Conference Agenda

The Early Cretaceous is characterized by the progressive breakup of Gondwana and the opening of new restricted basins between the South American and the African plates. Part of the sedimentary successions that filled these basins is now exposed along the coast of Brazil and represent useful records of the climatic and environmental conditions that dominated in this region at that time.

In this study we present new results of major and trace elements, used as paleoclimatic and paleoenvironmental proxies from the Sergipe Alagoas, Recôncavo, and Araripe basins, in eastern Brazil. The litho-geochemical composition of these mainly siliciclastic successions is used for inferring variations in detrital input, continental weathering, and redox and salinity conditions. We show that the weathering was moderate in most of the sections, which lead to the deposition of slightly immature sediments, formed mainly by quartz and clay minerals. The climatic conditions were mainly humid during the Valanginian and shifted to arid and semi-arid during the Hauterivian-Barremian. Brackish to marine conditions seem to have occurred in the Recôncavo basin in the Valanginian, indicating possible marine ingressions already at that time. Our results contribute to unravel the complex paleoclimatic and paleoenvironmental history during the opening of the South Atlantic Ocean.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The Recôncavo Basin (Caruaçu Mb./Maracangalha Fm.) forms an aulacogen system linked to the early opening stages of Gondwana and South Atlantic margin development. The basins are characterized by mainly lacustrine shales, with turbiditic, deltaic, fluvial, and alluvial fan systems and despite extensive research, important gaps remain in understanding paleoenvironmental and sedimentary controls during the Early Cretaceous. This study addresses part of this gap through an integrated analysis of mineralogical, geochemical, and paleomagnetic data from the Maracangalha Formation, based on samples collected from two outcrops on Itaparica Island (Gameleira and Manguinhos), in the central portion of the Recôncavo basin. A total of 37 samples were analyzed using X-ray diffraction (DRX) and X-ray fluorescence (XRF). Mineralogical results reveal a predominance of quartz, feldspars, and clay minerals, suggesting continental sources and possible recycling of sedimentary rocks. Geochemical signatures indicate predominantly humid, non-marine conditions with redox variations, mostly oxic, and weak to moderate chemical weathering. Anisotropy of Magnetic Susceptibility (AMS) analyses allowed the inference of preferred sediment transport directions aligned with the extensional structure of the basin. The results show significant vertical variations in mineralogical and geochemical patterns, reflecting paleoenvironmental changes, redox conditions, and sediment sources over geological time. The integrated dataset provides a paleoenvironmental reconstruction of the Reconcavo Basin’s rift phase and offers insights into the sedimentary and tectonic evolution of the South Atlantic margin during the Early Cretaceous.

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

During the Early Cretaceous, Gondwana rifting led to the formation of multiple sag basins, including the Santos Basin, which evolved from riverine/deltaic/lacustrine environments to a carbonate-dominated system. The lacustrine Barra Velha Formation preserves unique facies cyclothems composed of laminated carbonates, shrubs, and spherules, reflecting both climatic and tectonic influences. In this study, we performed spectral analysis on gamma ray (GR) data and K, Th, and U content from three offshore cores of the Barra Velha Formation. These cores alternate between crystalline limestones, grainstone/rudstone, and mudstones. GR data in carbonates are typically interpreted as reflecting clay content—due not only to structural K but also to the adsorption of K and Th, and the association of U with organic matter. Our results reveal dominant 15–20 m cycles in both GR and elemental data, interpreted as orbital in origin. Shorter cycles (up to 7.8 m), particularly in the Th data, correspond to the typical thickness of Barra Velha cyclothems and may reflect variations in erosion and precipitation. The Th spectras display a greater number of short-wavelength peaks compared to GR and K, suggesting higher-frequency variability in erosion and precipitation processes not fully captured by the cyclothems. Evolutionary spectral analysis indicates these shorter cycles are inconsistent through the cores and are more likely linked to changes in cyclothem thickness than to orbital forcing.

The mass extinction at the Cretaceous-Paleogene (K-Pg) boundary significantly changed the earth's ecosystem, and profoundly influenced the global animal and plant evolution. In order to better understand the vegetation succession and climate change, detailed palynological investigation was engaged again on the K-Pg boundary transition from the XHY2008 borehole in Jiayin of Heilongjiang Province, China. A total of 153 species assigned to 72 genera were identified from 157 palynological samples in a 14.50 meters long borehole striding the K-Pg boundary. Two palynological assemblages and one assemblage were recognized for the latest Cretaceous and earliest Paleogene, respectively. The latest Maastrichtian palynological assemblages were named as in ascending order: 1) Gabonisporis vigourouxii – Pinuspollenites microinsignis – Aquilapollenites stelckii Ass., and 2) Laevigatosporites spp. - Monocolpopollenites spp. – Ulmoideipites krempii Ass.; and the earliest Danian assemblage was named as Osmundacidites spp. – Pesudointegricorpus clarireticulatus – Wodehouseia spinata Ass. The two latest Maastrichtian assemblages were productive in palynomorphs and with high pollen concentration, while the earliest Danian samples were much lower in pollen concentration. From the general view on vegetation succession, there were not any great event happened on the K-Pg boundary. Meanwhile, the TOC, δ¹³C_org, whole-rock elements data of XHY2008 drilled borehole showed the climate was getting more and more arid, and a disruption in the global carbon cycle and a collapse of terrestrial ecosystem. This would be helpful for better understanding the vegetation, climate change and the collapse of ecosystem.

Keywords: XHY2008 borehole, K-Pg boundary, Palynofloral succession, Heilongjiang River area, collapse of terrestrial ecosystem.

As an ancient element, Cycadopsida is an important and index fossil plant group in the Mesozoic, especially in the Cretaceous deposit. The Early Cretaceous floras are well developed in the western Liaoning region, northeastern China showing significant palaeoclimate implications. In our recent investigations, over 171 pieces of Cycadopsida fossils were collected in coal mines in the Tiefa Basin and Fuxin Basin in western Liaoning; among them, 58 specimens with cuticles were studied in details. About 8 species of 3 genera are identified into Nilssoniopteris, Nilssonia and Pterophyllum. This enriches the fossil plant diversity and assemblages of the Early Cretaceous floras in western Liaoning. Comparisons with other Early Cretaceous floras from northern and southern China shows similarities with cycads taxa in the Huolinhe flora and Hailar flora of Inner Mongolia and Shansong flora in Jilin province in North China. Other Cretaceous flora like Jiande flora in South China shows some differences from our floras in western Liaoning. In addition, although the Tetori flora in the Inner Zone of Japan shares some similar elements with the Fuxin flora, it also features a significant number of southern tropical-subtropical elements. The diversity and assemblages of the cycads based on both mega-fossils and micro-fossils implies that the the western Liaoning belonged to humid warm temperate climate in the late Early Cretaceous. This provides evidences for further exploring the floral aspects and climate variations of the Early Cretaceous in East Asian during the Mesozoic greenhouse period.

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

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

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

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

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

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

Acknowledgements: Mar interior Project

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

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

Interdisciplinary studies on a siliceous multicoloured shaly unit belonging to the Lagonegro-Molise Basin and named “argilliti e radiolariti di Campomaggiore”, late Valanginian to Turonian in age, allowed to identify the effects of Cretaceous global climatic variations on an oceanic sedimentary succession cropping out along the eastern margin of the Southern Apennines. This unit contains five black shale levels standing out by abrupt lithofacies changes and yielding high Total Organic Carbon content and good kerogen quality. These organic carbon-rich levels (Calanche Anoxic Events, CAE1-5) are best expressed in the Calanche section close to the city of Potenza (Basilicata Region, Italy). Geochemical data suggest that anoxic conditions were more severe during the deposition of CAE2, CAE3 and Bonarelli Level-equivalent (CAE5) horizons than in CAE1 and CAE4 ones. Based on radiolarian biostratigraphy, CAE5 correlates well to the latest Cenomanian Bonarelli Level from the Umbria-Marche Basin. Radiolarian faunas, however, cannot constrain the ages of CAE1-4, preventing a precise correlation with other Cretaceous anoxic events known at regional or global scale. A new detailed study, based on lithostratigraphy and Cretaceous microflora from CAE1-5 horizons gives rigorous chronostratigraphic constrains, providing to assign the CAE1 level to the Weissert oceanic anoxic event (Valanginian), the CAE2 to the Selli Level-equivalent (early Aptian), the CAE3 and CAE4 to the late Albian and to confirm the late Cenomanian for the CAE5 level (Bonarelli Level-equivalent).

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

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

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

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

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

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

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

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

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

Abstract

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

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

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

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

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

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

The mid-Cretaceous was characterized by extreme greenhouse conditions, long-term sea level rise, and tectonic processes that influenced the dynamics of oceanic systems. The global carbon cycle was affected by major perturbations during Oceanic Anoxic Events (OAEs). We present new integrated geochemical, magnetic, and mineralogical data from a core drilled through late Albian to early Turonian sediments in the Sergipe-Alagoas Basin, off northeastern Brazil, which includes one of the few records of the OAE2 from the South Atlantic Ocean. The obtained results show a major change in sedimentation in the middle Cenomanian when mixed carbonate and siliciclastic deposits were replaced by chalk. This transition reflects a major change in palaeoceanographic conditions toward a more stable circulation mode, with better connection between the different oceanic basins, persistent currents, and bottom ventilation. Cyclicity in the ln(K/Al) record indicates insolation-driven fluctuations in aridity and humidity. A new age model, based on the stable 405 kyr-long eccentricity cycles, places the onset of the OAE2 carbon isotope excursion at ~94.74 Ma. Sedimentation during the OAE2 seemed to be mainly controlled by long-term processes and local effects rather than global perturbations. Variations in ln(Sr/Ca) indicate increased primary productivity persisting for two long eccentricity cycles, while transient reducing conditions, inferred from loss in magnetic susceptibility compared to Fe, persisted across the earliest long eccentricity maximum phase, at least.

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

The Late Cretaceous Period was characterized by hothouse conditions, with elevated pCO₂ levels, high sea levels, and minimal ice sheets. This era transitioned into cooling trends during the Campanian-Maastrichtian interval (83.65–66.04 Ma). Tunisia's Upper Cretaceous successions, such as the Elles section in the southwestern Tethyan Ocean, serve as valuable archives for studying paleoenvironmental shifts, paleoclimatic changes, and sea-level oscillations. Quantitative analyses of benthic foraminiferal assemblages from the Elles section reveal significant paleobathymetric and relative sea-level insights. The Campanian Abiod Formation, deposited at upper to middle bathyal depths (540–675 m), reflected well-oxygenated conditions and minimal organic matter flux. The Campanian-Maastrichtian transition aligns with the lower El Haria Formation, characterized by outer neritic to upper bathyal settings under oligotrophic and oxygen-rich conditions. During the Maastrichtian, shallower depositional settings (436–515 m) with increased organic matter and reduced oxygen levels were observed. Eight major sea-level regressions (four in the Campanian, one at the transition, and three in the Maastrichtian) were identified, often accompanied by negative δ¹³C excursions. These findings were consistent with sea-level changes observed at the nearby El Kef section, highlighting the Elles section's significance in reconstructing Late Cretaceous paleoenvironmental dynamics and sea-level fluctuations.

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

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

Cretaceous Oceanic Red Beds (CORBs) are pelagic sediments typically associated with oxic conditions, yet their formation pathways remain debated. This study investigates two CORB intervals from the Trento Plateau (Southern Alps, NE Italy), dated to the Upper Aptian and Upper Albian–Lower Cenomanian, to evaluate how local environmental dynamics influenced their deposition. We apply a multiproxy approach—integrating stratigraphy, geochemistry (XRF, ICP-OES/MS), rare earth elements (REE), and rock-magnetic data (thermomagnetic curves)—to distinguish the depositional regimes of each interval.

Our results show that the Upper Aptian CORBs formed in a dynamic and relatively shallower setting, with intensified chemical weathering, fluctuating oxygenation, and a marked peak in marine productivity. In contrast, the Upper Albian–Lower Cenomanian CORBs reflect a deeper, more stable setting, with reduced productivity and consistent bottom-water oxygenation. Both intervals lack redox-sensitive elements (e.g., Mo, Cr), supporting persistent oxic conditions. Thermomagnetic data indicate partial oxidation of detrital magnetite, confirming early diagenetic iron oxidation in both intervals.

These findings demonstrate that CORBs are not limited to a single paleoenvironmental model. While the Albian–Cenomanian interval aligns with classical models—low productivity, slow sedimentation, oxic conditions—the Aptian CORBs reveal an alternative scenario of red bed formation under more dynamic and humid conditions.

We conclude that multiple environmental pathways can lead to CORB deposition, provided that oxygen levels remain sufficiently high to preserve iron oxides. This highlights the importance of regional controls and cautions against oversimplified genetic interpretations of red beds in the Cretaceous ocean.

During the late Early Cretaceous period, particular paleoceanographic conditions fostered multiple episodes of extensive organic matter deposition in sedimentary basins. The Sergipe-Alagoas sedimentary basin represents one of the most complete stratigraphic successions among the Brazilian continental margins. Considering that magnetic signals in sediments record past environmental conditions, this study aims to present paleomagnetic techniques for the identification of magnetic minerals, alongside geochemical data, to characterize the paleoenvironment of the Barra do Itiúba Formation in Brazil. Magnetic mineralogy investigations of this section included measurements of magnetic susceptibility (MS), hysteresis loops, isothermal remanent magnetization (IRM) acquisition curves, thermomagnetic curves, and X-ray diffraction (XRD) analysis. The environmental magnetism data suggest the presence of lithological variations along the stratigraphic profile, or alternatively, that the basin's sedimentation process was controlled by transgressive/regressive events. Geochemical data obtained from X-ray diffraction analysis indicate that distinct weathering and climate conditions prevailed during sedimentary deposition. Furthermore, the data suggest that the distinct pattern of sedimentary variation may be related to different depositional environments, where the dominant magnetic minerals are magnetite and hematite. The combination of environmental magnetic and geochemical data therefore constitutes a valuable tool for the reconstruction of environmental history from global to regional scales.

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

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

The Oceanic Anoxic Event 1b (OAE 1b) is a peculiar event, characterized by a much longer duration and different lithological expressions respect to the others Oceanic Anoxic Events (OAEs) of the Cretaceous. Despite the numerous studies in the last years, there are still many uncertainties about the paleoceanographic and paleoclimatic mechanisms that controlled this event and on whether they are similar to those of the other OAEs. The Marne a Fucoidi Formation from the Umbria-Marche Basin (central Italy) provides a well-preserved record of the OAE 1b and of the Aptian-Albian. It consists of an alternation of varicolored marls, limestones, and black shales, with four major black shale layers representing sub-events of the OAE 1b that can be correlated at regional scale, at least. This study presents a high-resolution, multi-proxy analysis of the OAE 1b interval of the Marne a Fucoidi Formation in the Poggio le Guaine core, by integrating δ¹³C, εNd in clay materials, and geochemical elemental analysis. Principal Components Analyses (PCA) were used to compare the geochemical signatures of different intervals selected according to the lithology and the stratigraphic position. Our results reveal that the Aptian-Albian interval was characterized by unstable, frequently changing, paleoceanographic conditions, controlled by the same mechanisms before, during, and after the OAE 1b. Therefore, the OAE 1b represents a period of enhanced climatic instability in an already unstable climatic scenario and was driven by different mechanisms respect to the others OAEs.

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

In this work, we analyzed magnetostratigraphy supplemented with planktic foraminifera biostratigraphy, environmental magnetic parameters, mineralogy, and major element chemistry from a well-defined Cretaceous-Paleogene (K/Pg) boundary section exposed in the Poty Quarry of Paraíba Basin, NE Brazil to establish the first age-depth model of the region, and to understand the impact of these events on equatorial shallow marine environments. To establish the age-depth model, oriented samples collected at ~15-20 cm intervals from ~11 m thick carbonate strata covering the uppermost Maastrichtian (Gramame Formation) and Danian (Maria Farinha Formation) were demagnetized using alternating field demagnetization and thermal demagnetization methods to retrieve the characteristic remanent magnetizations. Only ~26% of specimens showed reliable paleomagnetic directions, which, combined with the planktic foraminifera biostratigraphic tie points, indicated that the exposed Poty Quarry section recorded magnetic Chron between C29r and C27n. Two new unconformities (hiatus/erosion) were also identified at ~ 65.24 Ma and ~ 63.5 Ma, which corresponds to the global Danian sea-level fall events PDa2 and PDa3, respectively. The low terrigenous flux and slow sedimentation (~ 0.14 cm/kyr) in the late Maastrichtian is characterized by a high sea-level tract (HST) depositional environment, whereas higher sedimentation (~2.75 cm/kyr) and maximum terrigenous flux between ~62.6 and 62.3 Ma is characterized as regressive (prograding) depositional environment leading to shallowing of the Paraíba Basin towards the end of the Danian.

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

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