The discordant Doe Run thrust: Implications for stratigraphy and structure in the Glenarm Supergroup, southeastern Pennsylvania Piedmont
Detailed mapping and ground magnetic surveys in the area of Doe Run, southeastern Pennsylvania Piedmont, show the Wissahickon Group to consistently lie above, and locally with angular contact upon, an overturned stratigraphic sequence of Grenville-aged (≈1 b.y. old) gneiss above Setters Formation above Cockeysville Marble. These discordant relations reflect the emplacement of the Wissahickon Group along the Doe Run thrust (redefined herein) across a previously folded footwall. Identifying the Doe Run thrust makes untenable the long-standing assumption of stratigraphic continuity throughout the Glenarm Supergroup of southeastern Pennsylvania.