Northeastern Section (39th Annual) and Southeastern Section (53rd Annual) Joint Meeting (March 2527, 2004)
Paper No. 56-5
Presentation Time: 1:00 PM-5:00 PM

DETECTION OF FAULTS AND FAULT TRACES IN THE SHENANDOAH VALLEY, VIRGINIA USING LIDAR IMAGERY

WIECZOREK, Gerald F., HARRISON, Richard W., MORGAN, Benjamin A., WEEMS, Robert E., and OBERMEIER, Steve F., U.S. Geol Survey, National Center, MS 926A, Reston, VA 20192, gwieczor@usgs.gov

A limited area of LIDAR imagery taken with 5-m cell-size spacing in the eastern Shenandoah Valley reveals a linear trace near the town of Harriston in central Virginia. The shaded relief image produced from the LIDAR shows a linear trace that passes northwestward (N20W) from Paine Run for at least 6 km across Tertiary and Quaternary alluvium. The alluvium overlies lower Paleozoic Shady Dolomite and Waynesboro Formations. These rocks are largely weathered to saprolite, having undergone extensive dissolution; numerous sinkholes have propagated upward through the alluvium. At one location, sheared saprolite of the Waynesboro Formation suggests a vertical fault; the saprolite is extensively oxidized and water seeps are present in the outcrop. We interpret the linear trace to be a fault (called here the Harriston fault) of unknown age. The fault could be of Paleozoic or Mesozoic age and its surface trace a result of subsidence caused by ground water circulation along the fault in the underlying karst. Alternatively, the fault could be much younger and topographic expression in the alluvium a result of Pleistocene or younger movement. The linear patterns in the LIDAR imagery suggest a compressional stepover in a left-lateral strike-slip fault system. The northwest direction of the Harriston fault trace and steep orientation of the observed fault surface are consistent with focal mechanisms of monitored earthquakes deeper than 8 km in the central Virginia seismic zone. The LIDAR imagery should be a useful tool in the Shenandoah Valley to delineate faults and for exploration of ground water along buried faults, and detection of potential pollution problems, a concern for agriculture and industry.

Northeastern Section (39th Annual) and Southeastern Section (53rd Annual) Joint Meeting (March 2527, 2004)
General Information for this Meeting
Session No. 56--Booth# 31
Geologic Hazard Issues (Posters)
Hilton McLean Tysons Corner: Ballrooms A and B
1:00 PM-5:00 PM, Friday, March 26, 2004

Geological Society of America Abstracts with Programs, Vol. 36, No. 2, p. 120

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