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40948-B2
Stratigraphic, Paleontological, and Geochemical Investigation of Links among Ocean Chemistry, Microbial-Cement Precipitates, and Patterns of Metazoan Recovery during the Early Triassic

Daniel J. Lehrmann, University of Wisconsin (Oshkosh)

The purpose of this study is to evaluate the controls and environmental conditions associated with the end-Permian mass extinction and early Triassic biotic recovery from sections in south China, Turkey and Japan. Work completed this year consisted of three weeks of field work in the Nanpanjiang basin of south China, compilation and analysis of carbon isotope results from China, Japan, and Turkey, and completion and publication of eight papers on this research in peer reviewed journals.

Undergraduate students completed the compilation and correlation of the carbon isotope data between our sections in Guandao (south China), Takachiho and Kamura (southern Japan), and Taskent (western Turkey). A large component of our laboratory work has been petrography of microbialites and an associated erosion surface that truncates uppermost Permian strata in the PT boundary interval. Four undergraduate students have conducted most of this work focusing on large thin sections and polished slabs. Conodont identifications and correlations have been made for the Takachiho and Kamura and Taskent sections. Undergraduate students presented results of the carbon isotopes and petrography of the PT truncation surface at GSA and AGU meetings.

One of the most exciting aspects of this work was the discovery of a submarine erosion surface (interpreted as dissolution feature) that truncates limestone at the immediate PT in sections from China, Japan, and Turkey. We interpret the truncation surface to have formed by submarine dissolution resulting from a rapid unbuffered release of carbon dioxide to the atmosphere/ocean system at the same time of the extinction. Carbon isotope data from field areas spanning the global tropics reveals synchronous large isotope fluctuations, indicating that significant perturbations of the carbon cycle continued through the Early Triassic in the aftermath of the extinction. These data suggest perturbations of earth environments continued and prevented the re-diversification of life for approximately 5 million years after the extinction. Evaluation of several hypotheses indicates that prolonged thermogenic methane release from heating of coals during Siberian traps volcanic eruptions best explains these environmental and carbon isotope perturbations.

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