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<br />i" 1i?1.. I <br />1J_.. ~l"l <br /> <br />STUDY AREA RESOURCES <br /> <br />NATURAL RESOURCES <br /> <br />Geology <br /> <br />The area evaluated is located within the eastern margins of the Colorado Plateau, a <br />physiographic province of some 150,000 square miles that is generally typified by gently <br />dipping sedimentary rocks, high relief produced by deeply incised drainages, elevations <br />above 5,000 feet and a semi-arid climate. Because soils are thin and vegetation is sparse <br />in this dry region, infrequent episodes of brief but intense rainfall yield often massive <br />runoffs of surface water. These, in concert with the more insidious chemical and <br />mechanical effects of migrating groundwater, have eroded the nearly horizontal rock units <br />of alternating hardness exposed in the province to create its characteristic stair-step <br />topography. <br /> <br />Though the resulting erosional escarpments and benches are dominant landforms <br />throughout the Colorado Plateau, other features often reflect the distinct influence of a <br />local tectonic disturbance. Among these rather anomalous structures is the <br />Uncompahgre Uplift, a long, linear bulge in the earth's crust upon which the study area <br />is also situated. <br /> <br />During Mesozoic times (about 180 million years ago), sediments were laid down on the <br />flat, eroded surface of much older rocks. The sedimentary rocks underwent periodic <br />erosion and then were covered by volcanic flows, which subsequently were eroded away. <br />The Gunnison River established its course, cutting downward into the relatively soft <br />sedimentary rocks. Approximately two million years ago, as the river cut downward, the <br />land began to gradually rise. The river, established in its course, continued to cut <br />downward into the hard and resilient Precambrian rock, <br /> <br />Paleontology <br /> <br />There is one known paleontological site within the study area which consists of fragments <br />of a theropod posterior caudal vertebrae, a sauropod dinosaur rib, and numerous <br />fragments of vertebrae and limb bones that are unidentifiable. The bone fragments occur <br />in the Salt Wash Member of the Morrison Formation. The formation is a well-cemented <br />sandstone, mudball and pebble conglomerate. The site was located in the early 50s by <br />uranium exploration miners. BlM became aware of the site in 1984. This site has been <br />classified by BlM as a Category II. Category II classifications are identified as geologic <br />formations or parts of formations that have produced fossils of scientific value or known <br />vertebrate localities elsewhere, thus indicating potential for the discovery of fossils of <br />scientific value. Outcrops of the Morrison Formation and other geologic formations <br />elsewhere may also be Category II areas. <br /> <br />A letter from the Museum of Western Colorado dated March 19, 1986, states, "...due to <br /> <br />9 <br />