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<br />'2,875 <br /> <br />Water supply.--The Navajo Sandstone contributes small <br />. umounts of water to the three deep public-supply wells in <br /> <br />the Towaoc urea. AltJ10Ugh it lS a major a'll ifer on the <br /> <br />~av~jo :ndian Rcscrv~tion, it is near or at its depositional <br /> <br />limit in the project area, and yields are much less than <br /> <br />those obtained in parts of the Navajo country. It is <br />major <br />over lain by three"aquifers. and an udequ3. te wa ter supply <br /> <br />senerally can be obtained without tapping it. <br /> <br />Jurassic System <br /> <br />San Rufael Group <br /> <br />The San Rafael GI:onp was named by Gilluly and <br /> <br />Reeside \1928, p. 73), and the type locality is ~n the <br /> <br />San Rafael S\-Iell of southe;Jstern Utah. <br /> <br />At the type locality, <br /> <br />. <br /> <br />th".. 'jJ:"oup consists of the Car~,lel Formation, the Entrada <br /> <br />SCll1dstone, the Curtis Formation, a.nd the Summerville Forma- <br /> <br />tion. <br /> <br />The Junction Creek Sandstone and its equivalent, <br /> <br />the Bluff Sandstone, also arc now considered to be part of <br /> <br />the San Rafael Group in the Four Corners and San Juan <br /> <br />Mountain regions (Craig and others, 1955, p. 133, 134). <br /> <br />The Todilto Limestone in tIle Navajo country also is <br /> <br />considered to be a part of the San Rafael Group by Harshbarger, <br /> <br />Repenning, and Irwin, (1957, p. 38). <br /> <br />In the pcoject area the San Rafael Group is represented by <br /> <br />tlle En trada Sandstone, the Summerv ille Formation. and the <br /> <br /> <br />Junction Creek Sandstone, although the Todilto Limestone may <br /> <br /> <br />be present in the subsurface in the eastern part. In the San <br /> <br /> <br />Juan Mountain area, beds equivalent to the Summerville Forma- <br /> <br />tion arc included in the Wanakah Formation. <br /> <br />. <br /> <br />~5 <br />