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<br />002156 <br /> <br />Precipitation in the region varies from about 50 inches (127 cm) in <br /> <br />the Western Uintas to an annual average of about 10 inches (25.4 cm) in <br /> <br />the semiarid Monument. <br /> <br />GEOLO~ <br /> <br />Dominant geologic feature in the region is the Uinta Mountains, <br /> <br />largest east-west trending range in the Western Hemisphere. These <br /> <br />mountains are approximately 150 miles (241 km) long, and average about <br /> <br />35 miles (56 km) in width. <br /> <br />Boundaries of the uplift are rather indefinite, with mountain <br /> <br />flanks merging with various ridges and slopes. Central core of the <br /> <br />broad, asymmetrical uplift is composed of Precambrian metamorphic rocks. <br /> <br />The core is overlain by Paleozoic, Mesozoic, and locally Tertiary sediments <br /> <br />(fig. 2). Erosion has exposed older rocks, such as Precambrian, along <br /> <br />mountain crests. Regionally, beds are steeper dipping on the north <br /> <br />flank of the uplift than on the south, and they dip away from the mountains. <br /> <br />Along the flanks, and roughly paralleling the axis of the uplift, <br /> <br />are high-angle faults that apparently stemmed from the emergence of the <br /> <br />Uinta uplift during Laramide orogeny. Faulting is more prevalent along <br /> <br />the steeper north flank, the location of the Uinta Thrust Fault. This <br /> <br />major fault dips about 60 degrees to the south and extends from the west <br /> <br />side of Sheep Creek Canyon eastward into Colorado. <br /> <br />According to Hansen, in reference to the Flaming Gorge, area, "The <br /> <br />total thickness of stratified rocks exposed in the area, excluding the <br /> <br />metasedimentary Red Creek Quartzite, exceeds 42,000 feet lf2,802~. Of <br /> <br />this thickness, more than 20,000 feet (6,096 i1 - possibly as much as <br /> <br />, <br /> <br />\ <br /> <br />4 <br />