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• feet above the Tuentymile sandstone member. <br />The Lewis shale coot ormebty overlies the Mesaverde Group end, like the upper unit of the <br />Yilliams 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 end 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 end is about 7,000 to 1,500 feet thick. The Lance <br />Formation is comprised of interbedded shale, sandy shale, sandstone, end coal. Some of <br />the sandstone layers tan 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 es thick es 74 feet is some areas (Bass et al., 1955). <br />The Fort Union Formation of Tertiary age lies above [he Lance Formation. It consists of <br />interbedded sandstone, shales, end coals deposited during the VaLeocene epoch and is <br />appro:imately 7,400 feet thick (Bass et el., 7955). Compared to the Lance Formation, the <br />sandstones are coarser, the shales ere lighter gray in color, end there are more coal <br />• layers. The thickest regional coal seam present in the Fort Union Formation is the <br />Seymour Loel. <br />The Yesatth 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 />4asateh Formation in some areas, particularly along larger streams. <br />Site Soecific Geolocv <br />Structure. The Hayden Gulch Terminal permit area is situated about tuo miles north of the <br />rugged Yilliams Fork Mountains end about four miles north of the Sage Creek Anticline <br />(Figure 6-i). The axis of the Sege Creek Anticline is situated about one-half mile east <br />of the eastern edge of the Seneca II-Y permit area end 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 />• Toooaraoh v. Within the Hayden Gulch Terminal permit area, elevations range from <br />5 <br />