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- 8 - <br />surface facilities are located along the lower slopes and valley floor <br />of Scullion Gulch. Bedrock at the site is the Upper Cretaceous age <br />Mesaverde Group. In this area, the Mesaverde Group has been sub- <br />divided into three formations: (1) the Upper Williams Fork Formation, <br />(2) the Lower Williams Fork Formation, and (3) the Iles Formation. <br />The Upper Williams Fork Formation forms prominent sandstone outcrops <br />and shallow mlluvial-covered ~ubcrops along the northeastern rim of <br />Scullion Gulch, shown by Map Sym~l 4c/Kwu on Fig. 3. The lower <br />portion of the northeastern valley side and the entire southwestern <br />valley side are underlain ~' outcrops and shallow mlluvial-covered <br />subcrops of the Lower Williams Fork Formation, shown by Map Symbol <br />Qc/Kcal. Bedding planes strike toward the north and northwest and dip <br />gently toward the east and northeast. Dip of bedding measured at the <br />site ranged from 5° to 17°. <br />The Upper Williams Fork Ebrmation is a thick, massive, fine to <br />medium-grained sandstone interbedded with gray siltstone, shale, and <br />occasional thin, discontinuous .layers of carbonaceous shale and mal. <br />The Lower Williams Fork Formation is made up of interbedded gray to <br />black siltstone, shale, carbonaceous shale and coal. The Lower <br />Williams Fork Formation also contains thin, often calcareous, lenses <br />of fine to very fine rained silty, well-cemented sandstones. In this <br />area, the Lower Williams Fork Formation is about 300 to 900 feet thick <br />and is underlain bi' the Iles Formation, which is an interbedded fine <br />to very fine-grained sandstone, siltstone, shale and occasionally <br />thin, discontinuous layers of opal. The Iles Formation does not crop <br />out at the surface facility site. The Iles Formation is shown on the <br />Geologic Cross-Sections, Fig. 5, by Map Symbol Ki. <br />