During the Alagoas age, the Littoral Zone predominated. In addition to the previous study, analysis of ratios, grades of minor elements and trace elements, as well as the calculation of rare earth element anomalies, was. The enrichment of certain minor elements and traces may reflect variations in the depositional environment's oxidation state and solubility. In the intermediate to upper Alagoas, thick intervals with positive Eu anomalies indicated the influence of mafic magmatism or reworking of mafic rocks to the basin.

The Songliao Basin is one of the largest non-marine oil and gas bearing basins that developed during the Cretaceous period, recording an almost complete Cretaceous stratigraphy. Fossils are very abundant in the Songliao Basin, and three biotas, including the Jehol Biota sensu lato, the Songhuajiang Biota and the Mingshui Biota are recognized in the Songliao Basin. Of which the Songhuajiang Biota is the most typical and unique, serving as a window to understanding the Late Cretaceous terrestrial ecosystem. The Quantou to Nenjiang Formations yielded extremely abundant fossils,including: ostracoda, conchostraca, bivalvia, gastropoda, insecta, testudines, grocodylomorpha, dinosauria, palynofossils, dinoflagellates, charophyta, which are rich in quantity, diverse in types, and well-preserved in these strata, especially in the lower Qingshankou Formation and Nenjiang Formation. These fossil assemblages are named the Songhuajiang Biota. Here, we define and introduce the Songhuajiang Biota in terms of its definition, biological composition, and ecological significance. The Songhuajiang Biota, is defined by three typical elements: The ostracod Cypridea, the fish Sungarichthys, and the clam shrimp Eoestheria. The Songhuajiang Biota is the typical and unique terrestrial biota of the mid-late Cretaceous. As a typical and unique terrestrial biota of the mid-late Cretaceous, the Songhuajiang Biota is a key to decoding the Cretaceous terrestrial ecosystem.

Ostracod assemblages comprising over 30 species and a charophyte gyrogonite assemblage—including Platychara cf. sahnii, Nemegtichara grambastii, and Microchara sp.—have been identified from the Lameta Formation at Bara Simla Hill and Chui Hill near Jabalpur. These fossil-rich beds, underlying the Deccan basalts, are interpreted as pedogenically modified alluvial plain deposits laid down in semi-arid conditions. They are notable for abundant dinosaur bones and nesting sites containing three eggshell oospecies (Megaloolithus cylindricus, M. jabalpurensis, and Fusioolithus baghensis), indicating a Late Cretaceous (Maastrichtian) age. The ostracods are mostly endemic, while Microchara and Nemegtichara are also restricted to the Indian subcontinent. Biogeographically, the assemblage aligns with other infratrappean and intertrappean deposits across India. The co-occurrence of dinosaur remains, ostracods, and charophytes suggests lacustrine to palustrine conditions, with alkaline, shallow freshwater environments. Charophytes confirm the non-marine nature of the sediments and support age estimates, with Platychara and Nemegtichara known from Upper Cretaceous to Lower Palaeocene strata elsewhere. A Maastrichtian age is further corroborated by the presence of freshwater fish (Rhombodus, Apateodus, Stephanodus), endemic ostracods (Candona, Cyclocypris, Cypridea (Pseudocypridina), Cypridopsis, Cyprois, Limnocythere, Mongolocypris, Paracandona, Paracypretta, Stenocypris, Zonocypris and Wolburgiopsis sp.), and Aquilapollenites in the pollen record. Stratigraphically, the Lameta beds at Chui Hill show reversed magnetic polarity (Chron C29R), overlain by normally magnetized basalts, then a thick reversed lava pile, matching the Cretaceous–Paleogene boundary sequence. The Lameta Formation’s faunal and floral evidence, along with geochronology and magnetostratigraphy of the Deccan basalts (65.6 ± 0.3 Ma), firmly places these deposits in the latest Maastrichtian.

Inoceramid material from the Lachman Crags Member of the basal Santa Marta Formation (James Ross Island) was collected during the Czech Antarctic scientific expeditions in years 2009-2013. Fieldworks were conducted c. 2500 m SSW of the Czech Antarctic Station on the NW slopes of Lachman Crags, northern James Ross Island. The succession was sampled and analysed for calcareous nannofossils and foraminifers.

The inoceramids are dominated by the ‘Inoceramus’ steinmanni – ‘Inoceramus’ pacificus group, accompanied by juveniles of ?‘Inoceramus’ australis, rare ‘Inoceramus’ aff. andinus, and single Platyceramus sp. and ‘Inoceramus’ sp. A specimen assignable to the Cordiceramus mitraikyensis group constrains the assemblage to the upper Santonian–basalmost Campanian.

Calcareous nannofossils from the A90 section were poorly preserved, etched and mostly fragmented with the exception of small specimens of genera Biscutum, Prediscosphaera, and Discorhabdus. They indicate an interval from the first occurrence of Broinsonia parca expansa (UC9c zone) to the last occurrence of Eiffellithus eximius (UC15 Zone) that spans from the uppermost Turonian to the Campanian.

Microfossil taphocoenoses contain a low-diversity, low-abundance benthic foraminiferal community. Agglutinated foraminifera are represented by Haplophragmoides spp. and Spiroplectammina vagaensis, while calcareous benthics include Gavelinella sandidgei, Planularia sp., Pyrulina sp., Hemirobulina sp., and Quadrimorphina sp.

The presence of ‘Inoceramus’ neocaledonicus in the underlying Hidden Lake Formation—apparently equivalent of the late Coniacian ‘Inoceramus’ africanus of Madagascar—suggests a stratigraphic gap at the base of the Santa Marta Formation.

The inoceramid assemblage reflects the Weddellian Biogeographic Province, but with distinct connections to the East African bioprovince.

The revised edition of "Fossilien aus dem Campan von Hannover" (Schneider & Girod, 2023) provided a comprehensive overview, but revealed numerous undescribed gastropods. Consequently, this gastropod revision project has begun.

Key challenges included unreliable old literature, drawings, stratigraphy, and incomplete knowledge of references. We also addressed type species, new sampling, and collection access (including private ones). Our collection-based research analyzed ~8,000 specimens (32,000 photos) necessitating multiple publications.

Beyond Campanian gastropods, our investigation included Maastrichtian and Santonian species to gain evolutionary insights, leading to the development of higher taxonomic hypotheses. Pterocerellidae and Xenophoridae serve as illustration of our findings:

Gene sequencing has revealed a close relationship between the Xenophoridae and Aporrhaidae, despite their markedly different morphologies (Irwin et al., 2024). Our discovery of new Acanthoxenophora species exhibiting long spines on the last whorl echoes a pattern observed in the Jurassic genus Diempterus and the Lower Cretaceous "Murex calcar". This shared characteristic suggests a novel hypothesis regarding their evolution.

The Pterocerellidae, a group of aporrhaid-like species with a widespread Cretaceous distribution, are represented by six distinct lineages in the boreal European fauna. Our analysis has led to a more consistent taxonomy of this group.

References

Irwin, A. R., Bouchet, P., Crame, J. A., Harper, E. M., Kronenberg, G. C., Strong, E. E., & Williams, S. T. (2024). Molecular phylogenetics of the superfamily Stromboidea (Caenogastropoda): New insights from increased taxon sampling. Zoologica Scripta, 53(6):818-838.

Schneider, C. & Girod, P. (eds) 2023. Fossilien aus dem Campan von Hannover, 4. Auflage; Hannover: AP-H; pp. 712.

Finn Surlyk and Anne M. Sørensen

Department of Geosciences and Natural Resource Management

University of Copenhagen

Øster Voldgade 10

1350 Copenhagen K

Denmark

Well-exposed rocky shores and their associated faunas are rare in the geological record. A prominent example is Ivö Klack in southern Sweden a small Campanian island at the northern margin of the Late Cretaceous Chalk Sea. The fauna is the richest ancient rocky shore fauna known, with about 260 shell-bearing invertebrate species and about 70 vertebrate species, including 3 birds inhabiting the shoreline and the adjacent waters. The preserved fauna provides information on virtually all trophic levels in the ecosystem and offers an unparalleled opportunity for reconstruction of the ecosystem. Six trophic levels are recognized based on modes of life, feeding strategies, diets, and preferred habitats of the individual species. The ecosystem matches modern analogues in terms of richness. This is quite remarkable for a fauna, which lived about 77.5 myr ago. However, this to some extent reflects that the richness of the fauna is time averaged over about 500 kyr, but stratigraphic changes in faunal composition have not been observed. The reconstructed ecosystem thus gives a unique picture of the life on and around an ancient rocky shore.

A total of 158 terminal Maastrichtian deep-sea sediment samples (IODP Exp. 342, Site U1403, palaeo-water depth 3,600 m) yielded 850 atelostomate (spatangoid, holasteroid) and cidaroid spine fragments, plus a spine type that cannot be assigned to any echinoid group. Hollow, non-verticillate spines with a large lumen and a thin cylinder show narrowly spaced, low septae, bearing irregularly distributed thorns. Ovate, elongated pores between the ridges perforate the cylinder. Comparably voluminous, hollow lumen, thin cylinders and thorned septae occur in the Diadematacea (Diadematoida, Micropygoida). Because most Diadematoida spines are verticillate, and thorn-bearing spines of Micropygoida have a meshwork-filled lumen, Diadematacea are no likely source. Hollow spines occur also in the Echinothuriacea (Pedinoida, Aspidodiadematoida, Echinothurioida), but Pedinoida spines are more solid and weakly serrated, while shafts of the Aspidodiadematoida are verticillate with a lumen subdivided into dissepiments. Of all spines seen so far, only some aboral spines of Echinothurioida (e.g., Asthenosoma: Echinothuriidae; Phormosoma: Phormosomatiidae, Kamptosoma: Kamptosomatidae) show remote similarities with our material by the occurrence of oval pores, septae bearing irregularly distributed thorns, a thin cyclinder and a wide lumen. However, neither occur hoof-like spine terminations (Echinothuriidae) nor irregularly curved septae (Kamptosomatidae), why both groups are no likely source. Data on Phormosomatidae are discussed during the symposium. No Upper Cretaceous record of this spine type exists from the neighbouring Site U1407 (ca. 1,600 m palaeo-water depth), nor exist post-Cretaceous records in general. The “beast from the deep” could, therefore, represent an extinct deep-sea echinothurioid lineage, not surviving the K/Pg boundary impact event.

This study presents detailed micropaleontological analyses of the Cenomanian Turonian shallow water carbonate system of the Ajlun Group in a regionally defined sequence stratigraphic framework. Two outcrop sections were studied with a total thickness of 700m representing proximal (Bustani) to distal (Mujib) settings. Over 300 thin sections and disaggregated analyses were produced and integrated with existing sedimentological, nannopaleontological, and isotopic data. The Early/Middle Cenomanian boundary interval is marked by the highest abundance and diversity of benthic foraminifera including index fauna, Praetaberina bingistani and Nummufallotia apula in the Bustani section and Praelaveolina tenuis and Meandropsina vidali in the Mujib section. Benthic foraminiferal diversity declines significantly at the K130 sequence boundary surface that corresponds to a sealevel drop positioned around this substage boundary. It marks the change from a rimmed carbonate platform to a shallow ramp dominated by oyster shells and small planktic foraminifera interbedded with faverina and ostracods. Larger benthic foraminifera reappear briefly in Late Cenomanian prior to Oceanic Anoxic event 2, marked by the abundance of dwarf heterohelicids and buliminids coinciding with a positive carbon isotope excursion.

Following OAE2, the Turonian interval shows a recovery of planktic foraminiferal diversity followed by carbonate platform settings but with large gastropods and rare small benthic foraminifera. The Middle/Late Turonian boundary is represented in a thin interval dominated by Cuneolina pavonia parva? in peloidal grainstone facies. In addition to the age dating contribution, this study illustrates how micropaleontological information can document subtle environmental changes that refine the sequence stratigraphic model.

Benthic foraminiferal records from the Cretaceous of the Austral southern high latitudes offer valuable insights into paleoenvironmental changes and biostratigraphic correlations across the Southern Hemisphere. We integrate data from IODP Sites U1512, U1513, U1514, and U1516, with selected deep sea drilling and regional records, to examine the significance of both calcareous and agglutinated benthic foraminifera for biostratigraphy and paleoenvironments. In this study, we contextualize benthic- and planktonic foraminiferal data and calcareous nannofossils to present a robust biostratigraphic framework.

In the Albian of Site U1513, the transition from shallow to deeper marine settings is reflected in a shift from agglutinated assemblages (e.g. Trochammina, Haplophragmoides) to calcareous forms, including Gavelinella intermedia and Osangularia schloenbachi. These assemblages correspond well with those from the Kerguelen Plateau, Great Artesian Basin, and parts of South America.

The Cenomanian–Turonian interval, including the Oceanic Anoxic Event 2, is marked by reduced diversity in calcareous benthic foraminifera and the relative increase of agglutinated taxa at the Sites U1512, U1513, and U1516, indicating periods of low-oxygen bottom water conditions, correlating with records from South Africa and Walvis Ridge.

Coniacian–Santonian strata at Site U1513 show stable bathyal conditions, dominated by Gavelinella berthelini and Notoplanulina rakauroana. These faunas support correlations with the Falkland Plateau and New Zealand. Overall, benthic foraminifera provide reliable biostratigraphic correlations throughout the Cretaceous of the southern high latitudes and add to our understanding of Southern Hemisphere paleoceanography during the Cretaceous.

The Cretaceous Period was marked by numerous episodes of transient environmental perturbation, several of which profoundly impacted global ecosystems. These events included one of the ‘Big Five’ Phanerozoic mass extinctions at the end of the Cretaceous, multiple intervals of globally widespread marine oxygen depletion (Oceanic Anoxic Events, or OAEs), and a range of other episodes of profound Earth surface change. A common factor that appears to have linked all of those times is that the environmental change was related to geologically rapid change(s) in climate. However, the nature and/or rate of climate change varied between events, and they remain debated in many cases.

This presentation gives an overview of new and published work pertaining to some of the outstanding questions and issues regarding how changes in global climate related to environmental (and/or ecosystem) degradation during the Cretaceous. A key focus is placed on events that occurred during the early–middle part of the period, and the extent and nature of their link with major volcanic activity. For example, how did carbon emissions vs basalt weathering impact global climate during the early Valanginian? Were the major Cretaceous OAEs driven by volcanic CO₂ emissions and warming, or volcanic nutrients intensifying primary productivity? And either way, what was the primary source? Establishing the nuances in how Earth’s climate changed during these intervals of environmental change is key to resolving the similarities and differences of those events, and understanding the interactions between different phenomena across the Earth system during the Cretaceous Period.

During the mid-Early Cretaceous, the Lower Saxony Basin expanded onto the Central German, Pompeckj and Altmark swells. At the turn of the Valanginian/Hauterivian, the Braunschweig embayment was formed in what is now SE Lower Saxony between the Harz Mountains in the south and the Flechtingen-Roßlau Thrust in the north-east, expanding into the Subhercynian Basin in the course of the subsequent Cretaceous transgressions. The deposits of the Hauterivian transgression were analysed in terms of stratigraphy, bio- and microfacies on the western and southern margins of the Elm, a halokinetic uplift structure east of Braunschweig, and its corresponding marginal depressions, the western Schandelah and the southern Schöppenstedt synclines. The strata reflect a coarse-grained bioclastic carbonate facies (Hilsconglomerate facies = Grenzlerburg Member of the Salzgitter Formation) while different degrees of subsurface salt migration and synsedimentary tectonics differentiated the depositional environments. On the shallow-water shelf of the Elm, patch reefs developed with highly diverse habitats, documented by fossils from around ten classes, representing a range from calcareous sponge and bryozoan reefs to oyster and brachiopod beds. In front of the western margin of this platform, mainly clays were deposited in the basins, intercalated by highly diverse allochthonous bioclastic rud- and floatstones. Despite their fragmentation, the microstructural preservation of the components is excellent due to rapid embedding in an argillaceous matrix. The biofacies with a dominance of bryozoans, brachiopods, echinoderms and oysters characterises the Hilsconglomerate facies as a temperate, moderately productive echino-bryomol carbonate factory, characterised by the absence of significant amounts of micrite (periplatform muds).

The early Albian succession in the Jebel Serdj-Bargou mega-anticline (Northern Atlas, Central Tunisia) is characterized by well-developed carbonate platforms, representing a significant component of the last carbonate unit (Cu5) stratigraphic interval of the Serdj Formation. This study investigates the paleoenvironmental evolution of these platforms, addressing a key knowledge gap in the southern Tethys.

Thirteen microfacies (MF1 to MF13) and seven facies associations (FA1–FA7) were identified, primarily based on fossil assemblages (corals, rudists, benthic foraminifera), texture, and fabric. These facies associations reflect a biogenic composition typical of an inner to outer ramp environment within a warm tropical climate.

The succession vertically evolves from an open marine basinal setting (T4) to moderate to high-energy shallow marine carbonates (Cu5), with high productivity evolving laterally from inner platform to marginal settings. Two distinct domains of high carbonate production are recognized: Jebel Bargou in the south and Jebel Cheirich in the north. In contrast, the Drija area, situated between these zones, is characterized by reduced carbonate production (50% lower) and reworked mixed facies suggesting an local intrashelf graben.

A well-developed coralline platform is observed in the northern Cheirich area, indicating favorable conditions for coral growth. This platform displays diverse biogenic components, including porcelaneous larger benthic foraminifera (alveolinids and soritids), which indicate euphotic, shallow marine conditions.

These findings enhance understanding of the early Albian carbonate platform dynamics in Central Tunisia, providing insights into facies distribution, carbonate production, and paleoenvironmental evolution, offering a valuable reference for similar Tethyan settings.

The Sergipe-Alagoas Basin, located in northeastern Brazil, is a key area for geological and paleontological research, as it hosts some of the most complete Cretaceous stratigraphic successions among Brazilian sedimentary basins. These successions record all tectono-sedimentary stages related to the initial opening of the South Atlantic Ocean during the Early Cretaceous, associated with the f Gondwana breakup. Within this context, the Riachuelo Formation stands out, representing a transitional restricted environment that grades into shallow to deep marine settings. Globally the Early Cretaceous was marked by the widespread development of carbonate platforms, with significant oceanic records. Microfacies analysis is a powerful tool for identifying such records, reconstructing depositional systems, and characterizing associated marine biota. Despite its importance, microfacies-based studies of the Riachuelo Formation remain limited. This study analyzes petrographic thin sections from three onshore cores (SER-01, SER-03, and SER-04) in the Sergipe-Alagoas Basin. The successions represent a mixed carbonate–siliciclastic shelf system, including quartz-bearing sandstones and packstones deposited in a transitional zone protected by carbonate banks. These evolve from sand-bar and shelf-margin facies (packstones, grainstones, and rudstones) to deeper outer shelf environments dominated by mudstones and wackestones. The fossil assemblage is predominantly composed of planktonic and benthic foraminifera, echinoderms, and mollusks, along with local occurrences of cadosinids, green and red algae, microcrinoids, inoceramids, and microbial fragments. As a result, six distinct microfacies were identified, indicating a transition from shallow, high-energy marine environments to deeper, as well as low-energy settings typical of the outer shelf. [Acknowledgements: CNPq project: 405679/2022-0]

The present study is focused on the upper Campanian–Maastrichtian sequence of the Bazov Dyal Formation in the Central Balkan Mts (Central Balkan Zone) that is outcropped in four sections (Mountaineers’ Memorial, Polenitsi South, Polenitsi and Starna Reka) and one locality (Polenitsi North). The succession is characterized by variable thickness and ranges from a few centimetres up to 12 m. The lower part is composed of light grey limestones, which rapidly grade upwards into grey sandy bioclastic limestones. Scattered coarse-sand to granule-sized grains of quartz and lithic frag­ments also occur and are locally abundant in separate beds.

Four microfacies types (MFT 1–4) have been distinguished and described: MFT 1 Echinoderm packstone/grainstone; MFT 2 Bioclastic grainstone with coralline red algae; MFT 3 Sandy bioclastic grainstone/rudstone; and MFT 4 Sandy bioclastic-intraclastic packestone/grainstone. The observed fossil association (mainly echinoderms, bryozoans, coralline red algae, brachiopods) indicate normal salinity and open-water circulation. Grain-supported limestone varieties (packstones, grainstones and rudstones) characterise agitated hydrodynamic conditions. Commonly presented well-rounded quartz and feldspar clastic grains, as well as lithic fragments with various sizes and composition (different volcanic, igneous, metamorphic and sedimentary rocks), suggest possible fluvial terrigenous supply.

Based on the obtained preliminary data, it can be assumed that the carbonate deposits of the Bazov Dyal Formation have been formed in a high-energy open-marine setting with locally important fluvial terrigenous supply.

Acknowledgements. The Bulgarian National Science Fund of the Ministry of Education and Sci­ence, Grant KP-06-N74/3, supported this study.

Stylolites, pressure-solution features common in carbonate rocks, significantly influence fluid flow and permeability in reservoir systems. However, the role of clay accumulations along stylolite seams remains poorly understood. This study investigates the relationship between stylolite morphology, associated clay mineralogy, and their influence on permeability and fluid circulation. We present preliminary results from the first study area in southern Italy (Apulia), based on scanning electron microscopy (SEM) combined with micro-XRD and micro-XRF analyses.

The data reveal systematic variations in clay mineral assemblages and their distribution along stylolites, suggesting a potential sealing effect and anisotropic control on fluid pathways, which may influence proto-karst development. Preliminary findings also indicate a correlation between the orientation of major cave systems (under investigation) and dominant stylolite families in the area. Additional SEM and micro-XRD analyses help refine the characterization of mineralogical textures and controls on fluid behavior.

Ongoing work aims to better quantify clay content and evaluate its spatial correlation with fluid migration, porosity evolution, and early-stage karstification. Future research will extend karst-related analysis to two additional areas in Slovenia and the Czech Republic to test the broader relevance of these observations.

The Cenomanian/Turonian Boundary was a period of extreme environmental conditions, marked by hyperthermic climate, high sea-levels, and the Oceanic Anoxic Event 2 (OAE2). During this period, huge portions of the continental margins of North Africa were flooded, with the emplacement of an epicontinental carbonate platform known as North Saharian Platform.

The Akrabou Formation in Southeastern Morocco provides an intriguing window into the dynamics of this shallow-marine carbonate system. This formation, up to 100 m thick, is dominated by low-energy, shallow-water facies with fine-grained wackestone/packstone rich in micrite and oligotypic assemblage of small benthic foraminifera, alternated to oyster-rich beds. A temporary shutdown of the benthic community and the deepening of the platform is testified by a fast and short transition to laminated lime-mudstones with planktonic foraminifera. After the return to shallow-water benthic-dominated facies, an increase in energy is observed before the emersion of the platform.

Stable isotope analysis (δ13C) shows a positive excursion of +3‰ VPDB, aligning with global OAE2 signatures. Interestingly, the platform's maximum deepening occurs with a delay relative to the OAE2 isotopic peak, suggesting a complex interplay between global and local factors in platform evolution.

Despite the stress induced by OAE2, evidenced by the temporary shift to deeper environments, the shallow benthic carbonate community demonstrated resilience, quickly re-establishing after the crisis. This study highlights the Akrabou Formation as a valuable archive of epicontinental carbonate platform dynamics during extreme environmental changes, offering insights into the interplay between global events and local responses in shallow-marine carbonate systems.

Understanding the mechanisms that control dolomite distribution within Cretaceous coastal sedimentary sequences remains limited. This study presents an integrated assessment of dolomite occurrence and potential dolomitization processes based on five stratigraphic sections from lithologically heterogeneous coastal successions in the southern sector of the Lusitanian Basin (Ericeira, Portugal). These sections encompass approximately 40 million years of sedimentary record, spanning from the late Valanginian to the late Barremian (São Lourenço to Regatão Formations) and from the early Albian to the early Cenomanian (Rodízio and Galé Formations).

Mineralogical and petrographic datasets were combined to characterize dolomite presence, associated mineralogical assemblages and infer the underlying dolomitization mechanisms. Mineralogical analysis was performed using X-ray diffraction (XRD), and due to the large dataset (N=276), statistical tools were applied to discern compositional trends. These findings were further validated through petrographic and elemental analyses (SEM-EDS), and detailed examination of dolomite crystal structure based on diagnostic XRD peaks.

Dolomite was detected in all studied sections, with its presence ranging from 12% to 68% of the total sampled stratigraphic horizons. Relative abundance estimation indicates that dolomite is the dominant mineral phase (>50%) in 25 samples, typically co-occurring with quartz and calcite. Stratigraphic distribution pattern analysis showed that dolomite-bearing horizons preferentially occur interbedded with siliciclastic levels of mixed mineralogy (quartz and calcite), suggesting a significant control exerted by porosity and/or permeability on dolomitization processes.

Here we present a tectonic and seismostratigraphic study of the Cretaceous succession from the archetypal East African transform continental margin. This region underwent significant tectonic reconfiguration during the break-up of Gondwana, which began in the Early Jurassic (~183–177 Ma). As a result, Madagascar separated from eastern Africa and drifted southeastward along the Davie Transform Zone (DFZ), reaching its present-day position in the Early Cretaceous (~120.8 Ma). Transform faulting along the studied segment of the East African continental margin was associated with volcanic activity. The post-drift phase was dominated by tectonic and depositional processes related to passive margin development. Cretaceous sedimentation above the oceanic crust was dominated by shales, sandstones, and carbonates.

High-resolution regional 2D reflection seismic data of the East AfricaSPAN™ survey acquired by ION Geophysical has been used to decipher depositional architecture of the Cretaceous succession. The data reveal both regional and local unconformities, numerous erosional incision, and stratigraphic pinch-outs. These seismic features have been interpreted as being related to: (1) syn-depositional volcanic activity, (2) Late Cretaceous uplift of the northern DFZ, (3) bottom currents flowing along bathymetric highs, and (4) terrigenous sediment input from the African mainland, including gravity-driven mass flows. We propose that the observed depositional architecture was likely influenced by pronounced Late Cretaceous exhumation of the eastern Africa hinterland recorded by thermochronological data.

This study was funded by NCN (2024/08/X/ST10/00218), the NAWA Bekker Programme (BPN/BEK/2024/1/00102) and Exxon Mobil. Seismic data was provided by ION Geophysical; academic access to IHS Markit Kingdom software was granted by S&P Global.

A 49-m-thick succession from a drill core of Early to early Late Aptian age from Garbsen, a small city 6 km northwest of Hannover, has been studied with respect to sedimentology, bulk organic geochemistry and biostratigraphy. During Early Cretaceous times the Hannover area represented paleogeographically the eastern-central part and, thus, the depocenter of the Lower Saxony Basin.

The basal 14 m cover a paper shale-mudstone sequence (topmost Hoheneggelsen Formation) with a 2.3-m-thick “Fischschiefer” bed at the top. It is overlain by partly reddish-colored hemipelagic marlstones representing lithostratigraphically the Sarstedt Member (= Hedbergella Marls). The “Fischschiefer” represents the local expression of the global Oceanic Anoxic Event 1a in northern Germany.

In addition to lithological data, we present high-resolution δ¹³C_org, CaCO₃ and TOC data as well as a calcareous nannofossil biostratigraphy for this succession. This new core complements other records in the western part of the basin (Alstätte, Bottini et al., 2012) as well as southeast of Hannover (Hoheneggelsen KB9, Heldt et al., 2012) and, due to its completeness, provides new insights in the transition from the “Fischschiefer” deposit to the hemipelagic marlstones.

References:

Bottini, C., Mutterlose, J., 2012. Integrated stratigraphy of Early Aptian black shales in the Boreal Realm: calcareous nannofossil and stable isotope evidence for global and regional processes. Newsl Stratigr 45, doi:10.1127/0078-0421/2012/0017.

Heldt, M., Mutterlose, J., Berner, U., Erbacher, J., 2012. First high-resolution δ13C-records across black shales of the Early Aptian Oceanic Anoxic Event 1a within the mid-latitudes of northwest Europe (Germany, Lower Saxony Basin). Newsl Stratigr 45, doi:10.1127/0078-0421/2012/0019.

During the Late Turonian, the Bohemian Cretaceous Basin was affected by increased rates of subsidence as well as long-term clastic supply rates, as the tectonic inversion of Central Europe intensified. At the same time, signs of both long- and short-term, transgressive-regressive cyclicity are present in nearshore through hemipelagic facies. The present study focuses on reconstructing the depositional system and stratigraphic geometries along a proximal-distal transect in west-central Bohemian Cretaceous Basin, with the aim to address the relative roles of subsidence, sea level, hydrodynamic conditions, and climate-driven supply variations in the depositional patterns. Detailed correlation of c. 100 outcrop and about 130 well-log/core sections made it possible to revise the existing sequence-stratigraphic scheme in the region and construct isopach maps of newly defined genetic sequence units. The results show migration of the principal depocentre through time, likely driven by along-strike changes in flexural subsidence reflecting varying thrusting activity along the marginal fault system. Superimposed on this process were relative sea-level changes of 400-kyr long-eccentricity timescale and shorter. Higher subsidence rates in the basin centre made it possible to preserve record of falling-stage to lowstand interval that is missing in shallower parts of the basin.

This research resulted from a Master’s Thesis by JB, supervised by DU and SČ.

The Kreibitz-Zittau area (northern margin of the Bohemian Massif, Czech-German border region) exposes a ~1000-m-thick Cenomanian–middle Coniacian succession of quartz arenites with high compositional but low textural maturity. Translucent heavy minerals are almost exclusively composed of zircon, tourmaline and rutile (Ø-ZTR maturity index of 91) with tourmaline predominating (average of 60 %). Zr-in-rutile temperatures document upper amphibolite-eclogite to granulite facies between 700–930°C. Cr/Nb discrimination of rutile and geochemistry of tourmaline indicate that >95 % of these grains originate from Al-rich and Fe-Mg-poor metapelites. U-Pb-ages of detrital rutile show a distinct peak at 320–330 Ma. If present, garnets of the almandine–pyrope series are dominant. The 95 % predominance of Variscan ages in all samples and the high/ultrahigh temperatures of metamorphism exclude the Neoproterozoic greywackes and granitoids of the Lusatian Massif and the granitoids of the Jizera–Krkonoše Massif in the northeast as sources. Potential proto source rocks were high-grade metamorphic rocks similar to those today exposed within the gneissic-migmatitic Góry Sowie Massif, ca. 120 km east of the depositional area. Since the late Devonian, this massif was uplifted, reaching the surface in late Carboniferous times. Consequently, the widespread Permo–Carboniferous Variscan molasse is the major sediment source for the Cretaceous sandstones, which thus were deposited during at least their 2^nd sedimentary cycle. The study shows that integrated approaches combining careful petrography, heavy mineral analyses, mineral-specific geochemistry and thermometry as well as U-Pb age dating with high-resolution stratigraphy are suited to solve complex deep-time provenance puzzles.

Taxonomic studies of foraminifera in thin sections have known limitations. Micro-Computed Tomography (Micro-CT) offers an alternative to study the internal and external structures of foraminifera but suffers from long acquisition time. We have, therefore, designed a vertical holder which stacks up to 15 foraminiferal specimens for each circular scan. Our goal is to create a reference library of accurate 3D foraminiferal models to highlight morphological differences and similarities between different genera and enhance taxonomic identification. We generated digital models of many Cretaceous specimens including Omphalocyclus macroporous, Fissoelphidium operculiferum, Chrysalidina hensoni, and Fallotia sp. and produced cross sections at a variety of orientations. The combined database of 3D models and cross sections will assist micropaleontologists in the study and identification of foraminifera in thin section and eliminate ambiguities.

Holographic projection can be an even more effective tool for morphological studies of foraminifera, so we developed a workflow to optimize foraminiferal models for holographic displays. This workflow not only enables the holographic visualization of 3D foraminifera but also the intuitive interaction and creation of real-time cross-sections at any orientation. Finally, we started the development of a classification tool using Artificial Intelligence to match thin section images to best-fit digital slices from our database of 3D foraminifera. These developments aim to help future specialists identify foraminifera, communicate good taxonomic practices and educate audiences about foraminiferal studies.

Despite forming a distinctive diverse and sometimes abundant element of the preserved fossil assemblages of mid-Cretaceous Neotethyan and central American carbonate platforms, there is no generally accepted and well-defined bioevent/biozonation scheme for larger benthic foraminifera (LBF), which limits their utility as biostratigraphic tools. To achieve this requires, in turn, a review of the identity of the taxa involved and a critical review of published reports of their stratigraphic ranges. We have reviewed the published occurrences of almost 200 taxa to establish their stratigraphic ranges. Once misidentifications are discounted, it is apparent that the inceptions and extinctions of some taxa (e.g., the alveolinids) provides a useful basis for recognising Cenomanian substages and occasionally events at higher resolution. Endemic forms and facies control on stratigraphic distribution means that the choice and timing of some key bioevents differs between regions within the Neotethyan – central American realm. Intriguingly, some taxa are truly long-ranging and survive the end-Cenomanian extinction event, sometimes reappearing after an apparent absence of several million years. The reasons for this remain unknown but may include survival in refugia or homeomorphy of forms well-adapted to specific environmental niches. In summary, we present a draft biozonation for Cenomanian LBF, calibrated where possible to other fossil groups and the carbon isotope chronostratigraphic proxy, thereby increasing the biostratigraphic utility of this important fossil group.

Modern nautiloids are fore-reef slope dwelling cephalopods with distinct morphological and phylogenetic characteristics. We examined their habitat and trophic ecology across the Pacific Ocean regions where they live, using stable isotope analyses (SIA) of tissue samples from multiple populations. Unlike many cephalopods, Nautilus species exhibit scavenging behavior rather than active predation, with δ¹⁵N and δ¹³C values reflecting their unique ecological niches. But of relevance to understanding Cretaceous cephalopods is our finding that nitrogen isotopic values from shell and tissue are identical, and not just for bulk δ¹⁵N and δ¹³C; we show that nitrogen isotopic values of individual amino acids are the same for shell and tissue. Using this tool we have analyzed shells of exquisitely preserved Cretaceous ammonites and nautiloids and obtained not only values for individuals, but values for those individuals through ontogeny. Coupled with the use of the new C_meta estimations of the amount of dietary carbon individual species used, a proxy for relative energetics, we present a comparative graph of planispiral vs heteromorphic ammonite trophic levels.

Fossiliferous Cenomanian strata are superbly exposed in the North Cantabrian Basin (NCB) of Cantabria (northern Spain), yielding rich and diverse Cenomanian ammonite faunas. However, a systematic revision of the faunas is still lacking. The NCB is a relatively small, E–W-elongated extensional basin (~50 x 100 km), developing as an independent structural unit on the rifted North Iberian margin as a result of Valanginian distensional movements. During the Cenomanian, the basin formed a gulf-like embayment in subtropical palaeo-latitudes of ca. 30°N, opening to the deeper marine Basque Basin/Navarro-Cantabrian Ramp in the east and shallowing into the peri-Asturian domain towards the west. The successions yielded diverse Cenomanian ammonite faunas consisting of almost 40 taxa, dominated by representatives of the subfamily Acanthoceratinae. Based on the ammonites, the early Cenomanian Mantelliceras-mantelli and M.-dixoni, the middle Cenomanian Cunningtoniceras-inerme, Acanthoceras-rhotomagense and A.-jukesbrownei, and the late Cenomanian Eucalycoceras-pentagonum and Metoicoceras-geslinianum zones have been identified. There is no record of the latest Cenomanian Neocardioceras juddii Zone. Palaeobiogeographically, the NCB belongs to the "Northern Transitional Subprovince", located between the Tethyan and Boreal realms. The Cenomanian ammonoid faunas of the NCB are entirely dominated by cosmopolitan taxa, associated by some Tethyan forms; true Boreal taxa are absent. The ammonoid faunas are relatively diverse and compare well to Cenomanian ammonite assemblages known from other European localities mediating between the Boreal and Tethyan realms (e.g., Cassis, Bouches-du-Rhône, southern France). The Cenomanian ammonite record of the NCB, thus, provides an important piece in the complex palaeobiogeographic jigsaw puzzle of mid-Cretaceous ammonite faunas.