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Minor faulting of limited vertical displacement has been observed in other nearby mines. <br /> However,in the Bowie No. 1 Mine,a fault with a displacement of fifty feet was encountered during <br /> mining, and drill-hole data indicates the presence of other faults in the life-of-mine area with <br /> similar displacements. The faults which have been encountered in these mines tend to be <br /> high-angle, normal faults. <br /> The steep slopes of the stream valleys and the instability of the rock strata in the North Fork <br /> drainage basin have contributed to numerous landslides, mud flows and rock falls. These mass <br /> wasting features have been mapped by W.R. Junge of the Colorado Geological Survey and <br /> published as an open file report entitled "Geologic Hazards, North Fork Gunnison River Valley, <br /> Delta and Gunnison Counties, Colorado." <br /> Geologic units exposed in the North Fork drainage basin consist of Late Cretaceous to Early <br /> Tertiary Age sedimentary strata,Tertiary Age igneous intrusives, and Quaternary Age alluvial and <br /> colluvial deposits. The units of the Late Cretaceous in the general area are described below in <br /> ascending order. A stratigraphic column representing the geology of the coal member of the <br /> Mesaverde Formation in the permit area can be found on Map 2-10, Volume 2 of the PAP. <br /> The Mancos Shale is the oldest formation exposed in the region. This unit is composed of over <br /> 4,000 feet of gray marine shales and minor interbedded buff sandstones. This unit is highly <br /> erodible and unstable. Erosion and over-steepening of slopes in this formation produce the <br /> numerous rock falls and landslides observed in the lower North Fork drainage basin. <br /> The Mesaverde Formation conformably overlies the Mancos Shale. This formation consists of <br /> approximately 2,300 feet of marine and terrestrial sedimentary rocks. The Mesaverde Formation <br /> is the coal-bearing formation in the region and is divided into four main members - the Rollins <br /> Sandstone, the Lower Coal Bearing (Bowie) member, the Upper Coal Bearing (Paonia) member, <br /> and the Barren (Undifferentiated) member. <br /> The Rollins Sandstone member is a 120- to 300-foot-thick, massive, cross-bedded, medium- to <br /> fine-grained, buff to white sandstone. This sandstone is regionally extensive and resistant in <br /> outcrop and forms prominent cliffs. This member is used regionally as a marker horizon to define <br /> the top of the Mancos Shale and the bottom of the coal-bearing horizons. <br /> The Lower Coal Bearing (Bowie) member consists of 260 to 350 feet of interbedded gray shales, <br /> thin to thick lenticular beds of buff-colored, fine- to medium-grained sandstones, and coals. The <br /> top of the member is usually capped by a massive buff-colored sandstone up to 90 feet in thickness. <br /> This sandstone, however, appears not to be a single persistent bed, but is actually several thick <br /> lenticular sandstones occurring at progressively lower stratigraphic horizons from east to west. <br /> Three coal beds exist in the Lower Coal Bearing member - the A (Old King) horizon, the B <br /> (Somerset) horizon, and the C (Bear) horizon. The A horizon is immediately above the Rollins <br /> sandstone and is not currently mined. The B horizon contains two coal seams and occurs about <br /> 20 to 120 feet above the Rollins sandstone. The C horizon contains one coal seam that occurs 50 <br /> to 100 feet above the B horizon. <br /> 7 <br />