--> Abstract: Death, Destruction & Dirt: Using Paleosols to Reconstruct Environmental Changes across the Permo-Triassic Boundary; #90063 (2007)

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Death, Destruction & Dirt: Using Paleosols to Reconstruct Environmental Changes across the Permo-Triassic Boundary

 

Thomas, Stephanie1, Neil Tabor1, Wan Yang2 (1) Southern Methodist University, Dallas, TX (2) Wichita State University, Wichita, KS

 

Although the Permian-Triassic Boundary (PTB) marks the largest mass extinction of the Phanerozoic, the cause(s) of the extinction remains largely enigmatic. Paleosols provide a means for evaluating environmental and climatic changes across the PTB. Terrestrial exposures of the PTB are known primarily from high-latitude Gondwana, including sections from India, South Africa, Australia, & Antarctica, and from peri-Tethyan sections in China and Russia.

 

During the Late Permian, the demise of icehouse conditions led to widespread coal development in Gondwana due to increased high-latitude humidity. In western and equatorial Pangea climate shifted towards greater aridity, although Tethyan realms remained humid until earliest Triassic time. Paleosols from the Turpan-Hami Basin, NW China, show striking variations in morphology across the PTB. Paleosols of the Permian Wutonggou fm. are characterized by intense redoximorphy, accumulation of vascular plant matter, accumulation of clay minerals and Fe-oxides, slickensides, and clastic dikes, suggesting a soil moisture regime that ranged from perennially wet to one with distinct seasonal variations in soil moisture budget. The Lower Triassic Jiucaiyuan fm. contains pedogenic CaCO3 accumulations and gypsum pseudomorphs, indicating a drier environment characterized by net soil moisture deficiency. Modern soil analogs suggest that the Wutonggou paleosols formed in humid environments with >1000 mm of precipitation/yr, whereas Lower Triassic paleosols formed in environments with <300 mm/yr. A negative shift in the δ13C values of organic matter is observed across the PTB from ~-22‰ in the Upper Permian to ~-31‰ in the Lower Triassic, suggesting dramatic changes in atmospheric composition and OM burial.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California