Inversion of gravity data to define the pre-Tertiary surface and regional structures possibly influencing ground-water flow in the Pahute Mesa-Oasis Valley region, Nye County, Nevada

A three-dimensional inversion of gravity data from the Pahute Mesa–Oasis Valley region reveals a topographically complex pre-Tertiary basement surface. Beneath Pahute Mesa, the thickness of the Tertiary volcanic deposits may exceed 5 km within the Silent Canyon caldera complex. South of Pahute Mesa in Oasis Valley, basement is shallower (< 1 km) but between this valley and the Timber Mountain caldera complex is a basin that probably represents, in part, a moat related to the Timber Mountain caldera complex. Of particular interest is a NE-trending lineament, named here the Thirsty Canyon lineament (TCL), separating terranes at significantly different elevations. Southeast of the TCL, a highly undulating basement surface descends deeply into several calderas, whereas NW of the TCL basement is relatively flat and shallow. Because as many as four calderas seem to abruptly terminate at the TCL, the TCL may reflect a major buried fault zone, which influenced caldera growth. This inferred Thirsty Canyon fault zone and several EW basement ridges in the derived 3-dimensional basin thickness model may influence the flow of ground water from the Pahute Mesa region to Oasis Valley.