Laserfiche WebLink
<br />0935 <br /> <br />coal, and black carbonaceous shale (Donnell, 19611. Wasatch Formation <br />lithologies are generally nonresistant to erosion. <br /> <br />~pst of NOSR 1, this formation forms the lowland area between the Roan <br />Cliffs and the Grand Hogback. South of NOSR 1, the Wasatch Formation forms <br />the lowland area below the Roan Cliffs. The Wasatch Formation, therefore, <br />is found nearly everywhere on NOSR 3 and is not exposed on NOSR 1. <br /> <br />The Wasatch/Green River Formation contact is transitional and not well <br />defined. The principal criterion for placement of this contact has been <br />the color change from the brightly colored, irregularly bedded sedimentary <br />. " <br />rocks of the Wasatch, to the more regul arly bedded, grey marlstone rocks of <br />the overlying Green River Formation. The thickness of the Wasatch <br />Formation varies greatly, generally thinning toward the west. In the <br />vicinity of NOSR 1, the estimated formation thickness is 5,000 feet. <br /> <br />Fossils from the Wasatch Formation in this and adjacent areas indicate <br />an early Eocene age and a dominantly low energy fluvial depositional <br />envi ronment (Donnell, 1961l. <br /> <br />3.5.1.2 Green River Formation <br /> <br />The principal lithology of the Green River Formation is a thinly <br />bedded, fine grained argillaceous marl stone, composed primarily of, <br />dolomite, clay minerals, feldspar, and quartz, and containing varying <br />quantities of kerogen, a solid hydrocarbon. This formation is remarkable <br />for its regular thin bedding and the lateral continuity of some individual <br />units, and was deposited during Eocene time in large ancient lakes which <br />inundated northwestern Colorado, southwestern Wyoming, and northeastern <br />Utah. Figure 3-4 shows the extent of the Green River Formation in this' <br />tri - state area. <br /> <br />On NOSR I, the Green River Formation crops out along the Roan Cliffs <br />and in the deeper valley areas of the Roan Plateau. In the Piceance Creek <br />basin, the Green River Formation has been subdivided into four members <br />based on lithologic properties and stratigraphic position. From oldest to <br />youngest, these are the Douglas Creek Member, the Garden Gulch Member, and <br />the Parachute Creek Member. The fourth lithologic unit, the Anvil Points <br />Member, is a lateral facies equivalent of the Oouglas Creek, Garden Gulch, <br />and lower Parachute Creek Members. Surface and subsurface data indicate <br /> <br />3-7 <br />