LONE MOUNTAIN: AN ILLUSTRATIVE EXAMPLE OF RANGEFRONT MORPHOLOGY ALONG AN ACTIVE NORMAL FAULT

Lone Mountain provides a particularly illustrative example of rangefront morphology controlled by active normal faulting. Located in the western Great Basin 25 km west of Tonopah, the mountain reaches 2770 m elevation. The northwest flank of the mountain is bounded by a normal fault which is traceable for about 30 km. Displacement along the fault has produced at least three offset and now abandoned alluvial and pediment surfaces which show progressively greater offset with age. The oldest of these surfaces sits about 10 m above current grade and are characterized by deeply dissected fan remnants and pediments with rounded crests. Intermediate aged surfaces are moderate to deeply dissected and sit about 5 m above current grade with well developed pavements and a medium to dark varnish. The youngest surfaces are not dissected, and not far out of active stream grade. In sum, the geomorphic evolution of abandoned alluvial surfaces with time is well demonstrated at Lone Mountain. Additionally, there exist numerous youthful appearing single-event scarps ranging from 0.25 to 0.75 m high which locally cut Late Pleistocene pluvial lake deposits adjacent to the Range. Thus, the most recent movement has been active post-Late Pleistocene and probably late Holocene.