St. Marys Formation
| St. Marys Formation | |
|---|---|
| Stratigraphic range: | |
| Type | Formation |
| Unit of | Chesapeake Group |
| Underlies | Eastover Formation |
| Overlies | Choptank Formation |
| Location | |
| Region | Maryland, Virginia |
| Country | United States |
The St. Marys Formation is a geologic formation in Maryland and Virginia, United States. It preserves fossils dating back to the Tortonian stage of the Late Miocene epoch of the Neogene period (11 to 8 million years ago). It is the youngest Miocene formation present in the Calvert Cliffs and is part of the Chesapeake Group.