Rock Layers of Florissant

The Florissant Formation, if it were all in one place, would be about 200 foot thick and made up of mostly volcanic sediments. Only some of the layers contain fossils.

Dr. Emmet Evanoff's work was instrumental in mapping the Florissant Formation. His work led to the new stratigraphic interpretation, including describing the stratigraphic column above, as well as naming the six informal layes (Bolded in the image).

Evanoff and his students also discovered the fossil mammal sites that included a brontothere. The presence of a brontothere and single-crystal ⁴⁰Ar/³⁹Ar dating work with William Mcintosh indicated that the Florissant fossil beds were late Eocene in age.