Conference Agenda

In the interior Cretaceous basins of northeastern South America, a significant question concerns the timing of the earliest marine incursions and their effects on sedimentary stratigraphy. This study investigates the Barbalha Formation in Brazil’s Araripe Basin through analysis of two drill cores (1PS-06-CE and 1PS-10-CE) using a multi-proxy approach that includes stratigraphy, microbiofacies, ichnofossils, and microfossils. Three short-lived marine incursions, named Araripe Marine Incursions (AMI) 1–3, were identified. AMI-1 and AMI-2 occur within the Batateira Beds’ shales (lower Barbalha Formation) and are characterized by benthonic foraminifera, calcareous nannofossils, dinocysts, and a mass mortality of non-marine ostracods. AMI-3, found in the upper Barbalha Formation, is distinguished by ichnofossils and planktonic foraminifera, including the genus Leupoldina, which indicates an early to late Aptian age and allows correlation with global foraminiferal biozonation.In addition, sedimentological and ichnological data from six boreholes, supplemented by four additional cores, reveal two depositional sequences: the first includes fluvial meandering deposits overlain by lacustrine-lagoonal deposits (equivalent to Batateira Beds), while the second comprises alluvial plain and tidally influenced delta deposits overlain by bayhead delta deposits. The presence of microfossils and marine to brackish ichnofossils confirms marine incursions of varying intensity throughout these sequences. Preservation patterns suggest the eastern to southeast region of the basin experienced the strongest marine influence. These results provide important insights into the timing and nature of early marine flooding in northeastern Brazil’s inland basins, linked to the breakup of the Gondwana supercontinent and the initial opening of the South Atlantic Ocean. [Acknowledgements: Mar Interior Project]

An integrated palynological study at Byers Group, Livingston Island (Antarctica) has provided valuable information on dinoflagellate cysts and miospores for biostratigraphic interpretation and palaeoenvironmental reconstruction. On the Byers Peninsula, the Byers Group is exposed as a thick succession of Upper Jurassic–Lower Cretaceous sedimentary and volcanic rocks composed mainly of marine mudstones, sandstones, siltstones, and conglomerates. The Byers Group includes different formations and members, as the President Beaches Formation and the overlying Chester Cone Formation occupy a large area of the western part of the Peninsula. It has been found that the President Beaches Formation and the Sealer Hill Member of the Chester Cone Formation contain comparatively rich assemblages of dinoflagellate cysts, gymnosperms and pteridophyte spores. Dinocysts Batioladinium reticulatum Range Zone (uppermost Berriasian) and Senoniasphaera tabulata Interval Zone (mid Valanginian) have been indicated in the President Beaches Formation, while the Lithodinia stovery Zone (lower Hauterivian) has been found in the Sealer Hill Member of the Chester Cone Formation.

A neritic middle shelf depositional environment can be inferred from the overall composition of dinocyst assemblages and palynofacies data. The input of terrestrial material has been high in the basin, with consistently high continental to marine ratio. Anoxic intervals are evidenced within the President Beaches Fm demonstrated by significant parts of grey greenish amorphous organic matter. Land vegetation likely consisted of pteridophyte-spore producing plants and coniferous forests with equal amounts of Araucariacites and Podocarpidites, suggesting a temperate warm, humid palaeoclimate.

The study is contribution to Project 70-25-10/ Bulgarian Polar Program.

This study documents quantitative changes of planktonic and benthic foraminiferal assemblages in the Eastbourne section (Anglo-Paris Basin), one of the most expanded, complete, and well-studied records of Oceanic Anoxic Event 2 (OAE 2).

Before the onset of OAE 2, planktonic foraminiferal assemblages are indicative of a well-stratified upper water column. Benthic foraminifera suggest an outer neritic-upper bathyal environment with an oxygenated seafloor.

The onset of OAE 2 is marked by a sea-level fall supported by the maximum abundance of shallow water benthics (Ataxophragmium depressum, Arenobulimina, Plectina cenomana) and by the disappearance of bathyal taxa. Planktonic assemblages are dominated by rotaliporids and whiteinellids and suggest increased Tethyan influence in the source of surface waters.

Tethyan planktonic foraminifera are sharply replaced by assemblages dominated by Praeglobotruncana, Dicarinella and Muricohedbergella during the Plenus Cold Event (PCE). The coeval occurrence of Eggerellina, Textularia, Gaudryina and Quinqueloculina antiqua indicates the onset of a transgressive phase and improved oxygenation at the seafloor. All data converge on the incursion of Boreal surface waters in the Anglo-Paris Basin associated with a disruption of thermal stratification and re-oxygenation of the seafloor coeval with the extinction of rotaliporids.

The dominance of unkeeled planktonic foraminifera and the acme of the benthic genera Marssonella, Gavelinella, and Lingulogavelinella suggest the establishment of poorly stratified mesotrophic surface waters, increased influx of organic matter to the seafloor and a further relative sea-level rise in the final phase and after the end of OAE 2.

The Cenomanian-Turonian boundary interval (Late Cretaceous ~93.9 million years ago) coincides with a dramatic period of environmental change. This includes the global carbon cycle perturbation of Oceanic Anoxic Event 2 (OAE-2), rapid changes in seawater oxygenation and temperature (e.g., the ‘Plenus Cold Event’ and early Turonian thermal maximum), as well as sea level and productivity fluctuations. Despite a wealth of proxy and geological data, the effects of these events on the diversity and functional ecology of marine ecosystems remain uncertain. The UK Chalk Group of the Anglo-Paris Basin provides a complete and abundantly fossiliferous record across this interval which is currently the focus of the ChaSE (Chalk Sea Ecosystems) project. Using extensive macrofossil collections from the expanded Cenomanian-Turonian succession exposed at Eastbourne (East Sussex, UK) held at the Natural History Museum as well as new quantitative field data, we document several intervals across the broader C-T boundary interval where the marine macrofauna in this part of the Chalk Sea underwent significant changes in both taxonomic and functional diversity. We demonstrate how these data are related to the environmental changes outlined above, and how they provide important evidence for the complex regional response, and resilience, of marine ecosystems to Earth System perturbations in the ‘greenhouse’ world of the Late Cretaceous.

The Geological Conservation Review Series began in 1977 and, in a series of volumes, documents the key geological sites of the United Kingdom. Many of the selected sites were, or have subsequently become, Sites of Special Scientific Interest. Initially published in hard copy, the remaining volumes are being published on-line in the Proceedings of the Geologists’ Association. The marine, Lower Cretaceous sites extend from Speeton in the North-East of England to the Aptian and Albian sediments of the Isle of Wight and the Dorset Coast. Many of the stratigraphical units are famous parts of the UK Cretaceous succession, including the Speeton Clay Formation, the Spilsby Sandstone Formation, the Hunstanton Formation, the Gault Clay Formation and the Atherfield Clay Formation. The biostratigraphy of most of the marine Lower Cretaceous was initially based on ammonites (and belemnites), although many parts of the succession have now been described in terms of their microfossil assemblages (foraminifera, ostracods, calcareous nannofossils and dinoflagellate cysts).

Work on the present volume was begun in 1990’s by the late Simon Kelly and taken over by the present team following his sad death in 2023. Many of the sites listed in his initial survey have now been lost or are in a ‘poor’ condition and part of the current work is an assessment of what remains available. The GCR Series has several remaining gaps, and this volume is an important omission, coming just after the 200^th anniversary of the founding of the Cretaceous System in 1822.

A new hippuritid rudist bivalve is recovered from the Cretaceous allochthonous limestone body intercalated in the Eocene Caramoan Formation in the Caramoan Peninsula, southeastern Luzon Island, the Philippines. Its age is supposed to be Cenomanian, according to the stratigraphic range of co-occurring bivalves, Sr isotopic stratigraphy of a rudist shell and U-Pb dating of the tuff bed intercalated in limestone. The shapes and positions of ligamentary infolding, two pillars and myo-cardinal arrangement in its right valve have the characteristics similar to those of Vaccinites rousseli, one of the primitive hippuritid species (upper Turonian). Its left valve is stacking into the right valve, and possibly has a very thin outer shell layer, and thus the pores and canals system, diagnostic features of the hippuritids, are not probably present. These characteristics of the left valve are similar to those of the hippuritid genus Torreites (Santonian-Maastrichtian). The mode of development of the multiple-fold system in new hippuritid: the increase of the number of infoldings and their order of development during the ontogeny, is distinct from that of advanced multiple-fold hippuritid genera of the Campanian–Maastrichtian age. Furthermore, a cladistic analysis of the Hippuritidae including the new hippuritid, identifies its evolutionary basal position and the process of achieving diagnostic features in this family. Thus, the discovery of a new hippuritid in the Central Pacific, which represents one of the earliest records of this family and uniquely combines the variable morphological features, requests the complete revision of the early evolutionary history of the family Hippuritidae.