Geology of the Glenvar area, Roanoke County, Virginia

Abstract

Most of the Glenvar area, Roanoke County, Virginia, is in the Valley and Ridge Province of the Southern Appalachians. Poor Mountain of the Southern Appalachians is in the Blue Ridge Province. The area is underlain by rocks ranging in age from the Early Cambrian Unicoi Formation to the Early Mississippian Price Formation. All the rocks are allochthonous and constitute an imbricate structure the thrusts of which dip southeast. The four structural units which make up the area are, from northwest to southeast, the Pulaski fault block, the Salem fault block, the Max Meadows fault block, and the Blue Ridge fault block. The structure of the Pulaski fault block is dominated by the Catawba syncline. The normal northwestern limb of the syncline forms the crest of Fort Lewis Mountain and the overturned southeast limb forms the biconvex body of rocks along the base of the mountain. The southeastern limb is abnormally thin due to both stratigraphic omission and deletion by faulting of formations or portions of formation, which are present on the northwestern limb. The Salem fault block within the area is made up entirely of the Cambrian Elbrook Formation and the Max Meadows fault block is made up entirely of the Cambrian Rome Formation. Southeast-dipping thrust faults and drag folds, overturned to asymmetric to the northwest, dominate the structure of both fault blocks. The Cambrian Unicoi Formation crops out along the northwestern edge of the Blue Ridge fault block. Adjacent to the fault the Unicoi dips gently southeast. It is suggested that Blue Ridge fault developed in the basement and then broke upward to the base of the Rome Formation. As the mass moved northwestward, the Rome and the lower and middle Elbrook broke loose and were overridden by the Blue Ridge block. Continued compression overturned the southeastern limb of the Catawba syncline and finally caused the Salem and Max Meadows faults.