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
Investigating climatic extremes within the Paleocene Eocene Thermal Maximum using isotopic signatures in pedogenic carbonate nodules from the Green River Basin.
Paper number: 25-2
Program: Technical Sessions
Time: 8:30 AM – 8:30 AM
Authors
Abstract
Anthropogenic carbon dioxide (CO2) is causing rapid warming and is predicted to lead to an increase in climate extremes such as large storms or extended periods of drought. Investigating past times of increased CO2 can validate these predictions and help understand how current emissions will affect climate. One such time is the Paleocene Eocene Thermal Maximum (PETM), which occurred 56 million years ago. Rapid CO2 emissions during the PETM caused global temperature to increase by 5-8ºC, but relatively little is known about climate extremes on regional scales. Investigating stable carbon and oxygen isotope variability within pedogenic carbonate nodules could help fill in this gap of knowledge. Isotopic variations in pedogenic carbonate nodules have long been used in paleoclimatic studies to understand climate trends but have traditionally targeted only mean values with the goal of reconstructing long-term trends. Here, we densely sample multiple individual nodules spanning the PETM to evaluate if their heterogeneity could record extreme climate events on shorter time scales. Specifically, we collect 50 or more isotope signals each, in six nodules from the Green River Basin in western Wyoming and systematically evaluate isotope heterogeneity within each nodule. This sampling method will additionally evaluate if the true “mean” of a nodule can be captured by only sampling one or two sites from a nodule.
Results show significant isotopic heterogeneity with an obvious negative correlation between δ18O and δ13C in every nodule. Plausible explanations for this trend include variations between a warm wet climate with greater soil respiration and a cooler drier climate with less soil respiration, and a mixing of primary micrite and secondary sparite. This correlation is inconsistent with variations in the depth of nodule formation and with kinetic isotope effects. Scanning Electron Microscope analyses designed to evaluate this possibility showed no correlation between Si, Al and Mg impurities and isotopic anomalies. Nodules formed during the PETM generally showed lower isotopic variability, more negative carbon isotopes, and more positive oxygen isotopes in comparison to pre-PETM samples.
Geological Society of America Abstracts with Programs. Vol. 58, No. 4
doi: 10.1130/abs/2026RM-410557
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