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-23- <br />and is not currently mined. The "B" horizon contains two coal seams <br />and occurs about 20 to 120 feet above the Rollins sandstone. This <br />horizon is presently mined by U.S. Steel at the Somerset Mine The <br />"C" horizon contains one coal seam that occurs 50 to 100 feet above the <br />"B" horizon. This horizon has been mined at U.S. Steel's Elk Creek <br />Mine and the Bear No. 1 and 2 Mines, and is currently mined at the Bear <br />No. 3 Mine. <br />The Upper Coal-Bearing (Paonia) member consists of 200 to 500 feet of <br />gray shales, interbedded, buff-colored, lenticular sandstones, and <br />coals. The top of this member is generally considered to be capped by <br />a massive, cliff-forming sandstone. However, like the similar <br />sandstone ak the top of the Lower Coal member, this sandstone is not a <br />single persistent bed. Drill hole data for both the Mt. Gunnison and <br />the Somerset life-of-mine areas show this sandstone unit to occur as <br />several lenticular sandstones at slightly different stratigraphic <br />horizons. <br />Three coal horizons have been identified in the Upper Coal member, the _ <br />"D" (Oliver) Horizon, the "E" (Hawk's Nest) horizon, and the "F" <br />horizon. The "D" horizon occurs directly above the "massive" sandstone <br />of the Lower Coal-Bearing member and contains three seams. This <br />horizon is currently being mined in the Orchard Valley Mine, and is <br />planned to be mined at the Hawk's Nest Mine.: This seam is mined by <br />Bear Coal in the Bear No. 3 Mine. The "E" horizon occurs about 130 <br />feet above the "D" horizon and contains two coal seams. This horizon <br />is currently being mined at the Hawk's Nest Mine and at the Blue Ribbon <br />Mine. It may be mined at the Mt. Gunnison Mine and at the Bear No. 3 <br />Mine in the future. The "F" horizon contains two coal seams and <br />presently is only mined at the Mt. Gunnison Mine. Coal seams of the <br />"F" horizon do not exist to the north of the North Fork in thicknesses <br />sufficient for mining. <br />The Barren (Undifferentiated) member of the Mesa Verde Formation <br />consists of up to 1,600 feet of terrestrial sedimentary rocks. This <br />unit consists of fine-grained, buff-colored, lenticular sandstones, <br />gray shales and thin lenticular coal beds. The sandstones predominate <br />and are highly lenticular, discontinuous and of limited lateral extent <br />in outcrop (Johnson, 1948). <br />The Mesa Verde Formation is unconformably overlain by the Tertiary Age <br />Rudy or Wasatch Formation. This formation consists of red to <br />buff-colored shales, red sandstones, and red to gray conglomerates. <br />The sediments of this formation are weathered volcanic rocks. The Ohio <br />Creek conglomerate is the basal unit within the formation and is 100 to <br />200 feet thick. <br />Igneous intrusive rocks exist within the North Fork Drainage Basin. A <br />diorite plug about 1,000 feet in diameter outcrops along Hubbard Creek <br />in the SE 1/4 of Section 7. This may represent the erosional remnants <br />of a volcanic flow feeder. Sills have injected the Lower Coal-Bearing <br /> <br />