Laserfiche WebLink
• 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 II.B-1) <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 coal 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 bearing interval <br />has been measured and described at numerous locations along this outcrop. <br />Data gathered during exploration drilling indicates that the Upper Williams Fork Formation equivalent <br />can be separated from the Lower Williams Fork Formation on the basis of lithology and depositional <br />origin. The contact between the finer grained lagoonal-paludal, carbonaceous deposits of the Lower <br />Williams Fork and the coarser grained terrestrial deposits of the Upper Williams Fork is marked by the <br />thick cliff-forming lenticular sandstones that support the northeast rim of Scullion Gulch. North and <br />east of this rim, the surface of the mine plan area is developed upon dip slopes of the thick, lenticular <br />• sandstone layers of the Upper Williams Fork Formation. <br />The face up areas for both the east and west mine portals are located on the steeply sloping northeast <br />wall of Scullion Gulch. As mentioned, the strata exposed on this slope are of the siltstone, <br />carbonaceous shale predominated Lower Williams Fork Formation. The thickness, attitude and <br />lithology of these outcrops are described in detail in a report entitled "Preliminary Geologic Field <br />Mapping, Scullion Gulch area, Rio Blanco County, Colorado", by Cameron Engineers, dated June <br />1978. The results of surface mapping correlate very well with the lithologic and geophysical logs of <br />bore holes drilled in the Scullion Gulch area. Refer to the log of hole #21013-16 and its comparison <br />with the nearby measured section begun at Station 3. <br />11.6.2 Geologic Structure The Deserado Mine Permit area lies on the southwest flank of the Red <br />Wash syncline, an asymmetrical flexure on the northeast flank of the Rangely anticline. The axis of <br />the syncline trends northwest/southeastgnd plunges to the southeast into the much larger synclinal <br />structure of the Piceance basin. The proposed refuse disposal area lies astride the apparent synclinal <br />axis. Map 4 (in the Maps and Illustration Volumes is a geologic map of the area. <br />Dips within the mine permit application area vary from 7 degrees to the northeast in leases D-047201, <br />C-023703, C-0126669, C-8424, C-8425, 04693 and COC-51551 (hereinafter referred to as the <br />lease area), to flat beneath most of the refuse disposal area, to as much as 70 degrees to the <br />• south/southwest along the northern edge of the disposal area, clearly illustrating the asymmetrical <br />nature of the Red Wash syncline. The entire coal bearing sequence and much of the overlying <br />(Permit Renewal #3 1/99) II.B-3 <br />