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Science 13 January 1984:
Vol. 223. no. 4632, pp. 163 - 165
DOI: 10.1126/science.223.4632.163
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Articles

A Search for Iridium Abundance Anomalies at Two Late Cambrian Biomere Boundaries in Western Utah

CHARLES J. ORTH 1, JERE D. KNIGHT 1, LEONARD R. QUINTANA 1, JAMES S. GILMORE 1, and ALLISON R. PALMER 2

1 Los Alamos National Laboratory, Los Alamos, New Mexico 87545
2 Geological Society of America, Boulder, Colorado 80301

Iridium concentrations have been measured in samples taken across two Late Cambrian biomere boundaries (crisis zones) in search of evidence for possible elemental abundance anomalies similar to the one observed at the Cretaceous-Tertiary boundary. Sampling was performed in uplifted marine limestone deposits in the House Range of western Utah. Although the two trilobite-brachiopod extinction boundaries could be assigned to ±4 millimeters of vertical section by laboratory examination of the rocks, only background amounts of iridium (2 x 10-12 to 17 x 10-12 gram per gram of whole rock) were observed.

Submitted on September 7, 1983
Accepted on October 13, 1983


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Iridium profile for 10 million years across the Cretaceous-Tertiary boundary at Gubbio (Italy).
W Alvarez, F Asaro, and A Montanari (1990)
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Conodont Survival and Low Iridium Abundances Across the Permian-Triassic Boundary in South China.
D. L. Clark, D. L. CLARK, W. CHENG-YUAN, C. J. ORTH, and J. S. GILMORE (1986)
Science 233, 984-986
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Accretion Rate of Extraterrestrial Matter: Iridium Deposited 33 to 67 Million Years Ago.
F. T. Kyte, F. T. KYTE, and J. T. WASSON (1986)
Science 232, 1225-1229
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