Several weeks ago the significance of the breccia layer at the K-T boundary received some discussion. It has been claimed to be the result of one or more tsunamis produced by the presumed K-T impact at Chicxulub.
Sequence boundaries are often difficult to pin down.
But this is a spectacular deposit of the coarsest-grained chaotic material I've ever seen. The breccia layer is up to 100 feet thick, containing striated pebbles, cobbles, and boulders, in a matrix of finer material including sub-spherical clasts of green recrystallized glass. The striations are believed to have formed by a partially melted exterior scraping across country rock, or abrasion by smaller, high-speed projectiles. The exhibitors had samples for us to handle and look at close up. There was no Late Cretaceous glaciation in the Yucatan.