title: Isotopic evidence for the Cretaceous-Tertiary impactor and its type.
abstract: 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.
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0212, USA.
authors.forename: A
authors.initials: A
authors.lastname: Shukolyukov
authors.forename: G W
authors.initials: GW
authors.lastname: Lugmair
mesh_terms: D002857:Chromium / Q000032:analysis; D002859:Chromium Isotopes / Q000032:analysis*; D003718:Denmark; D018534:Earth, Planet; D019015:Geologic Sediments / Q000737:chemistry*; D013058:Mass Spectrometry; D019110:Meteoroids; D013030:Spain
chemical_list: D002859:Chromium Isotopes; D002857:Chromium