The boundary clay

One of the distinct features of the boundary between the Cretaceous and the Tertiary (paleogene) in the geologic record is found in this photo. Sandwiched in the middle of this section, you see what is called the “boundary clay” layer.

66 million years ago at the end of the Cretaceous, a rocky asteroid hit the Earth off the shore of the Yucatan peninsula. Near the site of the impact, rocks were tossed around by enormous waves creating tsunami-caused deposits several meters thick in places like Cuba.

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