The Calvert Formation is a geologic formation in Maryland, Virginia, and Delaware.
It preserves fossils dating back to the early to middle Miocene epoch of the Neogene period.
It is one of the three formations which make up the Calvert Cliffs, all of which are part of the Chesapeake Group.
The Calvert Formation is extremely fossiliferous.
Some of the fossil species represented include the following:[1][2]