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Geologic Provinces of the United States: Appalachian Highlands Gallery

Elk Ridge at Maryland Heights, Maryland

Elk Ridge at Maryland Heights, Maryland.

Harpers Ferry National Historical Park

Photo by Scott Southworth, USGS.

Looking north from Blue Ridge at Loudoun Heights, Virginia, to Elk Ridge at Maryland Heights, Maryland, a large recumbent fold pair of Lower Cambrian Weverton Formation is exposed along the water gap of the Potomac River at Harpers Ferry National Historical Park. The C&O Canal National Historical Park is along the Potomac River in the lower part of the photograph. Blue Ridge-Elk Ridge forms the prominent west limb of the Blue Ridge-South Mountain anticlinorium, a large allochthonous fold complex deformed, metamorphosed, and transported westward along the North Mountain fault during several orogenic episodes in the Paleozoic. The resistant light massive quartzites form the base of the Paleozoic rock section and reflect the end of the Late Proterozoic continental rift event that resulted in formation of the Iapetus ocean. These fluvial to beach sands and gravel were deposited unconformably above mafic volcanic basalt and locally Middle Proterozoic basement gneiss. Although the formal boundary of the Blue Ridge province and Great Valley of the Valley and Ridge province is to the west at the first carbonate rock (Tomstown Dolomite), the prominent mountain of Blue Ridge-Elk Ridge is recognized by many as the provincial boundary.

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