2012-12-20_GENERAL DOCUMENTS - C1981038

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Formation is composed of four members which are, in order of decreasing age, the Rollins Sandstone, the Lower and Upper Coal members and the Barren member. Minor faulting of limited vertical displacement has been observed in other nearby mines. However, in the Bowie No. 1 Mine, a fault with a displacement of fifty (50) feet was encountered during mining, and drill -hole data indicates the presence of other faults in the life -of -mine area with similar displacements. The faults which have been encountered in these mines tend to be high- angle, normal faults. The steep slopes of the stream valleys and the instability of the rock strata in the North Fork drainage basin have contributed to numerous landslides, mud flows and rock falls. These mass wasting features have been mapped by W.R. Junge of the Colorado Geological Survey and published as an open file report entitled "Geologic Hazards, North Fork Gunnison River Valley, Delta and Gunnison Counties, Colorado." Geologic units 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 of the Late Cretaceous in the general area are described below in ascending order. A stratigraphic column representing the geology of the coal member of the Mesaverde Formation in the permit area can be found on Map 2 -10, Volume 2. The Mancos Shale is the oldest formation exposed in the region. 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 over - steepening of slopes in this formation produce the numerous rock falls and landslides observed in the lower North Fork drainage basin. The Mesaverde Formation 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 four main members - the Rollins Sandstone, the Lower Coal Bearing (Bowie) member, the Upper Coal Bearing (Paonia) member, and the Barren (Undifferentiated) member. The Rollins Sandstone member is a 120- to 300 - foot - thick, massive, cross - bedded, medium- to fine - grained, buff to white sandstone. This sandstone is regionally extensive and resistant in outcrop and forms prominent cliffs. This 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) 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. 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 beds 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. The C horizon contains one coal seam that occurs 50 to 100 feet above the B horizon. 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 usually grades into a massive, Page 8 of 42