T183 Soils and Paleosols across Space and Time II: A Celebration of Steven G. Driese

Tuesday, 11 October 2022
1:30 PM - 5:30 PM
207

PALEOCLIMATE AND CHEMOSTRATIGRAPHY OF THE HENSEL FORMATION, KIMBLE COUNTY, TEXAS

Paper number: T183-3
Program: Technical Sessions
Time: 1:50 PM – 2:05 PM

Authors

Abstract

The Hensel Formation is one of the few dominantly terrestrial Cretaceous units in Central Texas and provides the unique opportunity to investigate paleoclimate archives preserved in paleosols in this area prior to the Cretaceous thermal maximum. Bulk sedimentary organic carbon isotopes, carbonate isotopes (δ13C, δ18O, and Δ47 ) of paleosol carbonates, and major element geochemistry were utilized to estimate paleotemperature, paleoprecipitation, pCO2, and to correlate the δ13C values in the Hensel Formation to existing carbon isotope chemostratigraphic records. Organic C isotope values range from -28.15‰ to -19.62‰ vs. VPDB. Carbonate oxygen isotope values range from about -4.97‰ to +0.23‰ vs. VPDB and carbonate carbon isotope values range from -8.29‰ to -5.04‰ vs. VPDB. As expected, samples are on average primarily dominated by SiO2, with other major element oxides in decreasing abundance including CaO, Al2O3, and MgO. Paleotemperature estimates were determined using the clumped isotope (Δ47) paleothermometer and paleoprecipitation estmates were determined using the chemical index of alteration and its relationship to mean annual precipitation. Preliminary paleotemperature and paleoprecipitation data (ranging between 35 and 42°C and ~314mm/year on average) suggests a subtropical desert biome existed in Central Texas during the Albian Stage. The temperature estimates are also consistent with and overlap temperatures from coeval temperature estimates farther north in the Cedar Mountain Formation and Newark Canyon Formation (Suarez et al. 2020, GSL spec. pub. 507; Fetrow et al., 2020, AGU, EP026-03) consistent with a shallow latitudinal temperature gradient. The soil carbonate paleobarometer indicates a range of CO2 concentration estimates from just under pre-industrial CO2 concentrations to as much as ~5 times pre-industrial CO2 concentrations. Refinement of paleosol paleobarometer variables will likely provide more constrained CO2 estimates. This will contribute to ongoing community efforts to improve Phanerozoic CO2 records.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-381823

© Copyright 2022 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.