2010-01-25_PERMIT FILE - C1981044A (3)

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2.04.6 GEOLOGY DESCRIPTION The EC mine area includes an irregular block of land, most of which is along the northeast flank of the Williams anticline and in parts of the adjacent round bottom and big bottom synclines. Geologic formations within the permit area, from oldest to youngest include: Iles formation Williams Fork Formation Lewis Shale All of these geologic formations are cretaceous in age and are all well consolidated. Overlying these coherent rock units is a series of unconsolidated sedimentary deposits of Quaternary Age including terrace deposits, alluvial fans, land slides, slump material, and recent alluvium. The aerial distribution and subsurface relationships of all consolidated and unconsolidated rock units is shown on the Geology Map (Map 7) and the geologic cross-sections, which accompany this permit. The following geologic cross-sections are provided in this permit: Geologic Cross- section A-A' (Map 7a), Geologic Cross-section B-B' (Map 7b), and Geologic Cross-section C-C' (Map 7c). The stratigraphy of the permit area is shown graphically on Figure 3, the Typical Stratigraphic Sections. Iles Formation The Iles formation is an alternating series of sandstones and shales with minor coal beds, none of which are known [o be of mineable thickness. The top of the Iles formation is marked by the Trout Creek sandstone member, which is generally described as a argillaceous, fine to medium grained, massive to cross-bedded sandstone. On the outcrop the Trout Creek Sandstone is tan colored (weathered in crop); however, in drill hole cuttings it appears white. The Trout Creek Sandstone ranges from 62 to 91 feet thick on the EC property and averages 87 feet thick overall. The thickness of the Trout Creek Sandstone is shown on Figure 4, Isopach of [he Trout Creek Sandstone. The thickness interval between the Trout Creek Sandstone and the "F" coal seam is shown on Figure 5, Isopach, Trout Creek Sandstone to the "F" coal seam. Williams Fork Formation The Williams Fork formation overlies the Iles formation and contains three (3) unconformities that occur at the base of each of the three (3) major sandstone units found within the formation. The lowest nonconformity is within the so called lower coat group and includes sandstones, shales, and coals above the Trout Creek Sandstone, but beneath the locally recognized Middle Sandstone. These geologic units are generally continental deposits of the transitional to lower delta plain environments. The economica]ly important "C", "E", and "F" coal seams occur in this interval. The interval thickness between the "F" coal seam and Middle Sandstone is presented in Figure 6, Isopach, "F" coal seam to the Middle Sandstone. The thickness of the Middle Sandstone is presented in Figure 7, Isopach Middle Sandstone. The first unconformity occurs at the base of the Middle Sandstone and marks the unrecorded transgression of the cretaceous epeiric seaway across the area. The Middle Sandstone is interpreted as a barrier and/or delta front sandstone. It contains sedimentary structures typical of this environment (climbing ripples, festoon cross strata) and is generally coarsening upward. Vertical permeability is reduced due to the presence of clay drapes on the cross beds and numerous fine grained interbies. Overlying the Middle Sandstone are a few thin coal beds, shales, continental sandstones, and two (2) important coal seams, the Hart coal seam, which was mined in the Hart and Wise Hill No. 3 and No. 4 Mines, and the stratigraphically higher "H" coal seam. The "H" coal seam does not outcrop as a significant seam; however, basinward it achieves thicknesses of almost 30 feet. The "H" Coal Seam is overlain by a massive sandstone that contains abundant shale Permit Revision 04-34 2.04-6 Revised 7/2/04