Metabasalts and Related Rocks of the Blue Ridge Province: Traces of Proterozoic Rifting in Eastern North America : Shenandoah National Park to Bull Run Mountains, Virginia, July 14, 1989 (Volume T203)

Published by the American Geophysical Union as part of the Field Trip Guidebooks Series, Volume 203.Rocks that once constituted parts of the southeastern margin of Proterozoic North America are widely exposed in internal and external massifs throughout the Appalachian orogen (Rodgers, 1987; Reed, 1987).

The oldest rocks exposed in these massifs are plutonic rocks and gneisses emplaced or metamorphosed during the 1000 to 1100 Ma Grenville orogeny.

These Middle Proterozoic basement rocks are unconformably overlain by metasedimentary and metavolcanic sequences of Late Proterozoic age that record rifting events during the early stages of opening of Iapetus, the early Paleozoic ancestor of the present Atlantic Ocean.Both basement and cover rocks are exposed in the Blue Ridge anticlinorium, a major tectonic element that extends for more than 300 km northeastward from near Lynchburg, Virginia to the vicinity of Carlisle, Pennsylvania (Figure 1).

Proterozoic rocks in the core of the anticlinorium are stratigraphically overlain by lower Paleozoic rocks.

On the northwest limb of the anticlinorium these strata include a basal Cambrian clastic sequence (the Chilhowee Group), a Cambrian through Middle Ordovician miogeoclinal sequence consisting of carbonates and mature clastics, and various shallow marine to terrestrial strata of Late Ordovician to Carboniferous age.

Collectively they constitute the classic sequence of the Valley and Ridge province of the central Appalachians.