Lower Triassic Sulfur Chemostratigraphy: Investigating the Biotic Recovery from the End Permian Mass Extinction

Pedro Marenco
University of Southern California Department of Earth Sciences
Los Angeles, California
marenco@usc.edu

The purpose of this project is to document and understand sulfur geochemistry during the Early Triassic and how it affected marine life during that time. Previously published gypsum-based sulfur isotope geochemistry has revealed that the largest sulfur isotope excursion occurred during the Early Triassic (+10 per mil during the Latest Permian to +30 per mil in the latest Early Triassic). However, the gypsum record is riddled with gaps during the Early Triassic, thus a robust understanding of Early Triassic sulfur geochemistry is lacking. New techniques to extract carbonate-associated sulfate in carbonate rocks provide the opportunity to construct a more complete sulfur geochemical record during the Early Triassic.

The sulfur geochemical record can be used to test the hypothesis that anomalous ocean chemistry, such as oceanic anoxia, delayed the biotic recovery from the Permo-Triassic mass extinction; this hypothesis is primarily based on lithologic and fossil data. My preliminary results using carbonate-associated sulfate and the existing gypsum record support the hypothesis and suggest that the changes in the sulfur system may have resulted from processes detrimental to marine metazoan life.