Tectonics of the Maryland Piedmont along the Potomac River; insight since 1960 and potential transfer to the Pennsylvania Piedmont

This is a summary of a half century of research in the Mary land Piedmont and how it may or may not have implications for the Piedmont of Pennsylvania. Much of the field mapping and all of the isotopic analyses of rocks and minerals of the Maryland Piedmont have been conducted since the 1960 Field Conference of Pennsylvania Geologists “Some tectonic and structural problems of the Appalachian Piedmont along the Susquehanna River”. The Piedmont rocks of Maryland and Pennsylvania occur in a critical place within the central Appalachian Pennsylvania embayment (Thomas, 1977), which likely contributed to the distribution of lithologies and structures.