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• <br />2 GEOLOGIC SETTING <br />The proposed Collom study area is located north of the Danforth Hills in the Wyoming <br />Basin physiographic province, which is a high, and plateau ringed by mountains. <br />General elevations range from 6,000 to 8,500 ft. The region is composed of a series of <br />basins broken up by low ridges. <br />Background information on the geologic setting of the proposed Collom Mine was largely <br />obtained from the "Geologic Summary of the 2004 Collom Exploration and Evaluation <br />Project ", written by the Collom Geologic Team (2005). <br />2.1 Regional geology <br />2.1.1 Regional stratigraphy <br />The coal seams at the Colowyo Mine and the proposed Collom Mine are contained <br />within the Williams Fork Formation. This formation conformably overlies the Trout Creek <br />Sandstone Member of the Iles Formation. Rocks of the Cretaceous Williams Fork and <br />Iles Formations constitute the Mesaverde Group. Local occurrences of Quaternary <br />alluvium, colluvium, alluvial fan deposits, and landslide deposits unconformably overlie <br />the Williams Fork Formation in the study area, particularly in the stream valleys. A <br />generalized stratigraphic column is shown in Figure 2.1. <br />The Williams Fork and Iles Formations comprise a sedimentary rock sequence that <br />originated from a deltaic and marginal marine depositional environment. The Trout <br />Creek Sandstone Member consists of thick marine sandstone that represents the marine <br />facies (beach) of the delta front. The lithology of the Williams Fork Formation is variable <br />in character and thickness. Individual lithologic units are most often discontinuous. The <br />formation consists predominantly of shale, sandy shale, and sandstone with subordinate <br />amounts of coal and carbonaceous shale (Brownfield and Johnson, 1986). Aside from <br />volcanic ash beds, the coal seams are the most laterally persistent units in the Williams <br />Fork Formation. <br />2.1.2 Regional structure <br />The Colowyo Mine property lies within the Rocky Mountain foreland province, a region <br />characterized by deep- seated, basement faults that have undergone periodic episodes <br />of movement. These complex structures are overlain by younger sedimentary <br />sequences that reflect upward- diminishing deformation. Periodic movements have <br />propagated these deep- seated fault structures closer to the surface, causing warping in <br />the overlying sedimentary sequence. The ancestral Axial Fault located north of the <br />2572 -R2 Colowyo Coal Company <br />Water Management Consultants <br />