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RULE 2 PERMITS <br /> <br />Rule 2 Permits 2.04-9 Revision Date: 6/4/25 <br /> Revision No.: MR-264 <br />forming unit in the Danforth Hills, has been called the “White Rock” because of its characteristic <br />exposures. <br /> <br />The deposition of the Trout Creek Sandstone marked a major regression of the Late Cretaceous <br />seaway over a large region. <br /> <br />The resulting clean, well sorted blanket sand formed by this migrating beach and barrier island <br />complex is an aquifer of regional extent in Northwest Colorado. Under the area to be mined within <br />the Colowyo Permit area, the Trout Creek sandstone underlies the lowest surface recoverable seam <br />to be mined by 800 feet. Considering the nature of the intervening strata which is comprised of <br />primarily claystone, shales, and siltstones; it is very doubtful the Colowyo operation will impact <br />the Trout Creek sandstone. <br /> <br />The Iles Formation in the permit area is estimated to be 1,375 feet thick. The Iles Formation forms <br />most of the cliffs that surround the Axial Basin. The Iles Formation lies approximately 1,700 feet <br />beneath the actual mining area; however, minor folds or faults in the regional trend bring the <br />formation nearer the surface. <br /> <br />Williams Fork Formation - The Williams Fork Formation consists of alternating beds of sandstone, <br />sandy shale and coal. It is distinguished from the Iles Formation by its thick zones of brick red <br />sandstone and shale, which have been colored from adjacent naturally-burning coal beds, a <br />common occurrence in the Axial area. The coal beds in the formation are uniformly distributed in <br />the vicinity of the mine but generally vary greatly within the regional extent of the unit. The <br />stratigraphic thickness of the Williams Fork Formation in the permit area has been estimated to be <br />about 1,600 feet; its degree of areal extent in the Axial Basin is similar to that of the Iles Formation. <br />The Williams Fork Formation is the predominant coal-bearing formation in the Mesa Verde <br />Group. Mesa Verde coals associated with the Fairfield Group, the coal-bearing zone above the <br />Trout Creek Sandstone, rank in quality about midway between bituminous and sub-bituminous. <br />Although the Twenty Mile Sandstone Member is a regional aquifer noted within the Williams Fork <br />Formation in the Craig, Hayden and Steamboat Springs area, a facies change within the Williams <br />Fork Formation has eliminated the Twenty Mile Sandstone in the Danforth Hills Area. <br /> <br />Structure <br /> <br />The area around the mine is dominated by the Axial Basin Uplift, an anticline, or arch, which is a <br />southeastward extension of the larger Uinta Mountain Arch. The Axial Basin anticline is an <br />asymmetrical fold, the axis of which trends north 60° west, with strata dipping (inclining) steeper <br />on the south side of the axis than on the north. The south flank of the anticline has several <br />secondary folds trending subparallel and at approximate right angles to the main anticlinal axis. In <br />general, the rocks of the broad anticline have not been stressed sufficiently to cause them to break <br />severely, but a few discontinuous normal faults trending primarily parallel to the anticlinal axis <br />are found in the area. <br /> <br />The structure of the permit area is geologically simple. The axis of the Collom syncline, a <br />downward fold, passes through the permit area as shown on the Geology Map (Map 7A). Bedding <br />orientation, as measured on surface outcrops, generally has a strike of N 70° W and is characterized