The Piedmont rock units in Delaware, and bedrock geologic map of Schenck et al. (2000) are revised in this report based on new rock geochemistry, geochronometric data, petrography, and recent detailed mapping. Major revisions include:
• revising the extent of the Christianstead Gneiss and Windy Hills Gneiss
• abandoning the Wissahickon Formation as originally mapped in Delaware by Bascom (1902, 1905) and Bascom et al. (1909, 1920, and 1932) and replacing it with the Mt. Cuba Gneiss, a lithodeme of the West Grove Metamorphic Suite (Bosbyshell et al., 2012, 2013, 2014, 2015), and reserving the Wissahickon Schist/Formation for the metasediments on the east side of the Wilmington Complex magmatic arc and referring to them herein as Wissahickon Formation (restricted sense)
• extending the Rosemont Shear Zone from Pennsylvania southwest through Delaware to Maryland separating the Mt. Cuba Gneiss and the Wilmington Complex
• formally naming and describing two new units in the Wilmington Complex - the Greenville Gabbro and the Thompsons Bridge Gneiss.
Plate 1 of OFR54 can also be viewed in a Web Mapping Application. Layers can be turned on and off and manipulated under the "Layers" icon in the upper right hand corner. Cross section is available by clicking on the cross section line. Rock unit descriptions available by clicking on the geologic map.
OFR54 Plate 1 (Bedrock Geologic Map of the Delaware Piedmont) Web Mapping Application
University of Delaware
Delaware Geological Survey Building
Newark, DE 19716
Mon - Fri; 8:00am to 4:30pm