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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 higherpCO2on southwestern US hydroclimate. The MCO and MCT comprised a globally warmer period with elevatedpCO2similar 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 new40Ar/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 CO2drives a shift toward 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.
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Thermal Evolution of the Impact‐Induced Cryomagma Chamber Beneath Occator Crater on Ceres
Abstract The faculae in Occator Crater on dwarf planet Ceres are an accumulation of salts that have been interpreted as cryovolcanic products. Current age estimates from crater counting suggest a maximum 18‐Ma difference between the crater forming impact and the formation of Cerealia Facula, the central and most recent region in the crater. Here we model the thermal evolution of the potential impact‐induced cryomagma chamber beneath Occator Crater and show that it cools in less than 12 Ma. To reach cooling times of 18 Ma requires initial melt volumes exceeding 11,000 km3. However, simulations suggest that smaller initial cryomagma chambers may lead to partial melting of the lower crust. This may allow recharge of the magma chamber by deep brines located in the porous upper mantle of Ceres and may extend the longevity of cryovolcanic activity.
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- Award ID(s):
- 1720349
- PAR ID:
- 10448822
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 46
- Issue:
- 3
- ISSN:
- 0094-8276
- Page Range / eLocation ID:
- p. 1213-1221
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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