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<br />Grams and Schmidt <br /> <br />2 <br /> <br />resistance. The streams have carved deep and narrow canyons through more-resistant <br />formations, or they meander through broad basins and smaller parks across less-resistant <br />formations (Harden, 1990; Hunt, 1969). John Wesley Powell (1875) cited the Green <br />River as a typical example of an antecedent stream, a river that had carved deep canyons <br />as mountains rose in the river's path. Subsequently, geologists questioned this theory and <br />offered alternate explantions (Davis, 1897; Jefferson, 1897; Sears, 1924; Bradley; 1936; <br />Hansen, 1960; Hunt, 1969). Hansen (1986) offered evidence supporting the explanation <br />fIrst proposed by Sears (1924) that the present course of the Green River was the result of <br />superposition from a course established on Tertiary sediments that fIlled local basins. <br />Entrenchment of the canyons began in late Miocene-early Pliocene time when the Green <br />River drainage was diverted from an eastward-flowing course across the present day <br />continental divide in Wyoming to a southward course across the eastern Uinta Mountains <br />(Hansen, 1986). The Canyon of Lodore (hereafter informally referred to as Lodore <br />Canyon) is about 5 myoId and the incision of its gorge, 760 m deep, occurred at an <br />average rate of 15 cm per thousand yrs (Hansen, 1986). <br />Geologists have also been interested in how bedrock geology controls specific <br />fluvial-morphological characteristics of modern streams within canyons. Powell (1875, p. <br />234) anticipated dangerous reaches of river by observing the lithology of nearby rocks, <br />:noting that: 1n softer strata we have a quiet river, in harder we find rapids and falls.' The <br />pool-drop pattern of the Green River was obvious to river travelers, yet was <br />undocumented until a channel prof1le was surveyed during investigations between 1917 <br />and 1922 (U.S. Geological Survey, 1924). Most subsequent studies have emphasized the <br />importance of either (1) bedrock lithology and structure, (2) tributary processes, or (3) <br />mainstem hydrology in determining the geomorphic organization of the large rivers of the <br />Colorado Plateau. <br />Leopold (1969) measured some of the fundamental geomorphic characteristics of <br />the Colorado River in Grand Ganyon including water-surface and bed profIle, channel <br />