T259 Mass Extinctions as Natural Experiments in Earth System Perturbations II

Wednesday, 18 October 2023
1:30 PM - 5:30 PM
301 / 302

TURNOVER IN AGGLUTINATED FORAMINIFERA ACROSS THE CRETACEOUS/PALEOGENE BOUNDARY IN THE WESTERN TETHYS: AN INTEGRATED GEOCHEMICAL AND BIOSTRATIGRAPHIC APPROACH

Paper number: T259-8
Program: Technical Sessions
Time: 3:10 PM – 3:25 PM

Authors

Abstract

Newly analyzed Paleocene samples from the Scaglia Rossa Formation of the Umbria Marche Basin, specifically the Contessa Highway and Bottaccione sections, were compared with our Upper Cretaceous record published previously (Kaminski et al. 2011). The comparison aimed to provide a broader understanding of the distribution and abundance of Deep-Water Agglutinated Foraminifera (DWAF) across the K/Pg boundary. The samples were collected bed-by-bed from the lowermost Paleocene. Our biostratigraphical analysis employed a robust methodology that allowed us to accurately determine the extinction rate of DWAF bioevents. This involved meticulous data gathering, consistent sample preparation, and thorough taxonomic investigation. We also conducted geochemical analyses, including mercury (Hg), on the Contessa Highway and Bottacione to assess the impact of large-scale volcanism on the marine environment and its impact on the DWAF communities.

Three groups of DWAF can be distinguished: survivor species (including Lazarus taxa), extinction species, and incoming species. The total foraminiferal record comprises 86 species, with the epifaunal morphogroup (Rhizammina, Caudammina, Ammodiscus, and Glomospira) dominating the assemblage. A notable decline in species richness is observed across the K/Pg boundary, particularly in the lowermost Paleocene, where approximately 38% of the species are lost, including Caudammina gigantea, C. ovuloides, Recurvoides retroseptus, and Gerochammina spp.. Blooms of opportunistic species are observed in the lowermost Paleocene, indicating a gradual reappearance of certain taxa that can be classified as Lazarus taxa. Our samples indicate the presence of approximately 9% incoming species, including some newly described species as well as Ammomarginulina aubertae and Spiroplectammina spectabilis.

No other study on benthic foraminifera has employed such an approach to quantify the extent of faunal turnover among the DWAF at the K/Pg boundary. By employing high-resolution sampling across the K/Pg boundary, a calculation of the extinction rate, detail recognition of foraminiferal assemblages, taxonomic studies, and paleoenvironmental analysis, we can now address the complex paleoecological problems associated with the K/Pg boundary in the western Tethys.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-394813

© Copyright 2023 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.