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1• <br />1 <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br /> <br />'• <br />rocks is considered the Ites Formation equivalent. Much o} the upper Iles is exposed in the steep <br />slope along the north bank of the White River immediately west of where County Road 65 bridges <br />the river. <br />The B Horizon sandstone is the uppermost continuous sandstone in the Iles Formation equivalent. <br />The top of B Horizon Sandstone shown on the accompanying stratigraphic column (see Figure 3-2) <br />is considered the contact between the Iles Formation and the Lower Williams Fork Formation. <br />Immediately above the B Horizon Sandstone, the lithology of the Mesaverde becomes notably finer <br />grained. Siltstones, mudstones, carbonaceous shales and coals predominate, with coarser grained <br />sediments filling a secondary role as sporadically occurring, laterally discontinuous sandstones. On <br />the basis of this lithologic change, Mesaverde Group sediments lying above the top of the B Horizon <br />are considered Lower Williams Fork Formation equivalents. The entire coal bearing portion of the <br />Lower Williams Fork is well exposed in the northeast wall of Scullion Gulch. The coal seams of the <br />Lower Williams Fork, as correlated by Western Fuels, are also shown in Figure 3-2. <br />Data gathered during exploration drilling programs indicates that the Upper Williams Fork Formation <br />equivalent can be separated from the Lower Williams Fork Formation on the basis of lithology and <br />depositional environment. The contact between the finer grained lagoonal-paludal, carbonaceous <br />deposits of the Lower Williams Fork and the coarser grained terrestrial deposits of the Upper <br />Williams Fork is marked by the thick cliff-forming sandstones that support the northeast rim of <br />Scullion Gulch. North and east of this rim are the thick, massive lenticular sandstones of the Upper <br />Williams Fork Formation. <br />9 <br /> <br />