Conference Agenda

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.

The Ra Stua sedimentary section, located in the southern Alps (northern Italy), mainly consists of fine-grained rocks formed in a slow sedimentation oceanic environment, favoring the formation of limestones and marls. This setting enables the investigation of magnetic and mineralogical variations associated with depositional processes influenced by Barremian-Aptian (Early Cretaceous) climatic changes, marked by shifts in the Earth's magnetic field, oceanic anoxia, and climatic transformations. This study aims to investigate the magnetic properties of the Ra Stua section to understand paleoenvironmental conditions and depositional processes, as well as to perform relative magnetostratigraphic dating to identify magnetozones. Rock magnetism analyses included magnetic susceptibility, hysteresis curves, isothermal remanent magnetization, FORC curves, thermomagnetic curves, and measurements of anhysteretic remanent magnetization and alternating field demagnetizations on over 100 samples collected along the section. Results indicate that magnetite is the primary magnetization carrier throughout the section. Increased magnetic susceptibility at specific depths suggests higher terrigenous input events under low-oxygen conditions, leading to black shale deposition, particularly in the Tethys region, Trento Basin. The environmental magnetism parameters reveal depositional changes throughout the depths, marked by alternating high-energy layers and calmer, oxidizing conditions, reflecting a dynamic paleoenvironment influenced by global climatic events during the Barremian-Aptian period. Magnetostratigraphic results suggest two possible chronostratigraphic scenarios: one indicating a Barremian age (124.5–126.51 Ma) with normal (M3n) and reverse (M3r) polarities, and another suggesting a Hauterivian age (126.5–127.92 Ma) linked to the Faraoni Oceanic Anoxic Event.

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 Katterfeld Formation, part of the Coyhaique Group (Austral Basin) in the Aysén Region of Chile, represents a marine deposit from the Valanginian–Hauterivian. Paleontological and biostratigraphic studies are key to understanding faunal events during the Early Cretaceous in Patagonia. This lithological unit, consists mainly of calcareous siltstones with calcareous concretions and subordinate sandstones.

The distribution of ammonites in the Aysén Basin, along with the regional stratigraphy, suggests a marine environment with anoxic conditions, which migth have favored the preservation of these fossils. The facies analysis indicates a transition from a shallow platform environment in Toqui Formation to deeper and lower-energy conditions in Katterfeld Formation.

Five different ammonite taxa are recorded in this unit, including: Favrella americana, Favrella wilckensi, Lyticoceras nodosplicatum?, Peltocrioceras deeckei? Cymatoceras perstriatum. These taxa show significant morphological variations, allowing inferences about their paleogeographic distribution and possible migratory routes within the southern Indo-Pacific realm.

Biostratigraphically, the ammonites of the Katterfeld Formation have enabled the establishment of a detailed biozonation. Specific Hauterivian biozones have been identified, with a predominance of Favrella americana in the middle levels and Favrella wilckensi in the upper levels, suggesting a faunal turnover. This reflects a considerable provincialism when compared with the standard biozones of the Tethys and Boreal realms.

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 Aptian–Albian interval was characterized by significant paleoclimatic changes, including volcanic events and monsoonal activity, though their precise timing remained poorly defined. This study introduces a ~20-million-year cyclostratigraphic framework and provides an extended astronomical timescale using magnetic susceptibility and anhysteretic remanent magnetization data from the Poggio le Guaine core (Umbria-Marche Basin, Italy). Through astronomical tuning, we establish new age constraints and timelines for: (i) the Aptian and Albian stages; (ii) the magnetic polarity Chron M0r; (iii) the Oceanic Anoxic Events; (iv) key bioevents; and (v) Cretaceous oceanic red beds. These findings improve our understanding of the interactions between paleoclimatic and biotic processes during the Early Cretaceous. This study sets a new chronostratigraphic framework for the Aptian–Albian, offering the most comprehensive resolution to date, integrating with other geochronological methods, and providing extensive temporal coverage. It delivers fresh insights into bio-chemical–geomagnetic interactions and refines the Geological Time Scale

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 Kopeh Dagh sedimentary basin, located in northeastern Iran, is primarily composed of Mesozoic and Cenozoic sedimentary successions. This study focuses on the foraminifera assemblages across the Cenomanian–Turonian interval within the Aitamir and Abderaz formations at the Maraveh Tappeh section, west of the Kopeh Dagh Basin.

The Aitamir Formation is subdivided into two members: the upper member consists of shale, silty shale and marl. The Abderaz Formation is characterized by thin- to thick-bedded limestone. The benthic and planktonic foraminifera were identified in the upper 35 meters of the Aitamir Formation and the lower 32 meters of the Abderaz Formation. Based on the foraminiferal content, two biozones are proposed:

Whiteinella archaeocretacea Interval Zone

Key foraminifera taxa include: Ammobaculites subcretaceus, Berthelina berthelini, Berthelina cenomanica, Dicarinella canaliculata, Gavelinella dakotensis, Gavelinella plumerae, Haplophragmoides concavus, Muricohedbergella delrioensis, Lingulogavelinella sp., Hoeglundina charlottae, Muricohedbergella planispira, Pyramidulina obscura, Saracenaria sp., Spiroplectammina rectangularis, Textulariopsis sp., Trochammina wetteri, Whiteinella aumalensis, and Whiteinella baltica. According to the literature and previous studies, this zone is indicative of a Late Cenomanian age.

Helvetoglobotruncana helvetica Interval Zone

The foraminiferal taxa include: Praeglobotruncana algeriana, Dicarinella hagni, Dicarinella primitiva, Helvetoglobotruncana helvetica, Helvetoglobotruncana praehelvetica, Marginotruncana marginata, Marginotruncana renzi, Marginotruncana cf. pseudolinneiana, Whiteinella baltica, Whiteinella aprica, Whiteinella archaeocretacea, and Whiteinella cf. paradubia. This zone, based on existing literature and previous research, representing an Early Turonian age.

The proposed biozones in the studied section correlate with other parts of the Tethys region. The C-T boundary in this section aligns with lithostratigraphic units, indicating a concordant transition.

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.

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 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.