2003-2004 USAP Field Season

Geology & Geophysics

Dr. Rama K. Kotra Program Manager

G-299-M	NSF/OPP 02-30086
Station: McMurdo Station
RPSC POC: Melissa Rider
Research Site(s): Beardmore Glacier, McMurdo Station
Dates in Antarctica: Mid November to late December

Permian-Triassic mass extinction in Antarctica

	Dr. Gregory J. Retallack University of Oregon Department of Geological Sciences gregr@darkwing.uoregon.edu http://darkwing.uoregon.edu/%7Edogsci/retall/rsch.html

Coalsack Bluff, a site for investigating the end-Permian mass extinction event. Photo by Luann Becker.

Deploying Team Members:

Luann Becker . Daniel P. Glavin . Christine Metzger . Shaun M. Norman . Robert Joseph. Poreda . Gregory J. Retallack . Nathan D. Sheldon . Roger MH. Smith

Research Objectives: We will study fluvial sediments in Antarctica for evidence of what caused the greatest mass extinction in the history of life on Earth. The Permian-Triassic boundary was, until recently, difficult to locate and thought to be unequivocally disconformable in Antarctica. New studies, however (particularly those using carbon isotopic chemostratigraphy, and paleosols and root traces as indicators), together with improved fossil plant, reptile, and pollen biostratigraphy, now suggest that the precise location of the boundary might be identified; these studies have also led to local discovery of iridium anomalies, shocked quartz, and fullerenes with extraterrestrial noble gases. These anomalies are associated with a distinctive claystone breccia bed, similar to strata known in South Africa and Australia, and accepted as evidence of deforestation. There is already much evidence from Antarctica and elsewhere that the mass extinction on land was abrupt and synchronous with extinction in the ocean. What led to such death and destruction? Carbon isotopic values are so low in these and other Permian-Triassic boundary sections that there was likely to have been some role for catastrophic destabilization of methane clathrates. Getting the modeled amount of methane out of likely reservoirs would require such catastrophic events as a meteor impact, flood-basalt eruption, or collapse of the continental-shelf, which have all been implicated in the mass extinction and for which there is independent evidence. Teasing apart these various hypotheses requires careful reexamination of beds that appear to represent the Permian-Triassic boundary and search for more informative sequences, as was the case for the Cretaceous-Tertiary boundary. Our research on the geochemistry and petrography of boundary beds and paleosols; on carbon isotopic variation through the boundary interval; and on fullerenes, iridiums, and helium is designed to test these ideas about the Permian-Triassic boundary in Antarctica and to shed light on the processes that contributed to this largest of mass extinctions. We will conduct our fieldwork in the central Transantarctic Mountains and in southern Victoria Land, with an initial objective of examining the stratigraphic sequences for continuity across the boundary. Such continuity is critical for the work to be successful. If fieldwork indicates sufficiently continuous sections, a full analytical program will follow.