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Geologic Map of the Divide Quadrangle Washington County Utah

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Geologic Map of the Divide Quadrangle Washington County Utah GEOLOGIC MAP OF THE DIVIDE QUADRANGLE, WASHINGTON COUNTY, UTAH by Janice M. Hayden This geologic map was funded by the Utah Geological Survey and the U.S. Geological Survey, National Cooperative Geologic Mapping Program, through Statemap Agreement No. 98HQAG2067. ISBN 1-55791-597-0 ,Ill MAP197 I"_.\\ Utah Geological Survey ..,, a division of 2004 Utah Department of Natural Resources STATE OF UTAH Olene S. Walker, Govenor DEPARTMENT OF NATURAL RESOURCES Robert Morgan, Executive Director UTAH GEOLOGICAL SURVEY Richard G. Allis, Director PUBLICATIONS contact Natural Resources Map/Bookstore 1594 W. North Temple telephone: 801-537-3320 toll-free: 1-888-UTAH MAP website: http://mapstore.utah.gov email: [email protected] THE UTAH GEOLOGICAL SURVEY contact 1594 W. North Temple, Suite 3110 Salt Lake City, UT 84116 telephone: 801-537-3300 website: http://geology.utah.gov Although this product represents the work of professional scientists, the Uah Department of Natural Resources, Utah Geological Survey, makes no warranty, expressed or implied, regarding its suitability for any particular use. The Utah Department of Natural Resources, Utah Geological Sur­ vey, shall not be liable under any circumstances for any direct, indirect, special, incidental, or consequential damages with respect to claims by users of this product. The views and conclusions contains in this document are those of the author and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Govemmenrt. The Utah Department of Natural Resources receives federal aid and prohibits discrimination on the basis of race, color, sex, age, national origin, or disability. For information or complaints regarding discrimination, contact Executive Director, Utah Department of Natural Resources, 1594 West North Temple #3710, Box 145610, Salt Lake City, UT 84JJ6-5610 or Equal Employment Opportunity Commission, 1801 L Street, MY, Wash­ ington DC 20507. ~ 't:J1 Printed on recycled paper 1/04 GEOLOGIC MAP OF THE DIVIDE QUADRANGLE, WASHINGTON COUNTY, UTAH by Janice M. Hayden ABSTRACT Geologic resources in The Divide quadrangle include gravel from alluvial-fan deposits, sand, and stone. Explo­ The Divide quadrangle in southwest Utah is bisected ration for gypsum, petroleum, uranium, and paleoplacer north-south by the Hurricane fault zone. The east half of the deposits of precious metals has been undertaken in the quad­ quadrangle is part of the Colorado Plateau whereas the west rangle. Water resources are increasingly important as popu­ half is part of the transition zone that leads into the Basin and lation growth continues in the area. Geologic hazards in the Range Province farther west. In the footwall of the Hurri­ quadrangle include earthquakes; floods and debris flows; cane fault zone, the Hurricane Cliffs expose just over 1,000 slope failures, including rock falls and landslides; expansive, feet (300 m) of Permian rocks, including the upper part of the soluble, and collapsible rock and soil; blowing sand; and Queantoweap Sandstone and the Toroweap and Kaibab For­ radon. mations. The Triassic Moenkopi Formation unconformably overlies paleotopography eroded into the Kaibab Formation and is about 1,700 feet (515 m) thick. The Moenkopi is INTRODUCTION unconformably overlain by the Chinle Formation, which averages 725 feet (220 m) thick. These two Triassic forma­ The Divide quadrangle is in south-central Washington tions form Little Creek Mountain along the east edge of the County in southwestern Utah (figure 1). This area, nick­ quadrangle; they are also partially exposed in Warner Valley named "Utah's Dixie," is one of the fastest growing areas in in the southwest part of the quadrangle. Slivers of Triassic the state and many geologic concerns are arising as the pop­ rocks are also present in the Hurricane fault zone. Jurassic ulation increases. Water supplies are limited. Construction strata exposed in the quadrangle consist of the Moenave For­ materials, particularly gravel, are in short supply. Expansive, mation, 400 feet ( 120 m) thick; the Kayenta Formation, 900 soluble, and collapsible soil and rock which can cause dam­ feet (270 m) thick; and the basal 1,000 feet (300 m) of the age to buildings, roads, and other structures are present and Navajo Sandstone. Normal faults repeat the Moenave For­ need to be recognized by planners and builders. Other poten­ mation several times in Warner Valley. The Kayenta Forma­ tial geologic hazards include earthquakes, blowing sand, tion and Navajo Sandstone comprise Sand Mountain in the flooding, debris flows, slope failures, radon, and volcanic northwest part of the quadrangle. eruptions. Five Quaternary basaltic flows are in the quadrangle. Maximum topographic relief is about 2,930 feet (888 m) Two flows lie west of the Hurricane fault (Ivans Knoll and from the top of Little Creek Mountain at 5,912 feet (1 ,792 m) Grass Valley), and two flows lie east of the fault (Gould above sea level to the northwest comer of the quadrangle at Wash and The Divide). The fifth flow (Remnants) straddles Sand Hollow Reservoir at about 3,060 feet (933 m). Little and is offset by the fault. Because of continued erosion, the Creek Mountain is an extensive mesa that rises above the older flows typically cap ridges and form inverted valleys. bench developed on top of the Hurricane Cliffs; the cliffs Alluvial-terrace deposits and other elevated alluvial surfaces bisect the quadrangle and create a formidable barrier that capped by thick pedogenic carbonate also document relative trends north-south. Warner Valley and Sand Mountain lie uplift and downcutting in the quadrangle. west of the Hurricane Cliffs. The Hurricane fault zone, a Many normal faults are in The Divide quadrangle, but major, active, down-to-the-west normal fault, lies at the base only three have more than a few tens of feet of displacement. of the cliffs. The largest is the down-to-the-west Hurricane fault zone, The Divide quadrangle receives about 8 inches (20 cm) which has about 5,000 feet (1,500 m) of displacement near of precipitation annually (Cordova and others, 1972). Natur­ the south end of the quadrangle. Most of the displacement al vegetation includes sparse grasses, sagebrush, creosote along the fault zone occurred during Quaternary time. Dis­ bush, and several varieties of cactus and yucca. The Virgin placement across the Hurricane fault zone increases north­ River lowland, which includes the western part of The ward to at least 6,000 feet (1,800 m) near the north end of the Divide quadrangle, has the lowest elevation, warmest cli­ quadrangle. Farther west, the Warner Valley fault also cuts mate, and the longest growing season in Utah. Quaternary deposits, and has about 1,800 feet (545 m) of Geologic investigations in the region started early, be­ stratigraphic separation. ginning with the Wheeler Survey in 1871 and 1872 (Wheel- 2 Utah Geological Su rvey 37°22'30" ,--------..--------- -,--..----------~------..-------------------, 37°22'30" Gunlock Signal Peak Pintura / Smith Mesa Hacker, 1998 Hintze and others, Pintur,\/' 1994 Pine Hurlow /I Valley and Biek, / Mts. 2003 f ~ t! .~~ f 1/' Higgins, 1997 Christenson and_____,. Higgins, 1998 Deen, 1983 MVW I 4: 1- ::, 37° N 37° N Whitmore ~ Point o N iY 4: Billingsley, 1992b 36°52'30" '-----------''--.....__.:,_____:::::..____ ....,..t_.l-l<,<:..__--"----tt.'----....J.._-- ...:..i...-...:.__J_J...._______ J...._ _____ __J 36°52'30" 113°52'30" E 113°45' 113°37'30" 113°30" 113°22'30" 113°15" 113°07'30" E 0 5 10 miles 0 5 10 kilometers Figure 1. Location of The Divide and surrounding 7.5' quadrangles, and major geographic and geologic features; basalt flows are shaded. MVW = Mountain Valley Wash , VRG = Virgin River Gorge, BD = Bloomington dome, TC = Timpoweap Canyon, and PT= Pah Tempe Hot Springs. er, 1886). The area was also visited by J.W. Powell in 1873 on figure 1. Many topical studies have addressed the struc­ (Powell, 1875), and by G.K. Gilbert, who worked with the ture, stratigraphy, volcanism, hazards, and economic and Wheeler Survey. Gregory ( 1950) gave a thorough history of water resources of the area. the early exploration of the region. Dobbin ( 1939) produced a small-scale geologic map of the greater St. George area that focused on structural geology. Gardner's (1941) report of the DESCRIPTION OF MAP UNITS Hurricane fault zone in southwestern Utah and northwestern Arizona included a 1:320 ,000-scale geologic map. Gregory Over 5,500 feet (1 ,680 m) of Lower Permian to Middle (1950) mapped the Zion Canyon area (1: 125,000) and estab­ Jurassic sedimentary strata are exposed in The Divide quad­ li shed many of the geologic names in use today in this rangle. They were deposited in a variety of shallow-marine, region. Marshall ( 1956) made photogeologic maps of the tidal-flat, sabkha, sand-desert, coastal-plain, river, and lake Little Creek Mountain quadrangle to the east and the Virgin environments reminiscent of the modem Caribbean Sea, quadrangle to the northeast, both at a scale of 1:24,000. Gulf Coast coastal plain, Sahara desert, and coastal Arabian Cook (1960) completed a map of Washington County Peninsula, among other places. Hintze (1993), Biek and oth­ (1: 125,000). Eppinger and others (1990) compiled a ers (2000), and Higgins (2000) provided popular narrative 1:250 ,000-scale map of the Cedar City 1° x 2° quadrangle, histories of these units. which includes The Divide quadrangle. Published 1:24,000- The oldest rocks exposed in The Divide quadrangle are scaJe geologic maps for surrounding quadrangles are shown the Early Permian Queantoweap Sandstone, Toroweap For- Geologic map of The Divide quadrangle, Washington County 3 mation, and Kaibab Formation. They form the Hurri­ cane Cliffs that trend north-south through the quadran­ gle (figure 2). East of the cliffs, the Early Triassic Moenkopi Formation and the capping Shinarump Con­ glomerate Member of the Late Triassic Chinle Forma­ tion comprise Little Creek Mountain.
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