Paleocene to Eocene Deep-Water Agglutinated Foraminiferal Acmes: A Global Perspective

Deep-water agglutinated foraminifera (DWAF) are crucial tools for paleoenvironmental analysis and biostratigraphic correlation in deep marine environments below the carbonate compensation depth (CCD). This study investigates the DWAF acmes in the Paleocene–Eocene sediments of IODP Hole U1511B, which was collected from the Tasman Abyssal Plain during Expedition 371. Cosmopolitan taxa, which have been previously documented from regions such as the Carpathians, Boreal North Atlantic, and Western Tethys, dominate the assemblages, which consist of 89 species across 43 genera. The identified acmes—Rzehakina, Spiroplectammina, Reticulophragmium, Trochammina, ammodiscids, and Karrerulina—display remarkable similarities to previously recognized events in the western Tethys and North Atlantic. The stratigraphy of Site U1511B exhibits a coarsening-upward sequence of greenish-gray Paleocene claystones that transition into reddish-brown Eocene sediments. The Paleocene/Eocene boundary is delineated by a hiatus. These acmes are associated with periods of ecological instability, such as the Paleocene–Eocene Thermal Maximum (PETM) and Early Eocene Climatic Optimum (EECO), which are indicative of changes in sedimentary regimes, oxygenation, and trophic conditions. The global extent of these faunal responses to climatic and oceanographic changes is illustrated by the observed DWAF successions, which align closely with acmes from the Western Tethys, Polish Carpathians, and Boreal North Atlantic, despite the semi-isolated position of the Tasman Sea during the Paleogene. The utility of DWAF as biostratigraphic indicators in abyssal environments devoid of calcareous fossils is emphasized by the presence of well-known acmes, including Rzehakina fissistomata and Spiroplectammina spectabilis. This research supports the hypothesis that DWAF acmes are triggered by substantial paleoenvironmental changes, such as global oligotrophy, sediment flux fluctuations, and organic matter redistribution during significant climatic events. The discovery of these acmes at Site U1511B contributes to the refinement of the Paleocene–Eocene stratigraphic framework in the abyssal ocean and the advancement of our understanding of global paleoceanographic events during the Paleogene.