Virginia Division of Mineral Resources Bulletin 86 Geology of the Shenandoah National Park, Virginia

This report on the geology of Shenandoah National Park has been compiled from data collected during detailed and reconnaissance geologic mapping by the author and several other members of the staff of the Virginia Division of Mineral Resources and from published geologic reports and maps that included portions of the park. It is an outgrowth of ground-water studies conducted in the park by the Virginia Division of Mineral Resources between 1961 and 1971 (DeKay, 1972). This report, it is hoped, will contribute to a better understanding of the rocks of the Blue Ridge by tying together for the first time the geology of a large area of the mountains in northern Virginia.

The first efforts to explore and describe the geology of the Blue Ridge were undertaken by William Barton Rogers between 1835 and 1841 during his extensive study of the geology of Virginia and West Virginia. Rogers' (1884) reports provided the first generalized picture of the distribution, structures, and mineral deposits of the rocks in the two states and were the first to depict, in a general sense, the geology of the Blue Ridge. During the next 100 years geologic studies of the Blue Ridge in the area that has become Shenandoah National Park were largely restricted to the evaluation of economic mineral deposits (manganese, iron, and copper) and to regional geologic studies. Reports by Arthur Keith (1894a,b) are of particular interest as they were the first to describe many of the rock formations in the park.

The manganese shortage that developed during World Wars I and II activated interest in the manganese deposits along the west foot of the Blue Ridge and initiated a number of studies of these deposits and of the geology of the Blue Ridge and adjacent Shenandoah Valley. One such study (King, 1950) became the first detailed geologic report to include a portion of the park. Within this report, geologic relationships and stratigraphic terminology were established which formed the basis for subsequent geologic studies of the Blue Ridge in this area. Beginning with King's report, papers dealing with portions of the park appeared more frequently. Of the more recent geologic studies the following have been most useful in preparing this manuscript and Plates 1, 2 and 3: Allen (1963, 1967), Bloomer and Werner (1955), Brent (1960), Hack (1965), King (1950), Nelson (1962), and Reed (1955, 1969). The geologic maps accompanying the above reports cover approximately three-quarters of the park area, including some or all of those portions in Albemarle, Augusta, Greene, Madison, Nelson, Page, and Rockingham counties. Other portions of the park, largely in Augusta, Rappahannock, and Warren counties, and those areas of the park for which these maps were inadequate were mapped by the writer under the supervision of R. H. DeKay and with the assistance of Donald Fulkerson, M. T. Lukert, E. B. Nuckols III, E. W. Nunan, and P. G. Nystrom, Jr., staff members of the Virginia Division of Mineral Resources. Geologic data acquired during this study suggested that some minor alterations to the geology shown on existing maps should be made, and these alterations are incorporated on Plates 1, 2, and 3.