Prevalence
Shocked quartz is found worldwide, in the thin Cretaceous–Paleogene boundary layer, which occurs at the contact between Cretaceous and Paleogene rocks. This is further evidence (in addition to iridium enrichment) that the transition between the two geological periods was caused by a large impact. Though shocked quartz is only recently recognized, Eugene Shoemaker discovered it in building stones in the Bavarian town of Nördlingen.
Read more about this topic: Shocked Quartz
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