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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> Geologic Setting <br /> The SMC area lies within the Colorado Plateau geologic province, an area of generally flat lying <br /> Paleozoic and Mesozoic rocks that has been gently folded and faulted with local areas of Tertiary <br /> intrusives and anticlinal structures associated with upwelling of Pennsylvanian age salt deposits. In <br /> the area of the SMC, the northwest trending axis of Big Gypsum Valley aligns with a collapsed and <br /> eroded anticline formed by the intrusion of deeper salt deposits the flowage of which ceased in late <br /> Jurassic time. Normal faults associated with the collapse are present on the northeast and southwest <br /> limbs of the anticline and intercept strata near the portals of some of the mine declines(see Figure 4- <br /> 4). <br /> At the SMC, the exposed rocks include the lower Salt Wash Member and upper Brushy Basin <br /> Member of the Morrison Formation of Jurassic age,which are overlain by the Cretaceous age Burro <br /> Canyon Formation and the Dakota Sandstone in the southwestern portion of the claim block. These <br /> strata form a high ridge or cuesta that dips to the southwest between 15°and 20°. Other strata in the <br /> area include older strata of early Jurassic and Triassic age(see Figure 4-5). <br /> Hydrologic Setting <br /> The hydrology of the area is limited with regard to surface water and groundwater resources. The <br /> relatively dry high desert climate of the study area produces few perennial streams in the region. The <br /> drainages of Big Gypsum Valley and Disappointment Valley are ephemeral and only flow from runoff <br /> produced by intense precipitation events. The only perennial stream is the Dolores River, located 2 <br /> miles to the north and 3.25 miles to the west of the SMC area. The headwaters of the Dolores River <br /> are located 60 miles to the southeast in the San Juan Mountains. U.S. Geological Survey(USGS) <br /> gaging stations on the Dolores River indicate that the river may slightly gain in flow in the reach <br /> northwest of the SMC area. <br /> Regionally, bedrock groundwater systems have been studied by numerous researchers, several of <br /> which have adopted the nomenclature first used by Avery(1986). Avery assigned letters to packages <br /> of strata that contained one or more notable aquifers.The shallowest bedrock aquifer in the area is <br /> the D aquifer which consists of the Dakota Sandstone and Burro Canyon Formation. The D aquifer is <br /> confined above by the Mancos Shale and below by the Brushy Basin Member of the Morrison <br /> Formation. The D aquifer is the preferred groundwater source in the region when depth and water <br /> quality are acceptable for development. <br /> Western Water& Land, Inc. viii <br />