Piedmont
The Piedmont Physiographic Region of Delaware only includes the hills of northern New Castle County, which rise to approximately 400 feet above sea level. The Piedmont extends into neighboring Pennsylvania and Maryland.
The rocks exposed in the Piedmont are metamorphic and igneous rocks that are approximately half a billion to 1.2 billion years old. The only Precambrian rock unit is the Baltimore Gneiss. Cambrian to Ordovician rocks include Wilmington Complex, Setters Formation, Cockeysville Marble, and Wissahickon Formation. Silurian rocks include the Iron Hill Gabbro, Bringhurst Gabbro, and Arden Plutonic Supersuite . The cities of Wilmington and Newark lie at the Fall line, where the northern margin of the younger Cretaceous coastal plain sediments overlie the older Piedmont rocks.
Read more about this topic: Geology Of Delaware