Setters Formation

The Setters Formation is a geological formation that is located in Maryland, Pennsylvania, and Delaware in the United States. The formation is metamorphic and consists of a complex suite of schist, gneiss, and quartzite.
It is the lowest unit of the Glenarm Group. The overlying formations of the group are the Cockeysville Marble and the Wissahickon Formation.

Outcrops

Some outcrops listed by the USGS are:

Setters Ridge, which forms north front of Chattolanee anticline, Baltimore County, Maryland.
Quarries in Avondale, Pennsylvania.
Eastburn's quarry, New Castle County, Delaware.