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West E!k Mine <br />lenticulaz in nature. Although typically fine to coazse grained, the sandstones may locally be <br />conglomeratic. <br />Tertiary Wasatch Formation <br />The Wasatch Formation of Tertiary age lies unconformably atop the Upper Cretaceous Mesaverde <br />Formation. Rocks of the Wasatch Formation aze only exposed in the easternmost portions of the <br />West Elk Mine coal lease azea where they cap the highest mesas, including West Flatiron in the <br />Box Canyon permit revision azea. Atop West Flatiron Mesa, the Wasatch Formation is represented <br />by brownish-gray to reddish mudstone and its chazacteristicbasal conglomerate of sandstone, chert, <br />and volcanic rocks. <br />Other Rocks and Deposits <br />Further to the south and east, igneous intrusives of Tertiary age form the laccoliths of Mt. Gunnison <br />and West Beckwith Peak. There is a low probability of intrusive dikes/sills within the permit azea, <br />based on an aerial magnetic survey completed in 1997. <br />Unconsolidated deposits of sand, gravels, and boulders (Pleistocene age) derived from the tertiary <br />intrusives and Wasatch Formation may cover the Barren and Ohio Creek Members of the <br />Mesaverde locally. These deposits aze the result of more recent erosion and mass-gravity <br />movements. <br />Coal Seams and Related Strata <br />B-Seam <br />The B-Seam is the lowermost minable coal seam within the lease azea. This seam constitutes a <br />lazge portion of the recoverable reserves and is of high economic importance. <br />The B-Seam and adjacent strata gently dip to the northeast at approximately 3.5 degrees (Map 11). <br />However, in the Box Canyon permit revision azea, the strike swings to nearly east-west and the dip <br />shallows to approximately two degrees to the north. This change of strike and lessening of the dip <br />is significant because it reduces the concern about block glide instability over the Oliver No. 2 <br />Mine and bedding plane failures in the Box Canyon area. Photo mapping by Intraseazch indicated <br />numerous flat and even some gentle south dips of surface outcrops in the Box Canyon area. B- <br />Seamoutcrops occur along the North Fork of the Gunnison River to the north and west of the mine <br />portal and along Minnesota Creek. Some burning of the B-Seam has occurred along outcrops on <br />Jumbo Mountain and in the Minnesota Creek drainage, predominantly on south and west-facing <br />slopes. <br /> <br />2.04-25 Revised Jun. l995 PR06; RevisedJan. 1998 PR08 <br />