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Mineral Belt because of the high concentration of <br />mineral deposits that occur along a belt following the <br />Continental Divide (Bomberger, 1980). In the White <br />River Uplift, the geology consists of carbonate rocks of <br />Pennsylvanian and Permian age, which include the <br />Leadville Limestone and Eagle Valley Formation con- <br />taining evaporative sequences. Many thermal mineral <br />springs are present throughout the White River Uplift. <br />The Uncompahgre Uplift, which is west of <br />the Gunnison and Uncompahgre Rivers, consists of <br />sedimentary rocks of Jurassic and Cretaceous age over- <br />lying igneous and metamorphic rocks of Precambrian <br />age. Sedimentary rocks of Jurassic and Cretaceous age <br />that crop out include the Entrada Sandstone, Morrison <br />Formation, and Dakota Sandstone. In the southeastern <br />part of the Uncompahgre Uplift, metallic mineral <br />deposits are associated with volcanic rocks of Tertiary <br />age. <br />Ios° . <br />~~~~1 <br />Io6°~ <br />EXPLANATION <br />- CRYOBORALFS-ROCK OUTCROP SOILS <br />HAPLARGIDS-CAMBORTHIDS- <br />TORRIORTHENTS <br />-~~~-. HAPLARGIDS-NATRARGIDS <br />CALCIORTHIDS-TORRIORTHENTS <br /> TORRIORTHENTS <br /> CRYUMBREPTS-CRYOCHREPTS- <br /> ROCK OUTCROP SOILS <br />CRYAQUOLLS-ARGIBOROLLS- <br />CALCIBOROLLS-CRYBORALFS- <br />CRYOBOROLLS-TORRIORTHENTIC- <br />HAPLOBOROLLS-ROCK OUTCROP SOII.S <br />Figure 5. Soil associations in the Upper Colorado River Basin study unit (modified from Heil and others, 1977). <br />In the western part of the study unit, the Piceance <br />Structural Basin is composed of rocks of Cretaceous <br />and Tertiary age such as the Mancos Shale, Mesaverde <br />Group, and Green River Formation. The Cretaceous <br />rocks form the outer edges of this tectonic basin, and <br />the Tertiary rocks are located in the upland areas of this <br />basin. <br />General Soils <br />There are six soil associations in the study unit <br />(fig. 5); a brief description of the general physical and <br />chemical characteristics of each soil association is <br />listed in table 2. Two soil associations are in the moun- <br />tainous areas of the basin, and the other four soil asso- <br />ciations are in areas that include mountainsides, <br />uplands, flood plains, alluvial valley floors, and alluvial <br />ENVIRONMENTAL SETTING 9 <br />0 20 40 MILES <br />0 20 40 KILOMETERS <br />