Resource assessment of the Bureau of Land Management's Winnemucca District and Surprise Resource Area, Northwest Nevada and Northeast California; geology and its relation to resource genesis

The U.S. Geological Survey (USGS) is a party to joint interagency Memorandum of Understandings (MOUs) with the Bureau of Land Management (BLM) and the U.S. Bureau of Mines (USBM) to coordinate resource assessments and evaluations of BLM administered lands. Resource assessments of BLM Resource Areas, that are conducted by the USGS under these MOUs, assist the BLM in meeting inventory and evaluation, resource-management planning, and other management requirements of the Federal Land Policy and Management Act of 1976 (FLPMA). This report is one of several to be generated as part of a resource assessment of BLMadministered lands in northwest Nevada and northeast California.

The project area is composed of three contiguous BLM Resource Areas (RAs), totalling 13.5 million acres, in northwest Nevada and northeast California (figs. 1, 2). The SonomaGerlach and Paradise-Denio Resource Areas in northwest Nevada together comprise the BLM's Winnemucca District. The Surprise RA is located in extreme northwest Nevada and northeast California and is part of the BLM's Susanville District, which is administered by the BLM's California state office. Henceforth in this report, the project area will be referred to as the Winnemucca-Surprise Resource Assessment Area (WSRAA).

Sources of geologic data used in this compilation include the state geologic maps of Nevada (Stewart and Carlson, 1978) and California (Jennings, 1977). Other regional, largerscale geologic maps of the area that were used include the 1:250,000 scale Nevada county geologic maps (Willden, 1964; Bonham, 1969; Willden and Speed, 1974; Johnson, 1977), l:125,000-scale geologic quadrangle maps (Ferguson and others, 1951, 1952; Muller and others, 1951), 1:62,500-scale geologic quadrangle maps (Gilluly, 1967; Silberling and Wallace, 1967; Wallace and others, 1969a, b) and several 1:48,000- and 1:24,000-scale geologic quadrangle maps (e.g., Erickson and Marsh, 1974 b, c; Vikre, 1985b; Theodore, 1991 a, b; 1994; Doebrich, 1994, 1995; Jones, in press a, b).

The geology of the WSRAA records a complex history of Paleozoic and Mesozoic accretionary and plutonic events followed by Tertiary extensional tectonism and magmatism. This report chronologically outlines sedimentologic, magmatic, and tectonic events that shaped the geology of the WSRAA and relates these events to the genesis and distribution of the region's mineral and non-mineral resources. This is the initial report of several scheduled to be prepared on the WSRAA. Others reports include geochemistry, geophysics, hydrothermal alteration classification using Landsat Thematic Mapper imagery, assessment of metallic mineral resources, assessment of non-metallic mineral resources, and assessment of oil and gas resources.