STRUCTURAL GEOLOGY AND STRATIGRAPHY OF THE SALTVILLE, VA 7.5 MINUTE QUADRANGLE

The Saltville, VA 7.5 minute quadrangle is in the Valley and Ridge Structural Province of the Southern Appalachian Orogen. The geology is dominated by folded Cambrian to Mississippian rocks and contains faults only at the southeastern and northwestern portions of the quadrangle. In the south, the Cambrian Honaker and Nolichucky Formations are thrust northwestward, along the Saltville Fault, over Mississippian Maccrady and Little Valley Formations on the inverted southeast limb of the Greendale Syncline. A faulted thrust slice of probable Upper Devonian rocks occurs along the fault in the eastern portion of the area. On the north, the Copper Creek and Narrows faults project into the quadrangle from the southwest and northeast, respectively, but separation seems limited to an unknown but small amount of northwestward transport of Lower Ordovician Knox Group carbonate rocks over locally intensely folded Knox Group and Middle Ordovician limestone units. Discontinuous areas of autobreccia and silicification and minor mesoscopic folding occur along the poorly exposed fault zone. The nine mappable and named folds in the area are relatively broad and generally have characteristic Valley and Ridge geomorphic expression. Except for the southern 20 percent of the area, the quadrangle had not been mapped at a scale > 1:90,000 in the past 60 years. The 22 mappable units contain many previously undescribed features. Notable features include large cliff exposures of Silurian Tuscarora Formation quartz arenite with extensive trace fossils and structurally and stratigraphically controlled silica cementation; and a Silurian Rose Hill section that shows marked thickness variations and lenticular stratigraphy resulting from sporadic diagenetic lithification by hematite-bearing fluids. An approximately 500 m-thick section of Middle Ordovician carbonate rocks locally contains thin beds of soft-sediment folded calcareous sandstone that may be paleoseismites. The section is capped by extensive Quaternary and possibly older sediments created by block slides, debris flows, slumps, periglacial block movements, and fluvial deposition.