Conference Agenda

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 The Weissert Event was a turning point: Antinomia got extinct, Pygites invaded new territorries, while Pygope was withdrawn from the Tethys and only documented from East Greenland.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

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

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

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

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

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

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

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

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

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

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

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

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

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