Extensional Tectonics of a Part of the Southwestern White Pine Range, Nevada: Implications for Petroleum Occurrence in Railroad Valley: ABSTRACT

Abstract

Extension exerts controls on migration and trapping of petroleum in rift settings, such as the Great Basin. Extensional controls are critical to the accumulation of petroleum in Nevada, including in Pine and Railroad Valleys. In these fields, reservoir permeability increased due to extension-related fracturing. These fractured reservoirs and structural traps may be contained within upper plates to regional detachments. Just northeast of Nevada`s most productive oil fields, a regionally extensive detachment is exposed in the White Pine Range. This detachment, the Blackrock fault, is a presently low, angle normal fault which dips <30{degrees} along most of its surface trace. The Blackrock fault is nonplanar and exhibits drastic changes in both orientation and geometry along its length. The amount of stratigraphic separation across the fault is also highly variable ranging from <30 to {approximately}3800 m. Upper plate structures to the Blackrock fault may influence oil fields in Railroad Valley. Rocks in the hanging wall of the Blackrock fault are more intensely faulted than rocks in the footwall. The upper plate faults strike north, northwest, east, and northeast. The {approximately}east-striking faults are youngest because they typically cut the other structures. These faults are closely spaced and largely interconnected which allows migration ofmore » hydrocarbons. Most of the hanging wall faults are high-angle normal faults which cut both Paleozoic and Oligocene rocks. In the Blackrock upper plate, Paleozoic, carbonate and minor siliciclastic rocks are unconformably overlain by Oligocene tuffs and tuffaceous sedimentary rocks of the Garret Ranch Group with interbedded rhyolites. Upper plate fracturing of the Paleozoic rocks and Garret Ranch Group is important because parts of both sections are producing reservoirs in Railroad Valley.« less