The Aquia Formation is a fossil-bearing sandstone unit of the Atlantic Coastal Plain that extends from the upper Chesapeake Bay to the James River near Hopewell, Virginia. Named for Aquia Creek, it is now classified as Paleocene and dates to about 59.0 to 55.5 million years ago, with lower Piscataway and upper Paspotansa members. Typically a clayey, silty, glauconitic, shell-rich sand, it can include hardened shell beds and reaches up to 100 feet thick in Maryland. Lying above the Brightseat Formation and below the Nanjemoy Formation, it preserves abundant marine invertebrates and vertebrates, plus rarer bird and mammal remains, making it an important record of early Paleogene shoreline life.