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• GEOLOGY Rocks exposed in the vicinity of Oxbow Mining's D-Seam exploration project area include the Upper Cretaceous, coal bearing Mesaverde Formation, and the Tertiary Wasatch Formation may also be present.. Because of the economic importance of the Mesaverde Formation, it has been subdivided into four stratigraphic units: the basal Rollins Sandstone member, the Coal-bearing member, Barren member, and the Ohio Creek member. The Rollins Sandstone Member is fine to very fine grained and becomes coarser grained. and more quartzose in the upper part; siliceous and some calcareous cement common but locally uncemented; tan to very lightgray. Where well cemented, this member will often form cliffs The coal-bearing Member consists of interbedded sandstones, siltstones; shales and coal. This member contains six major coal seams (A, B, C, D, E, and F) of economic significance. This unit is approximately 500 feet thick in the study area. There is a massive sandstone near the middle of the unit that has characteristics that resemble the Rollins Sandstone The Barren Member is characterized by interbedded lenticular sandstones, siltstones, shales and minor discontinuous coals. In the Bear Creek area this unit is approximately 700-800 feet thick. The thickness varies in part because the unconformable erosional • nature of the contact with the overlying Ohio Creek Member. There are many cliff- forming sandstones within the unit. The Ohio Creek Member consists of interbedded conglomerates, sandstone, siltstone, and shale. The conglomerate, which contains abundant pebbles of chert, jasperoid quartz, quartzite, and several kinds of igneous rocks, occurs erratically. Sandstones are. light gray to light tan; mudstones and shale are light gray to medium gray. Thickness varies from a few feet to 200 feet thick. The Tertiary Wasatch Formation lies unconformable on the Mesaverde. The Wasatch Formation consists of varicolored (mostly shades of brown, gray, and red) claystone and mudstones with local lenses of sandstone and volcanic sandstone, and a basal conglomerate. May also have local thin beds of coal near the base of the unit. This unit is often poorly consolidated and landslides and mudflows are common. Quaternary unconsolidated surficial deposits derived from late Tertiary volcanic rocks and Wasatch Formation. Clay, sill, and sand are primarily derived from the Wasatch Formation: gravel and boulders are primarily derived from extrusive rocks (basalts) capping Grand Mesa. It is difficult to differentiate between the Cenozoic units due to the thick vegetative cover and similarity of materials.. Alluvium is present in most of the tributaries as well as in the main valley of the North Fork of the Gurinison. The alluvium consists of unconsolidated rusty, gray and buff, very fine to coarse grained sandstones,' gravels, and boulders, 3