Structural geology of the Christiansburg area, Montgomery County, Virginia

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Virginia Polytechnic Institute and State University

The Christiansburg map area consists of about 19 square miles in Montgomery County, Virginia, and is underlain by sedimentary rocks ranging in age from Middle Cambrian to Middle Ordovician. Post-Ordovician strata have been eliminated by thrusting and erosion. From south to north the rocks belong to five fault blocks: the Max Meadows, Pulaski, Saltville, Salem, and Catawba blocks.

The Max Meadows block contains only the Middle Cambrian Rome Formation, the oldest rocks exposed within the area. The parautochthonous Saltville block includes rocks from Upper Cambrian to Middle Ordovician in age, which are exposed in windows of the Pulaski fault block. The Pulaski block contains highly fractured and brecciated Cambrian carbonates. The Salem block contains rocks ranging in age from Middle Cambrian to Lower Ordovician. The Salem fault terminates west of Christiansburg, Virginia. Rocks of the Catawba block range from Middle Cambrian to Mississippian in age, but only the section up to the Middle Ordovician is exposed in the map area.

The windows through the Pulaski thrust sheet expose the large Christiansburg anticlinorium of the Saltville fault block. The size of each window is proportional to the size of the anticlinal fold developed on the crestal portion of the anticlinorium. The faulting may have occurred shortly after deposition of the Mississippian strata exposed in the Price Mountain window north of the area. The apparent parallelism of the thrust sheets and the overridden strata indicates that much of the present structural relief was formed after emplacement of the thrust sheets.