Geology and Mineral Technology Geologic Investigation Series M Ap GI-2-A GEOLOGY TEMPE QUADRANGLE, MARICOPA COUNTY, ARIZONA
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State of Arizona Bureau of Geology and Mineral Technology Geologic Investigation Series M ap GI-2-A GEOLOGY TEMPE QUADRANGLE, MARICOPA COUNTY, ARIZONA Troy L. Pew8 Cathy S. Wellendorf James T. Bales •PhDenix Department of Geology Arizona State University 8upo ..dludon :::' Mh:; 1986 --, Prepared in cooperation with the cities of o, 10, Miles Tempe, Scottsdale. and Phoenix. and the Arizona State Land Department 111 ° 52' 30" INTRODUCTORY STATEMENT 33'30' , FEET ,.. The Tempe QuadranglE lies in the broacl valley of me Phoenix Basin, and includes parts of t he Cities of Tempe, Scottsdale, and Phoenix. The quadrangle has been intensely urba nized ex cept for t he Indian Reservation to the east, the Salt River channel east-west across the center, and Papago Park Pediment rlOrth of the river. Total relief is 645 feet (197 m), ranging from 1100 feet 1 ~f=Jj f l/t- '1~;fi1t~ (336 m) in the Salt Aiver bed to 1746 fee t (532 m) at the summit of Bam9fi Butte. With the excep 112i!OO~'lii~~~1[JiJlfiil~~!!i!:~1!i!!IIi!!!ii:ii!!!:~;;iii::::;;:::~!l:;;;!:;::I~!i~'Ii::~~~ilil::i!~;Ii;;iii~~iil:![~1:i~!.li~ tion of a few isolated rock masses , 11m area occupies a relatiyely flat desert plain formed primarily hy older and modaH' alluvial depo,;it!<. 7- C CLIMATE l7Q6ODOr'·N . The arid subtropical climate 01 the stlKly arBa is chara cterized by rapid heating by day and rapid cooling by nighl, producing diurna l temperature changes often exceeding 3O'"'F 0 7"C). Summers are hal with daytime temperaturAs normally warmer than 100° F ( 38~CI. W inter tC 'Tlr:>C '(I tu.cs are usual ly in the sixties, and may rise into the lower eighties, w ith an average of only 30 days when lows dip billow frcezing. The average daily temperature is 89 ° F (32°1 in July, and 50°F nOQCI in January . Pr aGi pi ta tion iJlTlounts me sliyht, averaging 7.2 inches f 19cm) annually. Drooght conditions are most severe in May and June. followed by tho "monsoon season" f rom mid-J uly to mid· September, when lato afternoon thunderstorms ore procedod by gusty winds and blowing dust. "",. December to February is the ra iny season, with gentle. often continuous w intl'lr rains ilnd cloudy days. '705 VEGETATION The Tempe Quadrangle is in ti'le Lower Sonoran life-zone with characteristic desert shrub vegetation. The creosote bush-white oursa~9 community inhabits lass rocky areas of low relier. The paloverde-saguaro community of small-leaved trees, shrubs, and cacti is well devalopad on Q me rocky, wall drained slopes of Papago Park Pediment, South Mountains, and Tempe Bullo. The dillerse cactus flora include cholla, p.ickly pear, hedgehog, pincushion , ilnd f ishhook. Z Riparian trees of the arroyos include blue paloveme, mesquite, catclaw, dooe.t willow, ilnd hackberry. Saltbush and tamarix form eKiensive stands across Salt Aiver bottomtand. Annual wildflowers and several species of natuml grilSses may bit remarkably aOOn d'lT1t following ex '31 tremely w et w inters REGIONAl. GEOLOGY Southem Arizona lies in the Basin and Range Province, characte rized by alternating broad, elongate !;)asins and long, narrow mountain ranges. This unique physiography resulted from e period of r ~ional b l oc k - f ault in ~ along stoop, normal faults, tha t began in Arizona approximately 17 million years ago. Basin and Range faulting is the result of ex tension due to thinnin g of the earth'S crulit. Vertical movament of crustal blocks created mountains on the up thrown sida and hasins on tha downthrown side. As erosion and downwasting lowered t he mountains, great thicknesses 01 clast ic sediments accumulated in the adjoining basins. GEOLOGIC HISTORY The earliest event recorded in the Tempe Quadrangle is the extrusion of silicic ash and lava flows, w hich were subsequently metamorphosed In Precambrian time producin g metamyolite. The metarhyolite is intruded by two granites. The relationship between those two granit es, Tovrea and Camelback Granites. is not evident within the quadrangle. The metamyolite and Camelback Granite show evidence of cataclastisis. During a period of faulting in mid-Tertiary time, the old rocks were uplifted to form moun tains. Alluvial fans formed at the !;)ase of these mountains, and thiCk deposits of coarse, angular rock debris accumulated Ithe Camel5 Head Formationl. These deposits were interbedded with ash and lava /lows extruded from local fiSSUHtS. The !:Illdesite of Tempe Butte has a radio!natric date of 17.6±O.4 million years (Scarborough and Will, 1979). (See the reverse side of this map for the geologic time scale). The badrock expootld <tt Pl':Ipagu Pilrk P!!diment , Tempe Bulle, Twin BUItIlS, <trid BIlIl Butte are small, tilted and uplifted fault· blocks allllost completely buried by aggrading yalley all uviu.n. 1'1 response to the continuBd uplift of the ranye!:! and Hl LatNO subsidltnce of the basin. the Sail River has cut sevaral terrace levels, <trld the pt"-jimenl colluvium and all uvial fans hav e belm elltrellGhed. ENVIRONMENTAL GEOLOGY The geology map serves as a besis for the development of additional maps depicting various environmental concerns. See reyerse side of this map for an introductory statement reo gardlng environmental geology and a brief description of each map in this enviro nmeJ1tal geology folio. SELECTED REFERENCES Atkinson, D. E., end Hey, S. M: , 1983, Prelimina ry repon of Motomla Chemical Leak Projoct, Section 2: Geology: in Gutierrez-Palmenberg. Inc .. 1983, Preliminary report of Motorola Chemica) Lea k Project: Phoenix, Arizona, p. 11 -1- 11-35. wilh Appendil( A, 42 p. Ctlampine . A . l.. 1982, The microstructures end petrofabrics of tna mylonite·chloritic breccia transition , South Mountains, Maricopa County, A rizona: unpublished M as ter of Science " ti'lesis, Arizona State University, ·102 p. I 18 , Christensen, G. E., Welsch, D. G., and ?ewe, T. L ., 197B, Environm ental geology of tna Mc· , "99 Dowell Mountains area, Maricopa County, Arizona: Arizona Bureau of Geology and Min a'" , aral Te ch nology. Gaologic Investigation Series, GI-l-A, 1:24,000. , , .r Cordy, G. E. , Holway, J . V., and P~'e , T. l., 19n, Environmental geology of t he Paradise Vallay , OU<ldrangle , Maricopa Cuullty. Arizuna: Tempe, AriwI18, unpuolished lolio of maps pre " I Gell , pared for Ihe City ul Scottsdale, 14 sheet s, 1 :24,000 .,, Green, C. R,. and Se llers, W 0 .,1964, Arizona clim<t ta: Tucson, A rizona, U" ivernity of AttLOna Press . 503 p. Kokalis, P. G., 1971. Terraces of the Lower Salt River Valley, Arilona: unpuuli~hed Master 01 Science thesis. Arizona State University. 103 p. I. it.,. Lowe, C. H .. 1964, A rizona landscapes and tlabitats. in Vertebrates of Arizona: Universi ty of • Arizona Press, p. 1·82. Nations, J. D., and lindsay, E., 1976, Pleistocene EQuuS from Salt RiYer terrace gravels. Phoenix. , t ', , .. , Ari~ona: Journal of the Arizona Academy of Science. Volume II , p. 27-2B. Pew!!, T. L" 1978. Terraces of the middle Salt River Valley in relation to the late Cenozoic fJistory of the Phoenix Ba sin, Arizona, in Burt. D. M" and P/!we, T. l., fEds.) Guidebook to the geology of central Arizona: Arizona Bureau of Geology and Mineral Technology, Special Paper number 2. p. 1-45 Cefm Reynolds. S. J .. 1985. Geology of the South Mountains. Central Arizona: Arizona Bureau of Geo "' logy and Minerai Technology, 8ulletin 195, 61 p ,- • Scarborough. R. B., 1981, Reconnaissance geology: Goldfiel d and Northern Superstittion Moun· • tains: Arizona Bureau of Geology and Mineral Technology. Fieldnotes. Volume I I . Num· ber 4, p. 6-10 Scarborough, A. B .. and W ilt, J. C•. 1979, A study of uranium favorabili1y of Cenozoic sedimen tary rocks. Basin and Range Province, Arizona, Part I: United States Geological Survey ! Open-file Report 79 ·1429, 100 p. W ilson, E. D. ,·Moofe. R. T .• lind Cooper, J. R., 1969, Geologic milp 01 Arizona: A.izona 8utl,au of M ines and U . S. Geologicol Survey, 1:500,000. MAP SYMBOLS Cont1lc t , dashod where lJfildotional or infe rred. " .",,-_y...- Fault, dashed w here inferred, dotted where buriBd. FEET D U, upthrown side; 0, downthrow n side. "5',.", Dip and strike of beds, in degrees * Vertebrate foss il locality. Radiometric dete - 17.6 ± 0.4 million vears. Deeply buried edge of Papago Park Pedimen!, as dete rmined by geophysical methods. A rea covared by Map GI-2-B 33'22'30" f/- ~ li!:;~~~:~~~~~~~~~~:-::bjT33°22'30" IS. 4.1 MI E. • • J 650 I V S W 111 "52' 30" Artificial cover, outcrops and contaGts buried. SCA LE 1 24 000 GEOLOGY BY T.L. PE'WE: 1966-19B5; BASE MAP FROM U.S. GEOLOG ICAL SURVEY C.S. WE LLEN OORF,1977-1985; TOPOGRAPHIC MA.P, 1:24,000 SER IES * ....===>== =<==OE==.l~=>===c==OE=oo===iO==================================~1 MILE J. T. BALES, 1977-19 85. TEMPE QUADRANGLE (1952. PHOTOREVISED 1967) '" Su .lil<X CO Vl!r qUllrried Addilio n1)1 revisions compilocl by the Geological I o ,"'" .ceo 6000 7mo rrn Survey from aerial photugraphs taken 1978 and / 13' /231 MILS other sources. This infOnTIalion not fie)d checked. I Map editocl 1982. I , CO NTOUR lNTERVAL 10 FEET I QATUM IS MEAN SEA l EV L U-M (lR IO A.NO l lrB2 MAGNET C NO.'lT'l OECt.INATlON AT CENTER OF SHEET TIME RELATION OF M AP UNITS EXPLANATION UNCONSOUDATED ROCKS CON60UDATED ROCKS SALT RIVER SAND AND GRAVE L - Moderately to well sortad, w all st ra ti·· VOLCANIC ROC K S - Dark gray to gJ<Jyish -pink, undifferentiat ed l<Jya flows SOUTH MOUNTAIN S GRANODIOR ITE - Gray, medium-grained, mylonitic fied sand and grav<tl; loca ll y interbedded willI silt.