98-2 Freeze or Food: Testing the Environmental Drivers of Extinction on the Plio-Pleistocene Florida Platform with Clumped Isotope (Δ47) and Trace Elemental (Ba/Ca) Sclerochronology

Session: Linking Biodiversity Loss to Environmental Stressors Through Integrated Approaches

Presenting Author:

Lucas Gomes

Authors:

Gomes, Lucas¹, Petersen, Sierra V.², Waters, Eric³, Hooper, Isaac⁴, Maliszewski, Emily⁵, Peace, Rowan⁶, Reitz, Karina⁷, Salazar, Anna⁸

(1) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (2) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA; Museum of Paleontology, Ann Arbor, MI, USA, (3) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (4) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (5) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (6) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (7) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA, (8) Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA,

Abstract:

Marine fossil deposits in Florida and along the US Atlantic Coastal Plain document faunal turnover and marine ecosystem restructuring in the shelf seas of the West Atlantic during the Plio-Pleistocene transition (~3.0–1.5 Ma). Two longstanding hypotheses to explain this regional extinction event invoke either (i) declining primary productivity or (ii) cooling water temperatures as the primary extinction mechanism. However, despite more than 60 years of research on the topic, these hypothesized environmental shifts have not been systematically tested by quantitative temperature or productivity estimates from the Florida Platform. In this study, we test both leading extinction hypotheses by applying an emergent trace elemental proxy for past productivity (Ba/Ca_shell) and carbonate clumped isotope (Δ₄₇) paleothermometry to fossil mollusks (n=60) collected from each of the major Plio-Pleistocene formations of southwestern Florida. We analyze the shells at high (subannual) resolution to reconstruct mean and seasonal temperatures and annual primary productivity across the Plio-Pleistocene extinction interval. We follow a multitaxonomic sampling approach to reduce the risk of taxon-specific seasonal growth biases and biologically-driven isotopic fractionation effects, sampling across >20 mollusk genera with a specific emphasis on 4 stratigraphically-abundant genera (Carolinapecten, Chione, Dinocardium, Mercenaria). Here, we use these two independent environmental records to evaluate both the productivity- and climate-driven extinction hypotheses previously proposed. Verifying the specific environmental drivers of extinction in the Plio-Pleistocene West Atlantic will help inform more sensible conservation strategies in the present-day as modern marine ecosystems along the U.S. Eastern Seaboard and elsewhere face steadily warming temperatures and human-induced alterations to local nutrient cycling.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9784

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