THE NEED FOR LEGACY GEOLOGIC MAPS IN THE NEW RIVER VALLEY, VIRGINIA

Many areas in the U.S. have unpublished geologic maps that can lend support to important ongoing infrastructure projects in the region. Recent publication of four geologic maps in the New River Valley by the Virginia Division of Geology and Mineral Resources (VDGMR) was a major step in completing legacy geologic studies. The 7.5-minute maps were updated and digitized by VDGMR under the Statemap component of the National Cooperative Geologic Mapping Program. The Radford North, Radford South, Dublin and Staffordsville maps are within the Virginia I-81 corridor, a major northeast-southwest commuting route, and are part of an ongoing effort by Virginia to provide updated geologic information for a variety of increasing infrastructure needs. Following completion of the mapping of this region in the early 1980s, considerable growth has occurred in the greater Blacksburg, Christiansburg and Radford, Virginia areas and requests to VDGMR for basic geologic mapping information have increased. For example, a newly proposed bridge over the New River on I-81 is located in an area of complexly faulted bedrock, which includes highly fractured carbonates, intensely folded mudstones and irregular large masses of tectonic fault breccia. Additionally, housing and commercial growth has occurred in a zone of well-developed sinkholes that have been the focus of studies related to groundwater contamination and ground collapse for many years. Finally, important tectonic features that have been described in several previous journal articles are present in the mapped area. These include the regional-scale Blue Ridge, Max Meadows, Pulaski, and Saltville faults, classic localities of the Max Meadows breccia, and a series of windows in which allochthonous thrust slices associated with tectonic evolution of the Pulaski thrust sheet are exposed. The VDGMR is making a focused effort to update and make legacy geologic data available to a variety of users through digital distribution of formal publications.