T138 Life on the Boundary: Cretaceous/Paleogene Environments, Ecology, and Extinction Dynamics in Antarctica

Monday, 23 September 2024
1:30 PM - 5:30 PM
204C

INVESTIGATING HABITAT USE OF SHARKS AND THEIR RELATIVES IN SEYMOUR ISLAND, ANTARCTICA, ACROSS THE EOCENE EPOCH

Paper number: T138-11
Program: Technical Sessions
Time: 3:50 PM – 4:05 PM

Authors

Abstract

The Southern Ocean is a crucial area for studying the changes that triggered glaciation at the close of the Eocene Epoch. One hypothesis suggests that the opening of oceanic gateways around Antarctica started this climatic transition. However, ambiguous proxy data near the remote Drake Passage complicate an understanding of when it fully opened and how that affected global climate. This climatic-tectonic transition is likely to have impacted marine vertebrates in high-latitude regions. Study of the occurrence and paleoecology in the time leading up to glaciation should help shed light on the dynamics of the opening passage, yet few studies exist.

Here, we report phosphate oxygen stable isotope values from the teeth of pelagic and benthic sharks (δ18Op; n = 243) from the Eocene deposits (TELM 2 to 7, middle to late Eocene) on Seymour Island (Antarctic Peninsula). We compare δ18Op values of sharks with carbonate isotope data from co-occurring bivalves and isotope-enabled climate model outputs (iCESM; δ18Op*) for the Eocene. Bulk δ18Op values exhibit high variability within TELMs (mean δ18Op = 22.0 ± 1.3‰) and no significant changes across TELMs. Unlike bivalves, the variation of shark δ18Op values is larger than the predicted seasonal range for δ18Op* values based on the iCESM model for Seymour Island. Similarly, the estimated δ18Op* distribution between South America and Antarctica shows fair agreement with empirical δ18Op values from fossil shark teeth. Pelagic (n = 149) and benthic (n = 94) taxa exhibit similar values across TELMs, although shifts relative to predicted δ18Op* values from bivalves and model for Seymour Island suggest movement to other areas.

The stability in mean δ18Op values across TELMs suggests that sharks generally sought habitats with their preferred environmental conditions. In pelagic taxa, lower or higher δ18Op values than predicted δ18Op* indicate movements to shallow or deeper waters, respectively. Benthic taxa have either lower, higher, or aligned δ18Op with predicted δ18Op*, indicating warmer waters and likely movements to low latitudes, colder temperatures and likely movements to deeper waters, or more sedentary habits, respectively. Our results provide insights into shark habitat use and highlight how climate model outputs can be coupled with empirical isotopic data to discern shark paleoecology during periods of global climate change.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-400732

© Copyright 2024 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.