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Science 18 August 1995:
Vol. 269. no. 5226, pp. 930 - 935
DOI: 10.1126/science.269.5226.930
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Articles

Emplacement of Cretaceous-Tertiary Boundary Shocked Quartz from Chicxulub Crater

Walter Alvarez 1, Philippe Claeys 1, and Susan W. Kieffer 2

1 Department of Geology and Geophysics, University of California, Berkeley, CA 94720-4767, USA, and Osservatorio Geologico di Coldigioco, 62020 Frontale di Apiro (MC), Italy
2 Department of Geological Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada

Observations on shocked quartz in Cretaceous-Tertiary (K-T) boundary sediments compellingly tied to Chicxulub crater raise three problems. First, in North America shocked quartz occurs above the main K-T ejecta layer. Second, shocked quartz is more abundant west than east of Chicxulub. Third, shocked quartz reached distances requiring initial velocities up to 8 kilometers per second, corresponding to shock pressures that would produce melt, not the moderate-pressure shock lamellae observed. Shock devolatilization and the expansion of carbon dioxide and water from impacted wet carbonate, producing a warm, accelerating fireball after the initial hot fireball of silicate vapor, may explain all three problems.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Impact and extinction in remarkably complete Cretaceous-Tertiary boundary sections from Demerara Rise, tropical western North Atlantic.
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Have distal impact ejecta changed through geologic time?.
B. M. Simonson and P. Harnik (2000)
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Carbon Isotope Excursion in Atmospheric CO2 at the Cretaceous-Tertiary Boundary: Evidence from Terrestrial Sediments.
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