3 Paleo-climate and -ecosystems of the Southwest and High Plains: From the Paleozoic to the Quaternary

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

Monday, 18 May 2026
9:00 AM - 12:00 PM
Alvarado C

Characterizing the Magnitude and Drivers of Neogene Temperature Change with Clumped Isotope Analyses in the Central Rio Grande Rift

Paper number: 3-3
Program: Technical Sessions
Time: 10:00 AM – 10:20 AM

Authors

Abstract

Large uncertainty surrounds efforts to model the regional response to CO2-driven warming in the southwestern U.S. The region hosts a seasonally variable hydroclimate and significant topography – much of which is tied to the region’s complex Cenozoic geologic history. These intricacies are difficult to reconcile in models, leading to disagreement even on the modelled sign of future precipitation change in the southwestern U.S. Previous and new stable isotope analyses of authigenic carbonates from the well-dated Santa Fe Group of the central Rio Grande Rift suggest a potential shift from a middle Miocene winter-wet climate towards the dual-wet season regime seen in the region today; this shift might be spurred by either a strengthening of the North American Monsoon or a weakening of the westerlies. New clumped isotope analysis of these pedogenic carbonates documents a long-term cooling of 18.5 ± 10.3°C between the Miocene Climatic Optimum (MCO) and the Pleistocene. This Neogene cooling trend in New Mexico tightly tracks the global benthic d18O record and Pacific sea-surface temperature records over the same period, suggesting that paleotemperature change throughout the record is controlled by global climate. However, climate models are unable to match the degree of continental MCO warmth in New Mexico indicated in our data even at CO2 concentrations 8x higher than pre-industrial levels. Illustrating the magnitude of disagreement, Miocene and modern simulations respectively predict 4.6 deg C and 3.2 deg C of warming in New Mexico under a 560-ppm climate while clumped isotope temperatures at the MCO are roughly 10 deg C warmer than modern mean annual temperatures in New Mexico. The disagreement between the magnitude of MCO warmth indicated by our clumped isotope record and that resulting from models can be explained either by (1) an underprediction of modelled temperature responses to CO2-driven warming in the southwestern U.S. or (2) other factors that modify local temperature, such as changes in elevation associated with ongoing rifting along the Rio Grande rift and/or long-wavelength uplift associated with passage of the Farallon plate beneath the southwestern U.S. We suggest that our record not only demonstrates that global drivers pace long-term temperature change in the U.S. Southwest but also provides evidence for intracontinental uplift in northern New Mexico since the early Miocene.

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

doi: 10.1130/abs/2026RM-410624

© Copyright 2026 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.