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Science 29 August 1986:
Vol. 233. no. 4767, pp. 984 - 986
DOI: 10.1126/science.233.4767.984
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Articles

Conodont Survival and Low Iridium Abundances Across the Permian-Triassic Boundary in South China

DAVID L. CLARK 1, WANG CHENG-YUAN 2, CHARLES J. ORTH 3, and JAMES S. GILMORE 3

1 Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706.
2 Nanjing Institute of Geology and Paleontology, Academia Sinica, Nanjing, People's Republic of China.
3 Isotope and Nuclear Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM 87545.

The Permian-Triassic sedimentary sequence of China includes one of the most complete and fossiliferous Paleozoic-Mesozoic boundaries known. Closely spaced sampling across the boundary, which is an important extinction event for most organisms, has produced good conodont faunas that show little diversity change. A drop in conodont abundance is the only apparent response to the extinction event. A low concentration of iridium in the boundary clay (0.002 part per billion ±20 percent), as well as in samples immediately below and above, that range from 0.004 to 0.034 part per billion do not support the proposal of an extraterrestrial impact event at this boundary in China.

Submitted on April 29, 1986
Accepted on July 11, 1986


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Abrupt Climate Change and Extinction Events in Earth History.
T. J. Crowley, T. J. Crowley, and G. R. North (1988)
Science 240, 996-1002
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