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Science 30 October 1998:
Vol. 282. no. 5390, pp. 927 - 930
DOI: 10.1126/science.282.5390.927
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Reports

Isotopic Evidence for the Cretaceous-Tertiary Impactor and Its Type

A. Shukolyukov, G. W. Lugmair

High-precision mass spectrometric analysis of chromium in sediment samples from the Cretaceous-Tertiary (K-T) boundary coincident with the extinction of numerous organisms on Earth confirms the cosmic origin of the K-T phenomenon. The isotopic composition of chromium in K-T boundary samples from Stevns Klint, Denmark, and Caravaca, Spain, is different from that of Earth and indicates its extraterrestrial source. The chromium isotopic signature is consistent with a carbonaceous chondrite-type impactor. The observed differences in the chromium isotopic composition among various meteorite classes can serve as a diagnostic tool for deciphering the nature of impactors that have collided with Earth during its history.

A. Shukolyukov, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0212, USA. G. W. Lugmair, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0212, USA, and Max-Planck-Institute for Chemistry, Cosmochemistry, Post Office Box 3060, 55020 Mainz, Germany.

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