2018-09-04_GENERAL DOCUMENTS - C1980007

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18 The geologic formations exposed in the North Fork Drainage Basin consist of Late Cretaceous to Early Tertiary Age sedimentary strata, Tertiary Age igneous intrusives, and Quaternary Age alluvial and colluvial deposits. The units are described below in ascending order. The Mancos Shale is the oldest stratum exposed in the region, and is of Late Cretaceous Age. This unit is composed of over 4,000 feet of gray marine shales and minor interbedded buff sandstones. This unit is highly erodible and unstable. Erosion and oversteepening of slopes in this formation produce the numerous rock falls and landslides observed in the lower North Fork Drainage Basin (Junge, 1978). The Mesaverde Formation is of Late Cretaceous Age and conformably overlies the Mancos Shale. This formation consists of approximately 2,300 feet of marine and terrestrial sedimentary rocks. The Mesaverde Formation is the coal bearing formation in the region and is divided into five main members; the Rollins Sandstone, the Lower Coal Bearing (Bowie) Member, the Upper Coal Bearing (Paonia) Member, the Barren (Undifferentiated) Member (Johnson, 1948), and the Ohio Creek Member. The Rollins Sandstone is a white to buff colored, well sorted, medium to fine grained sandstone, ranging from 150 feet to 300 feet thick. This sandstone is regionally extensive and resistant in outcrop and forms prominent cliffs. 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. Three coal horizons exist in this 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 at any operation in the vicinity. The B horizon contains two coal seams and occurs about 20 to 120 feet above the Rollins Sandstone and has been mined by MCC. This horizon has also been mined at the Elk Creek and Bowie #2 Mines. The C horizon contains one coal seam that occurs 50 to 100 feet above the B horizon. This horizon has been mined at the Elk Creek Mine and was mined at the Bear No. 1 and 2 Mines. 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. 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. Three coal horizons have been identified in the Upper Coal 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 was mined in the Bowie #1 and #2 Mines. 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 was mined at the Blue Ribbon Mine. The West Elk Mine is mining the E Seam, but did not mine the E seam on Jumbo Mountain because this seam is split and comprised of several thin (< 5 ft.) coal benches which are separated by rock partings. The F horizon contains two coal seams and has been mined at the West Elk Mine. At the mine site, the coal is immediately overlain and underlain by shale. Coal seams of the F horizon do not exist to the north of the North Fork of the Gunnison River in thicknesses sufficient for mining. In the Jumbo Mountain area, the F Seam thins to less than five