Eastern carbonate aquifer

The eastern and southeastern region of the NNSS is characterized by groundwater flow predominantly within a regional carbonate aquifer (Fig. 26.2) that is part of an extremely thick, sedimentary sequence of Neo­proterozoic to mid-Paleozoic (Devonian) marine carbonate and clastic rocks deposited at the western edge of a stable continental margin of the North American craton (Sweetkind et al. , 2010). The carbonate aquifer is the primary aquifer throughout much of the DVRFS (Mifflin and Hess, 1979; Belcher et al., 2004). This assemblage of mostly mid-Paleozoic rocks was deformed by Late Paleozoic and Mesozoic regional thrust faults which redistributed the assemblages of carbonate and clastic sediments (Cole,
1997; Cole and Cashman, 1999). These thrust-disrupted rock assemblages were intruded by small granitic stocks during the Late Cretaceous. The thrust faults are exposed at the surface primarily in and west of Yucca Flat; these rocks mark the approximate western boundary of carbonate — dominated groundwater flow (Fenelon et al, 2010).

image391 Подпись: Rainier /MeSa - Подпись: о о о о см

image286"Thick fanglomerate, alluvial deposits and the distal facies of eastward thinning volcanic rocks uncomformably overlie the Paleozoic sedimentary rocks in the extensional basins of Yucca and Frenchman Flat (Fig. 26.2), two of the major sites of underground testing.

Подпись: о о о о (У) о ‘ Shoshone ‘ Mountain

image396 Подпись: .Ash Meadows Flow System/ Подпись: о о о о CD о

Yucca ■ n Mountain ■

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26.2 Major hydrological flow systems of the NNSS modified from Fenelon et al. (2010). Regional groundwater flow in the eastern NNSS is primarily through the regional carbonate aquifer (brick pattern) with local contributions from isolated alluvial and volcanic aquifers (v-stiple pattern). The discharge areas for this flow system are Ash Meadows and Alkali Flats/Death Valley. Groundwater flow in the western NNSS is primarily in volcanic aquifers (v patterns) with discharge areas in Oasis Valley and Alkali Flats/Death Valley. These two flow systems control the migration of radionuclides produced during underground testing of nuclear weapons on the NNSS.

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