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Data from: The hydroclimate and environmental response to middle Miocene warming in the southwestern U.S.A.: Stable isotope evidence

Spaur, Siânin12; Koning, Daniel2; Heizler, Matthew23; Aby, Scott4; Williamson, Garrett5; Knott, Jeffrey6; Acosta, R. Paul7; Rugenstein, Jeremy1

Published May 08, 2025 on Dryad. https://doi.org/10.5061/dryad.kh18932k0

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Abstract

Predictions for the southwestern US with warming often suggest increased aridity. We investigate the sedimentary record of the Miocene Climate Optimum and Transition (MCO and MCT; ~17-14 Ma) in northern New Mexico to understand the impact of warmer global temperatures and higher pCO2 on southwestern hydroclimate. The MCO and MCT comprised a globally warmer period with elevated pCO2 similar to end-of-the-century (~400-800 ppm) projections. We present new stable isotope (δ18O and δ13C) records of vadose-zone and groundwater terrestrial carbonates and of modern precipitation, stream, and groundwater from the Española basin in northern New Mexico and establish a high-resolution age model using new 40Ar/39Ar ages. We interpret δ18O as reflecting the balance between summertime monsoonal and wintertime precipitation and δ13C as a reflection of plant productivity. Terrestrial carbonate δ18O is lowest during the MCO and MCT and is correlated with terrestrial carbonate δ13C and anti-correlated with the benthic δ18O record. We interpret these data as recording an overall winter-wet climate during the MCO and MCT, but that precipitation seasonality varied in response to changes in global climate during this period. The further correlation with carbonate δ13C suggests that plant productivity was driven by the amount of wintertime precipitation. Comparison with middle Miocene climate model simulations reveals that higher CO2 drives a shift towards wintertime precipitation. Though paleogeographic changes may obscure a direct comparison to modern warming, overall, our findings suggest that prolonged global warmth may be associated with increased wintertime precipitation and greater primary productivity in northern New Mexico. These datasets contain the original data associated with these records and in support of the conclusions.