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Description
Geologic mapping in the Big Bald Mountain area, White Pine County, Nevada, was undertaken in order to relate the structure and stratigraphy of this area with the Cordilleran Miogeosyncline. Mapping has revealed the presence of 17,087 feet of Paleozoic rocks that range in age from Cambrian to Mississippian. These rocks have been intruded by a Quartz Monzonite Porphyry stock and felsic dikes. Two major episodes of faulting have uplifted Big Bald Mountain resulting in deposition of fanglomerates that surround the mountain. Lower Paleozoic formations found in the Big Bald Mountain area are predominantly limestone, shale, and quartzite. These include the Cambrian Prospect Mountain Quartzite, Secret Canyon Shale, Hamburg Dolomite, Dunderburg Shale, and the Windfall Formation and the Ordovician Pogonip Group, Eureka dolomite deposition begins with the Hanson Creek Formation and includes the Silurian Lone Mountain Dolomite and most of the Devonian Nevada Formation. Limestone deposition returned to form the Devonian Devil’s Gate Limestone. Small exposures of the Mississippian Pilot Shale, Joana Limestone, and the Diamond Peak Formation were found. Chert pebbles derived from the Eugeosynclinal Vinini Formation to the west are found in the Diamond Peak Formation and indicate a clastic wedge formed in this portion of Nevada in the Mississippian. The Paleozoic rocks near Big Bald Mountain are extensively faulted, the faults having two major trends. An older set of faults trends northwest and is offset by younger faults which trend northeast. The youngest faults are probably Pliocene to Pleistocene in age and have uplifted Big Bald Mountain to its present elevation. Clast composition indicates two Quaternary conglomerates. An older Quaternary fanglomerate is composed of pre-Mississippian Paleozoic pebbles. A younger conglomerate, located near Overland Pass, is composed almost entirely of Mississippian clasts. The clasts come from an exposure of Mississippian rocks which were exposed by the last tectonic event in the Big Bald Mountain area.
