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<br />o::l" <br />00 <br />,~ <br />C'\I <br /> <br />o <br /> <br />Geo ..!Qgr <br />The narrow flood plain (a few hundred to a few thousand feet in <br />width) associated with the Virgin River channel is composed of Recent <br />and Pleistocene unconsolidated gravel, silt, and clay. These deposits <br />are from zero to about 100 feet in thickness. Pleistocene to Pliocene <br />age unconsolidated and semiconsolidated deposits of alluvial sand, <br />gravel, boulders, silt, and clay occur adjacent to the river valley <br />and form alluvial fans and terrace deposits to the northwest and <br />southeast of the river. All of the preceding may be underlain by <br />unconsolidated to semiconsolidated sand and silt with layers of gravel <br />and clay of the Muddy Creek Formation of t1iocene-Pliocene age. The <br />alluvial fan and Muddy Creek Formation deposits vary from zero to many <br />thousands of feet in thickness [3]. Sequences of Paleozoic carbonate <br />rocks found in the Vi rgi n Mounta i ns and Precambri an crysta 11 i ne rocks <br />lie under the Muddy Creek Formation. <br /> <br />,- <br />-' <br /> <br />Vegetation and Wildlife <br />The vegetation and wildlife in the area are characteristic of <br />much of the arid southwestern United States. The vegetation consists <br />primarily of the creosotebush-bursage plant community. The riparian <br />community along the Virgin River and Beaver Dam Wash is dominated by <br />the introduced salt cedar, although nativE' willows and occasional <br />cottonwood trees are also present. Saltgrass, greasewood, and inkweed <br />are found in areas of poor drainage and high salinity. <br /> <br />The most important game birds in the <br />mourni ng dove, and ri ngnecked pheasants. <br />visit the area for winter feeding stops. <br />badgers, skunks, weasels, rabbits, several <br />~ice inhabit the area. <br /> <br />a rea are Gambe 1 's qua i1 , <br />Ducks and Canadi an geese <br />Bobcats, coyotes, foxes, <br />species of squirrels, and <br /> <br />The endangered woundfin minnow (Plagopterus argentissimus) lives <br />in this reach of the river. The woundfin minnow, because of the <br />precarious nature of its existence, has been listed in the U.S. Fish <br />and Wildlife Service listing of Endangered and Threatened Wildlife and <br /> <br />6 <br />