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feet above the Twentymile sandstone member. <br />The Lewis shale conformably overlies the Mesaverde Group and, like the upper unit of the <br />Williams Fork Formation, is highly variable in thickness. It is principally a homogenous <br />marine shale. It tends to be more sandy in the upper portion of the formation and may <br />contain a few lenticular sandstone layers (Figure 6 -2). <br />The youngest Cretaceous rock formation exposed in the area is the Lance Formation. It <br />conformably overlies the Lewis shale and is about 1,000 to 1,500 feet thick. The Lance <br />Formation is comprised of interbedded shale, sandy shale, sandstone, and coal. Some of <br />the sandstone layers can be rather thick (about 100 feet). The only coal bed present in <br />the Lance Formation which is of any economic significance is the Kimberly coal bed which <br />has been found to be as thick as 14 feet is some areas (Bass et al., 1955). <br />The Fort Union Formation of Tertiary age lies above the Lance Formation. It consists of <br />interbedded sandstone, shales, and coals deposited during the Paleocene epoch and is <br />approximately 1,400 feet thick (Bass et al., 1955). Compared to the Lance Formation, the <br />sandstones are coarser, the shales are lighter gray in color, and there are more coal <br />Layers. The thickest regional coal seam present in the Fort Union Formation is the <br />Seymour Coal. <br />The Wasatch Formation of Eocene age unconformably overlies the Fort Union Formation. It <br />is comprised primarily of fresh water stream -laid sandstone and shale deposits. <br />Unconsolidated alluvial, terrace, and surficial deposits of Quaternary age overlie the <br />Wasatch Formation in some areas, particularly along larger streams. <br />Site Specific Geology <br />Structure. The Hayden Gulch Terminal permit area is situated about two miles north of the <br />rugged Williams Fork Mountains and about four miles north of the Sage Creek Anticline <br />(Figure 6 -1). The axis of the Sage Creek Anticline is situated about one -half mile east <br />of the eastern edge of the Seneca II -W permit area and trends northwesterly (Figure 6 -1). <br />The rock units in the permit area dip about 4 to 8 percent to the west - northwest and do <br />not appear to be affected by any significant faulting or folding. <br />Topography. Within the Hayden Gulch Terminal permit area, elevations range from <br />5 <br />