Geology of the southwestern end of Walker Mountain, Virginia

Walker Mountain, in Washington County and adjacent parts of Smyth County, Virginia, is on the northwest limb of a major syncline which is bounded on the northwest and southeast by the Saltville and Walker Mountain overthrusts, respectively. The formations, Middle Cambrian to Upper Devonian, composing the fault block have a maximum aggregate thickness of about 9500 feet. The most significant geologic feature near the southwestern end of the ridge is a great unconformity marked by the absence of all the Silurian and a part of the Lower Devonian strata. Southwest along the Walker Mountain fault, the overthrust Cambrian dolomite is in contact with successively older formations in the upper part of the Walker Mountain block. Near Lyons Gap, the overthrust Cambrian dolomite lies upon Upper Devonian shales and near the southwestern end of Walker Mountain upon the Lower Ordovician limestones. The regional structure is complicated by small folds with axes parallel to the strike of the beds in the fault block; by cross folds which trend northwest-southeast; and by cross faults, some of which cut both overridden and overthrust rocks and locally offset the trace of the Walker Mountain fault. It is thought that the cross faults represent shears produced during the formation of the cross folds by local rotational stresses in the horizontal plane. Perhaps the cross stresses were developed in the Walker Mountain block during the waning advance of the overthrust mass along an irregular surface of the Walker Mountain fault.