19 The Age of American Wastelands: Carboniferous-to-Jurassic Stratigraphy, Sedimentology. and Paleoenvironments of North America

Tuesday, 10 March 2020
8:00 AM - 12:00 PM
Meeting Room 201B

ASSESSING ARIDITY ACROSS THE PERMIAN LANDS OF NORTH AMERICA

Paper number: 19-7
Program: Theme Sessions
Time: 9:40 AM – 10:00 AM

Authors

  • Neil J. Tabor Presenting Author
    Southern Methodist University, Dallas, TX

Abstract

Stable carbon isotope analysis of co-existing soil calcite and organic matter sampled from modern, California soil profiles representing18 different USDA official soil series yields 51 paired calcite-organic matter δ13C values (Δ13Ccc-om values). These paired values correspond to atmospheric pCO2 estimates ranging from less than ~100 to 2200 ppmV using standard assumed soil pCO2 concentrations at temperatures spanning the typical range of modern soil calcite crystallization. Nevertheless, there is a strong negative correlation of Δ13Ccc-om values with mean annual precipitation (MAP) among these modern sites, offering a potential means to estimate paleo-MAP values from calcite and associated, occluded organic matter in paleosols. One-hundred-and-one Δ13Ccc-om values from Lower Permian–Lower Triassic paleosol profiles in the southwestern U.S.A. are presented as a proxy for paleo-rainfall over ~85° of paleolatitude. The results indicate substantial spatio-temporal variation in MAP and appear to reflect the development and strengthening of global megamonsoonal atmospheric circulation associated with assembly of the supercontinent Pangea. The data also indicate extremely low rainfall values in regions with endemic tetrapod fossil assemblages, suggesting that climate change was a principle driver of biogeography, biodiversity and evolution of tetrapod faunas across continental landscapes during Permian-Triassic time.

Geological Society of America Abstracts with Programs. Vol. 52, No. 1

doi: 10.1130/abs/2020SC-343285

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