Paleoenvironment and Paleoclimate Reconstruction through a Life Crisis: the Sedimentology & Geochemistry across the Permo-Triassic Boundary in NW China
Stephanie G. Thomas
Southern Methodist University
Department of Geological
Sciences
Dallas, TX
sgthomas@smu.edu
The
Permian-Triassic extinction is labeled as the most severe extinction event in
geologic history, yet the mechanism(s) by which it occurred remain largely
elusive. Marine and terrestrial
organisms were equally devastated, indicating that the mechanism(s) responsible
extended to both marine and terrestrial realms. The terrestrial Permian-Triassic
boundary (PTB) is known primarily from the high latitudes of Gondwana. This project will evaluate exposed
terrestrial section spanning the PTB from the Junggar Basin, NW China, a
northeastern Tethyan locality, with specific focus on paleoenvironmental
reconstruction and assessment of pCO2 through soil-formed proxy
minerals across the PTB.
Field efforts
will focus on identifying and describing paleosols, placing them accurately
within a stratigraphic framework, and collecting samples for XRD, petrography,
and elemental and stable isotope analysis of paleopedogenic minerals. Results of fieldwork
indicate the
presence of paleosol morphologies consistent with perennially wet soil moisture
regimes in the Late Permian, whereas paleosols containing soil-formed carbonate
and pseudomorphs after gypsum suggest a drier environment characterized by net
soil moisture deficiency during the Early Triassic. Chemical analyses may provide
quantitative information such as paleotemperature, paleoprecipitation, and
atmospheric pCO2 across the PTB. Preliminary data suggest that the rocks
appear to have undergone little diagenetic alteration. Accordingly, the Junggar Basin provides
an opportunity to examine pCO2 variability and environmental change
across the PTB through multiple proxy records. Morphological variations will be
examined in concert with geochemical data from organic matter and pedogenic
minerals to provide the most robust paleoenvironment record possible and greater
environmental context for the mass extinction.
AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid