Geologic map and report for the Theodore Roosevelt Dam area, Gila and Maricopa Counties, Arizona

36 Pages·1999·2 MB·English

by  Spencer, J., Richard, S.

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Geologic map and report for the
Dam
Theodore Roosevelt area,
Gila and Maricopa Counties, Arizona
by
Jon E. Spencer and Stephen M. Richard
ArizonaGeologicalSurveyOpen-FileReport99-6
April, 1999
Scale 1:24,000(1 sheet),with28pagetext
PUBLISHED BY THE
ARIZONA GEOLOGICAL SURVEY
416 W. CONGRESS, SUITE 100
TUCSON, ARIZONA 85701
[phone]

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RESOURCEROOMPROPERTY
Geologic map and report for the
Theodore Roosevelt Dam area,
Gila and Maricopa Counties, Arizona
by
Jon E. Spencer and Stephen M. Richard
ArizonaGeologicalSurveyOpen-FileReport99-6
April, 1999
Scale 1:24,000(1 sheet),with28pagetext
ArizonaGeologicalSurvey
416W. CongressSt.,#100,Tucson,Arizona85701
Thisreportispreliminaryandhasnot
beeneditedorreviewedforconformity
withArizonaGeologicalSurveystan-
dards
Digitized by the Internet Archive
in 2012 with funding from
LYRASIS Members and Sloan Foundation
http://archive.org/details/geologicmapreporOOspen
GEOLOGICMAPANDREPORT
FORTHETHEODOREROOSEVELTDAMAREA,
GILAANDMARICOPACOUNTIES,ARIZONA
by
JonE.SpencerandStephenM.Richard
Introduction
TheTheodoreRooseveltDamareaislocatedapproximately90kmeastofPhoenixonthesouthwest
flankofTontoBasin(Figure 1). ThemapareaencompassesthesoutheasternendoftheMazatzalMoun-
tainsandthenorthernTwoBarRidgeareaatthenortheasternendoftheSuperstitionMountains. The
areawasmappedduringNovember, 1997toApril, 1998,aspartofamultiyearmappingprogramdirected
atproducingageologicmapoftheTheodoreRoosevelt30'x60'Quadrangle. A 1:24,000scalemapis
theprimaryproductofthisstudy(Plate 1;Figure2),andtheaccompanyingreportdescribesrockunits
andothergeologicfeaturesandincludesmodalmineralanalysesofgraniticrocksthatwasdoneinorderto
classifythegranitoids.
ThegeologyofthemapareaischaracterizedbyadiversesuiteofProterozoicgraniticrocks,gneiss,
andmetavolcanicrocksthatareoverlainbyagenerallynortheast-dippingsequenceofmiddleProterozoic
ApacheGroupstrata,diabasesills,andPaleozoicstrataasyoungastheMississippianRedwallLimestone
(seemapandcrosssections). WeaklyconsolidatedMioceneconglomerateandsandstoneoverliesallof
theserocksandaregentlytiltedandslightlytomoderatelyfaulted.Variousyoungerdeposits,including
Quaternaryrivergravels,weredepositedonolderrocksandstrataafterfaultingandtiltinghadended. A
newlyidentifiedstructure,theDeerHillfault,appearstobeanorth-northeasttrending,faultedmonocline.
Itsageisuncertain,andcouldbeeitherLaramideormiddleProterozoicandassociatedwithProterozoic
diabaseemplacement. Nolargeareasofmetallicmineralsorhydrothermalalterationwereidentified,al-
thoughsmallquartzveinsandmineralizedfracturesarepresentatmanyscatteredlocations.
34°00'
33°30
111°30' 111°00'
R.
n
Sources of Map Data
Rj. 2.
H-
StratigraphyofyoungestProterozoic and oldestPaleozoic sandstones
DiscontinuoussandstoneunitsrepresentingtheMiddleProterozoicTroyquartzite,CambrianBolsa
Quartzite,andBeckersButteMemberoftheDevonianMartinFormationoverlieApacheGroupstrataand
underliecalcareousstrataoftheMartinFormation(Figure3). Distinctionofthesethreeunitsisdifficult
becauseofthelithologicalsimilarityofthesandstonesandmarkedlateralthicknessvariationsanddiscon-
tinuities(e.g.Tahmazian, 1964;Meader, 1977;seealsoMcConnell, 1972,forameasuredsectionthrough
theApacheGroupatTheodoreRooseveltdam).
AllthreeunitsareexposednearthesoutheastabutmentofTheodoreRooseveltdamwherea30-m-deep
channelhasbeenincisedintoTroyQuartzite,MescalLimestone,andbasaltassociatedwiththeMescal
Limestone.Thechannelfillincludesalowerferruginoussandstoneandanoverlying,verypoorlysorted
feldspathicsandstone(Seedetailmap,Figure4).WehaveassignedthelowerunittotheBolsaQuartzite.
Itistypicallyferruginousinitslowerpart,butvariablybleachedintheupperpartwithlocallystriking
Liesegangbanding. Sandismoderatelysorted,feldsparisnotaprominentconstituent,butinsomeplaces
magnetiteiscommon.Troughycrossbedsareabundant.
Overlying,poorlysorted,iron-poor,palecoloredsandstonewithinthischannelfillisassignedtothe
BeckersButteMemberoftheDevonianMartinFormation.Coarse,angularfeldsparfragmentsarepresent
inthissand. Crossbeddingiscommon,andboundariesbetweenbedsarenotsharp.Thesandgenerally
becomesfinerup-sectionandgreenishclay-richbeddingpartingsarepresent.Detrital(?)muscoviteis
commonlyvisibleonthesepartingsurfaces.ADevonianageforthesestrataissupportedbypaleomag-
neticanalysis(ElstonandBressler, 1978),andisconsistentwithTeichert's(1965)interpretationofthis
channelfillasBeckersButteMember.
Teichert(1965,p.22)describedtheBeckersButteMemberasconsistingof"predominantlypoorly
sortedquartzgrainsthatrangefromfinetocoarse"andthat"itdiffersfrommostsandstonesubunitsof
theJeromeMember,whicharegenerallywellsorted."Feldsparandchertarelocallyminorcomponentsof
theBeckersButteMember,andmostgrainsaresubangulartoangular.AtTheodoreRooseveltDamsand-
stoneoftheBeckersButteMemberis"easilydistinguishedbyitssusceptibilitytodisaggregationinhy-
drochloricacid,whereastheTroyQuartzitehassiliceouscementandcannotbesodisaggregated."
(Teichert, 1965,p.25). [SeealsoRansome(1916,p. 150-162),Hinds(1936,p. 33),andHuddleandDo-
brovolny(1952,p. 105-106)].ItisnotcleariftheTroyQuartzitereferredtobyTeichert(1965)isthe
sandstoneweareassigningtotheTroyQuartzite(seebelow),orifitisthesandstoneunderlyingtheBeck-
ersButteMemberinthechannelfillsequence,whichweassigntotheBolsaQuartzite.
Onthesouthflankofthechannel,thestratigraphicallyhighestpartoftheMescalFormation(argillite
member)ispreservedandisoverlainconcordantlybysandstoneweassigntoTroyQuartzite.Thissand-
stoneisalsoreddishbrownincolor,buthassharp,nearlyplanarbeddingboundaries,andalthoughthe
unitasawholeispoorlysorted(contrastingwithsandstoneinterpretedasBolsaquartzite),grainsize
variationswithinindividualbedsaresmallerthangrainsizevariationsbetweenbeds(contrastingwiththe
BeckersButtemember).Thisunitalsocontainsred-brownmudstonepartings.Inallotherareaswithinthe
maparea,sandstoneinterpretedasTroyQuartziterestsonthebasaltthatdirectlyunderliestheargillite.
AlthoughfragmentsofchertandbasaltfromtheunderlyingunitsarepresentinTroyQuartzite,andindi-
catesomeerosionofunderlyingunits,Troysandswerenotrecognizedinpaleochannelsthathadcut
throughthebasaltorolderunits. SignificantchannelformationthuspostdatesdepositionoftheTroy
Quartziteinthestudyarea.
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