The Virgin Valley-McGee Mountain area is located in the northwest
corner of Nevada in the northwestern part of the Basin and
Range structural province.
Rocks within the area consist predominantly of Miocene to
Pleistocene volcanic rocks and volcanic derived sedimentary rocks.
The volcanic rocks include rhyolite, rhyolite welded tuffs, and
basalt. Sedimentary rocks are volcanic conglomerates, sandstones,
siltstones, and mudstones with subordinate amounts of diatomite,
lignite, opaline chert, and volcanic tuff. Unconsolidated deposits
include Quaternary alluvium, landslide debris, and playa sediments.
The entire sequence is 2200± feet thick.
Rock units within the thesis area can be correlated with units
of the same age throughout northeastern California, northwestern
Nevada, central and southern Oregon, and western Idaho.
The principal structural features within the area are the
Virgin Valley syncline, Big Mountain-McGee Mountain anticline, and
the tilted fault-block mountain that gives rise to the Big Mountain-
McGee Mountain complex. The deformation that produced the broad,
gentle folds and fault-block mountain were part of the Basin and
Range orogeny. The episode of greatest faulting occurred during
Pleistocene time, producing the present features of the Basin and
Range structure within the thesis area and the surrounding region.