Blue Ridge province - The Geology of Virginia

The rocks in the Blue Ridge mountains of Virginia range in age from 250 million years to one billion years old
The northern Blue Ridge of Virginia, as seen
from Shenandoah National Park


n Virginia, the Blue Ridge province forms a basement massif with Mesoproterozoic crystalline rock in its core and Late Neoproterozoic to Early Paleozoic cover rock on its flanks. The Blue Ridge province is allochthonous and has been thrust to the northwest over Paleozoic rocks of the Valley and Ridge province A. Although earlier deformation events are recorded in the older igneous and metamorphic rocks, the Blue Ridge is a contractional structure that experienced deformation and crustal shortening during the Paleozoic.

The Blue Ridge experienced the intrusion of a diverse suite of plutons and granulite-facies metamorphism during the Grenvillian (1.2 - 1.0 Ga) orogeny. Late Neoproterozoic (750-700 Ma) granitoids intrude the Grenvillian rocks and are associated with an early phase of Iapetan rifting. Late Neoproterozoic sedimentary rocks range from non-marine alluvial conglomerates to deep-water distal turbidites and are derived from Grenvillian basement exposed along a rifted continental margin. In central and northern Virginia, the 570 Ma Catoctin metabasalts overlie the Late Neoproterozoic sedimentary units.

Generalized Stratigraphy of the Virginia Blue Ridge

By the early Cambrian, the Iapetus Ocean had opened to the east of the Blue Ridge and a westward transgression occurred along the ancient North American margin. In the western Blue Ridge, shallow marine siliclastics of the Chilhowee Group were deposited in the early Cambrian and eventually gave way to carbonates of Cambro-Ordovician age. In central and northern Virginia the Blue Ridge mountains rise to elevations in excess of 1200 m (4000 ft). Local relief on the east side of the Blue Ridge is up to 1000 m. In southern Virginia, the Blue Ridge forms a broad plateau-like upland that rises over 500 m from the Piedmont along a prominent escarpment. Mt. Rogers (1746 m), in the southwestern Virginia Blue Ridge, is the highest peak in Virginia.

In Depth