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~1 <br />~~ <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />Geomorphic Characteristics <br />Regional Geomorphic Setting. Yeend (1969) provides a <br />thorough description of the Quaternary geology of the Grand <br />Mesa area immediately to the north of the Red Canyon Mines. <br />According to Yeend, basalt flows in the late Tertiary <br />covered the top of Grand Mesa forming a "basalt plane." At <br />this time, epierogenic uplift of Grand Mesa caused extensive <br />downcutting of streams into the Green River, Wasatch, Iles, <br />Williams Fork, and Mancos Formations. Later, during the <br />early Quaternary, pediment surfaces formed around the <br />margins of Grand Mesa. In late Quaternary time, these <br />pediments were locally covered with mudflows and alluvial <br />gravels from melting icecaps which covered much of the <br />surface of Grand Mesa. Stream downcutting has been the <br />dominant process since the disappearance of the last <br />icecaps. <br />Study Area Geomorphic Setting. The Red Canyon Mines <br />are located between moist, glaciated Grand Mesa and the dry <br />arroyo country below. The mines are primarily in a region of <br />huge fans resulting from mudflows which occurred during the <br />melting of the icecaps on Grand Mesa. The transition from <br />the glaciated mesa to the dry arroyos is apparent in the <br />study area (resulting in a rapid change in only a few <br />miles). <br />76 <br />