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Science 3 March 1989:
Vol. 243. no. 4895, pp. 1182 - 1184
DOI: 10.1126/science.243.4895.1182
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Articles

Stishovite at the Cretaceous-Tertiary Boundary, Raton, New Mexico

JOHN F. MCHONE 1, RONALD A. NIEMAN 2, CHARLES F. LEWIS 2, and ANN M. YATES 2

1 Department of Geology, Arizona State University, Tempe, AZ 85287.
2 Department of Chemistry, Arizona State University, Tempe, AZ 85287.

Stishovite, a dense phase of silica, has become widely accepted as an indicator of terrestrial impact events. Stishovite occurs at several impact structures but has not been found at volcanic sites. Solid-state silicon-29 magic-angle spinning nuclear magnetic resonance (silicon-29 MAS NMR) and X-ray diffraction of samples from the Cretaceous-Tertiary boundary layer at Raton, New Mexico, indicate that stishovite occurs in crystalline mineral grains. Stishovite was indicated by a single, sharp resonance with a chemical shift value of -191.3 ppm, characteristic of silicon in octahedral coordination, that disappeared after heating the sample at 850° Celsius for 30 minutes. An X-ray diffraction pattern of HF residuals from the unheated sample displayed more than 120 peaks, most of which correspond to quartz, zircon, rutile, and anatase. Eight unambiguous weak to moderate reflections could be ascribed to d-spacings characteristic of stishovite.

Submitted on November 11, 1988
Accepted on January 19, 1989


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Extraterrestrial impacts on earth: the evidence and the consequences.
R. A. F. Grieve (1998)
Geological Society, London, Special Publications 140, 105-131
   Abstract »    PDF »
Nuclear Magnetic Resonance Spectroscopy in the Earth Sciences: Structure and Dynamics.
J. F. Stebbins, J. F. STEBBINS, and I. FARNAN (1989)
Science 245, 257-263
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Science. ISSN 0036-8075 (print), 1095-9203 (online)