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<br />"U819 <br /> <br />III. STUDY AREA TOPOGRAPHY <br /> <br />" A. GENERAL <br /> <br />Naval Oil"Shale Reserve 1 (NOSR-l) is located on the <br />southeastern rim of the Piceance Creek physiographic <br />The area is characterized by two topographic forms: <br />Roan Cliffs and the Roan Plateau. See Reference No. <br />Section IX, References. <br /> <br />high <br />basin. <br />the <br />1 in <br /> <br />The Roan Cliffs are generally parallel to the eastern and <br />southern boundaries of the Reserve, and are carved in the <br />resistant oil shales of the Green River Formation. They <br />reach sheer heights of more than 1,000 feet above steep, <br />talus-covered slopes which descend as much as 3,000 feet to <br />the valleys of Government Creek and the Colorado River. <br />Above and within the Roan Cliffs is the Roan Plateau topog- <br />raphy, consisting of a maturely dissected upland composed of <br />narrow, westward trending ridges incised by an intricate, <br />dendritic drainage system. The entire area is made up of <br />the slopes of V-shaped valleys, and neither extensive level <br />uplands nor valley flood plains are present. The ridges de- <br />cline unevenly westward with slopes between 50 and 200 feet <br />per mile. The main valleys have westward gradients of 100 <br />to 200 feet per mile. A multitude of short, steep tributary <br />valleys, mostly normal to the main valleys, dissect the <br />slopes and make an intricate topographic pattern throughout <br />the Reserve. The upper slopes are relatively gentle, formed <br />in the less resistant silty sands and shales of the Uinta <br />Formation. The inner valleys of the main streams are cut into <br />the marlstones of the Green River Formation and are markedly <br />steeper sided than the various gulches and dry canyons. <br /> <br />III-l <br />