25 Paleo-climate and -ecosystems of the Southwest and High Plains: From the Paleozoic to the Quaternary (Posters)

Many Phanerozoic climates and ecosystems serve as potential analogues for the future; others highlight the Earth system response to tectonic and climatic forcings. We invite abstracts that probe the paleoclimate/ecosystems of the US Southwest

Tuesday, 19 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Hot or not? A Dual Clumped Isotope Evaluation of Extreme Warmth During the Paleocene-Eocene Thermal Maximum in Green River Basin Soil Carbonates.

Paper number: 25-5
Program: Technical Sessions
Time: 8:30 AM – 8:30 AM

Authors

Abstract

The Paleocene-Eocene Thermal Maximum (PETM) is an abrupt global warming event in response to rapid increases in greenhouse gases that is often considered to be an analog for modern climate change. North America’s Laramide basins are a valuable archive of PETM climate that have constrained changes in temperature, precipitation and ecology via diverse proxies including the clumped isotope composition of soil carbonates. Carbonate clumped isotopes estimate temperature from the abundance of multiply substituted isotopologues, most commonly those of mass-47 CO2 (∆47). Application of this paleothermometer to PETM carbonates has been used to suggest peak temperatures of ~35ºC, which generally exceed estimates from independent proxies (e.g. leaf margins). While a portion of this apparent warmth likely reflects preferential carbonate formation during the warm season, it is also possible that kinetic isotope effects (KIEs) play a role. Disequilibrium could arise from multiple processes including exchange reactions in soil water or growth reactions at the carbonate mineral surface, potentially causing ∆47 temperatures to be inaccurate. Recent advances make it possible to evaluate this possibility by also measuring the isotopologues of mass-48 CO2 (∆48) using a dual clumped isotope approach. Here we apply this approach to soil carbonates from the Green River Basin of Wyoming from both before and within the PETM. Preliminary results suggest Δ47-based temperatures of 25-27ºC before the PETM rose to 33-39ºC during its peak carbon isotope excursion.  Dual clumped isotopes exhibit increasingly large deviations from apparent equilibrium as temperatures increase, although only our warmest reconstructed temperature is statistically different. The direction of disequilibrium is consistent with a KIE associated with CO2 degassing, suggesting that faster carbonate nodule formation under PETM conditions may cause Δ47 temperatures to be overestimated.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410674

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