GEOHERITAGE OF THE GREAT VALLEY OF VIRGINIA: CROSSROAD OF GEOLOGIC AND HUMAN HISTORY IN THE MID-ATLANTIC UNITED STATES

"Geoheritage" has been applied in a number of contexts to the interface between geology, history, and human interactions. The National Park Service (NPS) and the American Geosciences Institute (AGI) define geoheritage values to include scientific, aesthetic, cultural, economic, educational, recreational, and geologic aspects, underscoring why any given location represents has geoheritage. The Great Valley of Virginia (GVV) extending from the confluence of the Shenandoah and Potomac Rivers at Harpers Ferry, WV southwest towards Roanoke VA has inspired exploration, storytelling, scientific theories, mythology, and art. The geological complexity led to formulation of geosynclinal theory in the 19th century, but later gave evidence in support plate tectonic orogenic models. Extending over 1.2 billion year, the GVV records two rifting and four orogenic events. Neogene erosional incision exhumed this record of the past events through differential erosion and provided the current physiographic Valley and Ridge, Blue Ridge, and Piedmont provinces seen today.

These events also concentrated diverse resources that have influenced human history. The GVV has been populated by multiple groups since the Pleistocene, each group leaving vestiges of how they adapted to the environment. The Siouan-speaking Monacan people, provide a recent indigenous record through their settlements and ossuary mounds from the Valley and Ridge to the Piedmont. Erosional incision exposed resources for the Monacans, including native copper, highly valued by the coastal Powhatans, fostering long distance trading.

By the early 18th Century European colonizers found the carbonate rocks of the GVV to be a productive agricultural resource. The geologic conditions in the GVV favored the concentration of residual ores of iron, manganese, among others, extracted from the 18th to the 20th centuries. Karst features favored nitrate precipitation, useful for saltpeter extraction. These resources contributed to the economic growth of the mid-Atlantic states, but also to the capacity of the Confederate States of America to prolong the American Civil War. This presentation applies the NPS/AGI geoheritage values to the GVV, highlighting the geologic history and incorporating human histories underrepresented in contemporary narratives.