Isotopic Evidence for the Cretaceous-Tertiary Impactor and Its Type

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Science  30 Oct 1998:
Vol. 282, Issue 5390, pp. 927-930
DOI: 10.1126/science.282.5390.927

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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.

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