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2.04.6 <br />1 RESPONSE continued <br />the southern edge of the Wyoming Basin physiographic province <br />and immediately north of the White River plateau, a westward <br />extension of the Southern Rocky Mountains province (Raisz <br />1972) . The Williams Fork Mountains range in elevation from 6500 <br />ft. to 8500 ft. above sea level. They encompass roughly 150 <br />sq.mi. and are bounded by the Yampa Valley to the north and <br />the Williams Fork to the south. Regional drainage is described in <br />the surface water hydrology report. <br />Structure <br />With regard to major tectonic units, the Hayden Gulch area is <br />located in the structural limb separating the Sa~ Wash Basin to <br />the north and the White River Uplift to the south (Grose 1972). <br />Figure 2 shows the significant local structural features in the <br />surrounding area. Many folds and faults modify the regional <br />. structure, although the strata dips predominantly northward in <br />this area. Faulting in the area is northwest trending. The site <br />is situated on the southwestern limb of the small, northwest <br />plunging Watering Trough syncline (Phillips et al, 1976) . Strata <br />in the immediate area dip 4 to 8 degrees northeast (Bass et al. <br />1955). <br />In addition to the larger fault structures shown on Figure 2, a <br />fault zone consisting of a number of closely spaced normal faults <br />were found along the Hayden Gulch road (Phillips et al. 1976). <br />The zone apparently trends westward, but the combined dis- <br />placement is not known. <br />Stratigraphy <br />Figure 3 is a generalized geologic column of the area. All bed- <br />rock exposed in the Hayden Gulch area is Upper Cretaceous. <br />The youngest is the Lewis shale, followed by the Williams Fork <br />and Iles formations of the Mesa Verde group, and the Mancos <br />Shale. Since bedrock older than the Mancos shales is far below <br />