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member is used regionally as a marker horizon to define the top of the Mancos Shale and the bottom of the coal-bearing horizons. The Lower Coal Bearing (Bowie) members consist 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 sandstones 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 mined by the Somerset Mine, the West Elk Mine, and the Bear Mine. The C horizon contains one coal seam that occurs 50 to 100 feet above the B horizon. This has been mined at the Somerset Mine and•at the Bear Mines. 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 Coal member, this sandstone is not a single persistent bed. Drill hole data for both the West Elk 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 D (Oliver) horizon, the E (Hawk's Nest> horizon, and the F horizon. The D horizon occurs directly above the "massive" sandstone of the Lower Coal-Bearing member and contains three seams. This horizon is currently being mined in the Orchard Valley Mine. The E horizon occurs about 130 feet above the D horizon and contains two coal seams. This horizon has been mined at the Hawk's Nest Mine and at the Blue Ribbon Mine. It may be mined at the West Elk Mine and at the Bear No. 3 Mine in the future. The F horizon contains two coal seams and has been mined at the West Elk Mine. Coal seams of the F horizon do not exist to the north of the North Fork in thickness sufficient for mining. Overlying the Upper Coal Member is the Barren (Undifferentiated) member of the Mesaverde Formation. This unit consists of interbedded sandstones, shales, and coals. The unit is thought to be of marine origin and, as a result, the sandstones and the coals are highly _lg_