State of 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 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 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

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

Green, C. R,. and Se llers, W 0 .,1964, Arizona clim

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

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 EX TREMELY F IN~ ALLUVIUM - Gray to tan. moderately-well sorted, well -< tuff; boundaries between bads are ganerally sharp, locally gradational; Cefm m stratified, sa ndy silt and cla y; lew to 110 clasts, averagin g 25% sand, 75% bedding thicknesses and media n grain-size decrease upsection; abundant CAMELBACK GRANITE - Pink, coarse-grained to porphyritic grllnite; ""'m silt (Ind clay. Oefm , rnooe,al(!ly to stronUly calichificd silt over MIlSa Ter· contains large pink feldspar crystals. 1/ 4to 3/4 In. (0.7 t0 2.1 cm l. Locally Z" sedimentary slructures. l> rilce gravel. Oefl - weak ly to noncalichified silt over Lehi Terrace Grilvel. highly sheared; cut by veins of quartz. and dikes of aplite and greenstone; Oel b - noncalichified silt over I.mdrock. Ocfi - locally strongly G3 1i chified l(enoliths of metarhyolite and a dark litle-g rain ed rock. ""', -< n " m si lt of Indian Bend W iJ~h . Z o 8 CAMELS HEAD FORMATION TOVREA GRANITE - Gra,·. coarse-grained , large roundod cry s tal~ of gr~y n l o v"n I I VERY FIN E ALLUVIU M - Tan to urown. modaratllly ~ (.. t ed, modorately I Qvlm l w ell 9tratified. weak ly to moderately calichified, grayelly sandy silt and quartz, 1.14 to 1 y., in. (0:7 to 3.2 em); segregat ions of ferrOrna91llJSian I I aviv Papago Park M ember - Bright red to ten, moderately sorted. well stra tif ied, clay. averag ing 10% gravel, with subanguktr to subrounded clasts minerals altered to epidote and chlorite. Weathers deeply with red ol\ id", ­ arkosic fanglomerate composed of coarse-grained pebbly sandstones Tlb generelly not e)(ceeding 1/ 2 in. (1.3 cm). 35 % sand. and 55% silt and tion rind, 1/4 to 1/2 in. 10.7 to 1.3 cm) thick; cut by greenstone ond ilplitc with subangular to subroun:led clasts of granite and meta rhyolite, 1/2 to clay. Qyfg - composed largely of granitic clasts. Ovfm - composed large­ dikes. 12 in. jl ,3 to 30 cm) in diameter, alternating wim fine r- graillEld micaceous ly of metamorphic clasts. Ovlv - composed large ly of yolcenic clests. Top arkosic gritstones, sandstones, and si ttstones in gradad saquences.

T""b T" METARHYOUTE - Gray to pink, orange-weal hering. blocky. foliated; Stadium Breccia Memoor - Reddish brawn, c01orse-grained, poo.ly So rlan I' Tob locally porphyritic. commonly layered with flattened pum ice inclusions; FINE A LLU VIU M - Gray to tan. modarately sorted, moderately stratified, t and strmified, massi.... e ortcosic brecckt; subangular to angut;:11 clasts , 112 < > epidotized; locally cut by greenstone and ap lite dikes. Commonly highly weakly to moderately cal ichified, gravelly sandy silt and clay, averaging to 18 in. 11.3 to 45 cm) in diameter. slight ly imbricated; consists of granite T,... fractured and brecciated. 20 % gravel with subangular to subrounded granitic clasts generally not f40 to 70%] and metarhyolite (25 10 55%]. l()Cally 'U Barne s 8utte Breccia Member - Redd ish brown, coarse-grained, poo rly m MEDIUM ALLUVIUM - Gray, poorly sorted and stratified, moderately to SO iled and stratified. massive arkosic breccia ; subangular to angu lar n" strongly ca li chified, silty sandy Qravel, averaging 40 % subangular granitic l> clasts, 1/ 4 in. to 15ft 10.7 em to 4.5 ml in diameter, slightly imbricated; clasts generally not exceeding 1 It 130 cm), 30% sand, and 30% silt £100 s: comoosed 01 gra nite (70 to 85%) and me ta rhyolite 110 to 20%) in a matri~ clay. '" of rock fragments and ferrugenous cement. "j; Z p£mr Zoo Brecda Member - Pu rple to reddish-brown, coarse·gralned, unsorted, SLOP E COLLUVIUM - Gra y, poor ly Eorterl, strongly ca lichif ied, angular poorly stralified, massive breccia; clasts are angular and fresh. 1/ 4 in. to ta lus on lower bedrock sIOIM.!S; 112 t" 8 ill. (1.3 to 18.4 crn l clasts in matril( 2 It W.7 10 60 cm) in diameter; cons ists of metarhyolite (30 to 100%), 01 silt and rock fragrmm ts. granite W to 35 % ), and a sm all amount of a distinct dacite porphyry; matli~ of si lt and clay in ferrugenous cement.

PEDI M ENT COLLUVIUM-ALLUVIUM - Gray to white, very poorly sorted Basal Member - Red to purple to brown sendstone and diamictito, locallv and stratified, strongl\' calichified. angular to subangular rock fragments, interbe dded with green to white tuffaceous sandstone and brecckt; poor­ '.14 to 8 in. 10 .7 to 18.4 cm l in diameter. size genera))y decraasing away ly t o moderately sorted and stratified; angular clasts from 1/4to 8 in. (O.7 from the highland source to 20 cm) in diameter; of lo cal deriva tion.