Permian Triassic Boundary: Bogda Mountains, China

Under a NSF funded Integrated Earth Systems grant, Dr. Gastaldo and colleagues are expanding their studies on the end-Permian terrestrial mass-extinction event to western China in the Xinjiang Uygur Autonomous Region. Here, fully continental deposits are found in a series of rift basins where plant macrofossils, palynomorphs, conchostrachans (freshwater invertebrates), and vertebrate fossils are preserved in sections constrained by  a geochronology, magnetostratigraphy, and chemostratigraphy.  The project is designed  to test the overarching hypothesis (H1) that terrestrial ecosystems of the Bogda Mountains suffered dramatic extinction and restructuring at the end of the Permian, possibly coeval with events in the marine realm. Alternatively, we consider a hypothesis (H0) that mid-paleolatitudes of northeastern Pangea may not have been affected, suggesting a globally heterogeneous response of the biosphere to the end Permian crisis.

The Bogda Mountain section is the only locality on Earth where a fully continental succession of sediments accumulated over the extinction interval. Gastaldo and colleagues have shown that the rocks in South Africa, where the response of the terrestrial ecosystem has been thought to be conserved, are not coeval with the marine extinction event, nor is the currently accepted model of ecosystem response credible. Other stratigraphic sections reported to preserve the end-Permian event (Antarctica, Australia, Russia, South China, western U.S.) are either not well constrained in time, or ecosystem dynamics and the identification of the boundary event predicated on the South African record.

Western China exposes rocks from the uppermost Carboniferous–Lower Triassic along the foothills of the Bogda Mountains and the northern slope of Tianshan mountains. These deposits accumulated in intracontinental grabens of the Turpan-Junggar microplate along the NW Paleo-Tethys coast. Grabens developed on Carboniferous volcanic-arc and oceanic basement in a tectonic setting similar to the Neogene Basin-and-Range Province, western U.S., and were filled mainly by clastic sediments sourced from local horsts and the northern Tianshan suture zone. The conformable middle Permian to Lower Triassic fluvial-lacustrine deposits and paleosols are bound by two major unconformities. The succession overlies early-rift lower Permian alluvial, fluvial, and lacustrine sediments, and underlies Middle Triassic braided stream deposits.

Field work on the current project was to begin in May 2018 and continue for 3 years, simultaneously with the currently funded South African project. Late in May 2018, the team was informed by the provincial government that westerners were not allowed to enter the area for unstated reasons. Once field permits are issued, Colby Geology majors will have the opportunity to participate in the project.

The research team lead by Professor Wan Yang, Missouri University of Science and Technology, is working in collaboration with:

  • U.S. colleagues
    • Dr. Jim Crowly, Boise State University, Idaho (Geochronology)
    • Prof. Neil Tabor, Southern Methodist University, Dallas, Texas (Stable isotope geochemistry & paleosols)
    • Prof. John Geissman, University of Dallas, Texas (Magnetostratigraphy)
    • Dr. Ken Angielczyk, Chicago Field Museum, Chicago (Vertebrate paleontology)
    • Prof. Chris Sidor, University of Washington, Seattle (Vertebrate paleontology)
    • Dr. Peter Roopnarine, The California Academy of Sciences, San Francisco, CA (Ecological modeling)
    • Colby College undergraduate research assistants
  • Chinese colleagues
    • Dr. Jun Wang, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing
    • Dr. Feng Liu, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing
    • Dr. Mingli Wan, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing
    • Prof. Feng Qiao, Shandong University of Science and Technology, Quigdao
  • German colleagues
    • Dr. Frank Scholze, Technische Universtät Bergakademie Freiberg

Professor Gastaldo’s collaborative research team is undertaking their work through a grant from the National Science Foundation (NSF IES 171474917) and Colby College’s Dean of Faculty and Department of Geology endowments including the Selover Family and Barrett T. Dixon Geology Research and Internship endowments for students.