Shenandoah National Park - Geology

Geology

Shenandoah National Park lies along the Blue Ridge Mountains in north-central Virginia. These mountains form a distinct highland rising to elevations above 4,000 feet (1,200 m), local topographic relief between the Blue Ridge Mountains and Shenandoah Valley exceeds 3,000 feet (910 m) at some locations. The crest of the range divides the Shenandoah River drainage basin, part of the Potomac River drainage, on the west side, from the James and Rappahannock River drainage basins on the east side.

Rocks exposed in the park are among the oldest in Virginia dating to over one billion years in age. Bedrock in the park includes Grenville-age granitic basement rocks (1.2-1.0 billion years old) and a cover sequence of metamorphosed Neoproterozoic (570-550 million years old) sedimentary and volcanic rocks of the Swift Run and Catoctin formations and early Cambrian (542-520 million years old) clastic rocks of the Chilhowee Group. Quaternary surficial deposits are common and mantle much of the bedrock throughout the park.

The park is located along the western part of the Blue Ridge anticlinorium, a regional-scale Paleozoic structure at the eastern margin of the Appalachian fold and thrust belt. Rocks within the park were folded, faulted, distorted, and metamorphosed during the late Paleozoic Alleghanian orogeny (325 to 260million years ago). The rugged topography of Blue Ridge Mountains is a result of differential erosion during the Cenozoic, although some post-Paleozoic tectonic activity occurred in the region.