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Chromium at KT layer

WASHINGTON (Reuters) - New evidence found deep within the Earth's
crust adds support to the theory that a huge asteroid smashed into
the planet 65 million years ago and killed off the dinosaurs,
researchers said Thursday. They found extraterrestrial chromium in
the rocks that were on the surface of the Earth at about the time
dinosaurs disappeared. Writing in the journal Science, the scientists
said they measured levels of a chromium isotope, 53Cr, in rocks at
the K-T boundary, the geologic layer in the Earth that coincides with
dinosaur extinction. These rocks were at the surface when the
Cretaceous period ended and the Tertiary began, and when the
dinosaurs began their slide into extinction.