Nanjemoy Formation

The Nanjemoy Formation (Early Eocene - Ypresian) is made up of two members, the Potapaco and Woodstock.

The clayey sands and fauna of the primary collecting locale suggest a near shore (100-200m) marine environment. This fauna is rich in vertebrate fossils -- producing material from fishes, reptiles, birds and occasionally, land mammals. Besides abundant chondrichthyan teeth, this is one of the few locations where sea snake vertebrae may be deemed common.