Geology of the Saltville-Broadford area

Abstract

The Saltville-Broadford area is largely on the northwestern limb of the Greendale syncline in the Valley and Ridge Province of Virginia. The area mapped covers 12 square miles of the northwest corner of Smyth County, Virginia.

The rocks in the area ranging in age from Cambrian to Mississippian are found in three different structural settings, the hanging wall and footwall of the Saltville fault, and in two thrust slices located along the trace of the Saltville fault. The hanging wall consists of the Honaker Dolomite of Cambrian age and younger rocks outside the map area. The footwall consists of the Price Sandstone, Maccrady Shale and Little Valley Limestone all of Mississippian age and older rocks outside the map area. The larger of the two slices consists of an overturned sequence of the Juniata Sandstone of Ordovician age to the Brallier Formation of Devonian age. The smaller slice consists of undifferentiated Devonian shale.

The Saltville fault, a low-angle thrust, has overturned and cut off the southeastern limb of the Greendale syncline. During thrusting, two slices, at least one of which is overturned, were carried with the overriding block to their present positions. A total of 12,500 feet of movement was measured where the Cambrian, Honaker Dolomite is in fault contact with the Mississippian Little Valley Limestone. Total movement of the fault is believed to be of the order of 4 miles.

The upper part of the Mississippian Maccrady Formation is a sequence of evaporites. Halite and gypsum constitute the chief economy of the Saltville area.