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Cuba proposed site for K/T impact.

Cuba proposed site for K/T impact

The asteroid or comet that purportedly snuffed out the last remaining dinosaurs some 65 million years ago may have slammed into the Earth just south of Cuba, according to speculations by two scientists. Since 1979, when researchers first raised the impact theory, a number of investigators have proposed locations in Iowa, the Indian Ocean and elsewhere as possible sites for the impact at the boundary between the Cretaceous and Tertiary (K/T) periods. Recent work, however, has pointed to the Caribbean region, report Bruce F. Bohor of the U.S. Geological Survey in Denver and Russell Seitz of Cambridge, Mass., in a letter published in the April 12 NATURE.

Bohor and others have long proposed that the impact occurred in the vicinity of North America, because the largest pieces of "shocked" mineral grains -- apparently from the impact -- appear on that continent. The Caribbean attracted attention as a possible site last year after Alan Hildebrand and William V. Boynton of the University of Arizona in Tucson discovered an unusually thick K/T sediment layer in Haiti containing pieces of glassy stone chips, often taken as evidence of an impact. This evidence led Hildebrand and Boynton to propose an impact off the coast of Colombia.

After studying geologic reports written in the 1930s and 1940s, however, bohor and Seitz speculate the extraterrestrial body hit south of western Cuba. The K/T boundary layer on Cuba contains huge bounders that may have been ejected from a nearby crater. They suggest the Isle of Pines just south of Cuba might be uplifted rock, often seen in the center of impact craters. Diplomatic problems have so far stymied efforts to test the Cuba hypothesis, Bohor says.
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Title Annotation:Cretaceous/Tertiary geological periods
Publication:Science News
Date:Apr 28, 1990
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