Mapping the Smith River Allochthon: An Enigmatic Piedmont Terrane

To most of us, the Earth’s surface is static. Humanity has so long relied on this assumption of permanence that the theory of plate tectonics was not fully accepted in the scientific community until the early 1960s. In research done since, geologists have found evidence of several ancient super continents that predate the well-known Pangea. One of these is the 1-billion-year-old Rodinia, composed of the continents Laurentia and Gondwana. Laurentia is the name of the contemporary North American craton (the block of crust forming the nucleus of a continent) and Gondwana was a continent that contained the modern cratons of Africa, Australia, Antarctica, and South America.
In the Neoproterozoic (700 million years ago), Rodinia began to fragment and ultimately form the Iapetus Ocean. On either side of the Iapetus were the continents Laurentia and Gondwana. The Iapetus began to close in the Cambrian (500 million years ago) and the two continents eventually collided in the Ordovician (440 million years ago). The closure of the Iapetus is a significant event in the geologic evolution of the Blue Ridge-Piedmont boundary.
The Piedmont province, stretching from the Blue Ridge part of the Appalachian Mountains in the west to the Coastal Plain province in the east, consists of both Laurentian and peri-Gondwanan terranes (fragments of crustal material broken off a tectonic plate and accreted to another one) . The westernmost Piedmont is home to a proposed Blue Ridge-Piedmont boundary, though the identity of western Piedmont terranes as the easternmost extension of the Appalachian Mountains is debated. I aim to research enigmatic terranes along the Blue Ridge-Piedmont boundary to uncover their orogenic, kinematic, and structural histories.
One such terrane is the Smith River Allochthon (SRA), a proposed regional scale thrust sheet interpreted as either peri-Gondwanan or distal Laurentian. The SRA is mapped to the northeast of Lynchburg in the 1993 Virginia State Geologic Map along the postulated boundary with the Blue Ridge. This region of the Piedmont has not been mapped in detail since the acceptance of plate tectonics. I will investigate the SRA’s northern extent, affinity, and relation to the adjacent Blue Ridge mountains in order to interpret the geologic evolution of the Blue Ridge-Piedmont boundary.