Delaware’s oldest rocks are metamorphic crystalline rocks of the central Appalachian Piedmont Physiographic Province. Atlantic Coastal Plain sediments overlie the crystalline rocks of the Piedmont and range in thickness from a feather edge at the Fall Line to approximately 9,000 feet in the southeastern corner of Delaware. Sediments range in age from Early Cretaceous to Holocene.
Please give proper credit to the Delaware Geological Survey.
DGS Staff, 2000, Generalized Geologic Map of Delaware, Postcard: Delaware Geological Survey Special Publication 16