The Catoctin Mountain to U.S. Route 15 Transect at Morven Park

As discussed above, the layout of the transect at Morven Park paralleled (and preceded) the Selma transect, and was designed to sample the same general geology. Interesting differences occur at Morven Park, however, and attest to the truly three-dimensional character of the lithology and structure at depth. This figure is a northward-directed view of the 2-D electrical resistivity structure of Morven Park in Bostick depth section. The western border fault is interpreted to be steeply dipping at shallow depths (0-300 m), and then inflects to the east with depth at a more gentle dip in the deepest portions of the cross-section. As at Selma. the Morven Park section of the fault is constrained by mapping at the surface (Lee and Froelich, 1989, Smoot and Sutphin, personal communication, 2002), and by relatively lower resistivities at depth (~2300 to ~6000 Ohm-m; green-yellow to medium yellow to yellow-orange). Further to the east in this figure , the blues and greens (~35 to 1500 Ohm-m) are interpreted as being coincident with the weathered regolith and soils derived from the Leesburg member conglomerate, whereas the two relatively high resistivity hummocks at depth (~3800 to ~17,000 Ohm-m) are interpreted as a pair of Leesburg member conglomerate spires. The "wavelength" (mean horizontal spacings) and "amplitude" (vertical relief) of these spires in our data are consistent with those recognized in seismic reflection profiles collected nearby for the Loudoun county Government.

|| Culpeper Basin AMT || USGS - Eastern Earth Surface Processes Team || USGS - Geology || USGS ||

Contact: Herbert A. Pierce
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