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.

Programme

This Public Lecture will take place on Tuesday 21 April 2026.

This is a hybrid event, which can be attended in person at Burlington House, Piccadilly, London, or online via Zoom.

17:30–18:00: Guests arrive for the Public Lecture. Refreshments served in the Lower Library.

18:00–19:00: Talk takes place (including Q&A)

19:00-20:00: Drinks reception in Lower Library

20:00: Event end

Speaker bio - Prof Kathleen C. Benison

Kathleen Benison is a geologist and educator who studies the geology, geochemistry, and microbiology of modern and ancient acid salt lakes. She is especially interested in using fluid inclusions in halite and gypsum to decipher past conditions of environment, climate, and life from the rock record of Earth and Mars. Kathy grew up near the beach in Boston, Massachusetts, U.S.A., where she gained an interest in science and nature. She earned a B.S. in Geology and Chemistry from Bridgewater State College in Massachusetts in 1990, a M.A. in Geology from Binghamton University in New York in 1993, and a Ph.D. in Geology from the University of Kansas in 1997. Kathy was a professor at Central Michigan University from 1997 until 2012 and, since then, has been at West Virginia University, where she is now Professor of Geology. She was a Return Sample Selection-Participating Scientist for the Mars 2020 Perseverance rover mission, a member of a National Academies of Sciences’ National Research Council on planetary protection, and a Science Editor for the journal Geology. Kathy is a Geological Society of America Fellow, and an Explorers Club Fellow, a National Geographic Explorer, and is the Geological Society of America’s 2026 James B. Thompson, Jr. International Distinguished Lecturer. She is mom to three adult children and one big yellow dog; she and her spouse Chris live in a stone house in Morgantown, West Virginia.