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The Ohio Creek Conglomerate of very late Cretaceous and early <br />Tertiary age rests on the Mesaverde Group and is separated from it <br />by an irregular unconformity which indicates some channeling. The <br />formation consists of light-colored sandstone, locally containing <br />abundant pebbles of chert, jasperoid quartz, and several kinds of <br />igneous rocks. The sand of the matrix was largely derived from the <br />Mesaverde Group, from which it was eroded by early Tertiary <br />streams, and deposited chiefly in and around the channels of those <br />streams. The Ohio Creek Conglomerate is erratic and locally absent, <br />though in places it is as much as 200 feet thick. Where the pebbles <br />are scattered or lacking the Ohio Creek Conglomerate is difficult to <br />separate from the underlying Williams Fork Formation. <br />The Wasatch (Ruby) Formation lies unconformably on the Ohio <br />Creek Conglomerate or, where the Ohio Creek is absent, on <br />sandstone and shale of the Mesaverde Group. It is composed <br />principally of coarse red conglomeratic sandstone and dark red to <br />maroon sandy shale. Locally, an abundance of epidote and other <br />ferrous silicates produces a greenish color. The strong coloring of <br />the Wasatch (Ruby) Formation contrasts sharply with that of the <br />light-colored Ohio Creek Conglomerate and with the sandstone of <br />the Mesaverde Group. Conglomerate and sandstone predominate in <br />the lower 100 feet of the Wasatch (Ruby) Formation. Several <br />boulders of scoriaceuos basalt as much as 2-1 /2 feet in diameter are <br />present, and smaller pebbles of chert, jasperoid quartz, and a variety <br />of igneous and metamorphic rocks are widely distributed. Above the <br />conglomerate and sandstone zone, red and green shale and silt <br />predominate. <br />The local geology around the Blue Ribbon Mine consists ofTertiary <br />and Cretaceous sediments that strike north 77 degrees west and dip <br />from 1 to 3 degrees to the northeast. These sediments have been <br />incised by erosion, creating a topography characterized by deep <br />canyons that control drainage patterns which flow into the North <br />Fork of the Gunnison River and eventually into the Colorado River. <br />Geologic studies both in the field and of new large scale, color, <br />aerial photographs do not reveal any folding or faulting in the area. <br />This has also been upheld by the fact that no faulting had been <br />encountered in the workings of the Blue Ribbon Mine. However, <br />some slicken-sided jointing was reported to have led to poor roof <br />conditions in one section of the mine. It was not mentioned in the <br />permit application if the jointing was associated with any faulting. <br />The overburden of the Blue Ribbon Mine ranges from a few feet to <br />approximately 1,450 feet. <br />19 <br />