GEA236_20240.qxd 9/10/082:42PMPage742 Published online in Wiley Interscience(www.interscience.wiley.com).Published onlineinWiley DOI:10.1002/gea.20240 Periodicals,Inc. © 2008Wiley Vol. Journal, 23,No.6,742–778(2008) AnInternational Geoarchaeology: on alandscape.However, theseundertakingshavetypicallyinvolvedsourcingeither by trackingmovementofthestoneitselfawayfroma knowngeologicalsource(s) such investigationstrackthepeoplewhoprocured,knapped, andusedstonetools tool-making hominidancestorsmovedacrosstheland (Odell,2000,2004).Ineffect, have effectivelyinvokedstonesourcingdatatoreconstruct howhumansandtheir INTRODUCTION 4 Bellflower Blvd.,LongBeach,CA90840 3 84322 2 84322 1 and StephenT. Nelson Bonnie L.Pitblado, Quartzite, GunnisonBasin,Colorado Pilot StudyExperimentsSourcing *Corresponding author;E-mail:[email protected]. Geology Department,BrighamYoung University, S-389ESC,Provo,UT84642 Anthropology Department,CaliforniaStateUniversityLongBeach,1250 Department ofGeology, UtahStateUniversity, 4505OldMainHill,Logan,UT Anthropology Program,UtahStateUniversity, 0730OldMainHill,Logan,UT The archaeologicalliteratureisrepletewithstudiesfrom aroundtheworldthat MS. Futuretestingisrequiredtoevaluatethis in theGunnisonBasinmaylieamethodologycombiningpetrographicanalysisandLA-ICP- Gunnison Basin.Thegreatestpotentialfordiscriminatingamongdifferentsourcesofquartzite sions ofICP-MStodiscriminateamongquartzitesfromdifferentsourcelocalitiesinthe refine ourresults,thestudysuggeststhereispotentialforpetrography, INAA,andbothver- the specimensandsourcestheyrepresent.Althoughmoretestingisneededtoverify acid-digestion (AD-ICP-MS)andlaserablation(LA-ICP-MS)—asmeanstodifferentiateamong tron activationanalysis(INAA),andinductivelycoupledplasmamassspectrometry—both fluorescence (UVF),wavelengthdispersiveX-ray(WD-XRF),instrumentalneu- same twentyGunnisonBasinquartzitesamples,thisstudyevaluatedpetrography, ultraviolet gests reasonforoptimismthatquartzitesmaybeamenabletosourcediscrimination.Forthe are moremodest:todemonstratethatasmall-scaleexplorationofsourcingtechniquessug- Mountains andpotentiallyanywhereprehistoricpeopleusedquartzite.Thegoalsofthispaper tools. SuccesswouldfacilitatereconstructionofPaleoindianmobilityintheSouthernRocky southwest Colorado,usedbyPaleoindianpeopleca.11,500–8,000yearsagotomakestone The long-termgoaloftheresearchistofingerprintsourcesquartziteinGunnisonBasin, rock typetowhichgeochemicalandothersourcingtechniqueshaveonlyrarelybeenapplied. This paperreportstheresultsofpilot-studyeffortstodevelopmethodsprofilequartzite,a 1, * CarolDehler, 4 two-fold approach.© 2 Author ProoHector Neff, f 2008 Wiley Periodicals,Inc. 3 GEA236_20240.qxd 9/10/082:42PMPage743 ple. Variability thatuniquely“fingerprints”anystonetypeisusually notamongits Geochemical techniquesyieldquantitativeprofilesofthe elementspresentinasam- yields datasetsofprimarilyqualitative(butsome quantitative)observations. izes thecompositionandtextureofrockmacroscopically andmicroscopically to “petrography,” and“geochemical”sourcingtechniques.Petrography character- same rockpopulation. achieve lowerorhigherlevelsofprobabilitythatanartifact andsourcerepresentthe ‘sourced.’” Stonesourcingisastatisticalundertaking, andarchaeologistscanonly acknowledge andagreewithShackley’s (1998:261)pointthat “nothingiseverreally logical sourceofthatrawmaterialwithahighdegreestatisticalcertainty. We “sourcing,” werefertoeffortsmatcharocksampleofunknownorigingeo- GEOLOGIC ANDGEOCHEMICALTERMINOLOGY quartzite sourcinginColorado’s GunnisonBasinandelsewhere. limited datasetwillsupportandoffersuggestionsforfutureresearchtoadvance and downloading.Inthefinalsectionofpaper, wedrawthoseconclusionsour Public/projects.aspx?pid archived atthegeologicalcommunityWeb sitehttps://www.paleostrat.org/ that willdriveourfutureresearch,allrawdatafromofanalyseshavebeen and keyresults.Althoughwediscussindepthonlyourmostrobustresultsthose mary goal:presentingourGunnisonBasinquartzitesourcingpilotstudymethods of varioussourcingtechniquestoarchaeologicalsituations.We thenturntoourpri- geologic andgeochemicalterminologythenpresentanoverviewofapplications (AD-) andlaserablation(LA-ICP-MS).Inthesectionsthatfollow, wefirstdefine (INAA), andinductivelycoupledplasmamassspectrometry, bothacid-digestion persive X-rayfluorescence(WD-XRF),instrumentalneutronactivationanalysis Upper GunnisonBasin:petrography, ultravioletfluorescence(UVF),wavelengthdis- six methodswithpotentialtocharacterizequartzitesourcesandartifactsinColorado’s to fingerprintquartzitesthewaywecurrentlydootherrocktypes. it isfairtosaythatmanyearthscientistswouldbenefitenormouslyfromtheability geologists workingtocharacterizequartziteformationsacrossoftenlongdistances— many prehistoricknappers(andgrindersandsculptors)—andtheparallelneedsof thereby areparticularlyacute.However, giventhefrequentuseofquartzitebyso 2002, 2003;Stiger, 2001,2006),thisproblemandtheinterpretivelimitationsimposed or moreofmanychippedstoneassemblages(e.g.,Andrews,2005;Pitblado,1994,2000, Upper GunnisonBasinofsouthwesternColorado,wherequartziteconstitutes95% weak one.Quartzitehasvirtuallynosourcingtrackrecordatall.Inplaceslikethe toric toolmakerseverywhere,doesnotenjoyastrongsourcingtrackrecord—or with triedandtrue,ifimperfect,sourcingtrackrecords. volcanic (e.g.,obsidian)ormicrocrystallinechert)materials,bothrockclasses Because theyformthecruxofourpilotstudymethodology, werefer frequently When wediscussthe“sourcing”ofquartziteartifactsorotherwisereferencestone The purposeofthispaperistoreportkeyresultsapilotstudythatevaluated Quartzite, aubiquitousrocktypeworldwideandcommonchoiceforprehis- EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT e2bf1281-b96a-48ad-85e3-9b2a8df29b6a forpublicviewing e2bf1281-b96a-48ad-85e3-9b2a8df29b6a Author Proof 743 AQ1 GEA236_20240.qxd 9/10/082:42PMPage744 744 crystalline. Cementsotherthansilica,suchashematite, mayexistasaminorphase. grains comeinavarietyoftypes,includingmonocrystalline, undulose,andpoly- Such graintypesincludefeldspar, rockfragments,micas,and heavyminerals.Quartz exclusively quartz,othergraintypescanbepresentinsmall amounts(typically growths ofmicrocrystallinequartz.Althoughmanyorthoquartzites containgrainsof tacts areusuallytangentialandsurroundedentirelyor inpartbycrystallineover- a granulartexture,withcementfillingbetweenthegrains. Thegrainboundarycon- ( implications forinterpretingresultsofgeochemicalanalyses. potential geochemicaldifferencesbetweenthesetwotypesofquartzitecanhave pare Plate1C–Fwith2A–DinCarozzi,1993).Understandingthetexturaland ized bytheirdistincttextures,whichareindicativeofdifferentorigins(com- equal. Themaintypesofquartzite,orthoquartziteandmetaquartzite,arecharacter- granular texture(Howard,2005;Rapp,2002).Allquartzites,however, arenotcreated reous lusterand(often)conchoidalfracturemechanics,butmosthaveadistinctly the quartzitewestudied. precisely describesthemanyfine-grained,oftenknappablerocksthatcontrastwith quartz”; however, weinvoke thelattertermherebecauseitmoreinclusivelyand rial,” and“flint”areallroughlysynonymouswithRapp’s (2002)“microcrystalline exploited prehistorically(Luedtke,1992).Theterms“chert,”“cryptocrystallinemate- a diversespectrumofstructures(e.g.,nodules,lenses,beds),allwhichwere jasper, andchalcedonythatforminavarietyofgeologicalenvironmentsassume ( talline” rocktypesand,mostimportantofall,“quartzite.”“Microcrystallinequartz” program thatseekstoretainartifactintegrity. LA-ICP-MS mayprovetobethebestoverallchoiceforanarchaeologicalsourcing prehistoric artifacts, ure diagnosticsuitesoftraceelementsinGunnisonBasinquartzitesamplesand we concludethatAD-ICP-MSshowsthegreatestinherentabilitytodetectandmeas- rials. Aswewillshowanddiscuss,ofallthetechniqueswithwhichexperimented, powerful andincreasinglypopularmeansofchemicallyprofilinganarraymate- recently inminimallyinvasiveLA-ICP-MSform(e.g.,Speakman&Neff,2005)—isa acterization ofpotteryanditsconstituentsoftenreliesonINAA.ICP-MS—most using XRF(thoughINAAofobsidianispreferredundercertainconditions);char- and sourceartifacts:XRFINAA.Mosttrace-elementanalysisofobsidianisdone archaeology, twotechniqueshavebeenparticularlyfrequentlyemployedtoprofile must choosethemostappropriateofanarraygeochemicalanalyticalmethods.In others forprofilingparticularmaterials. ticular traceelementsthanothertechniques,andsomemethodsarebettersuited or evensmallerquantities.Somegeochemicaltechniquesaremoresensitivetopar- major orminorelements,butratheritstracepresentinpartspermillion AL. PITBLADO ET sensu 95%) andcementedbysilica(Carozzi,1993;Howard,2005). Allorthoquartziteshave Orthoquartzites aresedimentaryrockscomposedofdominantly quartzsandgrains Like microcrystallinequartz,quartzitesarealsoessentiallypurequartzwithavit- Finally, wewish tobeclearaboutwhatwemeanwhenrefer“microcrys- For anyprojectrequiringchemicalcharacterizationofanobject,theresearcher EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Rapp, 2002)describesfine-grained,silica-richrockssuchaschert,flint,agate, but that withmethodologicalrefinement,minimallyinvasive Author Proof 5%). GEA236_20240.qxd 9/10/082:42PMPage745 AQ2 wide), theeasternUnitedStates(Hughes,1992);east-central California(Hughes,1994); cally characterizeobsidiansourcesandartifactsfrom(among manyotherareasworld- INAA withatechniquethatwouldsooncometodominate obsidianstudies:XRF. In 1985,Wright andChaya(1985)refined Frisonetal’s (1968)findingsbycoupling Gordus (1970)successfullyappliedINAAtoobsidian artifacts fromSyriaandIraq. INAA tochemicallyprofileobsidiansfromthenorthwestern Plains.Shortlythereafter, geologic sourceswithdistinctchemicalprofiles.Asearly as1968,Frisonetal.used ideal conditionsforpermittingthematchingofartifacts fromunknownsourcesto homogenous chemicalsignatureandalimitedgeographic extentonalandscape— quartz andquartzite,obsidiansrepresentasinglevolcanicflowwithunique most oftenandwiththegreatestsuccess.Thisisbecauseunlikemicrocrystalline ian, microcrystallinequartz,andquartzites)archaeologistshavesourcedobsidian ARCHAEOLOGICAL APPLICATIONS OFSTONESOURCING important componentoffuturequartzite-sourcingefforts. important for“groundtruthing”theresultsofgeochemicalanalysesandwillbean anticipates aconclusionthatwewilldrawlaterinthispaper:petrographyis any analyticaltechnique,maynotbeabletodiscernonetypefromtheother. This different elementalsignatures,andgeochemistryalone,asassessedthrough chemically unique;rather, bothtypesofquartzitescanyieldverysimilaror not maketheirorigindiscernable.Thisistosaythataquartzitecannotbegeo- origins thataresufficientlyvariableandunpredictablegeochemistryalonemay were introducedduringthemetamorphicevent(s). Additionally, metaquartzites mayassumenewelementalsignaturesfromfluidsthat to reflectthegeochemistryofgrainsthatoriginatedfromavarietygeologicsources. and compressionofgrains.Bytheirnature,metaquartzitesalsohavethepotential changes bycrossingtemperatureand/orpressurethresholds,causingsilicadissolution quartz-grain types.Metaquartzitesformwhenaquartzsandstoneororthoquartzite other tectonicfabric.Aswithorthoquartzites,metaquartzitescanhaveavarietyof of grainboundariesandcanshowelongationgrainsparalleltofoliationplanesor Howard, 2005;Krynine,1968;Rapp,2002).Metaquartzitestypicallyexhibitsuturing tics, resultinginfeaturesthatcanbeidentifiedmicroscopically(Herz&Garrison,1998; and/or pressurehaveobliteratedoriginalgrainsize,shape,andothercharacteris- tures (Pettijohn,Potter, &Siever, 1987). have multiplecementphases,allofwhichmaycontainuniquegeochemicalsigna- igneous, metamorphic,sedimentary, oramixedsignature.Further, quartzitescan position (andhencethegeochemicalsignature)canbequitevariableandreflectan Therefore, althoughasedimentaryquartzitehasdistinctivetexture,thegraincom- the weatheringandtransportofothersedimentary, plutonic,ormetamorphicrocks. All grainswithinanorthoquartzite,butespeciallythequartzgrains,originatedfrom XRF, acost-efficientapproachtoobsidiansourcing,hasbeenused geochemi- Of threeofthemajorrocktypesusedbyprehistoricpeopleeverywhere(obsid- Pertinently forourpilotstudy, bothtypesofquartzites, althoughquartz-rich,have Metaquartzite ismetamorphosedorthoquartziteorquartzsandstone,whereheat EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Author Proof 745 AQ3 GEA236_20240.qxd 9/10/082:42PMPage746 746 quartzite sources.Church(1990,1996)studiednotonly microcrystallinequartzfrom sourcing successesatleastrivalingthoseachievedwith microcrystallinequartz. ical, relatedtoquartzitesourcing,butthefewextant studiesdocumentquartzite- that quartziteisunsourceable.Thereverylittleliterature, geologicorarchaeolog- been ignoredbyarchaeologistsare situation haschangedlittleintheinterveningtwodecades. Reasonswhyquartzitehas tion, basiclithicanalysis,andreplicativeexperimentation.” Shewasright,andthe largely ignoredthisrawmaterialwithrespecttoproper identification,sourceloca- world fromthetimeoffirststonetoolmanufacture .[but]archaeologistshave that “quartziteisamajorlithicmaterialemployedprehistoricallythroughoutthe because sofewhavestudiedit.Ina20-year-old paper, CarolEbright(1987:29)observed (Rockman, 2003;Rolletal.,2005). 1992), Fourierinfraredspectroscopy(Long,Silveira,&Julig,2001),andLA-ICP-MS via othergeochemicalmethods,includingXRF(Church,1990,1996;Warashina, ern Belize,butothershavehadencouragingresultsprofilingmicrocrystallinequartz had lesssuccessusingINAAtodistinguishchemicallyhomogenouschertsinnorth- 1995]; Lyons, Glascock,&Mehringer, 2003;Spielbauer, 1984).Cackleretal.(1999) Hatch &Miller, 1985;Hoard etal.,1992,1993[butseeChurch,1995,andHoard to effectivelysourcemicrocrystallineartifactsfromthroughoutNorthAmerica(e.g., element profilesofchertsfromtheMidwest.OtherarchaeologistshaveusedINAA INAA ofmicrocrystallines,demonstratingstatisticallysignificantdifferencesintrace- extensively withthem.Luedtke(e.g.,1978,1979;&Meyers,1984)pioneered crystalline rocksandsourcingartifactsmadeofthem,archaeologistshaveworked assign anartifactofunknownmaterialtoasourcecandidate(e.g.,Rolletal.,2005). that intra-sourcevariabilityexceedsinter-source variability, makingitimpossibleto 1998). Ontheotherhand,microcrystallinequartzcanbesochemicallyheterogeneous assessing thelandusebehaviorofknapper(e.g.,Cackleretal.,1999;Shackley, to it,evenwithhighstatisticalcertainty, isuselessforanarchaeologistinterestedin chemically homogenousacrossa1000-km-longformationthatmatchinganartifact acterize onesourcemaynotworkatallelsewhere.Microcrystallinequartzcanbeso forms undersuchawiderangeofconditionsthattechniqueworkswelltochar- have notexperimentedwiththeserocks,butratherbecausemicrocrystallinequartz microcrystalline quartzmaterials.Thisisnotbecausegeologistsandarchaeologists of archaeologicalobsidianintheprehistoricSouthwest.” rently knownandpublishedcanbetrustedasaccuratereflectionsoftheavailability Southwest. Itthereforefollowsthatsourcecharacterizationanddatalibrariesascur- unlocated or‘unknown’sourcesinarchaeologicalcontextstheU.S.portionof and Shackley(1997:241)notedthat“itappearstherearenolongeranysignificant 1997; Shackley, 1995).Obsidiansourcinghascomesofar, infact,thatPeterson, Mitchell, Holmes 1979);andNewMexicotheSouthwest(Peterson,Mitchell,&Shackley, the GreatBasingenerally(Jonesetal.,2003);westernUtahspecifically(Nelson& AL. PITBLADO ET Petrography hasprovedusefulforcharacterizingand distinguishingamong So wheredoesquartzitefitintothesourcingpicture?Theanswerisnowhere, Despite thegeologicallyrootedchallengesofchemicallycharacterizingmicro- Such absolutesourcingsuccessdoesnotapplytoeffortscharacterizeandsource EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: not A rooted inempiricalevidencedemonstrating uthor Proof AQ4 GEA236_20240.qxd 9/10/082:42PMPage747 flakes andtoolsfromthesitetoreconstructmobility patternsofthesite’s earliest the younger;and(3)long-termgoalofourresearch istosourcethePaleoindian flakes wouldhavedestroyedagreaterpercentageofthe olderassemblagethanitdid fewer artifactsthantheMiddleArchaiccomponent,so analyzingeightPaleoindian multiple formsofanalysis,somedestructive;(2)thePaleoindian componentyielded Middle Paleoindian component,but(1)theflakes aresmallerthantheir the ChanceGulchsite.Thesitealso contains an8000rcybplate large quartziteflakesfromaca.4500rcybp(Middle Archaic)componentat enough tojustifylarger-scale experimentation. sourcing techniquestodetermineifoneormoreoftheprovedeffective a modestdatasetoftwentyquartzitesamplesthatcouldbesubjectedtoanarray verse oftheGunnisonBasinoranythingclosetoit.Instead,wewantedassemble beginning stageofquartzite-sourcingresearch,tosampletheentirequartziteuni- Chance Gulchsiteandrelativelyfarawayfromit(Figure1).Ourgoalwasnot,atthis 2004), andgeologicsamplesfromquartzitesourceslocatedbothverynearbythe of southeast the multi-componentChanceGulchsite,locatedinGunnisonBasin,6.5km sources maybepossible.We electedtoworkwitharchaeologicalspecimensfrom petrography andgeochemistrythatdoexistsuggestdiscriminationof Field andLaboratorySamplingStrategy PILOT STUDYMETHODOLOGY effectively distinguishedamongquartzitesources—afindingourpilotstudysupports. orthoquartzite fromWisconsin. Inthefewtestcasesonrecord,variousmethodshave quartzite artifactsfromthePaleoindianCumminsSite,Ontario,andmatchthemto et al.(1988),Julig,Pavlish,andHancock(1987)employedINAAtocharacterize which formationtheyoriginatedfrom.”Finally, inkeepingwiththemethodsofStross concluded that“quartzitescontainedenoughtraceelementvariabilitytodetermine from ageographicareaoverlappingChurch’s alsoinvokedXRF. Schneider(2006:81) “XRF canprovidebasic,valuableinformation.”Acomplementarystudyofquartzites to permitsourceprofiling.Ofhisstudyoforthoquartzites,Churchnoted(1996:141), the resultshaveshownthemtobesufficientlysensitivetrace-elementvariability ferentiate quartzitesfromtwoancientEgyptianquarrieslocated900kmapart. Similarly, Strossetal.(1988)coupledpetrographiccharacteristicswithINAAtodif- with ahighdegreeofreliability,” afindinghecorroboratedandrefinedwithXRF. seems toofferquickandeasysourcingtheparentformationfororthoquartzites into fourclassesbasedontexture.Church(1996:141)concludedthat“thismethod acterizing chertsandchalcedonies,butquitehelpfulforquartzites,whichhegrouped to low-powermicroscopicexamination,whichhefoundbeoflittlehelpforchar- the BearlodgeMountainsofMontana,butalsoquartzite.Hesubjectedsamplesboth We compiledourtwentyquartzitesamplesasfollows.First,weselectedeight The purposeofourpilotinvestigationwastobuildonthosefewstudiesquartzite As withpetrography, whengeochemicalanalyseshavebeenappliedtoquartzite, Archaic counterpartsandnonewouldhavesupplied enoughmaterialfor Gunnison, Colorado(e.g.,Pitblado,2002;Stamm,&Camp, EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Author Proof 747 GEA236_20240.qxd 9/10/082:42PMPage748 748 have beencompletedforonlyafewisolatedlocalitiesintheGunnisonBasin. the ultimategeologicsourceforgravels.Unfortunately, detailedgeologicmaps point inourresearchprogramwhichquartziteformationorformationsservedas unlikely sourcesforChanceGulchknapperstohaveaccessed. of UintaMountainGroupquartzitefromnortheasternUtah(“UMG”samples),both Gunnison Basin,oneinMontroseCounty, Colorado(Source5),theotheroutcrops knapping. Theassemblagealsoincludedsamplesfromtwolocalitiesoutsidethe quartzite 0.5kmnortheastofChanceGulchandneitherquarriednorsuitablefor been quarriedprehistorically. Source2(Figures1,2b)isanoutcropofPrecambrian tance fromthesite.Threesources(1,3,and4;Figure1)areTertiary graveldeposits material locatedinsomecasesnearbytheChanceGulchsite,othersatdis- through time(Pitblado,2002). quarries wehavepreviouslyhypothesizeddrewpeopletotheChanceGulchsite sense ofwhethertheirsignatureswouldsuggestarelationshiptothenearbyquartzite value intestingarchaeologicalspecimensfromChanceGulchtogainapreliminary flakes towhateverformofanalysisprovesmostsuitable.Atthesametime,wesaw occupants. We wantedtorefineourmethodologybeforesubjectingthePaleoindian AL. PITBLADO ET 2 kmfromChanceGulch(e.g.,Figure2a).Allthreeshowclearevidenceofhaving In thecaseofgravelsourcesinGunnisonBasin,wedonotknowatthis Our remainingtwelvequartzitesamplesderivedfromgeologicsourcesofthe EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Figure 1. Location oftheChanceGulchsiteandsixsampledquarries. Author Proof GEA236_20240.qxd 9/10/082:42PMPage749 tion(s), ifany, werethesource(s)ofTertiary gravelswesampled. crucial componentofourfuturefieldresearchwillbe todeterminewhichforma- Tweto, 1987;Zech,1988).ThesegeologicsourcesaresummarizedinTable I,anda & Clark,1985;HedlundOlson,1974;Hunter, 1925;Olson,1976a;Streufert,1999; sandstone, andTertiary andQuaternaryquartzite-bearinggravel(DeWitt, Stoneman, quartzite-bearing conglomerate,PaleozoicandMesozoic contact-metamorphosed and quartzveins,PaleozoicMesozoicorthoquartzite, PaleozoicandMesozoic quartzite-bearing unitsintheGunnisonBasininclude Precambrianmetaquartzite We haveascertainedfromthemandmoregeneralizedgeologicmapsthat are locatedabout0.5kmnorthandnortheastrespectivelyoftheChance Gulchsite. Figure 2. (a) Source1,Tertiary graveldeposit;(b)Source2,Precambrianquartziteoutcrop.Thesources EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Author Proof 749 GEA236_20240.qxd 9/10/082:42PMPage750 750 IBAOE AL. PITBLADO ET

Table I. Geologically mapped quartzite-bearing units in the Gunnison Basin, Colorado. EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Quartzite-Bearing Units Location Type of Quartzite Source Type References

Precambrian metaquartzite Headwaters Chance Metaquartzite and Potential outcrop DeWitt, Stoneman, & Clark, 1985; and quartz veins Gulch, Fossil Ridge bull quartz Hedland & Olson, 1974; Olson, 1976a, 1976b; Zech, 1988 Cambrian Saguache Quartzite Fossil Ridge Orthoquartzite Potential outcrop DeWitt, Stoneman, & Clark, 1985; Ordovician Harding Sandstone DeWitt et al., 2002; Streufert, 1999; Ordovician Parting Sandstone Zech, 1988 Jurassic Junction Creek Sandstone Widespread Orthoquartzite Potential outcrop DeWitt et al., 2002; DeWitt, Cretaceous Dakota Formation Stoneman, & Clark, 1985; Streufert, 1999; Zech, 1988 Jurassic Morrison Formation Widespread Quartzite–clast Potential outcrop Gaskill, 1977; Gaskill et al. 1986; Cretaceous Burro Canyon Formation conglomerate Gaskill, DeLong, & Cochran, 1987; Hedland & Olson, 1974; Olson, 1976a; Streufer,t 1999 Cretaceous Dakota Formation ACretaceous Mesa Verdeu Formationthor Proof Cambrian Peerless Formation Fossil Ridge Contact metamorphosed Potential outcrop DeWitt et al., 2002; DeWitt, orthoquartzite Stoneman, & Clark, 1985; Zech, 1988 Ordovician Harding Sandstone Ordovician Molas Formation Tertiary gravels Eastern part of study Quartzite clasts in Potential cobble DeWitt, Stoneman, & Clark, 1985; area unconsolidated sediment DeWitt et al., 2002; Gaskill, DeLong, & Cochran, 1987; Olson, 1976a; Streufert, 1999; Zech, 1988 Quaternary gravels Widespread, confined Quartzite clasts in Potential cobble Streufert, 1999 mostly to drainages unconsolidated sediment GEA236_20240.qxd 9/10/082:42PMPage751 Goffer, 1980;Herz&Garrison.1998;NewsomeModreski,1981;Odell,2000,2004; marized, however, inPitbladoetal.(2006b)anddiscussedmanyvenues(e.g., not devotespaceheretooverviewsofgeneraltechnique mechanics.Thesearesum- other literatureasviablemethodsforsourcingabroad rangeofmaterials,sowedo previously discussed,thesetechniquesarewellestablished inarchaeologicaland and contrasted:UVF, petrography, WD-XRF, INAA,AD-ICP-MS, andLA-ICP-MS.As to whichwewouldsubjectthesamplesdevelopprofiles thatcouldbecompared Analytical Procedures experimented. shows examplesofthegeologicandculturallymodifiedsampleswithwhichwe ents anoverviewsofalltwentysamplesandidentifiesthetworeplicates.Figure3 from MontroseSource5,servedasreplicatesinourgeochemicalstudies.Table IIpres- of theChanceGulchartifacts.Two specimens,onefromgravelSource3and non-conchoidal fractureproperties(Source2)—torepresentthegeologicorigin not from UintaMountainGroupoutcrops(UMG-1andUMG-2),allspecimensonewould outcrop source(Source2),onefromtheMontrosegraveldeposit5),andtwo 2002). Next,weaddedtoourassemblageonesampleofthenearbyPrecambrian quartzites thatwehavehypothesizedChanceGulchknappersused(e.g.,Pitblado, terms ofcolorandtexture,approximatedthoseflakes.Thosespecimensrepresented located nearChanceGulch(Sources1,3,and4),eightgeologicsamplesthat,in our laboratorytable.We thenselected,fromtheprehistoricallyquarriedsources as experimentalcontrols). quartzite specimens(plustworeplicates—duplicatesofthesamesample—toserve explore. We thusfollowed theprotocolbelowtoselectanassemblageoftwenty to thesixdifferentandinsomecasesexpensiveanalyticaltechniqueswewished pilot-study budgettosubjecteachofthemorethan100totalsampleswehadcollected tical considerationsrequiredthatwesubsamplefurther:We could notaffordonour Gulch siteandfromtheUMGoutcropsinnortheasternUtah.Inlaboratory, prac- collected fivesamplesfromthePrecambrianoutcropsourcejustnorthofChance expressly tryingtomaximizevisualvariabilityincobblecolorsandtextures.We also Future studieswillnecessarilysampleafarlargerGunnisonBasinquartziteuniverse. assemblage ofeightflakes;orfromartifacttonearbygeologicsourcequartzite). similarities toeachother(within,forexample,asinglegravelsource;withinthesub- els vs.thePrecambrianoutcroplocatedclosetooneanother)andinothercasesshow to varyfromsample(e.g.,thoselocatedveryfarapartandtheTertiary grav- endeavored tobuildintooursampleassemblagepotentialforgeologicsamplesboth afield andunlikelytohavebeenquarriedbyChanceGulchoccupants.Insodoing,we ple geologicsourcesofquartziteneartheChanceGulchsiteaswellfarther After wecompiledourstudyassemblage,identified theanalyticaltechniques First, weassembledtheeightlargeChanceGulchflakestargetedforanalysison In thefield,wecollectedtwentyquartzitecobblesfromeachofgravelsources, For purposesofthismethodologicalstudy, however, ourgoalwas,again,tosam- reasonably expect—basedontheirgeography(Sources5andUMG-1-2)or EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Author Proof 751 GEA236_20240.qxd 9/10/082:42PMPage752 752 ing), compositionofgrainsorcrystals,cementcomposition, beddingorfoliation, described eachthinsectionintermsoftexture(grain/crystal size,sorting,round- ucts to30micronsthick.Geologygraduatestudent CarolineMyerthoroughly Tucson, Arizona,madethinsectionsfromthesebillets,handpolishingthefinalprod- mm) usingrocksawsintheGeologyDepartmentatUSU. QualityThinSectionsof research assistantscutthegravelandoutcropsamples intobillets(12 final database. Pitblado compiledthetwosetsofobservations,which matchedwell,todevelopthe was conductedfirstbyoneresearchassistantandthen independentlybythesecond. Although descriptionswerenecessarilysubjective,thiscomponentoftheanalysis or “pale”)andtexture(e.g.,somesampleslooked“velvety”whenfluoresced). which includedsubjectivedescriptionsofcolor(includingmodifierssuchas“bright” then tolong-waveultravioletlight.Theyimmediatelyrecordedtheirobservations, ditions, tworesearchassistantssubjectedquartzitesamplesfirsttoshort-waveand the UtahStateUniversity(USU)campus.Priortocrushingandunderdarkroomcon- conduct eachformofanalysis.CoauthorPitbladooversawUVFinherlaboratoryon 2005; Tykot, 2004). Orna &Lambert,1996;PollardHeron,Shackley, 1998;Speakman&Neff, County SourceType Source Sample ID Table II. AL. PITBLADO ET M- M oreOtrpSummit,UT Summit,UT Montrose,CO Gunnison,CO Gunnison,CO Gunnison,CO Montrose,CO Gunnison,CO Outcrop Gunnison,CO Outcrop Gunnison,CO Replicate5-1sample Gunnison,CO MontroseGravelsource Gunnison,CO Gravelsource Gunnison,CO Gunnison,CO Gravelsource UMGsource Gravelsource UMGsource Source5,cobble1 Gravelsource Source5,cobble1 Gunnison,CO Outcrop Gravelsource Source4,cobble19 Gunnison,CO Replicate3-6sample UMG-2 Source4,cobble14 Gunnison,CO Gravelsource UMG-1 Source4,cobble13 Gunnison,CO Source4,cobble3 5-1a Gunnison,CO Source3,cobble8 5-1 Gravelsource Gravelsource Gunnison,CO 4-19 Archaeologicalsite Source3,cobble6 Gunnison,CO Source3,cobble6 4-14 Archaeologicalsite Gunnison,CO Source2 4-13 Archaeologicalsite 4-3 Source1,cobble15 Archaeologicalsite Source1,cobble7 3-8 Archaeologicalsite 3-6a Archaeologicalsite ChanceGulch 3-6 Archaeologicalsite ChanceGulch 2-1 Archaeologicalsite ChanceGulch 1-15 1-7 ChanceGulch ChanceGulch G8-11 D4-26 ChanceGulch ChanceGulch C9-17 ChanceGulch C1-214 C2-72 B0-115 AC-23 A1-28 Coauthor Dehleroversawthepetrographicanalysis of oursamples.First,two We doofferanoverviewofthelaboratories,equipment,andprotocolsusedto EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: All quartzitesamplessubjectedtosourcingexperimentation. Author Proof 24 46 GEA236_20240.qxd 9/10/082:42PMPage753 crushed form.Theyanalyzedaselectedsuiteofelements onaSiemens(Brucker)SRS of GeologicalSciences)conductedWD-XRFanalysis ofourquartzitesamplesin microscope withaCanonPowershotG6andpoint-count mechanismsattached. characterization. To conductthepetrographicanalysis,Myerusedan Olympus BH2 each thinsection.Myertookphotomicrographsfor each thinsectionforsample Dehler establishedcategories,andthenMyerperformed a300-pointpointcounton secondary features(e.g.,fractures),andcrosscuttingrelationships. Sheandcoauthor macroscopically tobe). Source 1-15(shownthroughpetrographytobeanalteredvolcanictuff,ratherthanthequartziteitappeared artifact C9-17;(b)left,Source3-8;right,A1-28;(c)4-13;D4-26;(d) Figure 3. Coauthor SteveNelsonandDaveTingey (BrighamYoung UniversityDepartment Examples ofgeologicandartifactsamplesanalyzedintheresearch:(a)left,Source1-7;right, EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Author Proof 753 GEA236_20240.qxd 9/10/082:42PMPage754 754 were below0.5ppmforalmostalltraceelements,the exceptionsbeingSc,Cr, and runs formostelements(blankvalueplusthreestandard deviationsoftheblank) detector) usedastheinternalstandard.Detectionlimits calculatedonthequartzite sities toconcentrations,withsilicon(monitoredatmass 30toavoidsaturationofthe elements) togetherwithLittleGlassButtesobsidianto calibrate averagesignalinten- 0.7 ppmofmosttraceelements)andSRM612(approximately 40ppmofmosttrace for 5secondseach.IIRMESstaffusedNISTstandardglasses SRM614(approximately Dy, Ho,Er, Tm,Yb,Lu,Hf,Ta, Pb,Th,andU)weremeasuredbytheTOFfourtimes Co, Ni,Cu,Zn,As,Rb,Sr, Y, Zr, Nb,Sn, Sb, Cs,Ba,La,Ce,Pr, Nd, Sm,Eu,Gd,Tb, lation pass,signalintensitiesfor44analytes(Na,Al,Si, K,Ca,Sc,Ti, V, Cr, Mn,Fe, small rasterpatternatarateof50micronspersecond.Followinganinitialpreab- nel setthelaserat60%power, witha100-micronspotsize,andranthelaserover system coupledtoaGBCOptimass8000time-of-flight(TOF)ICP-MS.Labperson- LA-ICP-MS analysis.InstrumentationconsistsofaNewWave UP-213laserablation (IIRMES) archaeometrylabatCaliforniaStateUniversity–LongBeachcarriedout cate toleranceandinternalstandards. ferences. Thelabreportindicatesmaximumacceptableerrorof10%forbothdupli- PerkinElmer Elan9000ICP-MS,withappropriatecorrectionsforinter-element inter- then analyzedallsamplesandstandards(SY-4 andtwointernalstandards)witha HNO flux of3 diated fortwohoursintheOregonStateUniversityTRIGAreactorunderaneutron standards (e.g.,NISTSRM1633b,BCR-1,BHVO-1,andin-housestandards)wereirra- terbox. Aliquotsofsamples(~0.7geach,weighedtothenearest0.0001g)alongwith analysis. TheypowderedINAAsplitsto the WD-XRFanalysisare5–10%. elements ofinterest.Uncertaintiesforallabovedetectionlimit ments onpressedpowderpelletsratherthanglasstoincreasecountratesforthe 303 instrumentemployinganRhend-windowX-raytube.Theymadeallmeasure- AL. PITBLADO ET elements, theypreparedsamplesbyaciddigestionsof0.25gsampleinHClO Analytical uncertaintiesare Co, Ni,Zn,Rb,Sr, Cs,Ba, La,Ce,Nd,Sm,Eu,Tb,Yb,Lu,Zr, Hf,Ta, Th,and U. precision forshort-,intermediate-,andlong-livedradionuclidesofFe,Na,Sc,Cr, (after 5–6days,8–14and20 analyzer calibratedat0.22keV/ch.Hughesandcolleaguesconductedthreeanalyses an 80–2000keVspectralrangeusingtwohigh-purityGedetectorsandamultichannel 2–4% forCr, Ce,Yb,Hf,and Ta; 5–10%forRb,Cs,Nd,Tb,Lu,andTh; and Zr. Uncertaintiesfor all othertraceelementsare1–2%forSc,Co,La,Sm,andEu; then cooledanddigestedtheresultingmixturein100mLof4%HNO fusion at1000°Cof0.2gsampledigestedin0.9lithiummetaborateflux.They samples. Labpersonnelanalyzedtherareearthelements(REE),U,Th,andYby Ni, Zn,andU. The InstituteforIntegrativeResearchinMaterials,Environments,andSociety Coauthor DehlerandScottHughes(IdahoStateUniversity)conductedINAA The commerciallaboratoryALSChemexconductedAD-ICP-MSanalysisofour 3 , andHF. ResiduesweretakenupinadiluteHClsolution.Chemexpersonnel EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: 10 12 n ·cm 2 · s 1 . Labpersonnelmadesequentialgammaraycountsover 2% forallmajorelementsandtraceSr, Ba, days ofdecayfollowingirradiation)tooptimize Author Proo100 meshsizeinanaluminaceramicshat- f 3 . Forallother 10% for 4 , GEA236_20240.qxd 9/10/082:42PMPage755 ctive populations.AsamplesubsetfromSources1,3,and 4showssmallpercentages of varyingpercentages;othercementsincludeclayminerals andhematite. namely plagioclaseandmuscovite.Cementcompositionis dominatedbysilica,although positions ofallsamplesarequartz-rich,yetvary inothermineralcomponents, within andbetweencobbleoutcropsamplesets(Table IV, Figure4).Graincom- Cobble andOutcropSamples Petrography lie inanapproachthatintegratespetrographyandminimallydestructiveLA-ICP-MS. greatest potentialforsourcingquartziteandspecificallyartifactsmadeofmay phy andsegueingintoourgeochemicaltests,clarifyinginsodoingwhywebelievethe paper, wediscusstheresultsofthesefourformsanalysis,beginningwithpetrogra- ability amongGunnisonBasinquartzites,arequisiteforsourcing.Intheremainderofthis (INAA, AD-ICP-MS,andLA-ICP-MS)didyieldresultsthattentativelyshowsignificantvari- among GunnisonBasinquartzites. the basisof18%elementsdetected,wehaveruledoutXRFfordiscriminating ments andtheprobability(borneoutbyothertests)thatoursamplesdonotvaryon Based ontheinabilityofourXRFanalysistodetectabroadspectrumtraceele- imen orregisteredinamountsclosetoXRFdetectionlimits,yieldingsuspectresults. ring elementsintheperiodictable(Table 3).Ofthose,somefailedtoregisterinaspec- is notquartz.OurXRFanalysisdetected16elements-18%ofthe90naturallyoccur- to theextentthatitcandetectandmeasureoften rooted inthefactthatanygeochemicaltechniquewilleffectivelyprofilequartziteonly likewise showednoabilitytodiscriminateamongourquartzites.Thisoutcomeis paleostrat.org/Public/projects.aspx?pid cases tofluoresceatallwhenexposedshort-orlong-waveultravioletlight. Lyons, Glascock,&Mehringer, 2003;Pitblado,2000),oursamplesfailedinallbuttwo logical sources(e.g.,Benedict,1996;Cassells,1995;Hofman,Todd, &Collins,1991; used toassignmicrocrystallineandevenoccasionallyquartziteartifactspossiblegeo- acterization ofGunnisonBasinquartzitesareUVFandWD-XRF. AlthoughUVFhasbeen contributemeaningfullytochar- lytical techniquesthatourpilotstudysuggestscannot those thatworkedbest:petrography, INAA,andbothformsofICP-MS.Thetwoana- of eachanalyticalstrategyanddevelopedinterpretationsthedataproducedby PILOT STUDYRESULTS exceptions beingMg,Th,Cr, andNi. Sr. RSDsontheSRM612werebelow5%foralmostalltraceelements,main Cobble samplesvaryincompositionandshowmuchpromise foridentifyingdistin- Composition On theotherhand,ourpetrographicanalysisandthreegeochemicaltechniques Our WD-XRFanalysis,completeresultsofwhichcanbeaccessedathttps://www. On thebasisofover150totalobservations,wedrewconclusionsaboututility . Petrographicresultsshowvariabilityincomposition ofsamples EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Author Pe2bf1281-b96a-48ad-85e3-9b2a8df29b6a, roof 2% ofaquartzitesamplethat 755 GEA236_20240.qxd 9/10/082:42PMPage756 756 pm 1.)X(40.0) X(1.0) X(4.0) X(0.01) X(0.2) X(0.002) X(80.0) X(0.05) X( X( X(0.2) X(0.1) X(10.0) X( X(0.1) X(0.001) X(0.02) X(0.5) X(0.2) X(0.02) X(0.5) X(0.12) X(0.05) X(0.001) X(0.1) X(0.01) Sb (ppm) X(0.01) S (%) X(0.03) Re (ppm) X(0.39) X(5.0) Rb (ppm) X(0.01) X(0.35) Pr (ppm) X(0.08) X(0.01) X(0.1) Pb (ppm) X( X(0.2) X(0.008) P (ppm) X(0.005) X(0.01) X(0.5) Ni (ppm) X(0.02) X(0.001) X(0.01) Nd (ppm) Nb (ppm) X(0.05) X(0.002) X(0.08) X(0.1) Na (%) X(0.15) X(0.1) X(0.001) Mo (ppm) X(0.05) X(0.05) X(0.38) Mn (ppm) X( X(0.1) Mg (%) Lu (ppm) X(0.01) X(0.04) Li (ppm) X(0.01) X(0.47) X(0.05) X(0.1) La (ppm) X(0.1) X(0.006) K (%) X( X(0.28) X(0.1) X(6.0) In (ppm) X(0.03) X(0.001) X(0.2) Ho (ppm) Hf (ppm) X(0.05) X(0.09) X(1.0) Ge (ppm) X(0.02) X(0.36) X(0.1) Gd (ppm) X(0.30) X(0.01) Ga (ppm) X(0.6) X(0.08) X(0.13) WD-XRF Fe (%) X(0.02) X(0.05) X(0.004) Eu (ppm) X(0.88) Er (ppm) X(0.05) Dy (ppm) X(0.61) X(10.0) Cu (ppm) X(0.01) X(0.003) X(0.2) Cs (ppm) X(0.01) INAA Cr (ppm) Co (ppm) Ce (ppm) X(0.02) Cd (ppm) X(0.002) AD-ICP-MS X(0.18) Ca (%) Bi (ppm) Be (ppm) LA-ICP-MS* Ba (ppm) As (ppm) Al (%) Ag (ppm) (Units) detection levelsforeachelementtechnique). AL. PITBLADO ET Table III. Element EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Elements detectedinsamplesthroughLA-ICP-MS,AD-ICP-MS,INAA,andWD-XRF(and Element DetectionbyAnalyticalTechnique (DetectionLevelsinParentheses) Author Proof ( Continued 0.007) 0.006) 0.008) 0.007) 0.007) 0.005) ) GEA236_20240.qxd 9/10/082:42PMPage757 n(p)X(.7 20 X(1.0) X(1.0) X(0.008) X( X(0.1) X(2.0) X(0.1) X(0.01) X(0.1) X(0.01) X(0.1) X(1.0) X(0.02) X(0.27) X(0.1) X(0.49) X(0.002) X(0.1) X(0.13) X(0.2) X(0.002) X(0.05) X(0.005) X(0.15) Zn (ppm) X(0.003) WD-XRF X(0.003) Yb (ppm) X(0.08) X(0.1) Y (ppm) X(0.0003) X(0.001) X(0.05) W (ppm) X(0.2) V (ppm) X(1.0) X(0.2) U (ppm) X(0.1) Tm (ppm) INAA X(0.04) Tl (ppm) X(0.07) X(0.1) Ti (%) X(1.86) Th (ppm) X(0.04) Te (ppm) AD-ICP-MS X(0.32) Tb (ppm) Ta (ppm) X(1.32) Sr (ppm) LA-ICP-MS* Sn (ppm) Sm (ppm) Se (ppm) Sc (ppm) (Units) Table III. 3d, 4a).Ifgeochemicalanalysesweredoneonthesetwo samplesintheabsenceof (contrary toitsmacroscopicappearance),isavolcanic rock(alteredtuff)(Figures tions. Outcropsample2-1matchesonlyonecobblesample, 1-15,which,itturnsout a veryhighpercentageofdetritalmuscovite(14.4%). X(1.0) tains nothingbutquartzgrains.UMG-2alsocontains plagioclase grains(1.6%)and Sources 1,3,and4,showsthehighestpercentageofplagioclase (3.2%).UMG-1con- (and do)produceuniquegeochemicalsignatures.Sample 2-1,proximaltogravel tion ofthesesamplesshouldbeexpected(andaswewill latershow, occurs). X(3.0) assemblage, whetherdueto“cement”orgraintypes,thatgeochemicaldifferentia- and quartz.Thereissufficientvarietyinthecompositionaltypesrepresented sample 1-15isactuallythegroundmassofanalteredtuffandamixturefeldspar composed ofchert,makingthisauniquesampleintheassemblage.The“cement” sources butSource5.Asubpopulationofthequartzgrainsingravelsample5-1are X(0.5) entirely quartzgrains.Claycementisasmallcomponentinsamplesubsetfromall of plagioclasegrains(0.4–2.0%).AsamplesubsetfromSources3,4,and5contain https://www.paleostrat.org/Public/projects.aspx?pid X(0.27) Complete rawdatasetsforallformsofgeochemicalanalysisareaccessibleattheonlinedatabank, the elementsarebelowdetectionlimitsofLA-ICP-MS. in themethodusedforLA-ICP-MS;omissionfromtablethereforedoesnotnecessarilyindicatethat * Inthispreliminarystudy, anumberofelementsincludedintheAD-ICP-MSanalyseswerenot Zr (ppm) Element There aresomestrongmatchesbetweencobbleand outcropsamplecomposi- The outcropsamplesintheassemblage( ( Continued Element DetectionbyAnalyticalTechnique (DetectionLevelsinParentheses) EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: ). IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT n e2bf1281-b96a-48ad-85e3-9b2a8df29b6a. Au3) allvaryincompositionandshould thor Proof 0.006) 757 GEA236_20240.qxd 9/10/082:42PMPage758 P 4-3 andartifactsampleC9-17showing texturalsimilaritiesandcompositionaldifferences.Q sample UMG-2andgravel 5-1 showingtexturalandcompositionaldifferences;(d)gravelsample B0-115, andoutcropsampleUMG-1 showingcompositionalsimilarityanddifferingtextures;(c)outcrop ble sample1-15isporphyriticand texturein2-1ispoorlysorted);(b)gravelsample3-8,artifact 1-15 andoutcropsample2-1showingtexturaldifferencescompositional similarities(textureincob- Figure 4. plagioclase, M Photomicrographs ofcobble,outcrop,andartifactsamplesinthepilot study:(a)gravelsample mica, G groundmass (volcanictexture),H Author Proof hematite cement,Ma matrix. quartz, GEA236_20240.qxd 9/10/082:42PMPage759

Table IV. Results of petrographic characterization of pilot study quartzite assemblage. Cement/matrix/ Sample # Sample type Rock type Quartz groundmass Plagioclase Muscovite

1-15 cobble altered tuff 56.80% 41.2% (g) 2.00% 1-7 cobble orthoquartzite 99.20% 0.40% 0.40% 3-6 cobble orthoquartzite 92.40% 7.60% 3-8 cobble orthoquartzite 84.00% 15.20% 0.80% 4-13 cobble orthoquartzite 89.80% 1.20% 4-14 cobble orthoquartzite 93.60% 6.00% 0.40% 4-19 cobble orthoquartzite 96.40% 3.60% 4-3 cobble orthoquartzite 98.40% 1.60% 5-1 cobble orthoquartzite 87.60% 12.40% C2-72 artifact orthoquartzite 98.00% 2.00% AC9-17u artifactth orthoquartziteor 96.40% P 3.60% roof B0-115 artifact orthoquartzite 98.80% 1.20% A1-28 artifact orthoquartzite 98.00% 1.60% 0.40% D4-26 artifact orthoquartzite 88.40% 11.60% A0-23 artifact orthoquartzite 99.20% 0.80% G8-11 artifact orthoquartzite 91.60% 8.40% C1-214 artifact orthoquartzite 93.60% 3.20% 0.80% 2.40% UMG-1 outcrop orthoquartzite 98.80% 1.20% UMG-2 outcrop orthoquartzite 77.60% 6.40% 1.60% 14.40% 2-1 outcrop orthoquartzite 61.40% 35.4% (m, c) 3.20%

(Continued) GEA236_20240.qxd 9/10/082:42PMPage760 760 Table IV. (Continued). AL. PITBLADO ET Cement/matrix/ Grain/ EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Sample # Groundmass Roundness Crystal Size Sorting Other Comments

1-15 Quartz/feldspar Phenocrysts Fine to coarse N/A Silicified volcanic 1-7 Silica/clay Angular-rounded Fine–medium Moderate Graded bedding 3-6 Silica/clay Subrounded Coarse Well 3-8 Silica/clay Angular-rounded Medium–coarse Moderate–poor Crossbedding 4-13 Silica /clay Subangular-rounded Fine to medium Well 4-14 Silica Subangular- Medium–coarse Well subrectangular 4-19 Silica /clay Angular-rounded Fine to medium Moderate Crosslamination, pseudom 4-3 Silica Angular-subangular Coarse Well 5-1 Silica Angular-rounded Silt–coarse Poor Chert grains, crossbedding C2-72 Silica /clay Subrounded Medium–coarse Well Crosslamination C9-17 Hematite/silica / Subrounded Medium–coarse Poor clay B0-115 Silica /clay Subangular-rounded Fine-medium Moderate A1-28 Silica /clay Subangular Fine–medium Poor AD4-26 Silicau /clayth Subroundedor Silt–medium P Moderate–poorroof A0-23 Silica Subangular-subrounded Fine–coarse Poor G8-11 Silica /clay Subangular-rounded Fine–medium Moderate C1-214 Silica/clay Agular-subrounded Fine–coarse Moderate–poor UMG-1 Silica Subangular- subrounded Medium–coarse Moderate UMG-2 Silica Angular-rounded Fine–medium Moderate–well Cross-lamination, sub wacke 2-1 Silica/sericite Angular Silt–coarse Poor Subarkosic wacke GEA236_20240.qxd 9/10/082:42PMPage761 alone, themostrobustapproachistousecompositionand texturecombinedtoiden for sourcingstudies.Althoughtherearesomegoodcompositional andtexturaltrends lations and,insomecases,singleoutauniquesample thatmaybeespeciallyuseful the GunnisonBasin,Colorado). (despite thefactthatformeroriginatedinnortheastern Utahandthelatterin other sample.OutcropsampleUMG-texturallymatches manyofthegravelsamples sample UMG-2showsacombinationofsortingand grainsizenotseeninany canic gravelsample1-15andtheorthoquartzite 3-8(Figure4a).Outcrop cernible trends.Thepoorsortinginoutcropsample2-1 isalsoreflectedinthevol- exhibit adominantlyfinegrainsizeincombinationwithhighdegreeofsorting. outcrop samples(Figures4b,4c).SampleUMG-2istheonlysampleto poor sortingofoutcropsample2-1(Figure4a)distinguishesitfromtheothertwo that allows,aswiththecobblesamples,separationintodistinctpopulations.The show arangeofgrainsizes,rounding,andsorting.Thesortingischaracteristic teristics thataredifficulttogroupintomoredistinctpopulations. tures (compareFigures4band4c).Therestofthesampleshavetexturalcharac- Sample 3-8ismorepoorlysortedthananyothercobbleexhibitingsedimentarytex- rest ofthecobblesamplesandcontainschertgrainsnotapparentinothersamples. and issimplyasilicifiedtuff.Sample5-1appearstohavebetterroundingthanthe ture, composition),itfallsunderauniquecategory(i.e.,notmicrocrystallineeither) ple hassomeofthesamequalitiesasatrueorthoquartzite(e.g.,conchoidalfrac- surrounding thesephenocrystsdoesnothaveaclastictexture.Althoughthissam- tals thatshownosignoftransport(i.e.,phenocrysts).Additionally, thegroundmass (evidence oftransport).Rather, thissampleshowswell-developedplagioclasecrys- This canbediscernedbythelackofcoarsecomponentswithadetritalappearance (Figure 4a),hasavolcanicporphyritictexture,asopposedtosedimentaryone. ranges fromangulartorounded,andgrainsortingiswellpoor. Onesample,1-15 lations canbediscerned.Grainsizesrangefromfine-tocoarse-grained,grainshape geological sources. characteristic withgreatpromisefordifferentiatingamongquartzitefromdifferent poor, andgrainsareangulartowellrounded.Itappearsthatsortingisatextural population. Grainsizesrangefromsilttocoarsesand,sortingrangeswell some sufficientlyuniquetobedistinguishablefromothersamplesinthesmallpilot plagioclase-bearing samplesinSources1,3,and4. covite component(Figure4c).Therearenooutcropsamplesthatmatchthe is uniquewhencomparedtoeveryothersamplebecauseofitshighdetritalmus- ples fromSources3,4,and5thatdonotcontainplagioclase(e.g.,Figure4b).UMG-2 this pointinlaterdiscussionsofgeochemicalresults).UMG-1matchescobblesam- match, wheninrealitytheyhavedistinctlydifferentgeologicorigins(wereturnto petrography, theywouldlikelybeinterpretedasthesamerocktypeandagood Summary A comparisonoftexturesfromcobbleandoutcropsamplesshowssomedis- Textures oftheoutcropsamplesarestrikinglydifferentfromoneanother. They Textures inthecobblesamplesarequitevariableandyetseveraldistinctpopu- Texture . Thereisavarietyoftexturesinboththegravelandoutcropsamples, . Thereisenoughvarietyamongthesamplestodevelop distinctpopu- EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Author Proof tify 761 GEA236_20240.qxd 9/10/082:42PMPage762 762 for XRF, thesuitesofelementsdetectedbytwo methodsshareonly5incommon. (Table III).Althoughthisisstilljust24%ofthe90-elementperiodic tableversus18% low partspermillion(ppm).INAAofourquartzitesamples detected22elements ments insamplesofvariouskinds,andbothmeasure elementabundancesinthe Geochemical Analysis:INAA,AD-ICP-MS,andLA-ICP-MS production (apropositiontotestinthefuture). historic knapperspreferentiallyselectedthemostmature orthoquartzitesfortool sample inthepilotstudybothtexturallyandcompositionally, anditmaybethatpre- of thesecharacteristics.Theartifactsdoseemtorepresenttheaverageorthoquartzite sorting, androundness,theredoesnotappeartobeanytrendorgroupingsinterms the artifacts.Otherwise,texturesofartifactsamplesshowarangeingrainsizes, artifact samplesarebothalsopoorlysorted,makingthemauniquepopulationamong outcrop samples(UMG-2)(yettheydomatchwellwithUMG-1).Thetwomicaceous not matchthatofthelocaloutcropsample(2-1)noronetwonortheasternUtah ing artifactsamplesmatchcompositionsoffromallgravelsourcesanddo hematite cementnotseenelsewhereinthegreatersampleset(Figure4d).Theremain- has minormuscovite(2.4%)andplagioclase(0.8%).ArtifactC9-17adistinctive (88–99.2%), onesample(A1-128)hasminormuscovite(0.4%),andanother(C1-214) Although alleightartifactsexaminedinthinsectionaredominatedbyquartzgrains outcrop sourcescanbeeliminatedasrawmaterialforthoseartifacts(Table IV). range oftextures,yetsomepopulationsarestilldistinguishableandcertaincobble Artifacts make thedifferencediscernible. detected ingeochemicalanalysesalone,andsoitmaybethepetrographicdatathat from theGunnisonBasin).Again,however, intheorythisdifferencemaynotbe ologically speaking,highlylikelybecause5-1derivesfromalocationwellremoved other sampleandisprobablyadifferentsourceentirely(aconclusionthatis,archae- sources areadvised.Finally, cobblesample5-1exhibitschertgrainsnotseeninany ture, suggestingthatattemptstogeochemicallydifferentiateitfromGunnisonBasin however, matchthecompositionofaveragecobblesampleandtex- from allothersamples,aswewouldpredictitbe.The(UMG-1)does, has verysimilarsortingpropertiestooutcropsample2-1. discuss inthatsectionofthepaper. Sample3-8,althoughcompositionallydifferent, ticed, ascenariothatemergedinouranalysisofAD-ICP-MSdataandwhichwewill analyses wereperformedonthesetwosamples,ageneticdistinctioncouldgounno- crop sample2-1incomposition,yetithasavolcanictexture.Ifonlygeochemical the localoutcropsample2-1.Theremainingcobble(1-15)closelymatchesout- shows thatallbutoneofthecobblesamplesreflectsacompositionaldistinctionfrom populations. Anoverallcomparisonofthecobblesampleswithoutcrop AL. PITBLADO ET Both INAAandAD-ICP-MSyieldaccurateprecise measurements oftraceele- Petrographic resultsfromartifactsshowfairlyhomogeneouscompositionanda One oftheUtahoutcropsamples(UMG-2)iscompositionallyandtexturallyunique EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Author Proof GEA236_20240.qxd 9/10/082:42PMPage763 ensoe 1.01 Mean slope incomplete digestionofzircon(ZrSiO the INAArelativetoAD-ICP-MSdata.ForZrandHf,thiswasundoubtedlydue reported abundanceswereelevatedbyfactorsof3.5,6.8,and7.0,respectively, for excluding Co,Hf,andZrbecauseinitialevaluationoftherawdatashowedthat ducted alinearregressionof19the22totalelementsreportedinbothanalyses, ogists tobesomethingofagoldstandardinsourcinganalysis.To dothis,wecon- AD-ICP-MS andINAAdata,becausethelatterisstillconsideredbymanyarchaeol- the LA-ICP-MSanalyticaltechniquetopilotstudy, wecomparedthequalityofour sample basis.Inprinciple,regressionanalysisshouldproduceaslopeof1,an REE, theREEplusUandTh,forall19elementscollectivelyonasample-by- metaborate flux. died infuturestudiesthroughadditionalsamplepreparationbyfusionlithium ing duringAD-ICP-MSsamplepreparation,aproblemthatcouldperhapsbereme- org/Public/projects.aspx?pid Complete rawdatasetsforbothcanbeaccessedathttps://www.paleostrat. of sensitivitytothepresencevariouselements,AD-ICP-MSoutperformedINAA. detected byINAA,all16XRF, plusanother27traceelements.Interms the elementsdetectedbyXRForINAA(Table III).AD-ICP-MSdetectedall22elements detected 60elementsinoursamples—67%ofnaturallyoccurringandtriple That is,INAAdetected17elementsthatXRFdidnot.OurAD-ICP-MSanalysis Mean geologic andartifactsamples. Table V. rability ofINAAandAD-ICP-MStheoftenexcellent performanceofAD-ICP-MS by refiningAD-ICP-MSpreparatorymethods).Forother discussionsofthecompa- we canexplainandthatcouldbecompensatedforinfutureresearch(forexample, and AD-ICP-MSdataforourquartzitespecimens,withonlyafewdiscrepanciesthat ing Bafromconsiderationincreasedthemeanslope0.88tonearunity(0.96). Ba mayhaveexertedconsiderableleverageinourregressionanalysis.Infact,delet- Ba, Cr, Ta, andTb.Inthisregard, wenotethatarelativelyabundanttraceelementlike detected byAD-ICP-MS.Furtherscrutinyofourdatasuggeststheseelementsinclude U, andThhavesystematicallyhighervalueswhendetectedbyINAAthan mean slopeof0.88indicatesthatatleastsometheelementsotherthanREE, (Table V).Inouranalysis,wetreatedINAAdataastheindependentvariable.Thus,a REE andtheplusUTh,butnotwhenall19elementsareconsideredtogether ent thatINAAandAD-ICP-MSdoyieldstatisticallyindistinguishableresultsforthe of 1,anda Mean safrtse norassmn ftedt bandpirtotheintroductionof As afirststepinourassessmentofthedataobtainedprior We conductedlinearregression analysisoftheINAAandAD-ICP-MSdatafor In general,ourlinearregressionanalysisrevealsexcellentagreementamongINAA y R -intercept 2 Results oflinearregressionINAAandAD-ICP-MSdata(1922 sharedelements)forall y -intercept of0iftheresultsareidenticalforbothtechniques.Itisappar- EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT E ny E,T,U 19Common Elements REE,Th, U REE Only 0.99 0.09 0.11 1.01 .01 0.98 0.25 e2bf1281-b96a-48ad-85e3-9b2a8df29b6a. 4 ), whichcontainsbothelements,byacidleach- 0.01 A uthor Proof 0.10 0.88 0.02 0.99 0.20 0.43 0.13 0.02 0.43 R 2 value 763 GEA236_20240.qxd 9/10/082:42PMPage764 764 quartz. matite quartz,revealingtheenrichmentintraceelementssample assemblagecomparedtopure Figure 5. ments. Thisconditionisarequisiteforlarge-scalediscriminationamonggeologic scientists’ perceptionsofquartzite)isthatourquartzitesharbormanytraceele- quartz. Thesimpleconclusiontobedrawn(butonethatrunscontrarymanyearth the enrichmentsintraceelementsaboveandbeyondwhatwemightexpectofpure MS bythemeanvalueinpegmaticquartz,reinforcesthispoint,illustratingvisually and betweenartifactstheirgeologicsources. inherently excellentpotentialfordiscriminatingamonggeologicsourcesofquartzite ther “barren”norgeochemicallymonotonous.Rather, thelargedifferencessignify to theirmeanconcentrations,aclearindicationthatthepilot-studyquartzitesarenei- AD-ICP-MS. Thevariabilityintheabundancesoftheseelementsisasimilarorder Table VIshowsthemeanconcentrationof the REEinourspecimensasdetectedby cal techniquetodiscriminateamonggeologicandarchaeologicalquartzitesamples. what preliminaryconclusionswemightdrawaboutthepotentialofthisgeochemi- experiments inquartzitesourcingthroughgeochemicalmeansthandoesINAA. this phaseofanalysisconcludingthatAD-ICP-MSholdsmorepromiseforourfuture sensitive tothetraceelementspresentinourpilot-studysamples,weemergedfrom not yieldradioactivesamplesasbyproductsdoesINAA,andissignificantlymore can beperformedmorequicklythanINAA,isnodestructivedoes Pollard andHeron(1996).BecauseAD-ICP-MSanalysisislessexpensivethanINAA, analysis, wereferreaderstoMallory-Greenough,Greenough,andOwen(1998) AL. PITBLADO ET Figure 5,whichplotsthemeanconcentrationof30elementsdetectedbyAD-ICP- We thereforeproceededtolookmorecloselyattheAD-ICP-MSdatadetermine EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Mean concentrationofelementsdetectedbyAD-ICP-MSdivided themeanvalueinpeg- Author Proof GEA236_20240.qxd 9/10/082:42PMPage765 ( sented laterinthispaper).Althoughthesamplesizeusedtoproducegraph set ofelements(as,forexample,isthecasewithbivariateelementplotspre- took intoaccountcompletetrace-elementprofilesofoursamples,ratherthanasub- cluster analysisbasedonmeanEuclideandistances(Figure6).Thisdataexploration to discriminationamongsourcesandsamples,weperformedanaverage-linkage chemical studiesofquartzitecomposition. dently notyetembracedbyearthscientists,giventhevirtualnonexistenceofgeo- routinely detecttraceelementpatternsinthesekindsofrocks,anobservationevi- Table VIandFigure5confirmthattechnologyhasreachedthepointwherewecan quartzite artifactstolikelygeologicsourcesonthelandscape.Moreover, both sources ofquartzite,anditisarequisiteforfuturesuccessinstatisticallymatching ples. Thisresultisexpected,becauseSources1and3 arecobbledepositsthatwe sonably closeassociationbothwitheachotherand theSource3cobblesam- which, likeSource3,islocatedwithin0.5kmoftheChance Gulchsite,showarea- data andinsightsthatgeochemicaltechniquesmaymask. one another(seeTable IV),animportantreminderthatpetrographicanalysiscan yield discussed, petrographicdatashowthattheSource3samples differtexturallyfrom esize samplesfromthesamesourcewoulddo.On other hand,andaspreviously specimens fromSource3(3-6and3-8)clustertightlytogether, aswewouldhypoth- and 3-6ashowtheclosestrelationshipsofanysample couplets. Inaddition,thetwo AD-ICP-MS. Forinstance,andgratifyingly, replicatesamples5-1and5-1a3-6 n To gainapreliminarysenseofthestructureAD-ICP-MSdataasitpertains In theclusterdiagram,twogeologicspecimensfrom Source1(1-7and1-15), 22) issmall,theresultsyieldinsightsintodiscriminatorypotentialof tion limits. submitted asdatacontrols),somesampleshadconcentrationsbelowdetec- MeanConcentration(ppm) Element samples, asdeterminedbyAD-ICP-MS. Table VI. a Although 22sampleswereanalyzed(duplicatesoftwocobblesources u02 .318 22 13 22 0.23 21 1.39 22 0.24 19 1.42 22 0.48 17 2.21 22 0.40 22 2.33 22 0.22 0.43 1.28 22 2.41 0.26 22 1.28 11.63 2.97 0.40 1.88 28.20 10.63 0.34 Lu 1.92 Yb 0.36 Tm 1.87 Er 8.99 Ho 2.34 Dy 22.28 Tb 9.86 Gd Eu Sm Nd Pr Ce La EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Representative REEconcentrationsforallartifactandgeological Author Proof 1 Count a a a a 765 GEA236_20240.qxd 9/10/082:42PMPage766 766 imentary textureand1-15avolcanicone.Itisthereforeunlikely boththattheSource1 (hence theirproximityintheclusterdiagram),yet,as we havenoted,2-1hasased- artifacts. Samples2-1and1-15arealmostidenticalmineralogically tooneanother markedly bothfromtheSource1and3geologic samplesandfromthethree rographic datailluminatethesituation,revealingthat outcropsample2-1differs more distantlywithsamples1-15and2-1,alsofromnearby sources.Yet againpet- three artifactsinturnclusterwithsample1-7fromanearby gravelsourceandslightly part ofChanceGulchartifactsA1-28,C2-72,andAC-23. We further notethatthese the clusterdiagramsuggestsmarkedlysimilarholistic geochemicalprofilesonthe and inter-source profilingofgeologicsourcesintheregion.However, wenotethat logic sourcesofquartzite;thatsortconclusioncanonlycomewithmuchmoreintra- 1-7 isorthoquartzite. to allothersamplesinourassemblage(Figure3d,Table IV),isalteredtuff.Sample dramatically. Sample 1-15,contrarytoitsmacroscopicappearance(Figure3d)and analysis): ThetwoSource1samplesdiffertexturallyfromoneanother, andrather a distinctionnotsuggestedintheAD-ICP-MSdataset(atleastcluster in futureresearch).Hereagain,however, wepointoutthatpetrographicdatareveal hypothesize originatedfromparentsourcesupstream(apropositiontobetested as are3-6and3-6A. other samplesareGunnisonBasinsourcingprojectquarries.Samples5-1and5-1areplicatesamples, G8-11, B0-115,A1-28,C2-72,AC-23,andC1-214arequartziteartifactsfromtheChanceGulchsite.All geologic andarchaeologicalsampleshavebeenincludedintheclusteranalysis.SamplesC9-17,D4-26, Figure 6. AL. PITBLADO ET The ChanceGulchartifactswetestedcannotyetbeassociatedwithknowngeo- EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Average-linkage clusteranalysisbasedonmeanEuclideandistances(AD-ICP-MSdata).All Author Proof GEA236_20240.qxd 9/10/082:42PMPage767 as effectivelyornearlyAD-ICP-MS. preferable choice- the other. Giventhevirtuallynon—destructivenatureofLA-ICP-MS, itisclearlythe sis toprofileartifacts.Rather, allsamplesmustbeanalyzedusingonemethod or AD-ICP-MS tocharacterizegeologicsamplesandnon-destructive LA-ICP-MSanaly- sourcing universe,wecannotaddresstheartifact-destruction issuebysimplyusing pling andcharacterizationofquartzitelocalitiesthatconstitute theGunnisonBasin comparable tooneanother. Therefore,aswelooktowardfuturelarge-scalesam- the equation. step inourpilotstudy:introducingminimallyinvasiveLA-ICP-MSanalysisto newable, humanlyproducedartifactsisundesirable.Thisrealityunderlaythenext how theyusedthelandscape.CrushingPaleoindianspearpointsandothernonre- Rocky Mountains’mostancientresidentsobtainedtheirstonerawmaterialsand match extremelyrarequartziteartifactstogeologicsourcesdeterminewherethe Crushing ubiquitousgeologicspecimensisacceptable,butweaimtoeventually to powderaspartoftheAD-ICP-MSsample-preparationprocessisproblematic. tial todiscriminateamongquartzitesources,therequirementthatsamplesbecrushed formed inourexperimentsandregardlessofthetechnique’s apparentlystrongpoten- goal ofsourcingPaleoindian-ageartifacts.RegardlesshowwellAD-ICP-MSper- but rather, towhat not will bepossible.Theappropriatequestiontoguidefutureresearchmaytherefore pate, principalcomponentsanalysis),geochemicaldiscriminationamongsources samples andfiner-grained multivariateinvestigation(mostparticularly, weantici- preliminary lookatthedataaffordedbyclusteranalysissuggeststhatwithmore we sampledandinthequartziteartifactsfromChanceGulchsite.Moreover, the ble ofregisteringextensivevariabilityinquartzitesamplesfromthegeologicsources However, weemphasizeinclosingthatviewAD-ICP-MSdataasinherentlycapa- than wealreadyhave.Thesamplesizeistoosmallandthedataarepreliminary. sample withholisticallysimilartrace-elementsignatures. can—and inourdatasetdo—differentiateamongquartzite(andevenonevolcanic) samples thatlookalikebutwhichhaddifferentgeneses.However, petrographicdata chemical analysis.Trace-element compositionscandifferentiateamongquartzite for fingerprintingGunnisonBasinquartzitesshouldcombinepetrographicandgeo- alluded toalreadyandwhichwewillreturninourconclusions.Futureprotocols cating aspuriousassociation)areimportantbecausetheyinformaninferencewehave outcrop sampleUMG-2clustertogetherinFigure6,theydiffertexturally, likelyindi- quartzite orcobbleslike1-15. Chance GulchoccupantsmadeartifactsA1-28,C2-72,andAC-23fromSource2 (and Source3)cobblesderivedfromtheoutcropthatyieldedsample2-1and Unfortunately, datageneratedthroughLA-andAD-ICP-MSanalysisarenotdirectly However, thereisonemore importantissuetobeconsideredgivenourlong-term We arenotcomfortablecarryingourinterpretationsoftheFigure6datafurther These observationsandothers(forexample,thatalthoughartifactC1-214 whether discrimination ofGunnisonBasinquartzitesourcescanbeachieved, EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: if IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT , and this is a big “if”—it candiscriminateamongquartzitesources , andthisisabig“if”—it degree discrimination ofthosesourcescanbeachieved. Author Proof 767 GEA236_20240.qxd 9/10/082:42PMPage768 768 the laserduringLA-ICP-MS. Mg. Thesewillallbemoreabundantthanzirconand likelytobeaccessedby Ca, K,Na,andRb;thepresenceofbiotitemayexplain thestrongcorrelationof during petrographicanalysisprobablyaccountsforthe strongcorrelationsforAl,Ba, represent them.Ontheotherhand,presenceof micas andfeldsparsobserved Zr. However, theywillbelowinabundanceandlaserablationsmay miss orunder- Zircon, apatite,andsphenewillhaveabundantREE,U, Th,andinthecaseofzircon, used inLA-ICP-MSwillcontactatraceelement–abundant crystalinthesample. and analyzedinbulk. whereas AD-ICP-MSresultsreflectalargersamplethathasbeenpowdered,digested, that LA-ICP-MStargetsatinyarea(inthiscasefourareassubsequentlyaveraged), our methodologysection;and(2)therearesamplingissuesthatarisefromthefact tion isthat(1)thereanalyticalerrorinbothanalysesatmagnitudesdiscussed strong consistency. Thegeneralexplanationforthelackofperfectpositivecorrela- obtained whenwecomparedourAD-ICP-MSandINAAdata,whichoverallshow in common.AsTable VIIshows,theresultsarelessstraightforwardthanthose the fourLA-ICP-MSspotanalysestoourAD-ICP-MSvaluesforelementsmeasured would havefoundthem. for moreelementsinourLA-ICP-MSanalysisofquartzitesamples,weprobably refined tomaximizedetectionofallelementspresent.Inotherwords,hadwelooked the IIRMESlabhasanalyzedforpasttwoyears),andfuturemethodswillbe case (thequartzitespecimensaremuch“dirtier”thanthemicrocrystallinesamples sumption thattheconstituentelementswouldbesimilar. Thisprovednottobethe analysis ofmicrocrystallinequartztothequartzitetesting,operatingunderpre- tion, theIIRMESlabappliedlaser-ablation methodstheydevelopedforLA-ICP-MS present inourgeologicsamplescouldnothavebeendetectedbyLA-ICP-MS.Inaddi- tested onlygeologicspecimens.Elementsuniquetoanyofoureightartifactsandnot be stated.First,thesamplesizewassmallerinourLA-ICP-MSanalysisbecausewe 16 fewerelementsthanthe60detectedbyAD-ICP-MS;however, twocaveatsmust to them. twelve geologicsamplesandtworeplicates,discussionhenceforthpertainsonly had beenexpendedtotestotherdestructivetechniques.We proceededwithour we notethatbythisphaseinourpilot-studyresearch,eightquartziteartifacts these questionsinmind,weundertookLA-ICP-MSanalysisofoursamples,although result inasignificantlyreducedabilitytodiscriminateamongoursamples.With AD-ICP-MS dataandwhetherthelossofelementsnotdetectedbyLA-ICP-MSwould ples wouldsuggestaninterpretivepicturesimilartothoseofourhigh-resolution for usthereforebecamewhetherLA-ICP-MSdatageneratedfromourquartzitesam- common (e.g.Habicht-Maucheetal.,2002;Rockman,2003).Theobviousquestions MS, thetwotypicallyyieldcomparabledistributionsofelementstheydetectin ally yieldsmoreaccuratedeterminationsoftrace-elementcompositionthanLA-ICP- AL. PITBLADO ET More specifically, thekeytostrongcorrelationisprobabilitythat thelaser To analyzetheresultsofourLA-ICP-MStesting,wefirstcomparedmeans LA-ICP-MS detected44totalelementsinourquartzitesamples(Table III).Thatis Past comparisonsofthetwotechniqueshaveshownthatwhileAD-ICP-MSusu- EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Author Proof GEA236_20240.qxd 9/10/082:42PMPage769 b96a-48ad-85e3-9b2a8df29b6a. online databank,https://www.paleostrat.org/Public/projects.aspx?pid Complete rawdatasetsforbothformsofICP-MSanalysisareaccessible atthe lmn ofietCoefficient(OutliersRemoved) Coefficent Element logic samples. paring allelementsdetectedbybothAD-ICP-MSandLA-ICP-MSacrossgeo- Table VII Zr n0.69 0.62 0.59 0.93 0.81 0.82 0.32 Zn Y 0.86 V 0.97 U 0.43 Ti Ta 0.99 Sr 0.99 Sn 0.96 Sc 1.00 Sb 0.97 Rb 0.96 Pb Ni 0.71 Nb Na 0.76 Mn 0.97 Mg Li 0.18 K Hf 0.92 Fe 0.60 Cu 0.94 Cs 0.32 Cr 0.20 Co 0.42 Ce 0.41 Ca 0.44 Ba 0.49 As 0.42 Al 0.04 Lu 0.17 Yb 0.25 Tm 0.29 Er 0.24 Ho 0.17 Dy 0.27 Tb Gd Eu Sm Nd Pr Ce La . Table showingPearson’s correlationcoefficientsobtainedwhencom- ero’ orlto Correlation Pearson’s Correlation 0.13 .40.65 A0.04 u0.31 t0.11 0.77 h 0.75 0.21 0.67 o0.15 r0.13 0.03 P0.37 roof e2bf1281- GEA236_20240.qxd 9/10/082:42PMPage770 770 spread, forexample,betweenthe3-6and5-1replicate setsintheAD-ICP-MSdata, for RbandMn(Figure9b).Figure9bshowsthatwhile thereispredictablyless rate AD-ICP-MSdataversusourLA-ICP-MSdata,weplotted theAD-ICP-MSresults gence ofLA-ICP-MSandpetrographicdata. samples—at somedistancefromsamplesdiscussed above,suggestingaconver- plots showsamples2-1and1-15—revealedthroughpetrography todifferfromother analyses mustevaluatesuchissues.We alsonotethatallthreebivariate differences inRbconcentrationthatarecriticalforoutcrop discrimination.Future analysis. Itcouldbe,forexample,thatmobilityduring formationdeterminedlocal mobile element,butthisdoesnotnecessarilymeanitisapoorchoiceforsourcing ent pairofelementsthanshowninFigures7and8.Rubidium,weshouldnote,isa clustering oftheSource4samples—butthistimeonbasisanentirelydiffer- association ofthe3-6and3-6areplicates;5-1,5-1a,5-1a-2 not andcouldshow. Finally, theRb–Mnplot(Figure9a)showssameclose samples 4-14and4-19aredivergingtowardhighCa—somethingtheSr–Feplotdid Plotting CaandFe(Figure8)reinforcesthesefindings,whilealsorevealingthat among thefoursamplesfromSource4,agraveldepositquarriedprehistorically. of sample5-1wasanalyzedviaLA-ICP-MS)andsuggestscompositionalsimilarities replicate samples3-6and3-6a,5-1,5-1a,5-1a-2(athird can discriminateamongquartzitesources. are intendedtoserveasexemplarsofthepotentialLA-ICP-MSyielddatathat and someelementswillnot.Theexamplesweshowherefallintheformercategory sample population)willbeimportantfordiscriminatingamongsamplesandsources more sophisticatedprincipalcomponentsanalysiswilleventuallyshowwithalarger Regardless ofgeochemicaltechnique,certainelements(orsuiteselements,as 7, 8,and9a,wepresentthreeofthosebivariateplots:Sr–Fe,Ca–Fe,Rb–Mn. cate samples,andofsamplesderivingfromthesamegeologicsources).InFigures tain which,ifany, yieldedmeaningfulsamplegroupings(e.g.,of,mostbasically, repli- small LA-ICP-MSdatasetbycreatingbivariateplotsofpairselementstoascer- nificant potentialfordiscriminatingamongquartzitesamples.We evaluatedour resolvable byincreasingthenumberofablationspersample. that theproblemoflasercontactingtoofewspotsandmissingelementsmaybe using moreappropriatestandards)willyieldbetterresultsforbothtechniques;and and negativecorrelationsshowninTable VII;thatrefinementofbothapproaches(e.g., MS resultsarethattherestraightforwardexplanationsformanyofthepositive range. ThereallycrucialmessagestodrawfromourcomparisonofAD-andLA-ICP- elements onlyhasabout40ppm,apoorbasisforcalibratingdatainthepercent over-represented Zrbecausethehigheststandard(SRM612)usedtocalibratemost the presenceofthistraceelementinourquartzites.LA-ICP-MS,however, probably AD-ICP-MS (zirconisextremelyrefractory)causedtounder-represent explanation. ItislikelythatincompletedigestionofZrduringsamplepreparationfor AL. PITBLADO ET To assesshowdifferentthebivariateplotswouldlookforourostensiblymoreaccu- The bivariateplotofSrandFe(Figure7),forinstance,properlygroupsthetwo This said,andevenastheycurrentlystand,thepilotLA-ICP-MSdatastillshowsig- The negativecorrelationofZrshowninTable VIImayrequireamorecomplex EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Author Proof GEA236_20240.qxd 9/10/082:42PMPage771 (duplicates ofthesamesample)andareenclosedinovals. to theleftofhyphensindicatesourcelocality(1,2,3,4,5,orUMG). Sampleswith“a”arereplicates Figure 8. (duplicates ofthesamesample)andareenclosedinovals. to theleftofhyphensindicatesourcelocality(1,2,3,4,5,orUMG).Sampleswith“a”arereplicates Figure 7. Bivariate plotofstrontiumandironingeologicsamplesasmeasuredbyLA-ICP-MS.Numbers Bivariate plotofcalciumandironingeologicsamplesasmeasured byLA-ICP-MS.Numbers EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Author Proof 771 GEA236_20240.qxd 9/10/082:42PMPage772 772 profile. Althoughsomeofourquartzitescontainedupto98%SiO cherts andflintsthatmanyresearchershavepreviouslyattemptedtogeochemically selves were,toaperson,surprisedathow“dirty”ourquartzitesarerelativethe archaeological sites)suggestthattheundertakingisanythingbutfutile.We our- among differentquartzitesourcesonalandscape(andeventuallyatPaleoindian DISCUSSION ANDCONCLUSIONS ing mustthoroughlyevaluatethishypothesis. blesome requirementthattheybecrushedtoapowderintheprocess.Futuretest- Basin quartzitesaswellas,ornearlyAD-ICP-MS—andwithoutthetrou- good potentialforyieldingresultsthatwillultimatelydiscriminateamongGunnison that LA-ICP-MSmustbeviewedatthisstageofournascentresearchasharboring for Mn(0.96)andRb(0.97)showninTable VII. Theyalsodrivehomethecrucialpoint complementary resultsareanticipatedbythehighcorrelationcoefficientobtained UMG-1 and3-8plotrelativelysimilarlyregardlessofhowtheyweremeasured.These 2-1, 1-15,UMG-2,and1-7appearinroughlythesamepositionbothplots;even are somewhathomogenousanddistinctfromothersourcesinbothplots;samples the structureofourAD-andLA-ICP-MSdataisparallel.TheSource4specimens AL. PITBLADO ET in theprofile.Indeed,AD-ICP-MSdetectedbyfar greatest numberofelements because crushingsamplesensuresthatalltraceelements presentwillberepresented greatest potentialofallthetechniqueswetestedto discriminate amongsources, samples musthavederivedfromdifferentsources). in asamplefromparticulargeologicsetting,orwhy twogeochemicallysimilar answer why, forexample,aparticulartraceelementappearsanomalously highorlow its abilitytohelpgeochemistsunderstandtheirtrace-element datasets(helping criminate amongsources.However, petrography’s greatervaluewill probablyliein in theGunnisonBasinandelsewhere,petrographymay aloneyielddatathatdis- more samplesenroutetodevelopingadatabaseofsignaturesquartzitesources be quartziteasinsteadanalteredvolcanictuff.Asfutureresearchcharacterizes in ourquartzitesamples,evenidentifyingonesamplewebelievedatcollectionto ing researchstrategy. Evenlow-powerexaminationrevealedsignificantvariability strategy, willserve asanimportantcomponentofacomprehensivequartziteprofil- quartzite profiling,weconcludethatpetrography, a low-tech,low-costanalytical of thatrocktype. sources andtoeventuallymatchculturaloccurrencesofquartzitesgeologic potential—given alotmoreleg-andlab-work—tosuccessfullydiscriminateamong quartzites areanythingbutgeochemicallymonotonousandthatthereisexcellent sourcing, ourmodestresultssuggesttheopposite:thatatleastGunnisonBasin ogists alikehastraditionallybeenthatquartzitesareill-suitedtofingerprintingand host ofothers.Inotherwords,althoughtheperceptionbyarchaeologistsandgeol- crystallines), manyhadhighlevelsofelementsincludingiron,manganese,anda First andforemost,ourpiloteffortstodevelopmethodseffectivelydiscriminate Our geochemicalresultssuggestthatdataobtainedvia AD-ICP-MSmayhavethe In termsofwhichmethodsmayworkbestinfutureeffortstoconductexpanded EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Author Proof 2 (like mostmicro- GEA236_20240.qxd 9/10/082:42PMPage773 criminatory signalsimilartothatofAD-ICP-MS,and LA-ICP-MSmaytherefore Figures 9aand9bshowthatevenwithjustfourablations, ourLAdatayieldadis- contact themineral(s)containingthemduringablation. Thatsaid,Table VII and However, italsomeansthattraceelementswillbemissedifthelaserdoesnot quartzite artifactcouldbeprofiledwithoutcompromising theintegrityofobject. of sample,virtuallyinvisibly. Archaeologically, thisiscrucial,becauseevenarare the mostaccurateresultsdestroyssamples.LA-ICP-MS impactsonlythetiniestbit of thegeochemicalanalysesweperformed.However, thecrushing thatproduces cates (duplicatesofthesamesample)andareenclosedinovals. Numbers totheleftofhyphensindicatesourcelocality(1,2,3,4,5,orUMG).Sampleswith“a”arerepli- Figure 9. Bivariate plotofrubidiumandmanganeseasmeasuredby(a)LA-ICP-MS(b)AD-ICP-MS. EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: IO TD EXPERIMENTSSOURCINGQUARTZITE, GUNNISONBASIN STUDY PILOT Author Proof 773 GEA236_20240.qxd 9/10/082:42PMPage774 774 between discretesourcesofquartzite(whethergravel depositsoroutcrops)than between graveldepositsandlikelyparentformations upstream. (3) amongGunnisonBasingraveldepositsand exposedoutcrops;and(4) and withinquartziteoutcrops;(2)amonggravelsinasingle, discretegraveldeposit; tain theextentandnatureofvariability(1)withinsingle cobblesfromgravelsources rographic andLA-ICP-MSanalysesofhundreds,eventhousands ofsamplestoascer- possible quartzitesourcesintheGunnisonBasin.We mustthen performbothpet- scale analysisofmanysamplesusingtheprocedure. in theend,LA-ICP-MSwillperformsufficientlywellthatwecanproceedwithlarge- significantly increasethecomparabilityoftwotechniques.We hypothesizethat rable toAD-ICP-MSformanyelements.Ten ormoreablationspersampleshould study andeventhatsmallnumber, whenaveraged,yieldedresultsbroadlycompa- our methodologyaccordingly).We performedfourablationspersampleinourpilot ibration oftheLA-ICP-MSlaser, selectionofstandards,andsoon(andfurtherrefine ples tolookforsystematicdifferencesthatcanbeattributedmatrixeffects,cal- quality datasetsandwhetherthiseffortistractableinsourcingartifacts. then allowustodeterminetheamountofeffortrequiredproducehighest- mean valuesoftheREE,U,Th,andotherdiagnosticelementsstabilize.Thiswill do this,ourteamplanstoablaterepresentativequartzitesamplesrepeatedlyuntilthe ICP-MS profilescanapproximateinherentlymoreaccurateAD-ICP-MSprofiles.To form experimentstoquantifyhowcloselygeochemicalprofilesgeneratedbyLA- researcher carestoexplorequartzitesourcing).Firstandforemost,wemustper- a quartzitesourcingmethodologyfortheGunnisonBasin(andanywhereelsethat research directionsthatweseeasthemostimportantnextstepsindeveloping around theworldmaypaysimilardividends. therefore optimisticthatfutureeffortstoprofilequartzitesinourstudyareaand many researchdoorsopenedasaresultofthatgroundbreakingwork,andweare ble offingerprintingthem.We havetheadvantage,however, ofknowingjusthow subjecting whatwouldbecomethousandsofsamplestoanalytictechniquescapa- crystalline quartzsourcingwereinthe1960sand1970s,whenresearchersbegan data. We considerquartzitesourcingnow, in2008,tobewhereobsidianandmicro- can bereplicatedinotherregionswherequartzitesourcingcouldprovidevaluable ated fromoneanother, and(2)whethertheapparentlyrobustresultsinthatregion done todetermine(1)whatdegreeGunnisonBasinquartzitescanbedifferenti- more attentionfromarchaeologistsandgeologistsalike—thereismuchworktobe appears tobehigh—highereventhanformicrocrystallinesthathavereceivedfar logical siteisthatwhilethepotentialforprofilingdiscretesourcesofquartzite twenty quartzitesamplesfromsixgeologicsourcesandtheChanceGulcharchaeo- essary. yield datasufficientlyresolvedthatcrushingsamplesforAD-ICP-MSwillnotbenec- AL. PITBLADO ET In theend,ifpetrographyandgeochemicalprofilingdonot revealgreatervariability The nextphaseofresearchwillrequireourteamto sample asexhaustively We willthencompareourresultstoAD-ICP-MSdatageneratedforthesamesam- We concludeourreportof ourpilot-studyexperimentswithcommentsonthe The finalandmostobviousconclusionwedrawfromourpilotsourcingstudyof EACAOOY NITRAINLJOURNAL,VOL.23,NO.6 INTERNATIONAL AN GEOARCHAEOLOGY: Author Proof GEA236_20240.qxd 9/10/082:42PMPage775 AQ5 Goffer, Z.(1980).Archaeologicalchemistry:Asourcebookontheapplications ofchemistrytoarchaeol- Gaskill, D.L.,DeLongJr., J.E.,&Cochran,D.M.(1987). 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Author Queries AQ1: Andrews 2005 not in Refs. Please supply. AQ2: Krynine 1968 not in Refs. Should this be 1948? If not, please supply 1968 citation. AQ3: Hughes 1994 not in Refs. Should this be 1992? If not, please supply new ref. AQ4: Spielbauer 1984 not in Refs. Should this be 2005? If not, please supply new ref. AQ5: Please specify publisher of DeWitt maps; also Gaskill et al. maps, Hedland map, Odell maps, and Zech map at end of Refs. AQ6: City of publication?