State of Arizona Bureau of Geology and Mineral Technology

INTRODUCTORY STATEMENT

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 quadrang le has been intensely urba nized ex­cept 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), rang ing from 1100 feet (336 m) in the Salt Aiver bed to 1746 fee t (532 m) at the summit of Bam9fi Butte. With the excep­tion of a few isola ted rock masses, 11m area occupies a relatiyely flat desert plain formed primarily

hy older and modaH' alluvial depo,;it!<.

CLIMATE

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 .

PraGipi 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 gus ty winds and blowing dust. December to February is the ra iny season, with gent le. often continuous w intl'lr rains ilnd cloudy

days.

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 me rocky, wall drained slopes of Papago Park Pedimen t, South Mountains, and Tempe Bullo.

The dillerse cactus f lora include cholla, p.ickly pear , hedgehog, pincushion , ilnd f ishhook. 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 ex­tremely 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 mounta in ranges. This unique physiography resulted from e period of r~ional bl oc k-faultin~ 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 thinning of the earth'S crulit. Vertical movament of crustal blocks created mountains on the upthrown sida and

hasins on tha downthrown side. As erosion and downwast ing 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 producing metamyolite. The metarhyoli te is intruded by two granites. The relationship between those two granit es, Tovrea and Camelback Granites. is not evident within the quad rangle. 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 moun­tains. 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 mill ion 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 faul t· blocks allllost completely buried by aggrading yalley alluviu.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 alluvial fans have belm ell trellGhed.

ENVIRONMENTAL GEOLOGY

The geology map serves as a besis for the development of additional maps depicting various environmen tal concerns. See reyerse side of this map for an in troductory statement reo gardlng environmental geology and a brief description of each map in this environmeJ1tal geology folio.

SELECTED REFERENCES

Atkinson, D. E., end Hey, S. M: , 1983, Preliminary repon of Motomla Chemical Leak Projoct, Sec tion 2: Geology: in Gutierrez-Palmenberg. Inc .. 1983, Preliminary report of Motorola Chemica) Leak 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 Mas ter of Science ti'lesis, Arizona State University, ·102 p.

Christensen, G. E., Welsch, D. G., and ?ewe, T. L ., 197B, Environmental geology of tna Mc· Dowell Mountains area, Maricopa County, Arizona: Arizona Bureau of Geology and Min­aral Technology. Gaologic Invest igation Series, GI-l-A, 1:24,000.

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

pared for Ihe City ul Sco ttsdale, 14 sheet s, 1 :24 ,000

Green, C. R ,. and Sellers, W 0 .,1964, Arizona clim<tta: 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.

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 f rom Salt RiYer terrace gravels. Phoenix. 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 Basin, Arizona, in Burt. D. M" and P/!we, T . l., fEds.) Guidebook to the geology of central Arizona: Arizona Bureau of Geology and Mineral Techno logy, Special Paper number 2. p. 1-45

Reynolds. S. J . . 1985. Geology of the South Mountains. Central Arizona: Arizona Bureau of Geo­logy 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.

a"

MAP SYMBOLS

Cont1lc t , dashod where lJfildotional or infe rred.

" .",,-_y...- Fau lt, dashed w here inferred, dotted where buriBd. D

Ope

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

Artificial cover , ou tcrops and contaGts buried.

Su .lil<X COVl!r qUllrried

TIME RELATION OF M AP UNITS

am, Of, [a~fo~m/L [

Oafi

GEOLOGY

TEMPE QUADRANGLE, MARICOPA COUNTY, ARIZONA Troy L. Pew8 Cathy S. Wellendorf James T. Bales

Department of Geology Arizona State University 1986

Prepared in cooperation with the cities of Tempe, Scottsdale. and Phoenix. and the

Arizona State Land Department

112i!OO~'lii~~~1[JiJlfiil~~!!i!:~1!i!!IIi!!!ii:ii!!!:~;;iii::::;;:::~!l:;;;!:;::I~!i~'Ii::~~~ilil::i!~;Ii;;iii~~iil:![~1:i~!.li~ 33'30' ,

, ..

1~f=Jjf l/t- '1~;fi1t~

l7Q6ODOr'·N .

'705

FEET

33'22'30"

Qefb

Oef l

Cefm

I'

•

, t ' , , .. ,

BASE MAP FROM U.S. GEOLOGICAL SURVEY TOPOGRAPHIC MA.P, 1:24,000 SER IES TEMPE QUADRANGLE (1952. PHOTOREVISED 1967)

Addilion1)1 revisions compilocl by the Geological

Survey from aerial photugraphs taken 1978 and

other sources. This infOnTIalion not fie)d checked.

Map editocl 1982.

"'"

""'m

""',

Tlb

Top

T""b

< T, ...

T" Tob >

p C l> -< m

" Z l>

" -< n m Z o 8 n

<~ __ --,p:.:C=-d __ --">

p£mr

'U

" m n l> s: '" " j; Z

l o v"n I I I Qvlm l I I aviv

I. it.,.

J 650 I V S W

SCALE 1 24000

I Gell , .,

, " ,

,- • •

.... ===>===<==OE==.l~=>===c==OE=oo===iO==================================~1 MILE *

'" I / 13'

/231 MILS

I I ,

I U-M (lR IO A.NO l lrB2 MAGNET C NO.'lT'l

OECt.INATlON AT CENTER OF SHEET

UNCONSOUDATED ROCKS

o

SA LT RIVER SAND AND GRAVE L - Moderately to well sortad, w all st ra ti··

fied sand and grav<tl; loca ll y interbedded willI silt. Wall rounded clasts. 2 to 12 in. (5 to 30 cml of Terti ury vo ll!lIn ic rocks (36.3%), Preca mbri an metamorph ic rocks (48.4% 1. and Precambrian granit ic rocks (16.3%) . Qsgs ~ strongly calichified sand and grayel of Sawik Terrace. Qsgm -strongly ca lich ified sElnd and gl9vel of Mesa Terrace . Osg - noncalichified sand end gravel of the modern channel.

EXTREMELY F IN~ ALLUVIUM - Gray to tan. moderately-well sorted, well stratified, sandy silt and cla y; lew to 110 clasts, averaging 25% sand, 75% silt (Ind clay. Oefm , rnooe,al(!ly to stronUly calichificd silt over MIlSa Ter· rilce gravel. Oef l - weak ly to noncalichified silt over Lehi Terrace Grilvel. Oel b - noncalichified silt over I.mdrock. Ocf i - locally strongly G3 1ich ified si lt of Indian Bend WiJ~h .

VERY FIN E ALLUVIU M - Tan to urown . modaratllly ~ ( .. ted, modorately w ell 9tratified. weak ly to moderately calichified, grayelly sandy silt and clay . averag ing 10% gravel, with subanguktr to subrounded clasts generelly not e)(ceeding 1/ 2 in. (1.3 cm). 35 % sand. and 55% silt and clay. Qyfg - composed largely of granitic clasts . Ovfm - composed large­ly of metamorphic clasts. Ovlv - composed large ly of yo lcenic clests.

FINE A LLU VIU M - Gray to tan. modarate ly sorted, moderately stratified,

weakly to moderately cal ichified, gravelly sandy silt and clay, averaging 20% gravel with subangular to subrounded granitic clasts generally not excaading 1 ~ in. 13.8 cm) , 40% sand, and 40% sil t and clay.

MEDIUM ALLUVIU M - Gray, poorly sorted and stratified, moderately to strongly ca li chified, silty sandy Qravel, averaging 40 % subangular granitic

clasts generally not exceeding 1 It 130 cm) , 30% sand, and 30% silt £100 clay.

SLOP E COLLUVIUM - Gray, poor ly Eor terl, strongly ca lichif ied, angular ta lus on lower bedrock sIOIM.!S; 112 t" 8 ill. (1.3 to 18.4 crn l clasts in matril( 01 silt and rock fragrmm ts.

PEDIM ENT COLLUVIUM-ALLUVIUM - Gray to wh ite, very poorly sorted

and stratified, strong l\' calichified. angular to subangular rock fragments, '.14 to 8 in. 10.7 to 18.4 cm l in diameter. size genera))y decraasing away from the highland source

, "'" .ceo 6000 7mo rrn

CO NTOUR lNTERVAL 10 FEET QATUM IS MEAN SEA l EV L

t

EXPLANATION

CON60UDATED ROCKS

VOLCANIC ROC K S - Dark gray to gJ<Jyish -pink, undifferent iat ed l<Jya flows

including alkali ()Iiv i m~ IJ~Sillt. illnvgdaloidal basalt, intermedia te la1 i1e, and rhy odllc ite; loce l xenoliths of granite and sandstone.

TEMPE BEDS - Interb edded $lrata COnSi$ling of abundant pink to red, poor ly to moderately sorted , pebbly arkosic sandstone; fess abundant tan, brownish-green, yellow, and purple, moderately·wen sorted sil t­stone; pink to graen, poo...,. sorted vo lcanic aren ite and green to wh ite

tuff; boundaries between bads are ganerally sharp, locally gradational; bedding thicknesses and median grain-size decrease upsect ion; abundant sedimentary sl ructures.

CAMELS HEAD FORMATION

Papago Park M ember - Bright red to ten, moderately sorted. we ll stra tif ied, arkosic fanglomerate composed of coarse-grained pebbly sandstones with subangular to subroun:led clasts of granite and meta rhyolite, 1/2 to 12 in. jl ,3 to 30 cm) in diameter, alternating wim fine r- gra illEld micaceous

arkosic gritstones, sandstones, and si ttstones in gradad saquences.

Stadium Breccia Memoor - Reddish brawn, c01orse-grained, poo.ly Sorlan and strmified, massi .... e ortcosic brecckt; subangu lar to angut;:11 clasts , 112 to 18 in. 11.3 to 45 cm) in diameter . slight ly imbricated; consists of granite f40 to 70%] and metarhyolite (25 10 55%]. l()Cally <llmost entirely metarhyolite; matrix of silt and fine sand with rocl< fragments, fefTugen·

ous cement.

Barne s 8utte Breccia Member - Redd ish brown, coarse-grained, poo rly SO iled and stratified. massive arkosic breccia; subangular to angu lar clasts, 1/ 4 in. to 15ft 10.7 em to 4.5 ml in diameter, slightly imbricated; comoosed 01 gra nite (70 to 85%) and meta rhyolite 110 to 20%) in a matri~

of rock f ragments and ferrugenous cement.

Zoo Brecda Member - Purple to reddish-brown, coarse·gralned, unsorted, poorly stralified, massive brecc ia; clasts are angular and fresh. 1/ 4 in. to 2 It W.7 10 60 cm) in diameter; cons ists of metarhyolite (30 to 100%), granite W to 35% ), and a small amount of a distinct dac ite porphyry; matli~ of si lt and clay in ferrugenous cemen t.

Basal Member - Red to purple to brown sendstone and diamictito, locallv interbedded with green to white tu ffa ceous sandstone and brecckt; poor­ly t o moderately sorted and stratified; angular clasts f rom 1/4to 8 in. (O.7 to 20 cm) in diameter; of local deriva tion.

4.1 MI E. • •

Geologic Investigation Series M ap GI-2-A

PhDenix •

8upo .. dludon :::' Mh:;

--, o 10 Miles , ,

FEET 111 ° 52' 30"

"",.

a'"

Cefm "'

!

'31

" I 18 , , ,

, , ,

. r

7-

C

Q

Z

"99

f/li!:;~~~:~~~~~~~~~~:-::bjT IS. -~ 33°22'30" 111 "52' 30"

GEOLOGY BY T.L. PE'WE: 1966-19B5; C.S. WE LLENOORF,1977-1985; J. T. BALES, 1977-1985.

SOUTH MOUNTAIN S GRANOD IOR ITE - Gray, medium-grained, mylonitic g ranodio rit e With gneiSSIC loliation.

GREENSTONE DIK E - Green to greenish-black . highly altered and

f rac tured, fine·grained intruEive rock.

CAM ELBACK GRANITE - Pink, coarse-gra ined to porphyritic grllnite;

contains large pink feldspar crystals . 1/ 4to 3/4 In. (0.7 t0 2.1 cm l. Locally highly sheared; cut by veins of quartz. and dikes of aplite and greenstone; l(enoliths of metarhyolite and a dark litle -g rain ed rock.

TOVREA GRANITE - Gra,· . coarse-grained , large roundod crys tal~ of gr~y quartz, 1.14 to 1 y., in. (0:7 to 3.2 em); segregat ions of ferrOrna91llJSian minerals altered to epidote and chlo rite. Weathers deeply with red ol\ id", ­t ion rind, 1/4 to 1/2 in. 10.7 to 1.3 cm) thick; cut by greenstone ond ilplitc

dikes.

METARHYOUTE - Gray to pink, orange-weal hering. blocky. folia ted; locally porphyrit ic. commonly layered with f lattened pum ice inclusions;

epidotized; locally cut by greenstone and ap lite dikes. Commonly high ly fractured and brecciated.