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Somerset Mine and at the Bear Mine and is currently being mined at <br />the West Elk Mine and the Bowie No. 3 Mine. The C horizon <br />contains one coal seam that occurs 50 to 100 feet above the B <br />horizon. This horizon was mined at the Somerset Mine and at the <br />Bear Mines. <br />The Upper Coal-Bearing (Paonia) member consists of 200 to 500 <br />feet of gray shales, interbedded, buff-colored, lenticular sandstones, <br />and coals. The top of this member is generally considered to be <br />capped by a massive, cliff-forming sandstone. However, like the <br />similar sandstone at the top of the Lower Coal member, this <br />sandstone is not a single persistent bed. Drill hole data for both the <br />West Elk and the Somerset life-of--mine areas show this sandstone <br />unit to occur as several lenticular sandstones at slightly different <br />stratigraphic horizons. Three coal horizons have been identified in <br />this member; the D (Oliver) horizon, the E (Hawk's Nest) horizon, <br />and the F horizon. The D horizon occurs directly above the <br />"massive" sandstone of the Lower Coal-Bearing member and <br />contains three seams. This horizon was mined at the Bowie # 1 <br />Mine (formerly known as Orchard Valley Mine) and at the Bowie <br />No. 2 Mine. The E horizon occurs about 130 feet above the D <br />horizon and contains two coal seams. This horizon has been mined <br />at the Hawk's Nest Mine and at the Blue Ribbon Mine. The F <br />horizon contains two coal seams and has been mined at the West <br />Elk Mine. Coal seams of the F horizon do not exist to the north of <br />the North Fork in thickness sufficient for mining. <br />Overlying the Upper Coal Member is the Barren (Undifferentiated) <br />member of the Mesaverde Formation. This unit consists of <br />interbedded sandstones, shales, and coals. The unit is thought to be <br />of marine origin and, as a result, the sandstones and the coals are <br />highly lenticular, discontinuous, of limited lateral extent in outcrop. <br />The unit ranges up to 1,500 feet in thickness. <br />The Mesaverde Formation is unconformably overlain by the <br />Tertiary aged Ruby or Wasatch Formation. This formation consists <br />of red to buff-colored shales, red sandstones, and red to gray <br />conglomerates. The sediments of this formation are weathered <br />volcanic rocks. The Ohio Creek conglomerate is the basal unit <br />within the formation and is 100 to 200 feet thick. <br />Igneous intrusive rock exists within the North Fork Drainage Basin. <br />A diorite plug about 1,000 feet in diameter outcrops along Hubbard <br />Creek in the southeast quarter of Section 7. This may represent the <br />erosional remnants of a volcanic flow feeder. Sills have injected the <br />Lower Coal-Bearing member, particularly the B and C seams. These <br />sills consist of diorite and appear to have their source to the <br />northwest of Terror Creek. <br />18 <br />