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-32- The Lower Coal-Bearing (Bowie) Member consists of 260 to 350 feet of interbedded gray shales, thin to thick lenticular beds of buff-colored, fine- to medium- grained sandstones, and coals. The top of the member~is usually capped by a massive buff-colored sandstone up to 90 feet in thickness. This sandstone, however, appears not to be a single persistent bed, but is actually several thick lenticular sand- stones occurring at progressively lower stratigraphic horizons from east to west. Three coal horizons exist in the Lower Coal-Bearing Member; the "A" (Old King) horizon, the "B" (Somerset) horizon, and the "C" (Bear) horizon. The "A" horizon is immediately above the Rollins .sandstone and is not currently mined. The "B" horizon contains two coal seams and occurs about 20 to 120 feet above the Rollins Sandstone. This horizon is presently maned by U.S. Steel at the Somerset mine and may be mined at the Mt. Gunnison mane. The "C" horizon contains one coal seam that occurs 50 to Z00 feet above the "B" horizon. This has been mined by U.S. Steel, and is currently mined at the Bear mines. It may be mined at the Mt. Gunnison mine in the future. The Upper Coal-Bearing (Paonia) Member consists of 200 to 500 feet of gray shales, interbedded, buff-colored, lenticular sandstones, and coals. The top of this member is generally considered to be capped by a massive, cliff-forming sandstone. However, like the similar sandstone at the top of the Lower Member, this sandstone is not a single persistent bed. Dri11 hole data for both the Mt. Gunnison and the Somerset life-of-mine areas show this sandstone unit to occur as several lenticular sandstones at slightly different stratigraphic horizons. Three coal horizons have been identified in this member; the "ZY' (Oliver) horizon, the "E" (Hawk's Nest) horizon, and the "F" horizon. The "D" horizon occurs immediately above the "massive sandstone" of the Bowie member and contains three seams. This horizon is currently mined in the Orchard Valley mine. It may be mined in the Hawk's Nest mine, at the Mt. Gunnison mine, and by Bear Coal at the Bear No. 3 mine in the future. The "E" horizon occurs about 130 Feet above the "D" horizon and contains two coal seams. This horizon is currently being mined at the Hawk's Nest mine and at the Blue Ribbon mine. It may be mined at the Mt. Gunnison mine and at the Bear No. 3 mine in the future. The "F" horizon contains two coal seams and presently is only mined at the Mt. Gunnison mine. Coal seams of this horizon do not exist to the north of the North Fork in thicknesses sufficient for mining. The Barren (undifferentiated) Member of the Mesa Verde Formation consists of terrestrial sedimentary rocks up to 1,600 feet in thickness. This unit consists of fine-grained buff-colored Zen titular sandstones, gray shales and thin Ienticvlar coal beds. The sandstones predominate and are highly lenticular, discontinuous and of limited lateral extent in outcrop. The Mesa Verde Formation is unconforno-ably overlain by the Tertiary aged Rudy or t9asatch Formation. This formation consists of red to buff-colored shales, zed sand- stones, and red to gray conglomerates. The sediments forming this formation are weathered volcanic rocks. The Ohio Creek conglomerate is the basal unit within the formation and is Z00 to 200 feet thick. Igneous intrusive rock exist within the North Fork Drainage Basin. A diorite plug about 2,000 feet in diameter outcrops along Hubbard Creek in the SE'a of Section 27. This may represent the erosional rem¢:ants of a volcanic flow feeder. SiI1s have injected the Lower Coal-Bearing Member, particularly the "B" and "C" seams. These sills consist of diorite and appear to have their source to the northwest df Terror Creek.