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<br /> <br />~J <br /> <br />Iloolo <br />t:) <br />.~";. ,t.Q,' <br />",,'.,t;,:l,...,'." <br /> <br /> <br />" I <br />'.j <br />..j <br /> <br />water from a very large drainage area, that has percolated through a <br />geologic section some 3,000 feet thick. All this contact with the rocks <br />provides the salt load of the water, but there is little doubt that the 1300 <br />or so feet of Supai and Hermit provide a considerable share. Triassic <br />shales, particularly the Moenkopi, are a different matter. <br /> <br /> <br />In Triassic time the sea entered the Colorado Plateaus area from the <br />west, and the Moenkopi Formation along the Virgin River in southern <br />Utah (Fig 6), contains prominent beds of gypsum (as seen in Hurricane <br /> <br />"." <br /> <br /> <br /> <br />Figure 6. Moenkopi Formation and gypsum beds, Hurricane Mesa, <br />Utah. <br /> <br /> <br />Mesa, Utah). These must be responsible, in part, for the poor quality of <br />the Virgin, apart from the salt added by La Verkin Springs. At Flaming <br />Gorge, the white Moenkopi is silt, not gypsum. The highly colored <br />Chinle shale, maker of spectacular badlands in many areas, particularly <br />the Painted Desert (Fig. 7), must have considerable affect on the quality <br />of the Little Colorado above Blue Spring, and on the flow from Chinle <br />Wash into the San Juan, but its affects of water quality are probably <br />less per unit area of exposure than that of the less colorful, but more <br />gypsiferous Maticos shale, higher in the section. However, it also makes <br />colorful landscapes at Clay Crossing in San Juan County. <br /> <br />,'.... . <br /> <br />6 <br /> <br />"."",', <br /> <br />" ","',,'.' ", '," "'.~- .,. <br /> <br />