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West Elk Mine(C-1980-007) MT-9 <br /> sandstone, shale, and coal of upper Cretaceous and early Tertiary age. The geologic formations <br /> exposed in the North Fork Drainage Basin consist of Late Cretaceous to Early Tertiary Age <br /> sedimentary strata, Tertiary Age igneous intrusives, and Quaternary Age alluvial and colluvial <br /> deposits. The units are described below in ascending order: <br /> • The Mancos Shale is the oldest stratum exposed in the region and is of Late Cretaceous Age. <br /> This unit is composed of over 4,000 feet of gray marine shales and minor interbedded buff <br /> sandstones. This unit is highly erodible and unstable. Erosion and oversteepening of slopes in <br /> this formation produce the numerous rock falls and landslides observed in the lower North <br /> Fork Drainage Basin (lunge, 1978). <br /> • The Mesaverde Formation is of Late Cretaceous Age and conformably overlies the Mancos <br /> Shale. This formation consists of approximately 2,300 feet of marine and terrestrial <br /> sedimentary rocks. The Mesaverde Formation is the coal bearing formation in the region and <br /> is divided into five main members: the Rollins Sandstone, the Lower Coal Bearing (Bowie) <br /> Member, the Upper Coal Bearing (Paonia) Member, the Barren (Undifferentiated) Member <br /> (Johnson, 1948), and the Ohio Creek Member. <br /> o The Rollins Sandstone is a white to buff colored, well sorted, medium to fine grained <br /> sandstone, ranging from 150 feet to 300 feet thick. This sandstone is regionally <br /> extensive and resistant in outcrop and forms prominent cliffs. <br /> o The Lower Coal Bearing (Bowie) Member consists of 260 to 350 feet of interbedded <br /> gray shales, thin to thick lenticular beds of buff colored, fine to medium grained <br /> sandstones, and coals. Three coal horizons exist in this member: the A (Old King) <br /> horizon, the B (Somerset) horizon, and the C (Bear) horizon. The A horizon is <br /> immediately above the Rollins Sandstone and is not currently mined at any operation <br /> in the vicinity. The B horizon contains two coal seams and occurs about 20 to 120 feet <br /> above the Rollins Sandstone and has been mined by MCC. This horizon has also been <br /> mined at the Elk Creek and Bowie #2 Mines. The C horizon contains one coal seam <br /> that occurs 50 to 100 feet above the B horizon. This horizon has been mined at the Elk <br /> Creek Mine and was mined at the Bear No. 1 and 2 Mines. The top of the member is <br /> usually capped by a massive buff colored sandstone up to 90 feet in thickness. This <br /> sandstone, however, appears not to be a single persistent bed, but is actually several <br /> thick lenticular sandstones occurring at progressively lower stratigraphic horizons from <br /> east to west. <br /> o The Upper Coal Bearing (Paonia) Member consists of 200 to 500 feet of gray shales, <br /> interbedded, buff colored, lenticular sandstones, and coals. The top of this member is <br /> generally considered to be capped by a massive, cliff forming sandstone. Three coal <br /> horizons have been identified in the Upper Coal Member: The D (Oliver) horizon, the E <br /> (Hawk's Nest) horizon, and the F horizon. The D horizon occurs directly above the <br /> massive sandstone of the Lower Coal Bearing Member and contains three seams. This <br /> horizon was mined in the Bowie #1 and #2 Mines. The E horizon occurs about 130 feet <br /> Page 5 of 14 <br />