179 GSA James B. Thompson, Jr. Distinguished International Lectureship | Kathy Benison
The outgoing GSA James B. Thompson, Jr. Distinguished International Lecturer, Kathy Benison, is a dynamic speaker of established scientific stature living within North America who can present stimulating and cutting edge geoscience research through lectures outside of North America on topics that are at the forefront of research to raise visibility for The Geological Society of America within the international geoscience community.
Tuesday, 21 October 2025
10:00 AM - 11:00 AM
HBGCC, 213AB
Pangea on Acid: Extreme Environments, Climate, and Life during Permo-Triassic Time
Paper number: 179-2
Program: Technical Sessions
Time: 10:06 AM – 10:51 AM
Authors
Abstract
Continental rocks of middle Permian – middle Triassic age are dominated by red bed siliciclastics and evaporites. Multiple lines of sedimentological, mineralogical, and fluid inclusion evidence show that tropical Pangea hosted deserts with some of the most geochemically extreme waters known from the Phanerozoic Eon. Bedded and displacive halite and gypsum, and quartz- and Fe-oxide-rich fine-grained siliciclastic rocks cemented with halite, gypsum, and kaolinite were deposited in ephemeral lakes, saline and dry mudflats, desert soils, and rare dunes and ephemeral channels. Lake waters and groundwaters had pH as low as -1, salinities more than 10 times saltier than modern seawater, and complex compositions. Fluid inclusions in bedded halite are enriched in bisulfate and sulfate, as well as unusually high amounts of dissolved Al, Fe, and Si. Minerals known to form only from acids, including jarosite and alunite, are preserved in bedded halite. Primary fluid inclusions in halite attest to high air temperatures and high diurnal temperature ranges, suggesting a hot, dry climate. Rocks are notably poor in carbonates, macrofossils, and organic sedimentary structures, yet extremophilic microorganisms exist in primary fluid inclusions. These extreme environments were widely distributed across much of tropical Pangea, with red bed-hosted evaporites interpreted as acid brine lake and groundwater depositional systems throughout the midcontinental U.S.A., the U.K., Morocco, and Brazil. Stratigraphic trends suggest an evolution from freshwater lakes to perennial neutral saline lakes to ephemeral acid brine lakes as climate grew warmer and drier. Physical reworking of red muds, salts, and extremophilic microbes by wind may have transported them into shallow tropical seawater, where they potentially affected turbidity, chemistry, and biology of the Panthalassan Ocean at the approximate time of the end-Permian mass extinction.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-412140
© Copyright 2025 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.