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<br />APPENDIX D <br /> <br />GEOHYDROLOGY <br /> <br />~1 <br /> <br />Longwell (1965) indicates Quaternary alluvium and the Tertiary Muddy <br />Creek formation underlying the Virgin River from Mesquite, Nevada, south <br />into the Overton Arm of Lake Mead (see Figure D-l). <br /> <br />He describes the Muddy Creek formation as being coarse grained near <br />the mountain borders and grading basinward into regular beds of fine-grained <br />sandstone, siltstone, and clay. These strata are essentially horizontal <br />except adjacent to structurally disturbed (faulted) areas. <br /> <br />Longwell (1928) in his report on the geology of the Muddy Mountains <br />in Nevada presents an excellent description of conditions of deposition of <br />the Muddy Creek formation. His interpretations are based in large part on <br />the abundance of halite (salt) and gypsum, as well as horizontal attitude <br />of the stata and texture of sedimentary beds. In his interpretations he <br />refers to "the recurrence throughout the series of gypsum, probably asso- <br />ciated with other salts, is evidence of continuing conditions that favored <br />saline deposition." <br /> <br />In the St. Thomas Wash area (approximately 22 miles southwest of River- <br />side) Longwell (1928) describes large depqsits of rock salt and gypsum (see <br />Table D-l.). One exposure of salt has a height of more than 100 feet. Expo- <br />sures of salt as indicated by Longwell (1928) are located in the Overton <br />Arm of Lake Mead (Figure D-l). <br /> <br />TABLE D-l. SALT AND GYPSUM MINES IN THE MUDDY CREEK FORMATION, NEVAD~/ <br /> <br />SALT <br /> <br />SalvatioD Salt Kine <br /> <br />Secs. 27 and 34. T. 17 S., R. 68 E. <br />Sec. 34, T. 175.. R. 68 E. <br />Sac. 32, T. 185.. R. 68 E. <br /> <br />Badded ..It deposita In lower <br />part of the Huddy Cr..k For- <br />..cion. Relacively pur. halite <br />commonly incar.ixed with clay. <br />ailt and gyp.~. So.e large <br />bodie. of pure crystallina halite. <br /> <br />Big Cliff Mine <br /> <br />Calico Salt Hine <br /> <br />Salt Mina <br /> <br />SIIc. S. T. 19 S.. R. 68 E. <br /> <br />Black. Salt Kin. <br /> <br />Sac.. 15 and 16, T. 19 S. R. 68 E. <br />Sac. 4 T. 20 S., I. 68 E. <br /> <br />Bonalli Sale Kia. <br /> <br />Schuuker (Apex) <br />Gypl_ Hine <br /> <br />See 1. T. 20 S., R. 64 E <br />Sac. 12, T. 20 S., 1. 63 E <br /> <br />Len... and bad. of IYpaw. in the <br />Huddy Cr..k Foraati01l. <br /> <br />Gypaua C.W Kine <br /> <br />11 Lonpell and othu. 1965) <br /> <br />In summary it appears that the Muddy Creek formation was formed under <br />arid conditions conducive to saline deposition. <br /> <br />D-1 <br /> <br />:1 ,,. I~ '" <br />V U l' v V ,j <br />