Copyright 1984-2001 FileMaker, Inc. HBAM2016AUG95HPro 5.0Rcrest@mylonitic@tailleur@Scarbonaterockscentralbeltandpartofnorthernthrustass@phyllite@of@-till@]s%B?@E@r@@megafossil@Pmetamorphism@Fmetasedimentary@!mica-rich@Bmylonitic@Gour@2patton@#quartz-rich@Drepresent@several@3shungnak@Nsurfacestailleur@*thought@"unlike@'white@Hcarbonaterocksofcosmoshillscosmoshillssequence@:lithicsandstoneandshalephyllitebelt@/mudstone@terrane@EH AK S B @CAABD FHJLB$A(A&C)A,E-B0D1 B54 B6D7 B;DJ? BJDKFLHMHBAM3016AUG95@KÃ!>ÃF8Ä*Ä2Ä59Ä7!:Ä7aÄEÄZb2ÄaÄaÄa4ÄbDÄbQGÄbVÄfq)ÄfvÄf ÄsÄtÄtÄt1Ät9ÄtAIÄtB&ÄtqÄtvÄw"Äx15Äya*ÄzÄz%FÄz&Äz'HÄz6Äz8 !(KÄz@Äz?Äz#$Äz3Äz'ÄEÄAÄ6DÄa;Äq Ä6+ÄqÄrÄQ%ÄRJÄ6Ä Ä/Ä0ÄÄBÄCÄ",Äf-Är.ÄcÄV<Äq=Ä1Ä670.2-6.0PWBWCW0.5SW`W1LW^WeWwWJW1.3EW1.5qW10VW[W\W_WDWFW10'sKWPWBWCW10.2|W10.3LW100qW103yW105QW10:1AWVW11KW11-17uW11.3{W110yW120qW1200GWAW130-m-thickDW15GW^WqWAW16KW190sW1902TWUWVWWWXWZW[W\WsWtWFWIW1913UW^W1919VWtW1952UW^W1957TWUWVWWWXWZW[W\WsWtWFWHWIW1961ZWrWsWtW50LW705PW8CW8-km-longDW86AWaAWCWDWEWFWHWIWJWKWLWNWPWQWSWTWUWrA1990AConglomerate and finer grained sedimentary rocks exposed along the southern map boundary. The unit varies in character from massive, poorly stratified rocks rich in mafic intrusive and extrusive clasts at the base of the unit to well-sorted sedimentary rocks rich in quartz and metagraywacke clasts at the top. It contains sparse plant fossils that range in age from late Early Cretaceous to Late Cretaceous; south of the western map area it contains an ash-fall tuff that yielded a K/Ar age ofB 86 Ma and marine mollusks of Early Cretaceous (?) age (Patton and others, 2005). In the northeastern Shungnak and parts of the Ambler and Hughes quadrangles, the unit is deformed and regionally metamorphosed to low metamorphic grades (prehnite-pumpellyite to low greenschist-facies; Dusel-Bacon and others, 1989). Where deformed, rocks are strongly foliated and clasts have flattening ratios of 10:1 (Pallister and Carlson, 1988). In the Cosmos Hills, Box (1987) measured NE-trending stretchin H Pro 5.0 - 5.5M1,,./: AM PM AMYyTtNnFfNALL OCOMSP^SundayMondayTuesday WednesdayThursdayFridaySaturdayJanuaryFebruaryMarchAprilMayJuneJulyAugust SeptemberOctoberNovemberDecemberQ1Q2Q3Q4 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter,  , X5{iD  jD{wHEkD { PU} J_Aj xj4/4/2008@AGE DESCRIPTIONLABELNAMENSACLASSSOURCESDAnsaclassB GA descriptionB GAlabelB GAageB GAnameB GAsourcesB G`@@@ A Layout #1A Layout #1B$$$$@4E Pro 3.0 - 4.0F!2(2(   A $,.YesNo/,  , : AM PMfB  C $,.YesNo/,  , : AM PMfD  E $,.YesNo/,  , : AM PMfF  G $,.YesNo/,  , : AM PMfH  I $,.YesNo/,  , : AM PMfJ   K $,.YesNo/,  , : AM PMfL  MN $,.YesNo/,  , : AM PMO $,.YesNo/,  , : AM PMP $,.YesNo/,  , : AM PMQR $,.YesNo/,  , : AM PM MS $,.YesNo/,  , : AM PMT $,.YesNo/,  , : AM PMA/;!/6/!/+G!/N6_Q_+lT; o}I   BT ; # I &*o;  ,0=y ,~= ,g5 *; 0y~5C BnsaclassDlabelFnameHageJ descriptionLsources A A @BBA B *           70SunMonTueWedThuFriSatJanFebMarAprMayJunJulAugSepOctNovDec{KArial MS Sans Serif @  rA1 RPTH RolyNAME WSPC NAMEA nsakey.FP5 RPTHA NSAKEY.FP5 RolyAWSPCA E:\E.1\DB-5\ A1 rRPTH RolyNAME WSPC NAMEA SBunits.fp5 RPTHA SBUNITS.FP5 RolyAWSPCA E:\E.1\DB-5\ !@A,FMRLFMRLAA5FMRLFMRLA AnsakeyBunits`AnsakeyBnsaunits`AnnsakeyBnsaunitsts/ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.rgAFine-grained to conglomeratic sandstone and fine-grained laminated mudstone exposed along the south-central boundary of the map. Mudstone is locally tuffaceous. Clasts are predominantly intermediate and mafic volcanic and intrusive rocks and chert with subordinate amounts of quartz, metamorphic, and granitic clasts. Metamorphic detritus increases in abundance in the upper part of the unit. Graywacke is more common than mudstone; the unit is thought to represent middle and outer submarineB fan deposits (Patton and others, 2005). Late Early Cretaceous (Albian) marine mollusks are present in the map area and in adjacent areas. Equivalent to Kvg of Patton and others (2005) and part of unit Ks of Pallister and Carlson (1988)CKvgD CretaceousEaVolcanic lithic sandstone and mudstone, Angayucham Terrane, Serpentinite, and Yukon-Koyukuk BasinAAHP LaserJet 5/5M PostScriptw odXXP?Rp_A+RdB|Custom page 1|CCCustom page 2|CCCustom page 3|CCfA~0'd>PzZgayerrane and Yukon-Koyukuk Basin: Serpentinited6characterAWKWcharacteristicLWPWdWBWCWsticsCWcharacterizedVW[W\WchemicalCWchemistryCWchertBWCWTWUWVWWWXWYWZW[W\W^W_WaWbWchertyCWNWTW`WchesterianTWVWXWZWchieflyUWchloriteKWOWPWQWYWchlorite-albitePWchloriticPWcWchloritoidKWPWYW[W\WchondritesCWchristianGW^W`WaWcitedLWclastAWclasticUWaWclastsAWBWPWVWYW[W\W_WaWbWclearKWclinopyroxeneFWcloselyaWclotsKWclusters[W\WcmLWVW[W\W^WaWcm-scalePWcoarse`Wcoarse-crystallineNWcoarse-grainedVW[W\WcoarselyPWcoarsening-upward^Wcoarser[W\W`WcoatingUWcoevalUW`WbWcWcollapsedCWcollectedCWKW_WaWcollectionLWTW_WcollectionsCWLW`Wcolonial`WcolorNWTWdWcolumnalsLWcombinationKWcombinedHWUWcommonBWKWRWUWYW_WaWcommonlyCWNWPWUWZW^W`WdWcommunLWcommunicationsLWcompilation^WcomplexKWcomplexityUWcomplexlyUWcomponentsPWcomposedOWPWYW`W|=deformedAWUWVWaWW@WdelineatingUWdeltaicUWpositionHWLWdepositionalCWHWPWTWUWdepositsBWJWLWderivativeLWderivedFWHWPWSWdescribedTWdescriptionsKWdetailCWKWLWTWdetailedKWdetailsUWdetritalKWdetritusBWdevonianCWFWGWHWIWJWKWLWNWPWUWdextralEWdgKWNWOWPWRWdghOWdgsOWdiabaseCWdiagramsCWdiameterPWdifferUWdifferentCWdiffersTWdifficultHWdikesUWdillonHWKWLWPWTWdinklageKWPWdirectlyKWdiscontinuousKWUWdiscriminationCWdiscussionKWLWdisplayKWdistanceFWIWdistinctCWdistinctiveUWdistinctlyCWdistinguishHWdistinguishedCWPWdistributedCWdistrictLWdividedKWdmuUWdmwGWdnUWdnuUWdoCWUWdobUWdocumentedJWTWdoesPWdolomiticQWdolostoneIWJWNWPWTWUWdolostonesJWdomePWdominantKWdominantlyGWKWUWdominantlygray-greenlithicsandstonelesserbrownquartzsGVdominatedPWdoonerakTWdpKWLWMWOWPWdpcscQW86fossilsAWCWGWKWLWUWVWXWYW[W\W^W`WdWeWgWrWtWuWAWFWGWIWJWfoundDWLWPWVWaWdWeW{WW@WBWCWHWJWfourTWYWrWfragments[W\WjWsWFWHWfrasnianUW_W`WfWsWDWfrittsJWfromAWCWEWFWHWIWKWLWPWQWSWTWUWYW^W_WaWfWgWjWlWqWrWsWtWuWyW{W|WW@WBWCWDWGWHWfrost-rived~Wfrost-rivedrubbleonslopesandbroadlowridgesglacially~VgLWUWVWWWtWBWCWgabbrorWgabbrosCWGWgarnetCWKWPWRWnWpWqWBWCWEWGWgarnet-epidoteNWgarnetsqWgastropodsJWVWXW[W\W^WbWdWFWIWgaveKWgeanticlinewWgeneralgWtWgenerallyPWUW^W`WdWjWqWsWtW{WBWCWHWgenerallyfinegrainedphyllitictoschistosegray-weatherinjVgeologicKWghostsPWUWBWCWgiveKW`W{WgivenLWWWtorsAWEWHWindicesCWinitiallyCWinnokoCWintercalatedIWintermediateBWinternallyCWinterpillowCWinterpretedJWintervalsJWintoCWintrusiveAWBWWateAW>terraneAWBWCWDWEWvWwWGWtheCWNWUWdWeWlWrWGWJWthermalQWRWthrustSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWW@WDWFWHWIWJWKWundividedQW]WmW~WvolcanicBWuWvolcanicandsedimentaryrocksdoonerakantiformuVvolcaniclithicsandstoneandmudstoneangayuchamterraneseBVvolcanic-rockWyoungerdWyoungercarbonaterocksofthenanielikantiformcentralbeldVyukon-koyukukAWBWCWDWGWzoneSW1:500000AWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWaAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWWZW[WnanielikdWeWJWnoatak^Wnoataksandstonecentralbeltandpartofnorthernthrustas^VnorthernSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWW@WDWFWHWIWJWKWofCWIWJWNWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWW@WDWFWGWHWIWJWKWoldereWJWoldercarbonaterocksofthenanielikantiformcentralbelteVJVonlyJWordovicianJWorthogneiss{Worthogniess}WparagneissRWpartSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWW@WDWFWHWIWJWKWWBWGW^WschistKWLWMWNWOWPWQWRWschistandmarbleundividedarrigetch-igikpakthermalhighQVschistandparagneissarrigetch-igikpakthermalhighRVsedimentaryTWsedimentaryrockscentralbeltandpartofnorthernthrustaTVsequenceJWLWUWserpentiniteAWBWCWDWshaleAWGWVWXW_WshearSWsiliceousWWserpentiniteangayuchamterraneserpentiniteandyukon-koyukDVshaleAWGWVWXW_WAWDWIWshearSWsiliceousWWkWstronglyDWsubunitWBWCWsurficial~W@lateAWBWCWFWGWIWKWLWPWTWUWVWXWYWZW[W\W^W_W`WaWbWcWdWeWgWhWlWnWqWrWsWtWW@WAWBWCWDWFWGWHWIWJWKWlaterdWeWrWJWlaterallyKWUW`WlatestUWVWXWZW`WbWIWlathssWlaufeldbWlaurentiancWdWeWJWlava_WeWDWJWlawKWlawsoniteKWPWBWCWlayer^WlayeringjWpWlayersCWGWJWKWLWMWPWQWVWWWXWYWZW[W\W_W`WeWfWoWqWrWsWAWBWCWDWFWGWHWIWJWleastKWLWPWYW`WbWhWsWtWuWBWCWKWledgesPWBWCWleffingwellVWtWlengthCWPW_WaWW@WBWCWDWGWlensPWfWBWCWlens-shapedKWlensesCWKWLWNWPWUWZWiWpWuWBWCWEWGWleonardiantWlessKWPWUW_WgW{WBWCWDWabasiteEWmetachertCWFWIWmetagabbroFWmetagabbrosCWFWmetagraywackeAWHWmetalimestoneCWFWIWJWmetamorphicAWBWCWEWFWGWmetamorphismCWmetamorphosedAWCWFWHWmetamorphosedpillowbasalthyaloclasticbrecciabasaltictuCVmetaquartziteIW representBWJWLW`WbWeWgW{WJWrepresentedaWW@Wrepresents]W`WmWresearchersLWresembleYWgWtWresembles[W\WFWresistantKWQWrestqWrestrictedVWcWdWsWresultLWresults|WretainHWLWretainsCWGWrevisedrWreworkedTW_WcWDWDWiteaWW@WrhythmicPWBWCWribbonVWrichAWPWYWkWqWBWCWrichmondiandWridges~WriftedLWrippleHWripplescWriverCWDWFWIWJWLWMWNWPWSWTWUWVWYW[W\W^W_W`WaWbWcWdWeWgWiWkWmWnWqWsW{W}WW@WBWCWrockCWEWNWPWUWaWmWnWqWrWsWW@WBWCWrocksAWBWCWDWEWFWHWIWJWKWLWNWOWPWRWSWTWUWVWXWYWZW[W\W`WaWbWcWdWeWgWhWjWlWmWqWrWsWtWuWvWyWzW{W|W}WW@WBWCWroeskeEWwWroughlycWeWroundedKWVWrubble~WrubyAWJWwWyWzWrugoseJWrutileKWPWBWCWryherdbWsFWsableZWrWsWsadlerochitVWtWsameCWPWBWCWsampleLWgWuW|WsampledNWsamplesUW[W\WgWuW{Wsand`W~W DJDrassic radiolarians, conodonts, and megafossils have been collected from chert, cherty tuff, metalimestone layers, interpillow sediments, and fault slivers of carbonate rocks and chert (Pallister and Carlson, 1988; Jones and others, 1988). Conodonts of Late Silurian to Early Devonian age (Table A-1, Ambler River quadrangle) are the oldest fossils collected from the unit, and Early Jurassic radiolarians are the youngest (Pallister and Carlson, 1988; Jones and others, 1988). Pennsylvanian-EPermian, Permian, and Early Permian radiolarians were collected near the southeast corner of the Wiseman quadrangle (Jones and others, 1988). At two localities, Early Mississippian conodonts have been collected from the same localities that also have yielded distinctly younger micro- and megafossils. At Twelvemile Mountain (Sheet 2), in the southeast Wiseman quadrangle, tightly dated late Early Mississippian (middle Osagean) conodonts, and Mississippian and Mississippian to Early Pennsylva{)@da dg;dhfDdl dmu!?@dndob#doc$dpcgndpcmdpcscBCdpcsmdpsAdsc dsq jcsjdabGjdkkg9khskjmkm:kskvgmcmcpmdemder3mdkHmdk101FmkklmklImlmumzdm2mzpzsopcc%Jpcam1pcg=pzb+pzbq pzbs&pzj*pzm'pzp)pzpc pzpcb0pzpcbs6pzpccm-pzpcem,pzpcgqtb8scvs5spl"trcs4 @7pzsmÄdpcscÄqdpcsmÄrdpcgnÄ7akhsÄajcsÄajdkÄtmkklÄsmcpÄt9mklÄtqmcÄt1mlÄtvmuÄz&mdkÄtmdeÄzdnÄz6dhf Äz8 dl!Äz8!dmu"Äw"spl#Äz#dob$Äz$doc%ÄQ%opcc&ÄtB&pzbsFnian radiolarians were collected from carbonate and chert lenses. Bird (1977) identified Pennsylvanian(?) foraminifers from the same locality and noted that the rocks are lithologically similar to those of the Lisburne Group, a unit widely distributed to the north (in the Northern thrust assemblages). At Heart Mountain (Sheet 2), in the southwest Wiseman quadrangle, both Early Mississippian conodonts and Permian foraminifers, bryozoans, and brachiopods were identified (Table A-1; Patton Gand Miller, 1973). These contrasting ages could reflect structural juxtaposition of rocks of different ages, reworking of older fossils into younger strata, or problems in correlating age ranges of different fossil groups. The thermal indices of conodont collections in this unit are commonly high (CAI=5), though some are low (CAI=2-3). The basalts are tholeiitic, and fall into "within-plate" fields on trace element discrimination diagrams; LREE elements are enriched relative to chondriHtes in some basalts and gabbros, but show little to no enrichment in other rocks (Barker and others, 1988; Pallister and others, 1989). Based on these characteristics, the mafic rocks are thought to have formed oceanic plateaus or islands. In the Angayucham Mountains, where the unit has been mapped in detail, Hitzman and others (1982) and Pallister and Carlson (1988) recognized that several distinct subunits can be distinguished within the package, although the subunits are lithlogicallyI similar and each is internally imbricated. Pallister and Carlson (1988) initially distinguished three subunits on the basis of slight variations in metamorphic minerals and minor element chemistry, but the packages also can be distinguished by age. Jurassic radiolarians were collected from the southernmost subunit and Triassic radiolarians from the central subunit. Along the northern boundary of the central subunit and in the northern subunit, Triassic, Mississippian, and Devonian radioJlarians and conodonts were collected from fault-bounded lenses of chert and carbonate rock. The Angayucham terrane is thought to comprise parts of a collapsed ocean basin that were emplaced in a high structural position during the Brooks Range orogeny. Metabasalts of the terrane along the southern flank of the Brooks Range, the "Narvak panel" of Patton and Box (1989) are typically correlated with basalts of the "Copter Peak allochthon", which are exposed in the crest of the range (MooreK and others, 1994), also in a high structural position. The Maiyumerak sequence (MzDm), in the northwest corner of the map area, contains similar lithologies, but includes basalts with island-arc chemical affinities, unlike metabasalts along the southern or crestal parts of the range (Karl, 1992); we do not consider MzDm part of the Angayucham terrane. The Angayucham terrane is thought to be correlative with the Tozitna terrane and possibly the Innoko terrane in central Alaska (Patton an$Ld others, 1994) JCJDabDEarly Jurassic to DevonianEMafic metavolcanic and metaintrusive rocks, metachert, metalimestone, and amphibolite of the Angayucham terrane, Angayucham Terrane, Serpentinite, And Yukon-Koyukuk BasinATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A3498$CFsp of Hitzman and others (1982) and Ju of Mayfield and Tailleur (1978)"CMzPzsDMesozoic? to Paleozoic?EFSerpentinite, Angayucham Terrane, Serpentinite and Yukon-Koyukuk BasinATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A8852APelitic schist, metabasite, minor felsic orthogneiss and meta-ultramafic rock exposed in two small areas along the Kobuk fault zone in the northeastern Bettles and southwestern Chandalar quadrangles. The rocks exhibit amphibolite-facies metamorphic assemblages, mylonitic foliations and well-deveoped stretching lineations; white mica yielded a 40Ar/39Ar cooling age of 54.8 1.3 Ma (Roeske and others, 2003). Microscopic kinematic indicators from the eastern body, which corresponds to the FBmetasedimentaryAWDWPWRWVWYWaWeWlWmWW@WBWCWJWmetasiliciclasticZW[W\WFWmetasiltstoneSWUW^W_W`WaWbWW@WDWmetatuffCWPWUWBWCWGWmetavolcanicLWmWmetavolcaniclasticUWaWW@WmeterFWKWdWqWrWHWmeter-decameter-sizerWmeter-scaleKWmeter-thick^WmetersGWKWLWPWqWxWAWBWCWmethod{WmimWqWmicaEWKWMWPWYWaWgWhWpWqWW@WBWCWKWmica-poorKWPWBWCWmica-richKWurphyHWmyloniticEWmzdmCWmzpzmFWnarvakCWne-trendingAWnearCWFWnephriteDWnilsenAWnoCWnorthCWFWIWnorth-southCWnortheasternAWEWnorthernCWHWnorthwestCWnotCWnotedCWoccurCWoccursCWGWoceanCWoceanicCWofAWBWCWDWEWFWGWHWIWJWKWoldFWolderCWDWJWoldestCWoliveDWoliverIWJWonAWCWFWHWoneFWorCWDWGWHWJWKWordovicianFWoriginJWorogenyCWorthogneissEWosageanCWoscillationHWotherCWothersAWBWCWDWEWFWGWHWIWJWKWernGW+thoughtBWCWHWJWLWTWYWeWfWjWrWxW{WGWJWthreeCW[W\WeWtWuW{WFWGWJWthroughTWUW`WdWgWsWthroughoutRWTW^WthrustCWjWGWHWthusYW^WbWtightlyCW^W`WGWtillCWKWLWPWSWTWVWYWZWbWdWeWqW{WBWCWGWJWtimeFW`WdWtimingwWtinaygukTWtoAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyW{W|W}WW@WAWBWCWDWEWFWGWHWIWJWKWtogether^WpesNWPWtypicalKWLWPWtypicallyCWKWOWPWUWYW^Wu-pbLWultramaficKWuncertainVWZWuncommonPWunconformityVWundatedNWPW[W\WundeformedSWunderlainPWunderlyingHWJWTWYWunderstoodLWundifferentiatedHWKW]WundividedUWXW^WundulatoryTWuniformlyUWunitAWBWCWFWGWHWJWKWLWNWOWPWQWRWSWTWUWVWWWYWZW[W\W]W^WunitsFWGWHWIWJWKWLWMWOWPWSWUWVWXWYW[W\WunknownEWPWUWpattonAWBWCWFWHWIWJWTWwWGWpblWpb-zn-agcWpcJWpcameWnW}WpcgPWlW|WpeakCWGWpeakedQWpebbleaWhWtWW@WKWpebblesTW^W_WtWDWpebblyUW^WHWpelecypod[W\WFWpelecypods^WtWpeliteqWpeliticEWKWLWPWQWRWmWwWBWCWpeliticschistmetabasiteminorfelsicorthogneissandmeta-EVpeliticschistmetaquartzitemaficschistandotherlithologRVpelmatozoan`WdWgWsWpeloidaldWsWpeloidsgWpenetratedbWpenetrativeKWpeninsulaKWbWcWdW{WpennsylvanianCWUWWWtWGWpennsylvanian-permiaCWrWGWpercentGW`WAWperidotiteDWperitidaldWeWJWpermianCWTWUWXWtWGWIWpessel[W\W^WFWpetrogenetic{Wpetrographic^WWpopulationsKWporphyriesLWpositionCWpossibleIWLWPWpossiblyCWpost-carboniferousTWpost-middleLWpreciseIWprecludesUWpredominantXWpredominantlyBWpredominateCWPWpredominatesNWprehnite-bearingCWprehnite-pumpellyiteAWCWpresenceJWLW UBMosquito terrane of Jones and others (1988), suggest the formation of ductile fabrics in a high-strain dextral slip system (Roeske and others, 2003). Age and affinity of the protolith rocks are unknownCDpCmDDevonian to Proterozoic?E#Metamorphic rocks, Mosquito terraneATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A5145kareasBWEWLWPWUWXW[W\WgWiWqWFWHWIWarenigeWJWargillaceousTWcWsWtWargilliteUWWW^WhWrWHWKWargilliticHWarmstrongTW[W\WtWFWaroundKWPWgWqWBWCWarrigetchQWarthropodseWJWasDWHWJWKWLWPWTWUWVWXWYW[W\W^W`WbWcWdWeWgWlWnWpWqWrWtWBWCWFWHWIWJWascendingTWUW[W\WtWFWash-fallAWaspectsTWtWassemblageCWFWLWmWoWuWGWassemblagesCWEWPWQWRWYW^W`WbWcWdWqWBWCWGWHWassignedLW[W\WtWFWassignmentgWassociatedJWKWLWPWUWYWaWzWW@WBWCWassociationLWBWCWassuming{WasymmetricalKWatAWCWGWKWLWPWQWUWVWWWYWZW^W`WbWcWhWsWtWuWwW{W}WAWBWCWEWGWKWauthorsXWtWIWavailableSWgWpWaxesKWbCWKWPWXWBWCWGWIWb1TWtWb2TWb27VWbairdFWMWPWUWWWXWZW]W^W_W`WaWcWdWeWgWiWmWqWsW|W}WW@WBWCWDWHWIWJWbandedKWlWbandingLWdWrgillaceoustocVbelongKWPBM. The calcareous schist unit is equivalent to the "Kogoluktuk schist" of Hitzman and others (1982, 1986), "calcareous schist and marble of the Kallarichuk Hills" of Karl and others (1989b), parts of the Pzuc, Pzcq, and Pzcs units of Mayfield and Tailleur (1978); parts of the Pzsch, Pzca, DSso and DSsk units of Nelson and Grybeck (1980), the "calcareous schist" unit of Dillon and others (1986), the "Emma Creek schist", "unnamed calcareous schist", "Midnight Dome schist", and the "calcareoN2us schist and marble" of Brosg and Reiser (1964) HCDpCscDDevonian to ProterozoicE3Calcareous schist, albite-rich subunit, Schist beltATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.}unlikeCWGWunnamedPWhWsWBWCWKWunpublishedCWFWJWKWNWPWSWVWXW[W\W^WeWgWBWCWFWGWHWIWJWunrealistically{WunroofingAWunusuallyYW_WDWupCWDWGWKWLWPWSWUW_W`WbWeWfWqWsW{WAWBWCWDWGWJWupgradedQWupperBWJWTWUWVWYWcWdWeWfWgWsWtWwWHWJWupward`WeWJWuqmiWuseful{WutukoksWgPWveinsCWGWvenetieGWversusKWverticalPWveryKWPWvillagePWvoglQWRWYWvolcanicBWLWPWUWvolumetricallyKWPWXWvuggyTWw^WwachsmuthTWwacke_Wwackestone`WwasGWKWLWPWTWUWVWYW^W`WwaterTWweCWWWweaklyKW_Wweather`WweatheredUWweatheringKWZWweathers`WwebsterLWweldedLWwellHWPWTWVWXW^Wwell-definedUWVWwell-deveopedEWwell-sortedAWwereCWHWJWLWPWTWUWWWXW_WwestPWRWUWwest-centralUW[W\WwesternAWCWGWPWSW[W\W^WwesternmostSWwhereAWCWLWPWRWUW[W\W^W`WwhetherKWwhichCWEWKWSW[W\WwhileUWYQsliceFWslicesJWslightCWGWslightlyKWslipEWsliverCWFWGWsliversCWFWGWslopeTWUWWWbWgWslopesPW~WBWCWsmallEWHWMWPWUWWWXW[W\WgWqWtW}WBWCWFWHWIWsmallerSWsmithLWUW^W_WDWsn{WsneeZWdWeWqWJWsnowdenaWeWgWW@WJWsolitaryLW`WsolomonKWsomdWsomeCWFWIWJWKWLWNWPWTW[W\W^W`WaWdWeWgWjWlWnWqWtW{WW@WBWCWFWGWHWJWsomewhatcWtWsootyNWUWtWsorted^WHWsourceKWbWgWsourcesBWCWsouthAWFW[W\W`WcWwWFWsouth-centralBWsoutheastCWGWsoutheasternYWbWlWvWxWsouthernAWCWDWHWhWoWwWyWzW{W|W}WGWKWsouthernmostCWGWsouthwestAWCWQWGWsouthwesternDWEWFWIWYWgWspace`Wspan}WsparseAWspatialeWJWspatiallyZWspearYWspecificallyUWspessartinePWBWCWspheneKWPWqW}WBWCWEWsphericalKWspiculesPWTWVWXWBWCWIWspiculiticsWWWWstableRWYWstarvedTWstaurolitevWKUABble Early Devonian age (Brosg and Reiser, 2000). May be correlative to parts of unit Pzpg. Area with overlay pattern is schistose, due to crystallization of micas at low metamorphic grade, and contains quartz veins. Schistose varieties are equivalent to units "Dmw" and "Dpm" of Brosg and Reiser (2000). Dps is part of the Venetie terrane of Brosg and Reiser (2000), and was included in the Slate Creek subterrane by Moore and others (1994)CDpsDDevonianE)Lithic sandstone and shale, Phyllite beltATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A5565QtailleurDWIWJWKWLWMWPWTWUWVWXWYW[W\W^W_WaWbWcWeWiWkWmWqWsWtWW@WBWCWDWFWHWIWJWtakengWalefaultsliverFVtectonicallyHWtectoniteDWtemperatureLWtemperaturesYWtentativeLWtentativelyTW[W\WterraneAWCWDWEWFWGWterranesKWtexturesCWLWPWRW^W`WthamnoporoidLWthanBWLWPWUWVW`WthatAWCWFWGWHWIWKWLWPWSWTWUWVWWWXWYWZW[W\W]WaWbWtheAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWtheirLWVWthemPWUWthereKWLWPW_WthereforeKWLWthermalCWthermobarometryLWtheseCWLWNWTWUWVWXWYW[W\W^WbWtheyPWVWYW[W\WbWthickCWDWGWKWLWPW_W`Wthick-beddedVWthinGWJWKWPWSWVWYW^W_WaWthin-beddedJWthin-beddedtomassivedolostonemetalimestoneandmarbleloJVthinlyTWthisAWCWFWHWJWKWPWTWUWWWXWYWZW[W\W^W_W`WaWbWtholeiiticCWthoseCWFWHWJW[W\W_WthoughCWOWPW ironUWWW^Wironstone^WHWirregularsWirregularly-shapedEWisAWBWCWDWFWGWHWJWKWLWPWRWSWTWUWVWWWXWYWZW[W\W^W_W`WaWbWcWdWeWfWgWhWjWlWmWnWpWqWrWsWtWuW{WW@WAWBWCWDWEWFWGWHWIWJWKWisland-arcCWuWGWislandsCWGWisoclinalKWVWisoclinallyQWjWisolatedUWisotope{Wisotopic{WitAWJWKWLWPWTWUWVWWWXWYW[W\W^W`WbWfWgWnWpWqWsWtWBWCWFWHWIWitsCWKWUW`WhWGWHWKWjNW[W\WgWFWjadeDWIWjcsTWtWjdabAWDWFWjdkWW^WHWjessejWjonesCWEWGWjrLWjuDWjulianuWjurassicCWTWUWrW{W|WGWjust`WjuxtapositionCWFWGWk-aruWyW{Wk-feldspar{W}Wk/arAWkallarichukKWPWBWCWkanayutTWUWXW^W_WDWHWIWkarentWkarlCWFWKWPWUWWWXWZW]W^W_W`WaWcWdWeWgWiWmWqWrWsW}WW@WBWCWDWGWHWIWJWinatedBWNWPWSWaWcWeWlaminationsKWlaminitedWlargeLWOWSWlargelyaWlargerXWU1Cit is equivalent to the "phyllite belt" of Gottschalk and others (1998). Rocks in the southern subunit retain relict sedimentary features that may reflect contrasting depositional settings. Sedimentary structures, such as Bouma sequences, have been recognized and are thought to indicate deep-water turbidite fan deposition (Murphy and Patton, 1988); others, such as hummocky cross-stratification and oscillation ripple marks, were seen elsewhere and are indicators of shallow-water depositioDn (Gottshalk and others, 1998). Palynofloras from sandstones with shallow-water structures are Early Devonian (Gottschalk, 1998). The southern subunit is equivalent to the metagraywacke belt of Gottschalk and others (1998); the unit overall is equivalent to "metagraywacke and phyllite" of Dillon and others (1986), Slate Creek subterrane of Moore and others (1994) and the combined Pzpa and Pzg units of Patton and others (2005)xCPzpgD Paleozoic?E%Phyllite and graywacke, Phyllite belt16 Bn1, Ambler River and Hughes quadrangles). Corals of Devonian and possible Silurian age are reported from the Jade Mountains (Patton and others, 1968; Oliver and others, 1975). The fault-bounded blocks may have affinity with carbonate rocks some distance to the north (Central belt). Pzpc includes parts of map units DSba, Ml?, and Pzl of Mayfield and Tailleur (1978)\CPzpcD PaleozoicE Carbonate rocks of phyllite beltATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000. A6927dpmGWAWdpsGWAWdrownedtWdsUWaWbWW@WdsbaIWJWdscJWaWW@WdsgaWW@WdskdWmWdspaWW@WNWTWVWWW_W`WaWduniteDWduringAWCWKWLWdusel-baconAWQWRWdusty_WdutroTWUWVWWWXWZW[W\W^W`WaWdvOWeLWUWVWWWeachCWearlyAWBWCWGWHWIWJWKWLWNWPWTWUWVWXWZW[W\W_W`WaWeastGWUWeast-centralVW[W\W_Weast-westKWeasternEWPWSWYWZW[W\W`WeastwardFWechinodermNWVWXW[W\Wechinoderms^W_WelementCWLWelementsCWTWelevatedUWWWellersieckUWelongateNWelongationVWelsewhereHWUWVWaWemYWemmaPWemplacedCWemsianJWNWencompassesSWendicottTWUWVWXW]W^W_W`WaWendothyridXWenoughOWenrichedCWenrichmentCWentriesZWenvironmentTWVWepidoteKWOWPWequivalentAWBWDWFWGWHWJWKWLWMWOWPWQWRWSWUWWWYWZW]WaWequivalentsVWernieYWeruptedLWescapedLWestablished^WestimatedYWetivlukTWUWWWeuhedralKWeventSWklithicsandstoneandshalephyllitebeltGVmaficCWnWEWGWmaficmetavolcanicandmetaintrusiverocksmetachertmetalimCVGVmaficschistcentralbeltandpartofnorthernthrustassembnVmaficschistschistbeltEVmaiyumerakrWmarbleNWQWgWmarblecentralbeltandpartofnorthernthrustassemblagesgVmarbleoftheschistbeltNVmelangeFWmelangephyllitebeltFVmetachertCWCWGWmetaigneousaWW@WmetaintrusiveCWGWmetalimestoneCW`WbWGWmetalimestonecentralbeltandpartofnorthernthrustassem`VmetamorphicEWlWqWmetamorphicrocksmosquitoterraneEVVVaryandlessermetaigneousrockscentralbeltanaVmetasedimentaryandmetavolcanicrocksundividedcentralbelmVmetasedimentaryrockscentralbeltandpartofnorthernthru[VhVmetasedimentaryrocksofbluecloudmountaincentralbeltandpVmetasedimentaryrocksofjessemountaincentralbeltandparjVmetavolcanicCWmWmosquitoEWmountainjWpWmtqWbconstitutesKW_WDWconstraincWconstraints[W\WFWcontactCWFWJWMWNWPWTWVWYWZW`WaWdWpWtW{WW@WBWCWGWHWcontactsFWUWWWYW^WaWcWsWtW{WW@WW{WW@WWWBWCWGWcontactsFWWWYW^WaWcWsWtW{WW@WWW,-+ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000. A5570AFault-bounded blocks of marble, metalimestone, and dolostone that crop out in southwestern Ambler River quadrangle. Carbonate rocks are locally intercalated with black phyllite, black metaquartzite, and metachert, contain megafossils (corals, brachiopods, crinoid debris), and yield conodonts that indicate a range of middle Paleozoic ages; most precise ages are Late Silurian-early Early Devonian, Middle Devonian (Givetian), and Early Mississippian (Alaska Paleontological Database; Table A-nLourHWWW[W\WFWoutIW[W\WeWgWFWJWoutcropDWKWPWUWWWXWpWBWCWIWoutcropsKWPWUWgWjWqWBWCWouterBWcWgWoutsidesWtWover{WoverallHWUWovergrowthsHWoverlainTWWW^W_WcWdWfWtWDWHWoverlapfWoverlayGWPW_WaWeWhWqWW@WAWBWCWDWHWJWKWoverlieXW[W\WtWFWIWoverliesTWVWXW^W_WsWDWHWIWoverlyingTWaWW@WoverprintCWVWqWGWoverprintedqWovoidsnWoxide^Woxides{WpVWfWBWCWJWpackageCWKWaWW@WGWpackagesCWLWPWBWCWGWpackstone`WsWtWWWpanelCWparagoniteKWparallelKWMWeWparautochthonousVWparisbWpartBWCWFWGWJWKWLWPWSWTWUWVWXWZW]W^W_W`WaWbWcWdWeWgWhWjWlWmWnWrWsWtWpartiallyCWKWparticularlyRWpartlycWeWpartsAWCWGWHWIWJWNWOWPWQWYW]W_W`WaWcWdWeWfWgWiWkWlWmWoWqWsWpassFWLWOWQWUWXWYW[W\W^W_WaWbWeWfWgWlWnWoWpatrickLWQWpatternGWpatternsUW NseveralCWDWPWUWVW`WcWtW|W}WBWCWGWsewardKWbWcWdW{WshaleGWKWTWUWVWWWXW[W\W]W^W_WaWsWtWW@WAWDWFWHWIWshaleandsandstoneexposedinthenorthwestbairdmountains]VshallowUWcWeWgWHWJWshallow-marine^Wshallow-waterHWVWbWcWdWsWshallowestdWsWshallowing-upwarddWeWJWshardLWsharedJWKWLWsharpTWtWshearSWVWqWsheathKWsheepdWsheetCWNWPWsWwWBWCWGWshelfTWgWsWshishakshinovikVWshoal`WtWshoals`WshowCWKWLWMWPWWW}WBWCWEWGWshownPWUWYW_WaWeWhWqWW@WBWCWDWJWKWshublikXWtWIWetchingAWEWstrikeHWstromatoporoidsJWstronglyAWKWstructuralCWJWKWstructurallyDWFWKWstructuresHWsubmarineBWsubordinateBWDWsubparallelKWsubterraneGWHWsubunitCWHWsubunitsCWHWsuccessiveAWsuchHWKWsuggestEWKWsuggestedFWsuggestingAWsulfideJWsurfacesKWsurveyFWsystemEWtableCWFWIWJWtabulateJW%GLand others, 1994)KCJDabDEarly Jurassic to DevonianEMafic metavolcanic and metaintrusive rocks, metachert, metalimestone, and amphibolite of the Angayucham terrane, Angayucham Terrane, Serpentinite, And Yukon-Koyukuk BasinATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.HA69166< CHitzman, 1986). Lithofacies in DSc are in part similar to those of older part of unit Pzpc; the Cosmos Hills carbonate rocks may have shared structural history with units in the Phyllite belt. Hitzman and others (1982) interpreted the lower contact of the unit as conformable with the underlying schist, but considered the upper contact a fault. DSc includes parts of map units DSba, Ml?, and Pzl of Mayfield and Tailleur (1978); it is equivalent to map units Dbm and Dbd (Bornite marble) of HiDtzman and others (1982)CDScDDevonian and SilurianE6Carbonate rocks of Cosmos Hills, Cosmos Hills sequenceATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000. A8602-5 AThin-bedded to massive dolostone, metalimestone, and marble, locally graphitic or phyllitic, exposed in fault slices in the Cosmos Hills, Shungnak and Ambler River quadrangles. The unit includes minor thin, micaceous layers interpreted as airfall tuffs, and some buff to reddish gray dolostones thought to be of hydrothermal origin (Hitzman and others, 1982). Some intervals are fossiliferous and may represent biohermal build-ups. Brachiopods, corals, gastropods, and crinoids of Middle DevoniBan age were reported by Hitzman and others (1982); Early(?) and Middle Devonian tabulate and rugose corals and stromatoporoids were documented by Patton and others (1968), Fritts (1970), and Oliver and others (1975). Conodonts indicate the presence of Upper Silurian and Lower Devonian (lower Emsian) strata (A. Harris, unpublished fossil report, 1991; Table A-1, Ambler River quadrangle). This unit hosts the copper-rich Ruby Creek (or "Bornite") and associated stratabound sulfide deposits (?!+ ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000. A7260AInterlayered white- to medium-gray-weathering metarhyolite, dark-green-weathering metabasite, pale-gray-weathering marble, and brown- to dark-gray-weathering calcareous, pelitic and carbonaceous schist exposed in two areas in the Schist belt. The unit occurs as large lenses interfolded with units Dsq and DpCsc. "Metarhyolite porphyries" with megacrysts of feldspar up to 5 cm across and quartz eyes up to 1 cm across are typical of the unit (Hitzman and others, 1986). "Aphanitic metarhyoliAgivetianIW`WcWsWglacially~WglaucophaneKWPWBWCWgneisslWgneissicRWlW|W}WgottschalkFWHWKWPWBWCWgottshalkHWgradationalFWUW^WdWtWHWgradationallyTWtWgradeFWGWQWRWYWeWlWwWAWJWgradedbWHWgradesAWYW`WeWJWgradientHWgradingVWeWJWgrainUWnWgrainedAW`WjWtWHWgrainsKWPWTW^WaWbWeWgWnWrWW@WBWCWHWJWgrainstonesWgraniteNWqWyW}WgranitequartzmonzoniteandgranodioriteofthenorthernruyVgraniticBWKWPWRWVWlWzW{W|W}WBWCWgranodioriteyW}Wgranodioritic{WgrantzbWgraphiteKWMWPWBWCWgraphiticJWKWNWPWbWlWBWCWgraptolitesbWeWuWJWgravel~WgravitybWgrayJWKWNWPWQWTWUWVWXWYW[W\W^W`WaWdWgWkWmWsWtWW@WBWCWFWIWgraydark-grayorbrownish-grayweatheringdominantlypelitiKVgraymarbleorangedolomiticmarblemagnetite-bearingchloriQVgraytodark-graycarbonaceousphyllitelocallysilicarichkVVCcopterCWGWcoraljWsWcoral-richhWKWcorallineXWtWIWcoralsIWJWLWNWVWZW[W\W`WbWcWdWsWFWcoreuWcornerCWGWcorrelateVWeWgWhWsWJWKWcorrelatedCWVWtWGWcorrelatessWcorrelatingCWGWcorrelationsTWtWcorrelativeAWCWGWKWUWWWZW[W\WbW|WAWFWGWcorrespondlWcorrespondsEWcosmopolitandWeWJWcosmosAWDWJWcouldCW`WGWcoupletseWJWcpJWcpciceWcpcvceWcrackssWcreamqWcreatedSWcreekFWGWHWJWKWPWTWUW^WaWdWeWgWhWmWoWtWW@WAWBWCWEWHWJWKWWWcrestalCWGWcretaceousAWBWDWzW{WcrinoidIWLWXWgWIWcrinoidaltWcrinoidsJW[W\WFWHWcriticalYWcropIWeWJWcrops[W\WgWFWHWcross-beddedUWcross-beddingcWcross-beds^Wcross-laminaeeWJWcross-laminated`Wcross-stratificationHWtWcrossesPWjWnWpWBWCWcrossiteFWcWcrustal{WcryptalgaldWcrystallinePWgWlWBWCWcrystallizationGWaWnWW@WAWVcarbonaterocksofcosmoshillscosmoshillssequenceJVcarbonaterocksofphyllitebeltIVcentralSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWW@WDWFWHWIWJWKWchertWWconglomerateAWVWYW\WCWFWHWconglomeratesandstoneandshaleangayuchamterraneserpentiAVcosmosJWcreekUWdeposits~WdooneraktWuWt]VernielWfork_WgraywackeHWgroupVWXW]WcWhammondSWhammondrivershearzonecentralbeltandpartofnortherntSVhighQWRWhillsJWhunt_Whuntforkshalecentralbeltandpartofnorthernthrustass_VigneousrWigneousandsedimentaryrocksofthemaiyumerakmountainsnorVjessejWkanuyut\Wkanuyutconglomeratecentralbeltandpartofnorthernthrus\VkayakVWXWkayakshaleofendicottgroupandlisburnegroupcentralbelXVkekiktukVWkekiktukconglomeratekayakshaleofendicottgroupandlisbVVkivivikUWlakelWlesseraWlisburneVWXWlithicBWGWa+:ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.;A7250ATan- to gray-weathering, equigranular to porphyroblastic, fine- to coarse-grained metagranitic bodies ranging in size from less than a kilometer to over 20 km across, found in both the Schist and Central belts. Generally granitic in composition and made up of quartz, K-feldspar, albite, muscovite, and biotite. In the Chandalar quadrangle, the Horace Mountain pluton is dioritic to granodioritic in composition, and contains hornblende. Chlorite, sericite, Fe-Ti oxides, epidote minerals, an5 AGray, dark-gray, or brownish-gray weathering, dominantly pelitic or semipelitic schist that constitutes the major lithologic unit of the Schist belt. Outcrops vary from blocky and resistant (quartz-rich varieties) to platy and less resistant (mica-rich varieties), as the abundance of quartz versus mica and albite varies at centimeter to meter scales. Scattered lenses of mafic schist, calcareous schist, albite-mica schist, graphitic metaquartzite and marble up to 10's of meters thick are Btypical of the unit but volumetrically minor. Mafic lenses may be massive or schistose. In the Wiseman area, rare lenses of ultramafic rocks are up to 10's of meters thick. The dominant foliation is defined by parallel millimeter- to meter-scale variations in quartz versus mica or albite, or discontinuous layers and lens-shaped quartz segregations (Gottschalk, 1990; Little and others, 1994; Till, unpublished data). Foliation is weakly formed in mica-poor layers, and better formed but > Etrital zircons separated from the unit. Twenty-seven detrital zircons separated from micaceous metaquartzite varied from spherical, with pitted surfaces, to slightly abraded euhedral grains (Moore and others, 1997a). The rounded populations (n=16) yielded 207Pb/206Pb ages that suggest source terranes for the protolith of the quartz-mica schist included Archean and Proterozoic rocks. The euhedral grains (n=11) gave concordant ages of 370-360 Ma, indicating a Devonian maximum age for at leFast part of the protolith package. One Middle Devonian granitic orthogneiss body (unit Dg) is present within the quartz-mica schist unit in the Chandalar quadrangle. Geologic mapping is of insufficient detail to show whether there was an original intrusive relationship between Dg and Dsq, or if the orthogneiss was folded in with Dsq during penetrative Mesozoic deformation. It is not clear, therefore, whether or not the age of the orthogneiss bears directly on the age of the protolith of =? Gthe quartz-mica schist. The quartz-mica schist shared its early deformational and metamorphic history with other units of the Schist belt (DpCsc, Da, Dg); see the introduction for a discussion of that history. Common metamorphic minerals in pelitic schists include quartz, muscovite, chlorite, plagioclase, chloritoid, and accessory sphene, tourmaline, rutile, opaque, graphite, and calcite. Some pelitic schists contain garnet, and many contain glaucophane or pseudomorphs of chlorite and aHlbite after glaucophane. Metabasites typically contain a combination of actinolite, albite, epidote, garnet, chlorite, sphene, and quartz; many contain glaucophane or pseudomorphs after glaucophane. Rectangular inclusions of zoisite plus paragonite in garnet or other minerals are likely pseudomorphs after lawsonite. This unit may be a lithologic and metamorphic correlative to the Solomon schist of the Nome Group, Seward Peninsula, which has also yielded detrital zircons as young as Late >7z IDevonian (Till and others, 1986, 2006). Hitzman and others (1982, 1986) divided this lithologic package into the Anirak and Mauneluk schists. The "banded and knotty schist" of Dillon (1989) and Koyukuk schist of Gottschalk (1987) are dominantly pelitic schists that belong to this package. This unit is equivalent to the "quartz mica schist" and "siliceous schist of the Kallarichuk Hills" of Karl and others (1989b), "undifferentiated quartz-mica schist" and "massive quartz-mica schist" of JCMayfield and Tailleur (1978), "quartz-muscovite schist" of Nelson and Grybeck (1980), "schist" of Dillon and others (1986), "Marion Creek schist" of Moore and others (1997a,b), and "quartz-mica schist" of Brosg and Reiser (1964). The protolith was considered by Brosg and Reiser (1964) to be the Devonian Hunt Fork ShaleCDsqDDevonianEQuartz-mica schist, Schist beltalesserGWPWUW_W`WaWbWdWsWW@WAWBWCWDWHWlightUWZW`WaWcWdWoWpWsWtWW@Wlightmediumanddark-grayphyllitedark-graytoblackmetaqpVlighttomedium-grayweatheringdark-graymetalimestoneandZVlight-brown-weatheriUW`Wlight-coloreddWlight-grayPWeWqWtW}WBWCWJWlight-graybrownandlocallyorange-weatheringlithologicallPVBVCVlowerJWlreeCWmCWFWmaAWEWKWLWmaficAWBWCWFWHWKWLWOWPWmaiyumerakCWmajorKWPWmanyKWmapAWBWCWFWGWHWIWJWKWOWmappableNWmappedCWmappingKWmarbleIWJWKWLWNWPWmarblesNWmarginLWmarineAWBWmarionKWmarksHWmassiveAWJWKWLWNWOWPWmatrix-supportedFWmaunelukKWmaximumKWmayFWGWHWIWJWKWMWNWmayfieldDWIWJWKWLWMWmcclellandLWmeasuredAWmedium-beddedGWNWmedium-dark-grayNWmedium-grainedGWMWmedium-gray-weatheriLWmedium-light-grayNWmegacrysticLWmegacrystsLWmegafossilLWWBWCWEWFWGWKWW8gray-greenGW_WaWmW|WW@WAWDWgray-weatheringUWjWqW{Wgrayish-brownpWgraywackeBWFWaWW@WgrazingTWgreatlyPWBWCWgreenDWUWVWYW[W\W^W`WaWmWnWqWtWW@WEWFWgreenandgreenish-grayschistosetomassiveirregularly-shaEVgreen-weatheringnWgreenish-blackDWgreenish-grayDWoWEWgreenish-grayyellowish-greenolivegreenorgreenish-blackDVgreenschistFWPWUWYW^WwWEWHWgreenschist-faciesAWCW_WDWGWgreenstone`Wgrew[W\WFWgroupCWKWTWUWVWWWXWZW[W\W]W^W_W`WaWcWrWsWtW{WW@WDWFWGWHWIWgroupsCWGWgrybeckKWLWPWQWRWXWYW[W\W^WaWbWfWlWmWnWoWW@WBWCWEWFWHWIWguadalupiantWhad{WhammondSWSWhere[W\WeWheterogeneousPWSWaWmWheterogeneousassemblageofinterlayeredcalcareousmaficanmVheterogeneousexpansesofcalcareoussiliceousandvolcaniclaVheterogeneousmixoffinelylaminatedmostlymyloniticlithoSVhettangianUW!micaceousJWKW`WmicasGWAWmicroCWGWmicrofossilsdWuWmicrogabbroCWGWmicroscopicEWmid-famenniansWmiddleBWCWFWGWIWJWKWLWNWPWTWUWVWXW_W`WaWcWdWeWfWgWhWmWrWsWtWuW{WW@WAWBWCWDWGWIWJWKWmiddle-earlyUWWUW^W_WminorCWDWEWJWKWPWUWYW[W\W^W_W`Wmisheguk^WmississippianCWFWIWLWPWTWUWVWWWXWZW[W\W]WmixPWSWmixedDWmkXWYW[W\WmkeYW[W\WmkklUWVWYW[W\WmklUWXW]WmkoXWZWmlIWJWXWZW[W\WmltUWmmPWmm-cmPWmm-thickPWmn-richPWmobilityLWmoderateYWmoderately^Wmolluscan[W\WmollusksAWBWUWVW_WmooreCWFWGWHWKWOWPWSWUW_WmoreBWKWPWTWUW_WmosquitoEWmostIWLWQWVWYW[W\W^W`WmostlySWmounds`WmountainCWTW_WmountainsCWDWIWMWPWUWVWWWXWZW]W^W_W`Wmountains/amblerFWmovementAWmuUW[W\WmuchVW[W\W^WmudstoneBWHWTW`WmullTWUWVWWWmultipleKWmurphyHWmuscoviteKWmustPWo|a-1CWFWIWJWLWNWPWTWUWVWWWXW^W_W`WaWbWcWdWeWgWhWoWtWW@WBWCWDWGWIWJWKWa-2sWWaccessoryKWacrossCWLWSWactinoliteKWOWadamsTWadjacentBWDWFWNWOWQWRWSWaffinitiesCWFWaffinityEWIWafterKWPWageAWCWEWFWGWIWJWKWLWNWPWSWTWUWVWWWagesCWIWKWLWUWairfallJWakiakPWalapahTWalaskaCWIWalbianBWalbiteKWOWPWalbite-epidote-amphiCWQWRWalbite-micaKWalbite-richPWalbiticPWaleinikoffPWallNWPWTWUWallegroUWallochthonCWVWalongAWBWCWEWHWMWPWUWalsoCWKWPWTWUWalthoughCWVWamblerAWCWDWFWIWJWLWMWNWPWVWamountsBWMWPWamphiboleFWamphibolite-faciesCWEWanAWCWFWKWLWNWPWTWanalyzedLWanastomosingFWandAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWangayuchamAWCWDWFWangularVWanirakKWankeritePWantiformPWTWaphaniticLWapparentlyPWQWappearRWappearanceKWQWapproximatelyQWSWquartz-richKWPWSWVWYWBWCWquartziteNWSWUWVWYW[W\WgWmWtWFWHWquartziteconglomeratephyllitemetalimestoneslatedolostonVVquartzitepebblyquartziteconglomerateandminorsiltstoneHVquartzitephyllitesiltstoneconglomerateshalesandstonelitVg[W\WFWradiogenicuWradiolarianCWTWUWeWGWJWradiolariansCWFWPWTWUWbWBWCWGWradiometricLWrangeAWCWIWLWSWVWYWeWlWrWsWtWyW{WGWJWrangesCWFWGWranging{WrareCWFWKWLWPWUWVWaWhWW@WBWCWGWKWrarelyPWBWCWHWratermanLWratherLWratiosAWLWVWrb{WreactsYWreassignedrWrecessiveSWrecognizableVWdWpWrecognizedCWHWTWdWeWGWJWreconsideredLWreconstructionVWrecordAWYWaWqWW@WrecordedwWrecoveredLWPWaWuWW@WBWCWrecrystallizedbWgWsWrectangularKWredUWVWYW[W\WaWtWW@WFWreddishJWreddish-brown-weatheVWpWpWWHWIWJWLWOWUWVWXWYW[W\W_Wreports[W\Wq~exceptionsCWGWexcess_WDWexcludedcWsWexhibitEWexhumation{WexistinggWexpanse_WDWexpansesaWW@WexperiencedCWPWcWqWBWCWGWexploratorybWexposedAWBWCWDWEWFWGWHWJWLWMWPWQWSWTWUWWWXWYWZW]W^W_W`WaWcWdWeWfWhWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW|W}WW@WAWBWCWDWGWHWIWJWKWWWWWJWKWWVfaultsFWfaunalLWfavositidLWfeaturesHWfeldsparLWfelsicEWLWfewLWfieldHWNWPWfieldsCWfindingsLWfineGWKWMWNWPWfine-crystallineNWfine-grainedBWHWPWfine-grainedtoconglomeraticsandstoneandfine-grainedlamBVfine-scalePWfinelySWfinerAWflankCWflatteningAWflowLWfluid-rockLWfoldedKWQWfoldsKWfoliatedAWCWHWKWfoliationKWMWfoliation-formingCWfoliationsEWfollwedAWforKWLWNWforaminifersCWTWforkKWformNWPWformationEWTWformationsTWformedCWKWTWformsGWPWfossilCWJWfossiliferousJWTWq!metamorphismCWLWQWUW^WcWgWnWvWwW{W|WGWHWmetamorphosedAWCWFWHWeWhW}WEWGWJWKWmetamorphosedpillowbasalthyaloclasticbrecciabasaltictuCVGVmetapeliteqWmetapeliticqWmetaplutonicRW{WmetaquartziteIWKWMWPWRWjWlWpWqWwWBWCWmetarhyoliteLWmetarhyolitesLWmetasandstoneSWUWYWZW[W\W^W_W`WaWbWcWhWW@WDWFWKWmetasandstonemetasiltstoneandsubordinatephylliteexposed^VJmyloniticEWSWVWHWmzdmCWUWGWmzpzfwaWW@WmzpzmFWmzpzphaWW@WnKWn6jWnakolikUW`WcWnanielikZWdWeWJWnappejWnarvakCWGWnatureVWZWne-trendingAWUWnearCWFWLWMWPWVW[W\W^WfWtWBWCWFWGWnearbyPW}WBWCWnearesttWneitherLWnelsonKWLWPWQWRWXWYW[W\W^WaWbWfWlWmWnWoW{WW@WBWCWEWFWHWIWneodym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Dto Late Devonian. Few fossils are known in the Ambler sequence. One conodont collection from the Wiseman quadrangle is Devonian (Table A-1). Megafossil collections have been reported but are not now considered definitive. In an abstract, Smith and others (1978) reported that poorly preserved favositid corals, crinoid columnals, bryozoans, and ichnofossils were found at a locality in the Ambler district, and assigned the rocks a tentative Middle Devonian to Early Mississippian age. The fEaunal assemblage was examined by two researchers. G.D. Webster (written commun. to I.L. Tailleur, 1977) indicated a Devonian age for the corals, and considered crinoid columnals to be of probable Middle Devonian and possible Devonian or Mississippian age. William A. Oliver, Jr. (written commun. to I.L. Tailleur, 1977) suggested that the solitary corals indicate a post-Middle Ordovician age and that possible thamnoporoid corals suggested a Silurian-Devonian age. Both paleontologists hav)+ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6900ADominantly gray-green lithic sandstone, lesser brown quartz sandstone, and black shale and silty shale exposed in the western Christian quadrangle (Brosg and Reiser, 2000). Sandstones are fine- to medium-grained and thin- to medium-bedded. Black shale forms up to 50 percent of the unit and occurs in layers up to 15 meters thick. The unit may be 1200 meters thick. Localities east of the map area yielded Late Devonian plant fossils and spores that are of Middle or Late Devonian and probaAADark-gray to black phyllite and lesser gray-green phyllite with thin layers of siliceous or calcareous metasiltstone, lithic wacke, metasandstone, and minor layers of fossiliferous metalimestone exposed along the length of the northern boundary of the map. Locally massive mafic sills and dikes up to 10 m thick are common. One locality of pillow lava was reported in the Baird Mountains quadrangle (Karl and others, 1989b). A basal conglomerate containing clasts of quartz, chert, siltstone,B slate, and a few limestone and dolostone pebbles was mapped in Wiseman and Chandalar quadrangles (Dillon and others, 1986; Brosg and Reiser, 1964) . In excess of 300 m thick, the unit depositionally overlies parts of units Dl, Dmu, and Pzm. The Hunt Fork Shale is depositionally overlain by the Noatak Sandstone (Dn) and Kanayut Conglomerate (MDk), and with those units constitutes a major part of the Endicott Group (Tailleur and others, 1967). Originally designated the Hunt Fork Shale by"&+ ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6980AMetacarbonate rocks form an elongate belt in the central Ambler River quadrangle and are the only mappable occurrence of massive carbonate strata in the Schist belt. The unit surrounds the Redstone pluton (Sheet 2) and includes a variety of rock types (J. Dumoulin, unpublished field notes, 1986). White, gray, and black, fine- to coarse-crystalline marble predominates; these rocks are commonly color laminated on a millimeter to centimeter scale, contain local interlayers and lenses of graph3YshungnakAWDWJWsiYWsiberiancWdWeWgWuWJWsignificanceLWsignificantlyCWGWsiksikpukTWXWIWsilicaYWkWsiliceousKWTWUWWWZW_WaWbWmWW@WDWsiliciclasticVWZW`WbWsilicifiedZWgWsillsUW_WDWsilt-sizedaWW@WsiltstoneTWUWVWXW_W`WsWtWDWHWIWsiltyGWTW`WcWtWAWHWsilurianCWIWJWPWbWcWdWgWuWBWCWGWsilurian-devonianLWsilurian-earlyIWgWsilverUWWWsilveryUWsimilarCWHWJWPWTWUWWWYW[W\WbWmWtWwW{W}WBWCWFWGWsimilaritiesaWcWdWW@WsimpleaWW@Wsingle_WjWDWsitDWYWaWW@Wsits}Wsixtymile}WsizenW{WHWsizedrWskajitlWskarnNWQW{Wskarn-bearingNWskarnsPW{WBWCWWFWKWstructureLWstructuresHWLWstudiedLWsubmarineBWLWsubordinateBWDWsubparallelKWsubterraneGWHWsubunitCWHWsubunitsCWHWsuccessiveAWsuchHWKWsuggestEWKWLWsuggestedFWLWsuggestingAWsuiteLWsulfideJWLWsupportedLW \increasesBWHWindeedYWlWindicateCWHWIWJWLWPWVWWW_W`WbWdWeWgWqWsWtW{WBWCWDWGWJWindicatedLWindicatesNWHWindicatingKWcWsW{WindicationLWindicative^WindicatorsAWEWHWindicesCWGWindividual{WinferWWinferredUWinformalTWdWeWJWinformationTWdW{WinheritedHWinitiallyCWGWinnereWsWJWinnokoCWGWinputUWinsteadVWinsufficientKWintenseVWintensityVWinterbeddedTWinterbedstWintercalatedIWNWUW`WcWinterfoldedLWinterlayeredLWPWQWXWaWbWlWmWqWW@WBWCWIWinterlayeredwhitetomedium-gray-weatherimetarhyolitedarkLVinterlayeringPWqWBWCWinterlayersNWPWUWVW[W\W^WbWeWgWtWBWCWFWHWJWintermediateBWUWaWW@WintermixedzWintermixedgraniticrocksbiotiteschistandhornblendehornzVCWKWUWWW`WeWuWintrafolialKWVWintroductionKWLWintrudedPWUWlWintrusiveAWBWKWNWintrusivesaWjqmegafossilsCWIWZW`WaWbWdWW@WGWmelangeFWrWmemberTWtWmembersTWmeramecianTWVWZWmeramecian-earlyTWXWZWsWIWmesozoicKWmeta-argilliteaWhWjWmWW@WKWmeta-ultramaficEWbasalticcWmetabasaltsCWDWmetabasiteEWLWPWeWlWmetabasitesKWLWmetacarbonateNWVW[W\WcWmetacarbonaterocksformanelongatebeltinthecentralambNVmetachertCWFWIWPWUWWWmetaconglomerateUWVWZW[W\WaWhWiWoWW@WmetaconglomeratesPWaWW@WmetadioritePWmetafelsiteLW{WmetagabbroFWSWqWmetagabbrosCWFWmetagraniteqWmetagranitic{W|W}Wmetagraniticrocksofseveralproterozoicagesexposedinso}VmetagraywackeAWHWhWmetaigneousPWaWW@WmetalUWWWmetalimestoneCWFWIWJWNWUWVWWWXWZW[W\W_W`WaWbWcWdWeWgWiWW@Wmetalimestoneandlessermetasandstonemetasiltstonephyllit`VmetalimestonesaWWmetamaficLWmetamorphicAWBWCWEWFWGWKWLWPWYWeWlWpWqWwWmetamorphicallyQW*FsurfacesKWUWsurrounded`WsurroundingYWsurroundsNWsurveyFWLWQWXWYW[W\W^WaWbWeWfWgWlWnWoW{W}WW@WEWFWHWIWJWsystemEWUWsystems{WtableCWFWIWJWLWNWPWTWUWVWWWXW^W_W`WaWbWcWdWeWgWhWoWsWtWW@WBWCWDWGWIWJWKWtabulareWJWtabulateJWx1962@1990@b1997@2002@oa-1@Cabout@ages@amounts@=analyzed@andesite@are@kareas@%bare@belt@Iblue@breadth@burrows@pcarbonate-rich@dcharacter@characteristics@clusters@composition@bconstitutes@0contain@copter@9copter@99mentaryr@0contain@copter@999formations@fossils@givetian@8gray-green@Ahigh@linclusions@Oinvolves@+late@lesser@@light-gray-weatherin@alisburne@clittle@mayfield@jmegafossils@Pmetamorphism@Fmetasedimentary@!mica-rich@Bmiddle-early@mylonitic@Gold@zour@2patton@#phengite@present@Tpyrophyllite@quartz-rich@Dredeposited@represent@sandstone@{several@3shungnak@Nslate@Ysteep@gsurfaces@Qtailleur@*tan@their@thought@"too@undifferentiated@unlike@'values@wackestone@white@Hwithin@antiform@black@sequence@:lithicsandstoneandshalephyllitebelt@/mudstone@terrane@EH AK S B @CAABD FHJLB$A(A&C)A,E-B0D1 B54 B6D7 B;DJ? BLDKFJH[ @MAUBZAXAWCVE\G]I^K_M`AeDfAhEiBmDnFoArCsEtGuIvKwMxOyB}D~FHBACEBDFBACEACEpresentBWCWFWKWPWUWWW`WtW{WBWCWGWpresentedXWIWpreservedLW^W`WdWeWjW{WHWJWpressureLW{W|WpressuresYW{WpresumablyHWprevailedsWprimaryCWLWPWVWBWCWGWprobableGWLWPWXW^WbWtWAWBWCWIWprobablyFWVWgWnWproblemsCWGWproducedUW[W\WgWtWFWprogradationalUWprospectcWproterozoicKWPWSWYWeWlWqW}WBWCWJWprotoconodontseWJWprotolithEWKWPWSWpWBWCWprotolithsPWBWCWprovideTWdWtW{WpseudomorphsKWPWnWBWCWpsvqWpublicationsLWpumpellyiteFWpurePWBWCWpurple`WaWW@WpyroclasticaWeWuWJWpyroclasticsW@WpyrophylliteYWpyroxenezWWJWOWSWXWYW[W\W^W_W`WquartzAWBWGWKWLWMWOWPWUWVWYWZW[W\W^W_WaWquartzchertquartziteandslate-clastconglomeratewithminYVquartzconglomeratequartzitemetasandstonephylliteshalea[V\Vquartz-carbonate`Wquartz-chertVWquartz-micaHWKWPWquartz-muscoviteKW),ADark-gray to black phyllite and brown-weathering lithic sandstone, sandstone, and mudstone are exposed along the southern boundary of the schist belt. The unit varies in breadth along strike. In the Wiseman and Chandalar quadrangles, two subunits are recognized (undifferentiated on our map): a northern dark, fine-grained phyllite or phyllonite, and a southern metamorphosed lithic sandstone-rich unit. The two subunits are difficult to distinguish in the field. The northern unit is litholBogically homogeneous, locally well foliated, and locally contains small bodies of mafic schist similar in composition to those in the underlying Schist belt (Dsq; Moore and others, 1997b; Gottschalk and others, 1998). Little and others (1994) reported a strain gradient within the subunit that increases towards the underlying Schist belt; parts of the subunit may be a phyllonite tectonically derived from underlying quartz-mica schist in the Schist belt (Moore and others, 1997b). This subun\WJ and others, 1997). At one locality in the Ambler River quadrangle, undated stromatolites occur near the probable boundary with the Central belt (Hitzman and others, 1982). A dolostone breccia exposed nearby yielded Ordovician to Early Devonian conodonts (Table A-1, Ambler River quadrangle). As the contact has not been mapped well in this area, it is possible that the dolostone breccia and the stromatolites are part of the Central belt. In the western exposure of the calcareous schist unKit, at the Akiak antiform, similar stromatolites are part of a fault-bounded lens of the OpCc unit within the calcareous schist; there, they occur as part of a lithologic sequence similar to that found in OpCc. Metamorphic assemblages in the calcareous schist unit show that it experienced the same early high-pressure/low-temperature metamorphic and deformational history as the quartz-mica schist (Dsq; Gottschalk, 1990; Little and others, 1994; Dinklage, 1998). Chloritoid, glaucophane, psV'Leudomorphs after glaucophane and pseudomorphs after lawsonite are present in pelitic and mafic layers in the unit (Little and others, 1994; Dinklage, 1998; Till, A., unpublished data). Some calcareous lithologies contain pseudomorphs after glaucophane and lawsonite as well, but more typically consist of calcite, quartz, albite, chlorite, white mica, and ankerite, with lesser garnet, epidote, sphene, and rutile. The calcareous schist unit is equivalent to the "Kogoluktuk schist" of HitzmaMn and others (1982, 1986), "calcareous schist and marble of the Kallarichuk Hills" of Karl and others (1989b), parts of the Pzuc, Pzcq, and Pzcs units of Mayfield and Tailleur (1978); parts of the Pzsch, Pzca, DSso and DSsk units of Nelson and Grybeck (1980), the "calcareous schist" unit of Dillon and others (1986), the "Emma Creek schist", "unnamed calcareous schist", "Midnight Dome schist", and parts of the "Nugget Creek greenschist" of Moore and others (1997b), and the "calcareous schi FA6914quartz, calcite, and sphene, though exposures in the central Chandalar quadrangle adjacent to unit Dg contain hornblende, garnet, and biotite. Equivalent to unit "Dgs" and parts of unit "Dgh" of Brosg and Reiser (1964), parts of "Dv" of Nelson and Grybeck (1980), and parts of the "Nugget Creek greenschist" of Moore and others (1997b)@CPzsgD PaleozoicEMafic schist, Schist beltATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.FA6914N(SslateFWGWHWUWVWXW[W\W_W`WjWuWAWDWFWHWIWslate-clastYWslightCWslightlyKWslipEWsliverCWFWsliversCWFWslopeTWUWWWbWgWslopesPW~WsmallEWHWMWPWUWWWXW[W\WgWqWtW}WsmallerSWsmithLWUW^W_Wsn{WsneeZWdWeWqWsnowdenaWeWgWW@WsolitaryLW`WsolomonKWsomdWsomeCWFWIWJWKWLWNWPWTW[W\W^W`WaWdWeWgWjWlWnWqWtW{WW@WsomewhatcWtWsootyNWUWtWsorted^WsourceKWbWgWsourcesPWsouthAWFW[W\W`WcWwWyWsouth-centralBWsoutheastCWsoutheasternYWbWlWvWxWsouthernAWCWDWHWhWoWwWyWzW{W|W}WsouthernmostCWsouthwestAWCWQWsouthwesternDWEWFWIWYWgWspace`Wspan}WsparseAWspatialeWspatiallyZWspearYWspecificallyUWspessartinePWspheneKWOWPWqW}WsphericalKWspiculesPWTWVWXWspiculiticsWspinesNWspl[W\WbWgWspongePWTWVWXWsporesGWAWsrAW{WstabilizedQWstableRWYWstarvedTWstaurolitevWM,B) and include interlayered quartz-mica schist, metaquartzite, calcareous schist, graphitic phyllite, and metabasite. Bodies of granitic gneiss of unit pCg that occur within this unit yielded U-Pb zircon ages of 971 5 Ma (Late Proterozoic) and intruded marble (McClelland and others, 2006). The marble and possibly other parts of the unit are therefore older than 971 Ma, and are the oldest known rocks in the Brooks Range. The western part of the unit (Survey Pass quadrangle) consists predoCminantly of marble, mapped as "Skajit Limestone" (DSsk) and "Orange dolomitic marble" (DSso) by Nelson and Grybeck (1980). No Proterozoic orthogneisses (pCg) are known. Some of the marbles in the southeastern Survey Pass quadrangle may indeed be Paleozoic. Dillon and others (1980) and Nelson and Grybeck (1980) reported kyanite from metasedimentary rocks in this unit, but metamorphic grade and history are not documentedCPzpCemDPaleozoic to ProterozoicJ# Fe reconsidered their findings (written communications to A. Till, 1992), and neither now suggest a Middle Devonian to Early Mississippian age for the assemblage. Therefore, the age reported in Smith and others (1978) and derivative publications (e.g., Hitzman and others, 1982; 1986) can not be supported by megafossil collections. However, Devonian conodonts have been recovered from the sequence (Table A-1, Wiseman quadrangle), and given the radiometric ages cited above, the unit is at leaGst in part Devonian. The presence of marble within the unit and relict pillow structure in metabasite indicate that deposition was submarine. Hitzman and others (1986) thought the Ambler sequence originated as a compositionally bimodal volcanic association erupted on a rifted continental margin. The Ambler sequence has a shared structural and metamorphic history with the other lithologic packages in the Schist belt (Hitzman and others, 1986); see the introduction for discussion of that ]VHn both subunits in the Wiseman area. Marble in the western part of the unit hosts a Late Proterozoic granitic orthogneiss (unit pCg: 705 35 Ma; Karl and Aleinikoff, 1990); at least part of the unit must be Late Proterozoic or older. In the eastern part of the unit, near the village of Wiseman, Silurian to Devonian conodonts were recovered from a dark gray marble containing black calcite "clasts". Early Devonian (Lochkovian) conodonts were recovered from a dark gray fine-grained dolostoIne lens in the same area (Moore and others, 1997a). In the Baird Mountains quadrangle, conodonts of Middle Ordovician to Middle Devonian and Silurian to Mississippian age have been identified. All but one of the Late Devonian granitic orthogneisses (Dg) within the Schist belt are associated with DpCsc; this may indicate that the protolith of DpCsc was host to Late Devonian plutonism. Skarns around orthogneisses in the Chandalar quadrangle occur within the calcareous schist unit (Newberry^\F and mafic-rich rocks are known in the western and eastern parts of the belt; in these areas, calcite-chlorite-albite schist, chlorite-albite schist, and marble are common, and quartz-rich rocks are uncommon. In the western part of the schist belt, in the Akiak antiform (Sheet 2), these rocks are characterized by abundant albite porphyroblasts and are shown with an overlay of vertical lines. Similar mafic- and carbonate-rich rocks occur near Wiseman. Also present in near Wiseman is a seGcond lithologic subunit, shown with an overlay of crosses. This subunit is dominated by metachert (mm-cm scale laminated quartz-rich rock) and calcareous schist, and contains several types of metaconglomerates. The metachert commonly contains cm-scale lenses and thin, mm-thick layers of spessartine (Mn-rich) garnet and mafic metatuff. Metabasite bodies are associated with the metachert as well (A.B. Till, unpublished data). The medium-gray marble with the black calcite "clasts" is found i_]Dserved in outcrop. In the Wiseman area, light-gray- and orange-weathering, medium-gray platey marble is interlayered at a scale of meters with brown- and orange-weathering calcareous schist and impure marble. The medium-gray marble contains subrounded to subangular clasts of black calcite 0.2-6.0 mm in diameter. The black calcite grains are rich in graphite and make up 5-60% of the layers that contain them. Some clasts show relict internal textures, including ghosts of radiolarians and Esponge spicules, bivalves, volcanic textures (replaced by calcite), and fine graphite laminae. The matrix does not contain graphite and is composed of calcite with very small amounts of plagioclase and white mica. In some outcrops, the fine-scale, rhythmic interlayering of this marble with calcareous schist is suggestive of a turbidite protolith. It is likely that the calcareous schist unit is composed of several lithologic packages that have unknown depositional relationships. Carbonate-$^Bonly interlayered; pelitic interlayers and pelitic components in calcareous schists are also characteristic. Calcite marble comprises up to 40% of the unit locally, but generally forms less than 25%. Where marble is present, layers, lenses, and boudins of light-gray-weathering coarsely crystalline, pure calcite marble meters to 10's of meters thick form bare, steep slopes and ledges. Rare dolostone occurs as lenses up to several meters thick. Graphitic varieties of carbonate rocks (marblCe and dolostone), quartz-rich schists, and albite-rich schists are typical of the unit, as are chloritic varieties of marble, dolostone, and metaquartzite. Metabasite, metadiorite, and chlorite-albite schists are characteristic, but vary greatly in abundance along the strike length of the unit. Metaconglomerates that contain quartz or carbonate clasts are volumetrically minor but are found at several localities. Rarely, textures suggestive of primary sedimentary relationships can be ob+*+ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A2650AHeterogeneous mix of finely laminated, mostly mylonitic lithologies derived in part from adjacent units exposed in the eastern Wiseman and western Chandalar quadrangles. Unit is recessive, poorly exposed, and includes large (up to 0.5 km across) bodies of black quartzite and smaller exposures of quartz-rich schist, metagabbro, dark-brown marble, and relatively undeformed metasandstone and metasiltstone (Moore and others, 1997b; Till, unpublished data). In thin section, minerals are strai@clight-gray-weatherinPWeWBWCWJWlight-greenqWlike[W\WtWFWlikelyFWKWPWSWUWWW`WcW}WBWCWlimeTW`WsWlimestoneTWUWXW^W_W`WjWlWrWsWtWuWDWIWlimestone-pebble`WlimestoneissWlimestones_WDWlimitedLWUWfWmWlimoniticaWW@WlimyXWHWIWlineaWeWW@WJWlineatedCWGWlineationsAWEWVWlinesPWBWCWlinkYWmCWFWmaAWEWKWLWmaficAWBWCWFWHWKWLWOWPWmaiyumerakCWmajorKWPWmakePWmanyKWmapAWBWCWFWGWHWIWJWKWOWmappableNWmappedCWmappingKWmarbleIWJWKWLWNWPWmarblesNWPWmarginLWmarineAWBWmarionKWmarksHWmassiveAWJWKWLWNWOWPWmatrixPWmatrix-supportedFWmaunelukKWmaximumKWmayFWGWHWIWJWKWMWNWmayfieldDWIWJWKWLWMWmcclellandLWmeasuredAWmedium-beddedGWNWmedium-dark-grayNWmedium-grainedGWMWmedium-grayPWmedium-gray-weatheriLWmedium-light-grayNWmegacrysticLWmegacrystsLWmegafossilLW0compositionHWUW{WcompositionallyLWcompositionsAW{WcompriseCWcWGWcomprisesPW[W\WbWBWCWFWconcentratetWconcordantKWconcretionsTW^WHWcondensedeWJWconditionsLWYWqWwW{W|WconfirmVWXWIWconformableJWdWsWconformablyTWsWconglomerateAWTWUWVWXWYW[W\W^W_W`WaWeWhWtWuWW@WDWFWHWIWJWKWconglomerateandfinergrainedsedimentaryrocksexposedaloAVconglomeratesYWconglomeraticBWconodontCWLWTW_WcWgWjWoWrWsWDWGWconodontsCWFWIWJWLWNWPWUWVWWWXWZW^W_W`WaWbWcWdWeWgWhWmWsWtWuWW@WBWCWDWGWIWJWKWconsiderCWGWconsideredJWKWLWVWYWconsistPWZWbWeWBWCWJWconsistentUWYWconsistingaWW@WconsistsTWUWXW[W\W^W`WbWeWlWsWtWFWHWIWJWconsistsinascendingorderofdevonianmarinesedimentaryrUVconstituteqWWNWPWTWVWYWZW`WaWdWpWtW{WW@WBWCWcontactsFWUWWWYW^WaWcWsWtW{WW@WalisburneCWTWUWVWWWXWZW[W\WbWsWtWFWGWIWlisburne-siksikpukTWlithicFWGWHW^W_WaWbWrWW@WAWDWHWlithlogicallyCWGWlithofaciesJW`WcWdWeWgWsWJWlithologicKWLWPWaWgWjWpWuWW@WBWCWlithologicallyCWHWPWWW[W\WaWbWW@WBWCWFWGWlithologiesCWFWKWNWPWQWRWSWdWeWlWqWBWCWGWHWJWlithologylWmWlithostrotionidZWlowerJWQWRWTWUWlpmcUWWWlreeCWmCWFWmaAWEWKWLWPWQWmadeUWmaficAWBWCWFWHWKWLWOWPWRWUWmagnetite-bearingQWmainlyTWmaiyumerakCWmajorKWPWQWRWVWmakePWmametTWXWmanyKWmapAWBWCWFWGWHWIWJWKWOWTWUWWWXWmappableNWmappedCWPWWWmappingKWmarbleIWJWKWLWNWPWQWSWVWmarblesNWPWmarginLWmarineAWBWTWUWmarionKWmarksHWmaroonUWmassiveAWJWKWLWNWOWPWUWWWmaterialUWmatrixPWYWmatrix-supportedFWmaunelukKWmaximumKWmayFWGWHWIWJWKWMWNWPWQWSWUWVWYWafossilLWpcarbonate-richPWbWBWCWcarboniferousTWUWVWtWcarlsonAWBWCWFWGWcarnianUWcarterbWeWJWcastsbWcbJWcceWJWcentersnWcentimeterKWNWqWcentimeter-scaleKWcentimetersqWtWcentralCWFWIWNWPWQWSWUWVWYWaWeWgWiWkWmWoWtW{W}WW@WBWCWEWGWHWJWcephalopodsTWbWHWchancellorideWJWchandalarEWHWKWPWSW_W`WaWdWeWgWiWjWoWtWvWwWxWyWzW{WW@WBWCWDWEWJWchandlertWHWchannelstWchapmanUW_WDWUT2CG range in age from Devonian to Jurassic; chert and limestone in the matrix-free mlange yielded Devonian, Mississippian, Pennsylvanian-Permian, Triassic, and Jurassic fossils. Chert and argillite in the matrix-free mlange were originally mapped as Etivluk Group by Karl and others (1989b), but later reassigned by Karl (1992)#CMzDmDMesozoic? to DevonianEVIgneous and sedimentary rocks of the Maiyumerak Mountains, Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.3A6982M-Breen pelitic schist. Age control is limited to one locality in the Baird Mountains quadrangle, which yielded early Middle Ordovician conodonts (Karl and others, 1989b). The faunal assemblage and lithology of the host rock are similar to the Ordovician part of unit OpCc. Karl and others (1989b) suggested that the part of this unit exposed in the Baird Mountains quadrangle represents a basin that sat between the carbonate platforms on which units DOb and DOc were deposited. Equivalent toC@ the "metasedimentary and metavolcanic rocks of Tukpahlearik Creek" of Karl and others (1989b), parts of "Pzcs", "Pzmq", "Pzi", "mi", and "Pzm" of Mayfield and Tailleur (1978), parts of "DSso", "DSsk" and "Pzclq" of Nelson and Grybeck (1980), and parts of "Dc", "Dbb"?, "Dm", "Dbs", and "DSk" of Dillon and others (1986)CPzpCcmDPaleozoic to ProterozoicEgMetasedimentary and metavolcanic rocks, undivided, Central belt and part of Northern thrust assemblagesQsteepPWBWCWsteinkernseWJWsteppedqWstilpnomelanepWstorm`Wstorm-influencedTWstraddlehWKWstraddlingoWstrainHWstrainedSWYWstrataCWJWNWTWUWVWXWZW[W\W`WbWcWdWeWgWsWtWFWGWIWJWstrataboundJWstratifiedAWstratigraphicUWVWYWeWhWJWKWstratigraphicallyUWstratigraphytWstreamDWUWstretchedYW[W\WFWstretchingAWEWVWstrikeHWPWBWCWstromatolitesPWZWeWBWCWJWstromatoliticeWJWstromatoporoiddWsWstromatoporoidsJWNW`WcWdWgWstronglyAWKWVW_WtWDWstrontium{WstructuralCWJWKWLWUWVWYWGWstructurallyDWFWKWstructureLWEWstructuresHWLWVW^W_WcWdWeWgWDWHWJWJWsubunitsCWHWPWTWeWsucceededaWsuccessionTWUWVW[W\WbWcWeWsuccessionsVWsuccessiveAWsuchHWKWbWsuggestEWKWLWTWaWeWsuggestedFWLWVWYWsuggestingAWsuggestivePWsuiteLWsulfideJWLWWWsulfidesUWsummarizedVWsupportedLWsupportstoneseW/oCand Mamet (1978, Till Creek and Tinayguk River sections; see also Dumoulin and others, 1997). The Kayak is dark gray to black shale with subordinate beds of quartzitic sandstone and argillaceous, fossiliferous limestone. The lower part of the Lisburne (Wachsmuth Limestone) gradationally overlies the Kayak and consists of argillaceous limestone overlain by cherty, locally vuggy dolostone; it is mainly Early Mississippian (Osagean) in age and was deposited in an open marine environment. The Dupper part of the Lisburne (Alapah Limestone) is thinly interbedded black lime mudstone, shale, and chert and contains phosphatic pisolites, cephalopods, sponge spicules, and radiolarians; it is Late Mississippian (Meramecian through late Chesterian) and formed in deeper water slope and starved basin settings. A conodont collection from the upper Lisburne is late Meramecian-early Chesterian and has a CAI of 4-4.5 (Table A-1, Wiseman quadrangle). Post-Carboniferous strata (Siksikpuk and Ot mappedBWCWDWGWmappingKWmarbleIWJWKWLWNWPWQWSWVW`WaWcWdWeWfWgWhWjWlWmWoWpWqWrWW@WBWCWJWKWmarblesNWlWBWCWWWWWWWWPmayfieldDWIWJWKWLWMWPWVWYW[W\W^WaWbWeWiWkWmWqWsWW@WBWCWFWHWJWmcYWZW[W\WFWmcclellandLWlW}WmcpUWWWmdcpbWfWmde]W^WaWW@WHWmdersWmdkUW^W_WDWHWmdlUWmeasuredAWmedium`WmWpWsW}Wmedium-beddedGWNW^WAWmedium-crystallineUWmedium-dark-grayNWmedium-grainedGWMW^WAWHWmedium-grayPWZWBWCWmedium-gray-weatheriLWsWmedium-light-grayNWmegacrysticLWmegacrystsLWmegafossilLWrW%:areAWBWCWEWFWGWHWIWJWKWLWNWPWQWRWSWTWUWVWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWlWmWnWpWqWsWtW{W}WW@WAWBWCWDWEWFWGWHWIWJWareaAWBWCWDWFWGWKWPWTWUWWWYW[W\W^W_W`WaWbWeWgWjWnWrWsWtWwWW@WAWBWCWDWFWGWHWJWWJWWWWWHWJWWWWWfhighCWGWhigh-energyVWhigh-pressureLW{Whigh-pressure/low-tePWBWCWhigh-strainEWhighlyaWW@WhighwayeWJWhillsAWDWFWJWKWPWBWCWhimmelbergDWhistoryJWKWLWPWlWBWCWhitzmanCWDWJWKWLWPWBWCWGWhomogeneousHWoWhorace{WhorizontaltWhornVWhornblendeCWqWuWzW{WEWGWhornfelszWhughesAWFWIWhummockyHWhuntKWUW]W^W_WaWpWhyaloclasticCWhydrothermalJWhyolithidseWhypabyssalaWiLWiceWichnofossilsLWidentificationsWidentifiedCWPWYWifKWYWigneousCWFWLWimbricateCWimbricatedCWimmediatelyUWimpurePWaWbWeWjWpWinAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWzW{WincludeKWNWUWVWXWZW^W`WbWcWdWeWjWlWpWrWsWtWuWincludedGWKWLWUWXWYW[W\W^W_W`WaWeWtWincludesCWIWJWNWSWUWXW[W\W`WaWbWcWdWeWgWmWuWntAConsists, in ascending order, of Devonian marine sedimentary rocks equivalent to unit Dmu, sandstone, conglomerate, and shale of the Endicott Group (Devonian and Mississippian), limestone and tuff (Mississippian), chert and phyllite (Carboniferous), and Etivluk Group (Carboniferous to Jurassic), exposed in the northwestern Baird Mountains quadrangle. All unit contacts within this succession are gradational. The sequence also includes limited exposures of less stratigraphically well-defineBd shale (Devonian) and limestone (Devonian and (or) Mississippian). The sequence contains several units shown separately on this map elsewhere in the west-central Baird Mountains quadrangle; structural complexity and small scale of exposures precludes delineating them on this section of the map. As a group, the units were combined into the Kivivik sequence by Karl and others (1989b). The Devonian marine sedimentary rocks include green, gray, and maroon siliceous and calcareous phyllite,omGers, 1982) are tentatively recognized in this area. Regional correlations suggest an age of Early Triassic through Middle Jurassic and a shelf depositional environment for these rocks. The upper contact of the Otuk is not exposed in the map area CJCsDJurassic to CarboniferousEGSedimentary rocks, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A5001hnEuk formations) were documented by Adams (1991, 1994, Savioyak Creek and Gray Mountain sections; see also Adams and others, 1997). The Lisburne-Siksikpuk contact is sharp and undulatory; the basal Siksikpuk contains phosphate pebbles, trace bioclastic carbonate grains, and Mississippian foraminifers interpreted as reworked from the underlying Lisburne. The Siksikpuk consists, in ascending order, of siltstone with burrows and grazing traces (subunit A), silty shale and shale (subunits B1, B2F), siliceous shale and radiolarian chert (subunit C), and cherty shale with concretions of carbonate and barite (subunit D). The section is variegated in color throughout and thought to be Permian on the basis of regional correlations; it formed in a storm-influenced shelf setting. The contact with the overlying Otuk is not exposed; elements of all four Otuk members (shale, chert, and limestone informal members, as well as black, organic-rich shale of the Blankenship Member of Mull and othd'burrowsTWtWbutCWJWKWLWNWPWSWTWUWVWXW[W\W^W`WbWcWdWeWgWlWrWsWtWBWCWFWGWHWIWJWbyAWCWGWJWKWLWPWTWUWVWWW[W\W^W_W`WaWcWdWeWfWlWoWpWqWrWtWuW{WW@WAWBWCWDWFWGWHWJWcTWsWBWCWJWcaiCWTWXWsWtWGWIWcaisUWcalc-silicateQWcalcareousKWLWPWUW[W\W^W_W`WaWbWcWeWfWlWmWoWpWqWsWtWW@WBWCWDWFWJWcalciteKWPWqW{W}WBWCWEWcalcite-chlorite-albPWBWCWcalcitizedbWcalled`WsWcallsVWcambriancWeWgWuWJWcanCWKWLWPWuWBWCWGWcapebWcaradoceWJWcarbonaceousLWUWWWeWgWkWJWcarbonateCWFWIWJWNWPWTWVWZW`WaWbWcWdWeWgWjWmWrWsWtWuWW@WBWCWGWJWcarbonate-andBWCWcarbonate-maficBWCWWWWWCWWWWWEsexposureCWPWiWoW}WBWCWGWIWexposuresLWQWRWSWUWVWYW[W\WcWeW{WEWFWJWextendWWWWWxtrusiveAWeyesLWfabricsEWfaciesFWQWRWUWYWZWfallCWfamennianUWfamennian-kinderhookXWfanBWHWfaultCWEWFWJWNWUWVWfault-boundedCWDWIWPWVWXWfault-boundedblocksofmarblemetalimestoneanddolostonetIVfaultsFWUWfaunalLWfavositidLWfeaturesHWVWfeldsparLWfeldspathic[WfelsicEWLWfewLW[WfieldHWNWPWfieldsCWfindingsLWfineGWKWMWNWPWUWVWfine-crystallineNWfine-grainedBWHWPWUWfine-grainedtoconglomeraticsandstoneandfine-grainedlamBVfine-scalePWfinelySWfinerAWflankCWflat-lyingUWflatteningAWflowLWflowsUWfluid-rockLWfluvialUWfoldedKWQWfoldsKWUWVWfoliatedAWCWHWKWUWfoliationKWMW[Wfoliation-formingCWfoliationsEWfollwedAWforKWLWNWTWUWWWforaminifersCWTWUWXW[WforkKWUWformNWPWYWformationEWTWUWWWXWZW1Czg lineations and kinematic indicators suggesting top to the southwest movement during deformation of the metasedimentary rocks. Clast compositions record successive unroofing of the Angayucham terrane (JDab), followed by the Schist belt and the correlative schist of the Ruby terrane (Nilsen, 1989; unit PzpCsr on this map). Equivalent to Kqc and Kmc of Patton and others (2005)VCKsD CretaceousE]Conglomerate, sandstone, and shale, Angayucham Terrane, Serpentinite, and Yukon-Koyukuk BasinATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A2180~Cothers, 1967). The Kayak is black slate and phyllite with thin orange-weathering fossiliferous metacarbonate interlayers; it contains echinoderm debris, horn corals, brachiopods, and mollusks, as well as phosphatized bioclasts (including gastropods, ostracodes, bryozoans, and sponge spicules) and Early Mississippian (Kinderhookian) conodonts that indicate a shallow-water, relatively high-energy depositional environment (Table A-1, Ambler River quadrangle; A. Harris, unpublished fossil repoDrt, 1994). The Lisburne Group (Schrader, 1902; Bowsher and Dutro, 1957) is thin- to thick-bedded dolostone, metalimestone, and marble with nodules and layers of black chert, brachiopods, echinoderm debris, and corals of Mississippian (probably Meramecian) age (Mayfield and Tailleur, 1978; Toro, 1998). Lisburne conodonts are of Early and Late Mississippian age; restricted age calls include middle Kinderhookian-Osagean, late Meramecian, and latest Chesterian (Table A-1, Ambler River quadrangmuC and calcareous and quartzose metasiltstone, metasandstone, and metaconglomerate. No dated fossils are in this sequence, but correlative rocks in the west-central Baird Mountains quadrangle, shown as Dmu on this map, contain conodonts of Middle and Late Devonian age (Table A-1, Baird Mountains quadrangle; Karl and others, 1989b). These rocks formed in shallow marine depositional settings and are equivalent to Dmu of this map and the Nakolik River unit ("Dnu") defined by Karl and others (1D989b). The Endicott Group (Tailleur and others, 1967) is made up of Hunt Fork Shale (Chapman and others, 1964), Noatak Sandstone (Smith, 1913; Dutro, 1952; Nilsen and others, 1985), Kanayut Conglomerate (Bowsher and Dutro, 1957), and Kayak Shale (Bowsher and Dutro, 1957). The Hunt Fork is gray to green or black phyllite with intercalated metasiltstone and metasandstone; it is locally intruded by massive mafic sills and dikes and at one locality includes a 30-m-thick section of pillowed(?tvE) mafic flows (Ellersieck, 1985; Karl and others, 1989b). The Hunt Fork contains brachiopods and mollusks of Late Devonian (late Frasnian or early Famennian) age in the west-central Baird Mountains quadrangle (Nakolik sequence of Karl and others, 1989b). The Noatak is commonly cross-bedded quartz metasandstone, metasiltstone, and maroon and green phyllite; it has yielded Late Devonian brachiopods in the west-central Baird Mountains quadrangle, where it is shown on this map as Dn. The KanayFut is cross-bedded quartzite, pebbly quartzite, and metaconglomerate that has produced no dated fossils in the Kivivik Creek sequence. The Kanayut is shown as unit MDk elsewhere on this map. The Kayak is dark gray to black, siliceous or calcareous slate and phyllite, with subordinate intercalated metalimestone, metasiltstone, and metasandstone; it contains Early Mississippian conodonts and foraminifers; it is part of units Mkl, Mkkl, and Mu elsewhere on this map. The Endicott was deposituwGed in a progradational, dominantly marine deltaic system; only the Kanayut formed chiefly in nonmarine (fluvial) settings (Moore and Nilsen, 1984). The limestone and tuff subunit is orange-, tan-, or light-brown-weathering metalimestone, metatuff, and metavolcaniclastic rocks, and subordinate sills and plugs of intermediate to mafic composition. Metalimestone contains conodonts of early Early Mississippian (Kinderhookian) age. The unit is laterally discontinuous and forms lenses associateHd with the Kayak; similar volcanic strata occur in the Kayak to the north (e.g., Howard Pass quadrangle; see Mull and others, 1997). The subunit is equivalent to map unit Mlt of Karl and others (1989b). The chert and phyllite subunit consists of black carbonaceous metachert, siliceous or calcareous phyllite that may have a distinctive silvery blue (phosphatic?) coating on weathered surfaces, and subordinate interlayers of black metalimestone and quartzose metasandstone. Limestone containsvxI conodonts of latest Devonian (late Famennian) through Mississippian age. A low-oxygen slope or basin depositional setting is inferred. The subunit commonly contains abundant iron sulfides; stream sediment and rock samples contain elevated zinc, silver, and other metal values (Karl and others, 1985; Schmidt and Allegro, 1988; and Zayatz and others, 1988). Equivalent to map unit lPMc of Karl and others (1989b), this subunit is shown as Mcp elsewhere on this map and is similar to and likely Jcorrelative with the Kuna Formation (Mull and others, 1982) of the Lisburne Group (Schrader, 1902; Bowsher and Dutro, 1957). The Etivluk Group (undivided) is maroon, red, green, gray, black, and variegated chert and siliceous argillite, minor calcareous siltstone and argillite, and rare maroon or gray limestone lenses. No dated fossils were reported from the Etivluk in this sequence, but it contains radiolarians of Middle Pennsylvanian to Early Permian, Late Triassic (early to middle CarniwyKan and late middle Norian), and Early Jurassic (Hettangian) ages to the west in unit MzDm of this map. The Etivluk formed in a relatively deep marine setting with little input of clastic material. The unit was defined by Mull and others (1982) for rocks in the Howard Pass quadrangle to the north of the map area; the Etivluk in the Baird Mountains quadrangle contains notably more shale in its lower part and more chert in its upper part than do correlative sections in the type area. Shale (Lmap unit Ds of Karl and others, 1989) is black, sooty, siliceous and calcareous; it contains lenses of chert with rare radiolarian ghosts and fine-grained quartzose and calcareous sandstone that yield brachiopods of Middle-early Late Devonian age. The subunit is coeval with Devonian marine sedimentary rocks at the base of the Kivivik sequence, but the depositional relation between the two units is unknown. Limestone (map unit MDl of Karl and others, 1989b) is white- to gray-weathering, lix.Mght- to dark-gray, fine- to medium-crystalline metalimestone and lesser dolostone. It is exposed in small, isolated outcrops that are typically fault bounded and may include rocks correlative with various units including the Nakolik River unit, Kayak Shale, and Lisburne Group. The overall succession of the Kivivik Creek sequence is similar to that in the west-central Baird Mountains quadrangle, immediately to the east of the sequence (Nakolik River sequence of Karl and others, 1989b). HowNever, outcrop patterns, stratigraphic details, and structural style of the two areas differ. Older rocks (specifically the Baird Group, DOb) are not present in the Kivivik Creek sequence, but are common in the west-central Baird Mountains quadrangle. The Kivivik Creek sequence is complexly deformed along numerous NE-trending faults and folds, while structural grain in the west-central Baird Mountains quadrangle is flat-lying. The Kivivik sequence has been included in the Central belt beoldFW_W`WDWolderCWDWJWLWPWUWVWYW[W\WcWeWfWgWlWuWBWCWFWGWJWoldestCW`WcWlWGWoldowjWuWoliveDWolive-coloredqWqWWSWTWUWXW_W`WaWbWcWdWeWfWmWnWqWoncoidseWoneFWKWLWPWUWWWXWZW_W`WeWgWmWnWonlyNWUWeWgWooidseWopPWcWdWeWgWmWopaqueKWopceWopenKWTWorCWDWGWHWJWKWLWPWUWWWXWYW[W\W^W_W`WaWbWdWfWgWhWpWorangeQWUW`WaWdWeWlWmWorange-weatheringPWVWXWaWcWfWmWorderTWUW[W\WordovicianFWLWPWcWdWeWgWhWjWmWoWorganic`Worganic-richTWoriginJWoriginalKW^W`WeWoriginally_WcWoriginatedLWorogenyCWorthoconebWorthogneissEWKWPWQWRWVWorthogneissesPWlWoseWosageanCWTWoscillationHWostracode[W\WostracodesVWXWdWotherCWKWLWNWPWRWUWWWXWaWgWlWqWothersAWBWCWDWEWFWGWHWIWJWKWLWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWlWmWoWpWqWukTW  sandstoneBWFWGWHWTWUWWWXW]W_W`WaWhWrWsWtWuWW@WAWDWHWIWKWsandstoneshaleargillaceouslimestonelimestonedolostonemTVsandstone-richHWsandstonesGWHWAWsandysWHWsatmWsavioyakTWscBWCWJWscaleNWPWUWWWqWBWCWEWscalesKWPWBWCWscatteredKWscbuWschistAWCWDWEWFWHWJWKWLWNWPWQWRWSWaWbWeWgWiWlWmWnWoWpWqWvWwWzW{W|W}WW@WBWCWGWJWWWWWWWW\WsWtWscleriteseWscvstWsectionSWTWUW^WaWcWdWeWgWpWqWrWtWsectionsTWUW`WtWsedimentUWsedimentaryAWCWHWPWUWVW^W_WaWbWdWeWgWuWsedimentationaWsedimentologically[W\WsedimentsCWseeKWLWTWUW^WsWseenHWsegregationMWsegregationsKWsemipeliticKWsemischistose[W\W^Wseparate^WseparatedKWseparatelyUWWWsequenceCWDWLWPWUW^W`WcWeWpWsWuWsequencesCWHWbWuWserpentiniteDWFWsetsuWsettingTWUWbWeWgWtWsettingsHWTWUWWW^WcWdWgWldemonstrateeWJWdenotebWsWdependingqWdepositLWdepositedTWUW^WcWeWgWmWsW~WHWJWdepositionHWLWaWeWW@WJWdepositionalCWHWPWTWUWVWWWYW[W\W`WaWcWdWeWsWW@WBWCWFWGWJWdepositionally[W\W_WcWfWDWFWdepositsBWJWLW`WbWtW~WderivativeLWderivedFWHWPWSWYWBWCWdescribedTWXWYWdWeWpWsWHWIWJWdescriptionsKW^WdesiccationsWdesignated^W_WDWdetailCWKWLWTWgWsWGWdetailedKW^WtWdetailsUW`WsWdetectableqWdetermined{WdetritalKWYWhWKWdetritusBWbWdettermanVWtWdevelopednWWWWWstinguishHWdistinguishedCWPWdistributedCWdistrictLWdividedKWdmuUWdmwGWdnUWdnuUWdoCWUWdobUWdocumentedJWTWdoesPWdolomiticQWdolostoneIWJWNWPWTWUWVWdolostonesJWdomePWdominantKWdominantlyGWKWUWdominantlygray-greenlithicsandstonelesserbrownquartzsGVdominatedPWdoonerakTWdpKWLWMWOWPWdpcscQWHJ+)ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.*A6850AGenerally fine grained, phyllitic to schistose, gray-weathering meta-argillite, black-weathering metaquartzite, marble, and brown weathering impure marble, exposed in a single area in the eastern Wiseman and western Chandalar quadrangles. Carbonate rocks include some dolomitic varieties. Lithologic layering is locally isoclinally folded, and foliation crosses layering in some outcrops. Oldow and others (1998) collected pre-Devonian conodont forms from carbonate rocks in the lower part .sAQuartzite, conglomerate, phyllite, metalimestone, slate, dolostone, marble, and chert. The succession occurs in several fault-bounded exposures in the east-central Ambler River quadrangle. Within the fault-bounded exposures, the intensity of deformation is variable. Primary sedimentary features are recognizable locally; intrafolial isoclinal folds and stretching lineations strongly overprint primary structures elsewhere. The Kekiktuk(?) is fine- to coarse-grained quartzite and quartz-chBert metaconglomerate with interlayers of red, green, and gray phyllite and rare carbonate; clasts are well rounded and as much as 10 cm in diameter. Toro (1998) questioned inclusion of these strata in Kekiktuk Conglomerate of Brosg and others (1962) and suggested they may instead correlate with Devonian siliciclastic rocks. The nature of the contact between the Kekiktuk(?) and the Kayak Shale (Bowsher and Dutro, 1957) is uncertain; both units are part of the Endicott Group (Tailleur and sEle; A. Harris, unpublished fossil report, 1994; Toro, 1998). Mull and Tailleur (1977, p. B27) reported that "reddish-brown-weathering quartzose siltstone grading to black phyllitic shale" locally overlies the Lisburne near Shishakshinovik Pass; they considered these rocks to be Sadlerochit Group (Leffingwell, 1919; Detterman and others, 1975) but found no fossils to confirm their interpretation. The basal contact of the unit was interpreted as a major (angular?) unconformity by Mayfield aFnd Tailleur (1978), and was subsequently considered key to reconstruction of stratigraphic relations between upper Paleozoic and older rocks of the Brooks Range. However, Till and others (1988) and Toro (1998) considered the contact to be structural. Quartz-rich metasedimentary rocks at the contact contain deformed quartz clasts with 10:1 elongation ratios, ribbon quartz, and well-defined stretching lineations, and intrafolial isoclinal folds (Till and others, 1988; Toro, 1998). Deform0Gation is most intense near the contact with the subjacent granitic orthogneiss (Dg). Toro (1998) characterized the contact as a mylonitic shear zone. Although Mull and Tailleur (1977) correlated the Mkkl succession with parautochthonous rocks in the northeastern Brooks Range, fossil data summarized above indicate that the Kayak and Lisburne in Mkkl are in part older than their parautochthonous equivalents and correlate better with Carboniferous successions of the Endicott Mountains allocH]hthon in the central Brooks Range (e.g., Dumoulin and others, 1997; Dumoulin and Bird, 2002)  CMkklD MississippianEKekiktuk Conglomerate(?), Kayak Shale of Endicott Group, and Lisburne Group, Central belt and part of Northern thrust assemblagesb1962VWYW[W\WtWFW1964KWPWUW_W`WaWdWpWxWyWzWW@WBWCWDWEW1966YW1967TWUWVWXW^W_WcWsWtWDWHWIW1968IWJW1970JWeWJW1973CWGW1975IWJWVWbWtW1976tWuW1977CWLWVW[W\W^WFWGW1978DWIWJWKWLWMWPWTWVWYW[W\W^WaWbWeWiWkWmWqWtWW@WBWCWFWHWJW1979`WaW{WW@W1980KWLWPWQWRWXWYW[W\W^WaWbWfWlWmWnWoW{W}WW@WBWCWEWFWHWIW1981[W\WFW1982CWDWJWKWLWPWTWUWWWtWBWCWGWHW1983XWbWIW1984UWeWuWJW1985DWUWWW^W1986HWJWKWLWNWPWTWYW^W_WaWbWcWeWfWgWhWjWlWmWtWuW{WW@WBWCWDWHWJWKW1987AWKW`WbWcWdWeWgWtWuWyWJW1988AWBWCWEWFWHWUWVWWWYW^WbWcWdWeWfWqWsWGWHWJW1989AWCWKWQWRWUWqWwWGW1989aqW}W1989bFWKWPWUWWWXWZW]W^W_W`WaWcWdWeWgWiWmWrWsWW@WBWCWDWHWIWJWtWuWwWW@WAWBWCW1995LWZWdWeWqWwW{W|W|devonianCWFWGWHWIWJWKWLWNWPWUWVW^W_W`WaWcWdWfWgWhWrWsWuW{WW@WAWBWCWDWGWHWKWdevonian-earliestXWIWdevonian-mississippiWWdextralEWdfcaWW@WdgKWNWPWRWVWYWBWCWEWdghEWdgsEWdhf]WaWW@Wdhfs^WdiabaseCWGWdiagnostic[W\WFWdiagonalaWW@WdiagramsCWGWdiameterPWVW[W\W^WaWeWqWW@WBWCWFWJWJWWWdifferUWtWdifferentCWGWdifferentiatedXWdiffersTWtWdifficultHWdikesUW_WuWzWDWdillonHWKWLWPWTWYW^W_W`WaWdWfWhWjWlWmWtWuW{W}WW@WBWCWDWdinklageKWPWBWCWdioritic{W|Wdirect|WdirectlyKWdisconformablytWdiscontinuousKWUWXWdiscontinuouslygWtWdiscordant}WdiscriminationCWGWdiscussedtWdiscussionKWLWdisplayKW_WtWDWdisseminatedgWdistanceFWIWdistinctCWGWdistinctiveUWgWdistinctlyCWGWdistinguishHWdistinguishedCWPWBWCWGWdistributedCWgWGWdistrictLWXFAQuartz conglomerate, quartzite, metasandstone, phyllite, shale, and metalimestone in the Ambler River, Survey Pass, and Wiseman quadrangles. Includes metasiliciclastic and metacarbonate strata in Ambler River and Survey Pass quadrangles, most with few to no age constraints, assigned to various Mississippian units by Mayfield and Tailleur (1978) and Nelson and Grybeck (1980). In east-central Ambler River quadrangle, consists of undated quartz conglomerate that contains minor interlayers ofB coarse-grained quartzite and red and green phyllite (map unit Mc of Mayfield and Tailleur, 1978). Clasts are stretched and made of quartz, varicolored chert, quartzite, and gray slate. Here the unit resembles Kekiktuk Conglomerate of Brosg and others (1962). Along eastern border of Ambler River quadrangle, this unit comprises a depositional succession of, in ascending order, Kekiktuk Conglomerate, Kayak Shale (Bowsher and Dutro, 1957), and Lisburne Group (Schrader, 1902; Bowsher and DutrCaboutLWYWxWaboveDWLWVWYW`WdWeWJWabradedKWabstractLWabundanceBWKWPWBWCWabundantFWPWUWXWZW^WaWcWeWgWhWsWtWW@WIWJWKWaccessoryKWaccompaniedoWaccumulatedcWtWacrossCWLWSW[W\W`WqW{WFWGWacrotretideWgWJWactinoliteKWEWadamsTWtWadditional`WdWeWtWJWadjacentBWDWFWNWQWRWSW[W\WvWEWFWaffinitiesCWFWcWdWgWuWGWaffinityEWIWafterKWPWnWqWBWCWageAWCWEWFWGWIWJWKWLWNWPWSWTWUWVWWWXWZW[W\W^W`WaWbWcWdWeWfWgWhWmWoWpWqWrWsWtWvW{W|W}WW@WAWBWCWFWGWHWIWJWKWage-diagnosticYWYWYWleFWamphibolite-faciesCWEWanAWCWFWKWLWNWPWTWWWanalyzedLWanastomosingFWandAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWangayuchamAWCWDWFWangularVWanirakKWankeritePWantiformPWTWanyYWaphaniticLWapparentlyPWQWappearRWappearanceKWQWapproximatelyQWSWH3withinCWHWKWLWPWRWUWVWgWlWqWsW{W}WBWCWGWwithin-plateCWGWwolfcampiantWworkerstWworld-classLWwrittenLWfWyellow`Wyellow-brownsWyellowish-greenDWyieldIWUWuWyieldedAWCWEWFWGWKWLWNWPWUW[W\WaWfWhWlWmWoWqWrWuW{W|W}WW@WAWBWCWFWGWKWyorkcWdWyoungKWsWyoungerCW`WcWdWeWGWJWyoungestCW`WsWGWzayatzUWWWzincUWzirconLW^WaWlWqW{W}WW@WzirconsKWLW}WzoisiteKWzoneEWFWSWVWzonesqWalbite-richBWamblerLWamblersequenceschistbeltLVamphiboliteCWGWandAWBWCWDWGWHWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWuWW@WAWCWDWFWGWHWIWJWKWangayuchamAWBWCWDWGWangayukaqsraqqWqWyukon-koyukukbasinvolcangayukaqsraqqWWWWiniteandyukon-koyukukbasinvolcBVangayukaqsraqqWWWWWLWMWNWOWPWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWWformationsTWsWtWformedCWKWTWUWWWYWcWeWtW{WJWformsGWPWUWYWeWjWqWAWBWCWJWfossilCWJWVWXW[W\W^WbWdWgWFWGWHWIWfossiliferousJWTWVWXW_W`WbWtWDWIWIW13+ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6328APhyllite or slate, siltstone, sandstone, limestone, and chert exposed in two small areas in the northwestern Baird Mountains quadrangle and in a larger discontinuous outcrop belt in the northern Survey Pass quadrangle. In the Baird Mountains quadrangle, one occurrence of the unit is fault-bounded; the other includes map units Mk (Kayak Shale) and Mko (Kogruk Formation of the Lisburne Group) of Karl and others (1989b) and overlies Noatak Sandstone of the Endicott Group. In the Survey Pass+ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6360AQuartz- , chert-, quartzite-, and slate-clast conglomerate with minor thin layers of metasandstone and phyllite exposed in the Ambler River, Survey Pass, and Wiseman quadrangles. Quartz and chert clasts are most common; chert clasts are varicolored. The matrix of the conglomerate is composed of quartz, white mica, and chlorite, and clasts are typically stretched. Phyllite may be gray, green, or red. Rocks included in the unit resemble Kekiktuk Conglomerate of Brosg and others (1962), 3Date Mississippian endothyrid foraminifers in the Baird Mountains quadrangle (B. Mamet, unpublished fossil report, 1983), and middle Late Mississippian (late Meramecian-early Chesterian) conodonts in the Survey Pass quadrangle (Nelson and Grybeck, 1980). The Shublik Formation (Triassic) and Siksikpuk Formation (Permian), undivided, were reported to overlie the Lisburne Group in two small areas of the north-central and northeastern Survey Pass quadrangle (Nelson and Grybeck, 1980). These autEhors described the Siksikpuk as black slate and orange-weathering black chert and the Shublik as pink-weathering limestone but presented no age data to confirm the presence of post-Carboniferous strata. These rocks are not differentiated on this map and are included in MklCMklD MississippianEfKayak Shale of Endicott Group and Lisburne Group, Central belt and part of Northern thrust assemblages#phengiteLW{W|Wphillip_WDWphosphateTWphosphaticTWUWtWphosphatizedVWphylliteFWHWIWJWUWVWWWXWYWZW[W\W^W_W`WaWbWeWfWgWhWiWjWkWlWmWpWrWtWuWW@WDWFWHWIWJWKWphyllitefine-grainedschistandphylloniteofthecentralbiVpink`Wpink-weatheringXWpisoidseWpisolitesTWpittedKWplagioclaseKWPW^WplanarKW^W`Wplanes[W\WplantAWGW^WplateYWplateausCWplateyPWplatform`WaWbWcWeWgWplatform-margineWplatformalbWgWplatyKWgWplugsUWaWplusKWplutonNWQWplutonismPWpodsLWpolycrystallineKWpoorlyAWLWSW[W\W^W`WpopulationLWpopulationsKWporphyriesLWaWporphyriticaWportion_WpositionCWpossibleIWLWPWYWZW[W\WaWgWpossiblyCWcWpost-carboniferousTWXWpost-middleLWpowdermilkcWpreciseIWprecludesUWpredominantXWpredominantlyBWpredominateCWPWpredominatesNWprehnite-bearingCWprehnite-pumpellyiteAWCWpresenceJWLWXWeWDquartziticTWquartzoseUWVWeWsWJWquestionedVWradiating[W\WFWradiogenicuWradiolarianCWTWUWeWGWJWradiolariansCWFWPWTWUWbWBWCWGWradiometricLWrangeAWCWIWLWSWVWYWeWlWrWsWtWyW{WGWJWrangesCWFWGWranging{WrareCWFWKWLWPWUWVWaWhWW@WBWCWGWKWrarelyPWBWCWHWratermanLWratherLWratiosAWLWVWrb{WreactsYWreassignedrWrecessiveSWrecognizableVWdWpWrecognizedCWHWTWdWeWGWJWreconsideredLWreconstructionVWrecordAWYWaWqWW@WrecordedwWrecoveredLWPWaWuWW@WBWCWrecrystallizedbWgWsWrectangularKWredUWVWYW[W\WaWtWW@WFWreddishJWreddish-brown-weatheVWpWredepositedbWWFWreddishJWreddish-brown-weatheVWpWredepositedbWW250Flson and Grybeck (1980), and Dbc of Dillon and others (1986). Unit Mkkl also contains possible exposures of the Kekiktuk Conglomerate ,CMcDMississippian?ENQuartz-rich conglomerate, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A63202Band lack any age-diagnostic fossils. Conglomerates in the southeastern Survey Pass and southwestern Ambler River quadrangles are thought to sit in depositional contact with underlying metasedimentary rocks of the Ernie Lake area (PzpCem; Nelson and Grybeck, 1980; Dillon and others, 1986). If these contacts are indeed depositional, they record a critical stratigraphic link between upper Paleozoic and older rocks of the Brooks Range. However, a similar relationship in the eastern Ambler RiCver quadrangle between units Mkkl and Dg was shown to be structural (Till and others, 1988; Toro, 1998), and quartz-rich conglomerates associated with unit PzpCem are described as strained (Nelson and Grybeck, 1980; Dillon and others, 1986). Kyanite has been identified in at least four exposures of the unit in the Survey Pass quadrangle (Plate 2). Nelson and Grybeck (1980) suggested that the kyanite might be detrital, derived from underlying Late Proterozoic schists that also contain kya=eagesCWIWKWLWUW[W\WbWeWgWlWqWrWuW{W}WFWGWJWagnostideWJWairfallJWakiakPWeWBWCWJWalYWalapahTWtWalaskaCWIWZW`WcWdWeWgWsWGWJWalbianBWalbiteKWPWnWpW{W}WBWCWEWalbite-epidoteqWalbite-epidote-amphiCWQWRWnWqWGWalbite-micaKWalbite-richPWBWCWalbiticPWBWCWaleinikoffPWaW{W}WW@WBWCWalgaedWsWalignednWallNWPWTWUW[W\WgWsWzW{WBWCWFWallegroUWWWallochthonCWVWsWtWGWallowgWalongAWBWCWEWHWMWPWUW[W\W_WaWeWpWqWyWzWW@WBWCWDWFWGWJWalsoCWKWPWTWUWWWYW[W\W^WaWbWgWjWsW{WW@WBWCWFWGWHWalthoughCWVW[W\WFWGWaluminumYWamJWamawktWamblerAWCWDWFWIWJWLWMWNWPWVWYW[W\W^WaWbWdWeWgWiWkWmWnWqW{WW@WBWCWFWGWHWJWWJWJWJWJWWteandaqVamphibolite-faciesCWEWqWanAWCWFWKWLWNWPWTWWW_W`WbWcWdWeWgWqWsWtW{W}WBWCWW7:AQuartz conglomerate, quartzite, metasandstone, phyllite, shale, and metalimestone in the Ambler River, Survey Pass, and Wiseman quadrangles. Includes metasiliciclastic and metacarbonate strata in Ambler River and Survey Pass quadrangles, most with few to no age constraints, assigned to various Mississippian units by Mayfield and Tailleur (1978) and Nelson and Grybeck (1980). In east-central Ambler River quadrangle, consists of undated quartz conglomerate that contains minor interlayers ofB coarse-grained quartzite and red and green phyllite (map unit Mc of Mayfield and Tailleur, 1978). Clasts are stretched and made of quartz, varicolored chert, quartzite, and gray slate. Here the unit resembles Kekiktuk Conglomerate of Brosg and others (1962). Along eastern border of Ambler River quadrangle, this unit comprises a depositional succession of, in ascending order, Kekiktuk Conglomerate, Kayak Shale (Bowsher and Dutro, 1957), and Lisburne Group (Schrader, 1902; Bowsher and Dutrc+littleCWHWKWPWUWgWBWCWGWllandoverianbWlocalNWWW^W`WcWHWlocalitiesCWGWPWcWAWBWCWGWlocalityCWLWPWUWWWZW_WmWBWCWDWGWlocallyBWHWIWJWMWNWPWTWUWVWXWZW^W_W`WaWcWdWeWgWiWjWkWlWpWsWtW{WW@WBWCWDWHWIWJWoxygenUWWWlowerJWQWRWTWUW^W_WcWeWjWlowestjWlpmcUWWWlreeCWludlovianbWgWmCWFW_W`WeWfWmaAWEWKWLWPWQWaWlWmadeUW[W\WbWmaficAWBWCWFWHWKWLWOWPWRWUW_WaWeWmWnWmagnetite-bearingQWmainlyTW`WcWeWmaiyumerakCWcWmajorKWPWQWRWVW_WmakePW`WmakeseWmametTWXWmanyKWmapAWBWCWFWGWHWIWJWKWOWTWUWWWXWZW[W\W^W_W`WaWbWdWeWgWmappableNWmappedCWPWWW^W_WlWmappingKWmarbleIWJWKWLWNWPWQWSWVW`WaWcWdWeWfWgWhWjWlWmWoWpWmarblesNWPWlWmarginLWmarineAWBWTWUWmarionKWmarksHWmaroonUW^WaWmassiveAWJWKWLWNWOWPWUWWW_WaWcWdWeWgWmaterialUWbo)1997PWTWUWVWtW{WBWCW1997aKWPWBWCW1997bFWHWPWSW_WaWhWiWjWoWpWW@WDWEWKW1998FWHWKWPWQWRWVWYWeWjWuWBWCWJW2CWNWPWYW[W\WaWwWW@WBWCWFWGW2-3CWGW20^W`WeWgWuW{WJW2000GW^W`WaWW@WAWHW2001bWW207pb/206pbKW25PW250sW3YWtW{W30-m-thickUWaWW300_WxW300-400ocYW327{W35PW}W370-360KW372{W373-388uW375-395{W376ocLW378LW378-386LW390-396{W393aWW3kbYW4XWsWtW4-4.5TW4.5sWtW40PW`W400ocYW405LW40ar/39arEWhWqW416oc{W427oc{W432oc|W478uW5CWLW^WlW}W5-5.5UW5-60PW5.5XW50GWfW5079-84sW54.8EW5682ZW5683ZW6YWtW}W60CW680qW7aW{WW700-1850LW705PW}W750qW}W8CW8-km-longDW8.9{W80^W8494-96sW86AW96-112yW971lW}WaAWCWDWEWFWHWIWJWKWLWNWPWQWSWTWUWVWWWXWYW[W\W^W_W`WaWbWdWeWfWgWhWjWmWoWpWqWrWsWtW{W|W}WW:EcarbonaterockscentralbeltandpartofnorthernthrustassZVFCo, 1957) that consists of map units Mke, Mk, and Ml of Mayfield and Tailleur (1978); the succession is lithologically like that of our map unit Mkkl (which crops out ~10 km to the south) but has no reported age control. A similar succession, included in this unit, occurs in adjacent west-central Survey Pass quadrangle (map units Mke, Mk, Ml, and Mu of Nelson and Grybeck, 1980). These rocks have produced a few fossils, including crinoids, brachiopods, corals, and foraminifers, of Early and DLate Mississippian ages (Brosg and Pessel, 1977). The Kekiktuk in this area consists of semischistose metasandstone and metaconglomerate with minor interlayers of red, green, and gray phyllite (Nelson and Grybeck, 1980). Coarser layers contain quartz clasts as much as 2 cm in diameter; some intervals are calcareous and (or) feldspathic. Radiating clusters of chloritoid grew across foliation planes in some samples. Mu in all three of these areas is interpreted to depositionally overlie oldFEer rocks (units Pzm and Spl of this map) (Mayfield and Tailleur, 1978; Nelson and Grybeck 1980). Mu also occurs along the eastern border of Survey Pass quadrangle, where it consists of rocks tentatively assigned to the Kekiktuk and Kayak (Nelson and Grybeck, 1980) that have yielded no diagnostic fossils, and in a small area near the western border of Wiseman quadrangle, where Lisburne(?) metalimestone contains gastropods, molluscan and echinoderm debris, possible bryozoan, pelecypod, brachF;iopod, and ostracode fragments, and foraminifers of Mississippian(?) age (J. Dutro and A. Armstrong, unpublished fossil reports, 1980, 1981). Although the exposures in this unit may be correlative to those included in the unit Mkkl, they are relatively poorly characterized sedimentologically and paleontologically CMDk_101D&Early Mississippian? and Late DevonianEJKanuyut Conglomerate, Central belt and part of Northern thrust assemblages49 A6915pod, and ostracode fragments, and foraminifers of Mississippian(?) age (J. Dutro and A. Armstrong, unpublished fossil reports, 1980, 1981). Although the exposures in this unit may be correlative to those included in the unit Mkkl, they are relatively poorly characterized sedimentologically and paleontologically CMuD MississippianEKMetasedimentary rocks, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6915qextendsPWBWCWextensionFWextensiveKWextensivelysWextentSWextrusiveAWeyesLWfabriccWsWfabricsEWfaciesFWQWRWUWYWZW^W`WcWfWgWqWtWwWHWfallCWGWfamennianUW^W_WsWDWHWfamennian-kinderhookXWIWfanBWHWfaultCWEWFWJWNWUW`WGWfault-boundedCWDWIWPWVWXWdWeWpWBWCWGWIWJWfault-boundedblocksofmarblemetalimestoneanddolostonetIVfaultsFWUWcWfaunalLWgWmWfaunasgWfavositidLWfe-ti{WfeaturesHWVWbWgWfineGWKWMWNWPWUWVW^W`Wfine-crystallineNWfine-grainedBWHWPWUW^Wfine-grainedtoconglomeraticsandstoneandfine-grainedlamBVfine-scalePWfinelySWfinerAWflankCWflat-lyingUWflatteningAWflowLWflowsUWaWfluid-rockLWfluvialUWfoldedKWQWfoldsKWUWVWfoliatedAWCWHWKWUW^W_WaWfoliationKWMW[W\Wfoliation-formingCWfoliationsEWfollwedAWforKWLWNWTWUWWW_WbWforaminifersCWTWUWXW[W\WforkKWUW]W^W_WaW;y9BGranite, quartz monzonite, and granodiorite of the northern Ruby terrane, exposed along the southern boundary of the Chandalar quadrangle (Brosg and Reiser, 1964). K-Ar dates range from 1036 to 1106 Ma (Blum and others, 1987)CKgD CretaceousEGranitic rocksATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.:A2610AIntermixed granitic rocks, biotite schist, and hornblende hornfels; pyroxene hornfels and granitic dikes, associated with Cretaceous granitic rocks. All exposed in the northern Ruby terrane, along the southern margin of the Chandalar quadrangle (Brosg and Reiser, 1964)CKmD CretaceousE Migmatite;ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6300A=Shale and sandstone exposed in the northwest Baird Mountains quadrangle. Represents undifferentiated parts of the Endicott Group that are equivalent to the Hunt Fork Shale (unit Dhf), the Noatak Sandstone (unit Dn) and the Mississippian Kayak Shale (part of unit Mkl). Equivalent to "MDe" of Karl and others (1989b)=CMDeDMississippian and DevonianEOEndicott Group, undivided, Central belt and part of Northern thrust assemblages<Eer rocks (units Pzm and Spl of this map) (Mayfield and Tailleur, 1978; Nelson and Grybeck 1980). Mu also occurs along the eastern border of Survey Pass quadrangle, where it consists of rocks tentatively assigned to the Kekiktuk and Kayak (Nelson and Grybeck, 1980) that have yielded no diagnostic fossils, and in a small area near the western border of Wiseman quadrangle, where Lisburne(?) metalimestone contains gastropods, molluscan and echinoderm debris, possible bryozoan, pelecypod, brachF;iopod, and ostracode fragments, and foraminifers of Mississippian(?) age (J. Dutro and A. Armstrong, unpublished fossil reports, 1980, 1981). Although the exposures in this unit may be correlative to those included in the unit Mkkl, they are relatively poorly characterized sedimentologically and paleontologically CMDkD&Early Mississippian? and Late DevonianEJKanuyut Conglomerate, Central belt and part of Northern thrust assemblages?@eBlDkFjHiJN@@mApCvEuGtIrAA@}BBACEGIKM&C@PACEgGfI`KYMDASCEEDACECEDACEECECEDACEIKMDACEMDACEDACEDACECEDACEEACEDACEDACEDACEDACEEGIKMDACEDACEDACEKMDACEMDACEDACEGIKMMKMCCpbreadthCWHWGWbrecciaCWLWPWeWrWBWCWGWJWbroadFW~WbroadestCWGWbroadlyKWcWbrokenSWbrooksCWVWYWeWlWtW{WGWJWbrosgeGWKWPWVWYW[W\W^W_W`WaWdWfWpWtWxWyWzWW@WAWBWCWDWEWFWHWbrownGWLWPWXWaWjWsWW@WAWBWCWIWbrown-weatheringHWaWqWW@Wbrownish-grayKWbrownish-greenqWbryozoanXW[W\WhWsWFWIWKWbryozoansCWLWVWXWbWdWGWIWbuffJWmWbuild-upsJW`Wbuildups`W`Wuildups`WW.blackMWbWfWkWblackmetasedimentaryrockscentralbeltandpartofnortherfVblackphylliteandmetalimestonecentralbeltandpartofnobVblackphylliteandsiliceousphyllitecentralbeltandpartkVblackquartziteschistbeltMVbluecloudpWcalcareousPW@WBWCWcalcareousschistalbite-richsubunitschistbeltBVcalcareousschistmetachertandconglomeratesubunitschistCVcalcareousschistschistbeltPVcarbonaceousWWcarbonaceouschertandsiliceousphyllitecentralbeltandpWVcarbonateIWJWZWdWeWJWScarbonaterockscentralbeltandpartofnorthernthrustass@carbonaterocksofcosmoshillscosmoshillssequence@:eli@lithicsandstoneandshalephyllitebelt@/metamorphicrocksofmtangayukaqsraqcentralbeltandpart@nanielik@terrane@EH AK S B @CAABD FHJLB$A(A&C)A,E-B0D1 B54 B6D7 B;DJ? BLDKFJH[ @MAUBZAXAWCVE\G]I^K_M`AeDfAhEiBmDnFoArCsEtGuIvKwMxOyB}D~FHBACEBDFBACEACE+FATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.GA5140AMetamorphosed pillow basalt, hyaloclastic breccia, basaltic tuff, diabase, microgabbro, radiolarian and tuffaceous chert, minor metalimestone, and rare mafic schist in an imbricate package exposed along the southern boundary of the map area. The package varies significantly in breadth (north-south) along its exposure length; the area of broadest exposure is 8 km across (Pallister and others, 1989). Basalt and diabase predominate. Metachert occurs in both depositional (bedded and interpil;@B Ambler River quadrangle (unit Dss of Mayfield and Tailleur, 1978), northern Survey Pass quadrangle (unit Dhfs of Nelson and Grybeck, 1980), and northeastern Christian quadrangle (unit Dn of Brosg and Reiser, 2000). It also occurs as part of the Kivivik Creek sequence (unit JDk of this map) and the Endicott Group undivided (unit MDe of this map) in the Baird Mountains quadrangle (Karl and others, 1989b), and was mapped with the Kanayut Conglomerate (and thus included in unit MDk of this mCap) in the Wiseman quadrangle (Dillon and others, 1986). Throughout the map area, the Noatak overlies the Hunt Fork Shale and is overlain by the Kanayut Conglomerate (both are part of Endicott Group); both contacts are generally gradational. Dn consists of metasandstone and metasiltstone with subordinate interlayers of green, gray, and maroon phyllite and local ironstone concretions. Semischistose textures and minerals indicative of lower greenschist facies metamorphism occur locally, but @LF^are Late Devonian, locally Famennian (Brosg and Pessel, 1977; Nelson and Grybeck, 1980; W. Brosg, unpublished fossil compilation, 1988; Karl and others, 1989b). Conodonts from a thin limestone layer at the top of the unit in the western Baird Mountains quadrangle are of probable late Famennian age (Table A-1). Deposited in shallow-marine settings CDnDDevonianEFNoatak Sandstone, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6925dietrich_WDWdifferUWtWHWdifferentCWGWdifferentiatedXWHWIWdiffersTWtWdifficultHWdikesUW_WuWzWDWdillonHWKWLWPWTWYW^W_W`WaWdWfWhWjWlWmWtWuW{W}WW@WBWCWDWHWKWdinklageKWPWBWCWdioritic{W|Wdirect|WdirectlyKWdisconformablytWdiscontinuousKWUWXWIWdiscontinuouslygWtWdiscordant}WdiscriminationCWGWdiscussedtWdiscussionKWLWdisplayKW_WtWDWdisseminatedgWdistanceFWIWdistinctCWGWdistinctiveUWgWdistinctlyCWGWdistinguishHWdistinguishedCWBWCWGWdistributedCWgWGWHWdistrictLWdisturbed{W"tooFWWW}WtopAW^WsWtWtoroQWRWVWYWeW{WJWtourmalineKW^WtowardsHWtozitnaCWGWtraceCWTW^WtWGWtracesTWtransitionaWW@Wtransitional`WHWtransposedpWtrcsTWtWtrembleyhWKWtrendKWtrendingrWtriassicCWTWUWXWoWrWtWGWIWtrilobitesgWuWtrough^WtWHWtuffAWCWUWrWGWtuffaceousBWCWaWW@WGWtuffsJWtukpahlearikmWturbiditeHWPWbWBWCWturbiditesbWeWpWJWturbidityeWJWturner{WtwelvemileCWGWtwenty-sevenKWtwoCWEWHWLWPWUWXWcWeWhWrWuW}WBWCWGWIWJWKWtwo-holegWtypeUW^WtypesNWPWsWBWCWtypicalKWLWPWgWBWCWtypicallyCWKWPWUWYW^WoWqWBWCWEWGWu-pbLWaWlWqW{W}WW@WultramaficKWuncertainVWZWuncommonPWBWCWunconformablytWunconformityVWundatedNWPW[W\WbWBWCWFWundeformedSWunderwWunderlainBWCWunderlieiWunderlyingHWJWTWYWaWW@WunderstoodLWunderwentnWWAEGy and weakly foliated parts) display lower greenschist-facies minerals CDhfD Late DevonianEEHunt Fork Shale, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000. A6927AMetalimestone and lesser metasandstone, metasiltstone, phyllite, and minor conglomerate. Dl includes limestone of Nakolik River (map unit Dnl) of Karl and others (1989b) in the Baird Mountains quadrangle, limestone layers in the Chandalar quadrangle called Dl by Brosg and Reiser (1964), and limestone layers of the Beaucoup Formation (map unit Dbl) in the northwestern Christian quadrangle (Brosg and Reiser, 2000). The Beaucoup Formation was defined by Dutro and others (1979). Dumoulin an Bd Harris (1987, 1994), Dillon and others (1987), Table A-1 (Baird Mountains and Chandalar quadrangles), and Alaska Paleontological Database give additional details on lithofacies and fossils of this unit. In the Baird Mountains quadrangle, Dl consists of generally fossiliferous metalimestone and marble, subordinate quartz-carbonate metasandstone and metasiltstone, and phyllite (Karl and others, 1989b). Carbonate rocks are light to dark gray and fine to coarse grained. Original textures, whCere preserved, are mainly bioclastic packstone and wackestone; fossils include solitary and colonial corals, stromatoporoids, brachiopods, and pelmatozoan debris. Fossiliferous carbonate strata commonly form mounds several decameters across surrounded by lime mudstone and (or) siliciclastic rocks; some build-ups may have been organic reefs. Metasandstone weathers yellow to orange, is fine to medium grained, and planar to cross-laminated; metasiltstone and phyllite weather purple and are poUformNWPWYW`WqWBWCWformationEWTWUWWWXWZW`WaWsWtWW@WIWdark-graytoblackphylliteandlessergray-greenphyllitew_VDVdark-gray-weatheringLWdark-greenmWdark-green-weatherinLWdarkerdWdashedqWdasycladaceandWdataCWFWKWPWSWVWXWeWfWgWtW{WBWCWGWIWJWdatabaseIWZW`WcWdWeWgWsWJWdatedCWTWUW^W`W{WGWHWdatesyW{WdbbWdbbaWmWW@WdbcYWaWW@WdbcwaWW@WdbdJWdbl`WdblsaWW@WdbmJWdbsfWmWdbsgaWW@WdcaWmWW@WdebrisIWNWVWXW[W\W^W`WdWeWgWFWHWIWJWdecameter-scaleHWdecameters`Wdecimeter-scaledWdeepUWdeep-waterHWdeeperTWcWeWtWJWdefinedKWUW`WpWrWHWdefinitiveLWdefinitivelydWHWdeformationAWKWLWSWVWgWdeformationalKWPWwWBWCW Dorly exposed. Siliciclastic intervals are 0.5 to 40 m thick and make up 20 to 40 percent of most sections; coarser intervals likely represent storm and shoal deposits (Dumoulin and Harris, 1994). Conodonts and megafossils indicate an age of late Middle through early Late Devonian (latest Givetian and Frasnian)-younger than the youngest part of the Baird Group (DOb) and coeval with the oldest part of the Endicott Group. The unit grades upward and laterally into map unit Dmu; its basal contaEct is generally a fault but a depositional contact above DOb is preserved in at least one area (Karl and others, 1989b). In the Chandalar quadrangle, Dl is composed of pink- and light-brown-weathering, gray and black metalimestone, commonly micaceous and (or) silty, intercalated with calcareous to noncalcareous siltstone, calcareous sandstone, slate, and local purple and green phyllite, greenstone, and basal limestone-pebble conglomerate (Brosg and Reiser, 1964). Carbonate lithofacies in Fclude muddy biohermal buildups and carbonate sand shoals (Dumoulin and Harris, 1994). The unit contains corals, brachiopods, stromatoporoids, mollusks, and conodonts; the most tightly dated collections are early Late Devonian (Frasnian) but some assemblages could be as old as late Middle Devonian (Givetian) (Dumoulin and Harris, 1994). In the Christian quadrangle, Dl consists of fossiliferous cherty limestone locally present just above the base of the Beaucoup Formation; it contains coralsG and stromatoporoids of Middle(?) and Late Devonian age (Brosg and Reiser, 2000). The remainder of the Beaucoup Formation in the Christian quadrangle is included in map unit Dmu of this map. In both the western and eastern parts of the map area, Dl represents a facies transitional in time and space between carbonate platform rocks to the south (DOb, Pzm) and the siliciclastic depositional sequence of the Endicott Group to the north  ICDlDDevonianhp ECMetalimestone, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.!A6927AHeterogeneous expanses of calcareous, siliceous, and volcaniclastic metasedimentary rocks, with lesser metaigneous rocks, exposed along the length of the Central belt. Includes interlayered gray, maroon, purple and green siliceous phyllite, brown and black calcareous phyllite; gray-green, green, and purple metasiltstone, orange, brown and black calcareous metasiltstone; gray, green, and brown weathering metasandstone and lithic metasandstone, locally limonitic and calcareous; brown, red, !EbMetasedimentary and lesser metaigneous rocks, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000."A6686ABlack siliceous phyllite and metalimestone, metasandstone, metasiltstone, phyllite, and graphitic calcareous schist in the eastern Ambler River and western Survey Pass quadrangles. Conodonts and graptolites indicate Silurian ages for these strata in the Ambler River quadrangle (Dumoulin and Harris, 1988; Table A-1); rocks included in this unit in the Survey Pass quadrangle are undated but contiguous with, and lithologically similar to, Silurian strata in the eastern Ambler River quadranglBmidnightPWBWCWmightYWmillerCWGWmillimeterKWNWqWmillimeter-scaleKWmillimetersPWBWCWmineralCWQWcWqWGWHWmineralized{WmineralsCWKWSWUW^W_WpW{WDWGWminorCWDWEWJWKWPWUWYW[W\W^W_W`WaWiWoWqWrWtWW@WBWCWDWFWGWHWmisheguk^WmississippianCWFWIWLWPWTWUWVWWWXWZW[W\W]WgWrWsWtWBWCWFWGWIWmixPWSWBWCWmixedDWmkXWYW[W\WFWIWmkeYW[W\WFWmkklUWVWYW[W\WsWFWmklUWXW]WsWIWmkoXWZWIWmlIWJWXWZW[W\WsWFWIWmltUWmmPWaWW@WBWCWmm-cmPWBWCWmm-thickPWBWCWWCWCWCWCWCWWWWW_W`WeWmonoplacophoraneWmonzoniteyWmooreCWFWGWHWKWOWPWSWUW_WaWbWhWiWjWoWpWtWuWW@WAWBWmoreBWKWPWTWUW_WbWgWlWtWuW{WBWmorrowantWmosquitoEWmostIWLWQWVWYW[W\W^W`WdWeWgWlWsWtWmostlySWtWmounds`WmounttWmountainCWTW_WaWbWeWgWhWiWjWpW{WW@W'~valuesUWWWXWsWtWIWvariableVWnWvariationsCWKWGWvaricoloredYW[W\WFWvariedKWvariegatedTWUWvariesAWCWFWHWKWGWvarietiesGWKWPWjWAWBWCWvarietyFWNWbWvariousUW[W\WtWFWvariouslyeWHWJWvaryKWPWqWBWCWvaryingPWBWCWvcJWveinsCWGWAWGWvenetieGWAWversusKWverticalPWaWeWW@WBWCWJWveryKWPWcWdWfWgWpWtWBWCWHWverylighttodark-graylocallyorangeweatheringgraytobldVvesicularxWvioWvillagePWBWCWvisiblepWvoglQWRWYWvolcanicBWLWPWUWaWbWhWrWuWW@WBWCWKWvolcanicrocksvolcaniclasticrocksandclasticsedimentaryuVvolcanic-clastaWW@WvolcaniclasticaWrWtWuWW@WvolumetricallyKWPWXWqWBWCWIWvoluminousaWW@WvuggyTWw^WfWHWwachsmuthTWtWwacke_WaWrWW@WDWwacke-packstonedWW^W`WbWcWwesternmostSWwhereAWCWLWPWRWUW[W\W^W`WwhetherKWwhichCWEWKWSW[W\WwhileUW"Drids, and orthocone cephalopods, as well as conodonts of late Early to early Late Silurian (Wenlockian to Ludlovian) age. In east-central Ambler River quadrangle, a similar but more carbonate-rich succession of black metalimestone, graphitic calcareous schist, graphitic siliceous phyllite, and lesser impure chert contains probable calcitized radiolarians and conodonts of Wenlockian-Ludlovian and Ludlovian ages. Fossiliferous dolostone in this area (part of Pzm at Blind Pass Mountain) is coEeval with, and may represent a platformal source for, the off-platform strata of unit Spl. Spl includes map units "Pzbs" (part), "Ds", and "Db" (part) of Mayfield and Tailleur (1978) in the Ambler River quadrangle and map unit "MDcp" of Nelson and Grybeck (1980) in western Survey Pass quadrangle. Off-platform sequences of carbonate turbidites that are at least in part Silurian and thus correlative with this unit include strata on northern and southeastern Seward Peninsula (Till and otheh!Dchist, phyllite, and metasiltstone is shown with a diagonal line overlay. Parts of the unit that contain felsic to intermediate volcanic rocks or sedimentary rocks with abundant volcanic clasts are shown with a vertical line overlay. In the northeast Baird Mountains quadrangle, laminated to massive porphyritic rhyolite plugs, flows, and pyroclastic rocks are closely associated with siliceous and calcareous sedimentary rocks (Karl and others, 1989b). Along the northern part of the boundarEy between the Wiseman and Chandalar quadrangles, felsic to intermediate porphyries, metavolcaniclastic rocks, and rare massive hypabyssal rocks are associated with purple and green phyllite, lithic, quartz, feldspar metasandstone, and meta-argillite pebble conglomerate (Moore and others, 1997b). Elsewhere, volcanic-clast sandstone and conglomerate, feldspathic volcanic wacke or graywacke, and tuffaceous metalimestone occur with other sedimentary rocks of the unit. Megafossils and conod!Fonts collected from calcareous black phyllite and metalimestone interlayered with purple and green phyllite in the Snowden Mountain area are Middle and early Late Devonian in age (Dumoulin and Harris, 1994). Middle and Late Devonian conodonts were recovered from the unit in the northwest Wiseman quadrangle (Table A-1). A foliated felsic metavolcaniclastic rock collected in the northwestern Chandalar quadrangle yielded a U-Pb zircon crystallization age of 393 2 Ma (Middle Devonian; AleiGnikoff and others, 1993). This unit includes part of the Beaucoup Formation of Dutro and others (1979) and other rocks that record the transition from early Paleozoic platform carbonate sedimentation to voluminous, widespread clastic sedimentation represented by rocks of the Endicott Group. In the Baird Mountains, unit Dmu (and associated metalimestones of Dl) sit in depositional contact with underlying carbonate rocks of the Baird Group (DOb) (Karl and others, 1989b), and map relations!H elsewhere suggest that the deposition of rocks contained in Dmu succeeded sedimentation on the carbonate platform represented by units DOb and DOc. Depositional contacts between Dmu (and Dl) and overlying units of the Endicott Group (Hunt Fork Shale: Dhf) are found in the central Baird Mountains, north-central Survey Pass, northwestern Wiseman and northern Chandalar quadrangles. Equivalent to the "Nutirwik Creek metavolcaniclastic rocks" of Moore and others (1997b); unit "Dnu" and partIs of "Pzqs", "Pzr", "Pzbq", "MDe" of Karl and others (1989b); parts of "MzPzfw", "MzPzph", "Pzbq", "Pzl", "Pzmq", "Pzm", and "Dc" of Mayfield and Tailleur (1978); units ""Dfc" and "Dc" of Nelson and Grybeck (1980); units "Dbcw", "Dsg", "Dbc", "Dbb", "Dc", and "Dsc" of Dillon and others (1986); unit "Dls" and parts of units "Ds" and "Dsp" of Brosg and Reiser (1964); and units "Dbsg" and "Dbls" of Brosg and Reiser (2000) CDmuDMiddle and Late DevonianFI+&ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.'A6983AWhite to gray (less commonly black), fine to coarsely crystalline, massive to platy marble and subordinate metalimestone and dolostone occurs discontinuously in all quadrangles within the map area. Pzm locally contains abundant disseminated quartz or mica grains, and (or) interlayers of schist, quartzite, or phyllite. In some areas, these strata contain no relict sedimentary textures and few or no fossils; elsewhere, relict sedimentary structures and fossils occur, but rocks have not been TpzbqMWaWW@WpzbsbWfWkWpzcaPWBWCWpzclqmWoWpzcqPWBWCWpzcsPWmWBWCWpzgHWpzggnWpzimWpzkmgWpzlIWJWaWW@Wpzm[W\W_W`WaWbWeWgWmWW@WDWFWJWpzmqaWmWW@WpzmsmQWpzpJWpzpaHWpzpcIWJWpzpccbeWpzpcdeWpzpcemYWpzpcsrAWpzpgFWGWAWpzqmQWRWpzqsZWaWiWW@WpzraWW@WpzsQWRWpzschPWBWCWpzsgnRWpzsmNWpzucPWBWCWquadanglehWKWquadrangleCWDWFWGWIWJWKWLWMWNWPWQWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWkWlWmWoWpWqWtWuWvWwWxWyWzW{W|W}WW@WAWBWCWDWEWFWGWHWIWJWKWquadranglesAWDWEWFWHWIWJWSWXWYW[W\W^W_W`WaWbWdWeWfWgWjWlWmWnWtW{W}WW@WDWEWFWHWIWJWquartzAWBWGWKWLWMWPWUWVWYWZW[W\W^W_WaWbWgWnWqWrWtWyW{W}WW@WAWBWCWDWEWFWHWquartzchertquartziteandslate-clastconglomeratewithminYVthminYVVcoviteKW.VdocumentedJWTWWWeWlWwWJWdoesPWWWtWBWCWdolomiteeWJWdolomiticQWjWlWmWtWdolostoneIWJWNWPWTWUWVWZW_WaWbWcWdWeWfWgWmWqWrWsWtWW@WBWCWDWJWdolostonelimestoneargillaceousorsandylimestonesandstonsVdolostonemetalimestonemarbleandsubordinatequartzosemeteVJVdolostonesJWeWgWJWdomePWBWCWdominantKWdominantlyGWKWUWbWAWdominantlygray-greenlithicsandstonelesserbrownquartzsGVdominatedPWoWuWBWCWdone{WdoonerakTWtWuWdottedqWdpBWCWJWdpcscKWLWMWPWQWeW}WEWW.dsqHWKWLWMWPWBWCWEWdss^WdsskPWQWeWlWmWoWBWCWJWdssoPWlWmWoWBWCWductileEWdueGWQWAWdumoulinNWTWVWWW_W`WaWbWcWdWeWgWsWtWW@WDWJWduniteDWduringAWCWKWLWdWsW{WGWdusel-baconAWQWRWwWdusty_WiWDWdutroTWUWVWWWXWZW[W\W^W`WaWeWrWsWtWuWW@WFWHWIWJWdvEWeLWUWVWWWtWeachCWGWearliestgWwWearlyAWBWCWGWHWIWJWKWLWNWPWTWUWVWXWZW[W\W_W`WaWbWcWdWeWgWmWsWtWW@WAWBWCWDWFWGWIWJWearly-earliestgWearly-earlygWearly-latesWeastGWUWdWeWgWrWAWJWeast-centralVW[W\W_WbWgWDWFWeast-westKWeasternEWPWSWYWZW[W\W`WbWcWdWhWjWlWoW{WBWCWFWKWeastwardFWechinodermNWVWXW[W\WFWHWIWechinoderms^W_WDWechookatWedgebWeifeliancWeifelian-givetiansWeight{W{W{W{WWWescapedLWestablished^WcWestimatedYWetivlukTWUWWWeuhedralKWevaporitecWSDC Chapman and others (1964). Limestone layers contain Late Devonian (late Frasnian to early Famennian) brachiopods, mollusks, and echinoderms (Dillon and others, 1986; Brosg and Reiser, 1964). Middle to Late Devonian conodonts were collected in the east-central Wiseman quadrangle (Table A-1). In the Phillip Smith quadrangle, north of the map area, conodonts from the limestones are middle to late Frasnian (Late Devonian; Dumoulin and Harris, 1994). A single Middle Devonian conodont colleDction on Wiseman/Survey Pass quadrangle boundary is unusually old for the unit; the conodonts may be reworked, or may indicate there is an unidentified expanse of Dmu included in the unit. The portion of unit shown with overlay is more strongly foliated and sedimentary structures are less obvious. The "Dietrich River phyllite" and part of the "Dusty Mountain phyllite" of Moore and others (1997b) are included in this more schistose part of the unit. Mafic bodies in the unit (both strongl"Be. Sedimentary features and fossil assemblages denote an off-platform and (or) edge of platform setting for these rocks (Dumoulin and Harris, 1988). In western Ambler River quadrangle, the unit consists of black siliceous phyllite with recrystallized radiolarians and interlayers of black metalimestone; it contains early Early Silurian (latest Llandoverian) conodonts and late Early Silurian (late Wenlockian) graptolites. In northeastern Ambler River quadrangle, the unit comprises a succesCsion of interlayered metasandstone, metasiltstone, phyllite, and metalimestone with turbidite features including convolute laminae, flute casts, and graded beds. Metasandstone is made up of quartz, carbonate, feldspar, and chert grains, as well as sedimentary and volcanic lithic clasts. Carbonate interlayers are also gravity deposits, and consist of redeposited shallow-water carbonate detritus; they contain a variety of megafossils such as corals, gastropods, bryozoans, brachiopods, conulaB"Frs, 1986, Ryherd and Paris, 1987). Dominantly siliciclastic basinal sequences that are in part Silurian occur on Cape Lisburne and have been penetrated in exploratory wells on the North Slope (Carter and Laufeld, 1975; Grantz and others, 1983; Moore and others, 1994; Dumoulin, 2001)  CSplDSilurianEVBlack phyllite and metalimestone, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.#A6980 feldsparLW^WaWbWrW|WW@Wfeldspars{Wfeldspathic[W\WaWW@WFWfelsicEWLWaWtWW@WfenestralcWsWferruginous^WaWW@WfewLW[W\W_WgWqWDWFWHWfewerHWfieldHWNWeWgWBWCWJWfieldsCWGWfigurewWfindingsLWfineGWKWMWNWPWUWVW^W`WgWjWsWtW{WAWBWCWHWfine-crystallineNWfine-grainedBWHWPWUW^WcWeWiWoWpWuW}WBWCWHWJWfine-grainedtoconglomeraticsandstoneandfine-grainedlamBVfine-scalePWBWCWfinelySWCWflat-lyingUWxWflat-lyingvesicularolivinebasaltflowsexposedinthesouxVflatteningAWflowLWflowsUWaWeWuWxWW@Wfluid-rockLWflutebWfluvialUW~WfoldedKWQWjWfoldsKWUWVWfolgercWfoliatedAWCWHWKWUW^W_WaWnW}WW@WfoliationKWMW[W\WjWnWpWfoliation-formingCWfoliationsEWfollwedAWforKWLWNWTWUWWW_WbWdWeWgWsWtW{WforaminifersCWTWUWXW[W\WsWtWforeslopetWforkKWUW]W^W_WaWpWW@WredstoneNWreedYWreefs`WreflectCWHWeWGWJWreflectsdWregimeeWJWregimessWregionalTWgWtWregionallyAWreiserGWKWPW^W_W`WaWdWpWxWyWzWW@WAWBWCWDWEWHWrelatedZW}WrelationNWUWrelationsVWaWhW{WW@WKWrelationshipKWYWeWJWrelationshipsPWgWBWCWrelativeCWGWrelativelySWUWVW[W\WaWoWW@WFWrelativelyhomogeneousassemblagedominatedbylightgreenisoVrelativelylithologicallysimplesectioninthenorthandno@VrelictCWFWHWLWNWPWaWgWnWpWW@WBWCWEWGWremainder`WremnantLWremnants{WrepetskiuWreplacedPWBWCWreportJWVWXWIWreportedCWHWIWJWLWUWVWXWYW[W\W_WlW}WDWEWFWGWHWIWreports[W\WFWts[W\WFWWHWWWWBlow) and fault contact with metabasalt and metatuff; chert, basaltic tuff, and cherty tuff are present in sequences up to 60 m thick (Pallister and Carlson, 1988). Commonly, metamorphic minerals partially overprint primary igneous and sedimentary textures in the metabasalts and metagabbros, but some foliated and lineated metabasalts occur in the western Ambler River quadrangle (A.B. Till, unpublished data) and in the Angayucham Mountains. Mineral assemblages that indicate the unit experieCnced prehnite-pumpellyite- to greenschist-facies metamorphism, with some exceptions. Barker and others (1988) reported albite-epidote-amphibolite-facies assemblages in metabasalt. A sliver of mafic schist in the Angayucham Mountains retains relict hornblende and garnet from an amphibolite-facies metamorphic assemblage, contains a foliation-forming greenschist-facies assemblage, and is cut by prehnite-bearing veins (Pallister and Carlson, 1988). Devonian, Mississippian, Triassic, and JuC$Baracteristic of this unit and reflects shallowing-upward peritidal cycles of darker colored, bioturbated, bioclastic and (or) peloidal carbonate strata overlain by light-colored cryptalgal laminite. Recognizable fossils include corals, stromatoporoids, brachiopods, gastropods, bryozoans, pelmatozoan debris, ostracodes, and dasycladacean algae. Corals and conodonts indicate an age of Upper Ordovician through Silurian for most of the unit. Definitively Devonian rocks have not been found in tChe eastern Baird Mountains quadrangle, but stromatoporoid wacke-packstone of late Early to early Middle Devonian (Emsian-Eifelian) age occurs locally in the Chandalar quadrangle. The unit is generally fault-bounded but a gradational and apparently conformable contact above OpCc is locally preserved. Sedimentary structures and fossils indicate warm, shallow-water depositional settings that were shallowest and most restricted during Late Ordovician (Richmondian) time. DOc has similarities inBE#C Dmu originally. Oldest strata are Early and Middle Ordovician, locally contain reworked Late Cambrian conodonts, and comprise two roughly coeval lithofacies: dolostone with fenestral fabric and evaporite molds that formed in locally restricted, shallow to very shallow water, and bioturbated to laminated, argillaceous to silty metacarbonate rocks with local cross-bedding, ripples, and flame structures that accumulated in somewhat deeper platform settings. Several intervals of dark metalimDestone partly equivalent in age and biofacies to the Ordovician basinal section in OpCc are intercalated with the argillaceous lithofacies. Younger strata include Upper Ordovician and middle Silurian (Wenlockian) metalimestone deposited in middle to outer platform settings and Upper Silurian and Lower and Middle Devonian (Emsian, Eifelian, and possibly Givetian?) shallow-water dolostone and metalimestone with corals and stromatoporoids; the Emsian section includes an interval of calcareous*jtanUWqW{Wtantogray-weatheringequigranulartoporphyroblasticfine{Vtan-weatheringqWtectonicFWSWtectonicassemblageofmetertokilometer-scalefaultsliverFVtectonicallyHWtectoniteDWtemperatureLW|WtemperaturesYWsW{WtensqWtentativeLWtentativelyTW[W\WFWterrace~WterraneAWCWDWEWFWGWyWzWAWGWterranesKWtexturesCWLWPWRW^W`WgWBWCWGWHWthamnoporoidLWthanBWLWPWUWVW`WgWlWqWtW{WBWCWthatAWCWFWGWHWIWKWLWPWSWTWUWVWWWXWYWZW[W\W]WaWbWcWdWeWgWhWiWlWmWnWoWqWrWsWtW{WW@WAWBWCWFWGWIWJWKWtheAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}WW@WAWBWCWDWEWFWGWHWIWJWKWKWWCWFWHWJWKWPWTWUWWWXWYWZW[W\W^W_W`WaWbWcWdWeWfWtholeiiticCWthoseCWFWHWJW[W\W_WthoughCWOWPW09containIWKWMWNWPWRWUWVWWWXWYW[W\W_WaWbWcWeWgWtWW@WBWCWDWEWFWHWIWJWcontainedaWgWW@WcontainingPW_WqWWBWCWDWHWcontainsAWCWFWGWHWPWQWTWUWVWXWYWZW[W\W`WbWgWhWiWoWqWrWsWtW{W}WAWBWCWFWGWIWKWcontiguousbWcontinentalLWcontrasttWcontrastingCWHWGWcontrolSW[W\WmWpW|WFWconularidsbWconvolutebWcoolingEWhWKWcoppercWcopper-richJWJWRAcrest@crystallized@dark-graytoblackphylliteandlessergray-greenphyllitew@deformed@demonstrate@|devonian@dietrich@diverse@documented@dpm@.dsq@element@event@exceptions@Eexposure@qextends@feldspar@finer@form@formations@fossils@givetian@8gray-green@Aharris@high@lhost@including@increases@Ointernal@ iron@+katakturuk@late@lesser@@light-gray-weatherin@alisburne@clittle@located@mappedBimargin@matrix@mayfield@jmegafossils@Pmetabasalt@qmetamorphism@Fmetasedimentary@!micaceous@Bmidnight@mn-rich@mountains@Bmidnight@mn-rich@mountains@!micaceous@Bmidnight@mn-rich@mountains@urbrounded@surfaces@QE+eventSWqWevidenceKWexaminedLWIelementCWLWGWelementsCWTWGWelevatedUWWWelisWellersieckUWelongateNWelongationVWelsewhereHWUWVWaWgWW@WematWemmaPWBWCWemplacedCWGWemsianJWNWcWemsian-eifeliandWgWencompassesSWendicottTWUWVWXW]W^W_W`WaWtWW@WDWHWIWendothyridXWIWenoughEWenrichedCWGWenrichmentCWGWentriesZWsWenvironmentTWVWenvironmentssWepidoteKWPWnWqW{WBWCWEWepisodewWequaluWequigranular{WequivalentAWBWDWFWGWHWJWKWLWMWPWQWRWSWUWWWYWZW]WaWcWeWfWhWiWjWkWmWnWoWpWqWsWtWwWW@WAWBWCWEWHWJWKWequivalentsVWgWernieYW}WerrorsuWeruptedLWescapedLWespeciallycWestablished^WcWestimatedYWestimates{WetivlukTWUWWWrWsWeuhedralKWevaluate|WevaporitecWsWWzmoccursCWGWLWPWVW[W\W^WdWgWnWtWAWBWCWFWGWHWoceanCWGWoceanicCWGWocvuWofAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}WW@WAWBWCWDWEWFWGWHWIWJWKWoff-platformbWgWWWWs%BDGFHJ&AFA'BIDFD(BAH)A}*BJ+E,BZEM-BfA.B/AOA%0BR1ACE2AUCe3ATCEG4ACEGIXKV5AWC6C7D9B:A;;BaD Fd<Ac=AC>D$D lithofacies and biofacies to the younger part of DOb, as well as coeval strata of the York Mountains on Seward Peninsula. Ordovician biotas include some megafossils and microfossils with Siberian affinities and others with Laurentian affinities; Silurian and younger fossil assemblages are chiefly cosmopolitan (Dumoulin and Harris, 1994; Dumoulin and others, 2002). DOc includes map unit DOc of Karl and others (1989b) and Till and Snee (1995) in the Baird Mountains quadrangle and the informEwal Mathews River unit (SOm) of Dumoulin and Harris (1994) and parts of "DSk" of Brosg and Reiser (1964) in the Chandalar quadrangle. Dumoulin and Harris (1987), Dillon and others (1987, 1988), Table A-1 (Ambler River, Baird Mountains, and Chandalar quadrangles), and the Alaska Paleontological Database provide additional information on lithologies and fossils of this unit  /CDOcDMiddle Devonian to OrdovicianDG%Bnd Harris, 1994). Older rocks in the unit are orange- to light-gray-weathering, dark- to light-gray dolostone, metalimestone, and marble, with subordinate intervals of quartzose metasedimentary rocks, carbonate cobble conglomerate, and metabasite. Well-preserved tabular to club-shaped stromatolites and coated grains (ooids, oncoids, composite grains, and pisoids) occur locally in dolostones and suggest an intertidal to shallow subtidal depositional setting. Matrix-supported conglomerate foCrms massive layers as much as 20 m thick and may represent debris flows; clasts are mainly dolostone (locally stromatolitic) and ?1 m in diameter. Metabasite includes metamorphosed pillow breccia, pillow lava, and mafic pyroclastic rocks that contain blue amphibole in the Baird Mountains quadrangle. Younger strata consist of three subunits. The older rocks described above grade upward into subunit one, which consists of variously impure metalimestone, marble, and dolostone, with subordina%IbarePWBWCWbariteTWtWbarkerCWGWbarrenNWbasalTWVWWW_W`WgWtWDWbasaltCWFWrWxWGWbasaltlimestoneandtwobeltsofmelangeexposedinthenorrVbasalticCWDWGWbasaltsCWDWGWbaseAWUW`WsWtWbasedCWFWLWSWfWrWsWGWbasinCWTWUWWWmWGWbasinalbWcWbasisCWTWGWbeCWGWHWJWKWLWNWPWQWRWTWVWYW[W\W_W`WfWgWhWjWlWnWrWtWuWxW|WAWBWCWDWFWGWKWbearsKWbeaucoup`WaWW@WbecauseUWbeddedCWQWrWGWbeddingHWbedsTW^WbWsWtWHWbeenCWFWHWKWLWPWUWYW`WbWdWgWpWtWuW{WBWCWGWHWbeigecWbeigetoorange-weatheringlaminatedpartlyargillaceoustocVbeingHWbelongKWbelowDWcharacteristicsCWGWcharacterizedPWVW[W\WFWchemicalCWuWGWchemistryCWGWchertBWCWTWUWVWWWXWYWZW[W\W^W_WaWbWeWrWsWtWW@WDWFWGWHWIWJWchertyCWNWTW`WtWGWchesterianTWVWXWZWsWIWchieflyUWdWchloriteKWPWQWYWpW{W}WBWCWEWchlorite-albitePWBWCWchloriticPWcWeWmWBWCWJWchloritoidKWPWYW[W\WBWCWFWchondritesCWGWchristianGW^W`WaWgWW@WAWcitedLWclastAWHWclasticUWaWuWW@WclastsAWBWPWVWYW[W\W_WaWbWeWhWpWtWW@WBWCWDWFWHWJWKWclaytWclearKWclinopyroxeneFWcloseeWJWcloselyaWgWW@WclotsKWclub-shapedeWJWJWlectionsCWLW`Wcolonial`WcolorNWTWdWcoloreddWcolumnalsLWcombinationKWcombinedHWUWcommonBWKWRWUWYW_WaWcommonlyCWNWPWUWZW^W`WdWcommunLWcommunicationsLWcompilation^WcomplexKWcomplexityUWcomplexlyUWcomponentsPWcomposedOWPWYW`WHwackestone`WsWwahootWwarmdWgWwasGWKWLWPWTWUWVWYW^W_W`WcWdWeWsWtWuWwW{W|WAWBWCWDWHWJWwaterTWcWeWgWtWJWwattssWweCWWWGWweaklyKW_WhWDWKWweaklytomoderatelymetamorphosedmetasandstonemeta-argillhVKVweather`WweatheredUWweatheringKWZWaWdWjWmWqWsWW@Wweathers`WwebsterLWweldedLWwellHWPWTWVWXW^WbWcWdWtWBWCWHWIWwell-definedUWVWwell-deveopedEWwell-layeredqWwell-preservedeWJWwell-sortedAWwellsbWwenlockianbWcWwenlockian-ludlovianbWgWwereCWHWJWLWPWTWUWWWXW_WaWcWdWmWqWrWtW{W}WW@WBWCWDWGWHWIWwestRWUWrWsWBWCWwest-centralUW[W\WcWFWwesternAWCWGWPWSW[W\W^W`WbWcWeWiWjWkWlWoW}WAWBWCWFWGWHWJWwesternmostSWwetlands~WwhereAWCWLWPWRWUW[W\W^W`WpWsWtWwWBWCWFWGWHWwhetherKWwhichCWEWKWSW[W\WeWmWpWrWFWGWJWwhileUWjmatrixPWYWaWnWrWW@WBWCWmatrix-freerWmatrix-supportedFWaWeWrWW@WJWmaunelukKWmaximumKWeWHWJWmayFWGWHWIWJWKWMWNWPWQWSWUWVWYW[W\W_W`WbWeWfWgWhWlWnWpWtWwW|WAWBWCWDWFWJWKWJWKWW antiformdWeWtWuWJWarealWarrigetch-igikpakQWRWassemblagesSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWW@WDWFWHWIWJWKWbairdcWbairdgroupcentralbeltandpartofnorthernthrustassemblcVbasalt8basinAWBWCWDWGWbearingWbeltFWGWHWIWKWLWMWNWPWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWW@WAWBWCWDWEWFWHWIWJWKWbiotitevWbiotiteschistrubyterranevVKJBnd Harris, 1994). Older rocks in the unit are orange- to light-gray-weathering, dark- to light-gray dolostone, metalimestone, and marble, with subordinate intervals of quartzose metasedimentary rocks, carbonate cobble conglomerate, and metabasite. Well-preserved tabular to club-shaped stromatolites and coated grains (ooids, oncoids, composite grains, and pisoids) occur locally in dolostones and suggest an intertidal to shallow subtidal depositional setting. Matrix-supported conglomerate foCrms massive layers as much as 20 m thick and may represent debris flows; clasts are mainly dolostone (locally stromatolitic) and ?1 m in diameter. Metabasite includes metamorphosed pillow breccia, pillow lava, and mafic pyroclastic rocks that contain blue amphibole in the Baird Mountains quadrangle. Younger strata consist of three subunits. The older rocks described above grade upward into subunit one, which consists of variously impure metalimestone, marble, and dolostone, with subordina|IA6330APhyllite or slate, siltstone, sandstone, limestone, and chert exposed in two small areas in the northwestern Baird Mountains quadrangle and in a larger discontinuous outcrop belt in the northern Survey Pass quadrangle. One exposure in the Baird Mountains quadrangle is fault-bounded; the other includes map units Mk and Mko of Karl and others (1989b) and overlies Noatak Sandstone of the Endicott Group. In the Survey Pass quadrangle Mkl includes map units Mk (part) and Ml of Nelson and Grybn Survey Pass quadrangle. One exposure in the Baird Mountains quadrangle is fault-bounded; the other includes map units Mk and Mko of Karl and others (1989b) and overlies Noatak Sandstone of the Endicott Group. In the Survey Pass quadrangle Mkl includes map units Mk (part) and Ml of Nelson and GrybF%J Mountain area). Additional data on lithofacies and biotas of this unit are found in Carter and Tailleur (1984), Dumoulin and Harris (1987), Table A-1 (Ambler River, Baird Mountains, Chandalar, and Survey Pass quadrangles), and the Alaska Paleontological Database fCOpCcD!Middle Ordovician to Proterozoic?EdOlder carbonate rocks of the Nanielik antiform, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.&A6331%Hly equivalent to Middle Cambrian phyllite and metalimestone that crop out northwest of Snowden Mountain (here included in Pzm; Snowden Mountain unit of Dumoulin and Harris, 1994). Ordovician strata are roughly coeval with the older part of DOb, but formed in a deeper water setting. Fossils in OpCc are mainly cosmopolitan, but include some Siberian and Laurentian forms (Dumoulin and Harris, 1994; Dumoulin and others, 2002). Exposures that contain the Ordovician part of the section only are Ishown on the map with a vertical line overlay. OpCc includes map units PzpCcb and OCc of Karl and others (1989b) and CpCvc, CpCic, Cc, and Opc of Till and Snee (1995) in the Baird Mountains quadrangle, part of map unit DSsk of Mayfield and Tailleur (1978) in the western Ambler River quadrangle, map unit Om of Toro (1998) in the central Survey Pass quadrangle, and informal units PzpCd and Os (Snowden Creek unit) of Dumoulin and Harris (1994) in the Wiseman and Chandalar quadrangles (SnowdenG%F middle to inner platform bioclastic supportstones; graptolites and conodonts indicate an age of Arenig to Caradoc for this subunit. The stratigraphic succession of OpCc is most complete and lithologies are most diverse in the Baird Mountains and western Ambler River quadrangles. There, the close spatial relationship of the unit with Proterozoic metamorphic rocks (pCam) is thought to reflect an original depositional relationship. Conglomerate and metabasite intervals in older rocks and thGe lower two subunits of younger strata are known only in the Baird Mountains. The presence of OpCc as a fault-bounded sequence in the Akiak antiform (western Ambler River quadrangle) is documented in Dumoulin (1988) and Dumoulin (unpublished field notes, 1986, 1987). Older rocks in unit OpCc may correlate with parts of DpCsc in the schist belt (Dumoulin, 1988) and the Katakturuk Dolomite (Dutro, 1970; Blodgett and others, 1986) in the northeastern Brooks Range. The Cambrian subunit is partbclusters[W\WFWcmLWVW[W\W^WaWqWW@WFWHWcm-scalePWBWCWcm-sized}Wcoarse`WlWcoarsecrystallinemarbleorangedolomiticmarblequartz-miclVcoarse-crystallineNWcoarse-grainedVW[W\WsW{WFWcoarselyPWgWBWCWcoarsening-upward^Wcoarser[W\W`WtWFWHWcoatedeWtWJWcoatingUWcobbleeWJWcoevalUW`WbWcWdWeWgWtWJWcollapsedCWGWcollectedCWKW_WaWjWuW{WW@WDWGWcollectionLWTW_WDWcollectionsCWLW`WgWGWcolonial`WcolorNWTWdWcoloreddWcolumnalsLWgWcomagmatic{WcombinationKWcombinedHWUWcommonBWKWPWRWUWYW_WaWlWW@WDWcommonlyCWNWPWUWZW^W`WdWgWqWsWBWCWGWHWcommunLWfWcommunicationsLWcompilation^WHWcompleteeWJWcomplexKWcomplexityUWcomplexlyUWcomponent{WcomponentsPWBWCWcomposedPWYW`WhWnWqWtWBWCWEWKWcompositeeWtWJWQsurbroundedBWCWW+katakturukeWJWkayakTWUWVWWWXW[W\W]WtWFWHWIWkbLWYW{W|WkekiktukVWYW[W\WtWFWkellertWkellysWkeyVWkilometerrW{Wkilometer-scaleFWkinderhookianUWVWgWsWtWkinderhookian-osageaVWkinematicAWEWkivivikUW^WHWkiwalik{WkjmFWklerygWkmCWSW[W\W{WFWGWkmcAWknotsqWknottyKWknownLWPWeWlWvWJWkobukEWkogoluktukPWBWCWkogrukXWZWsWkoyukukKWkqcAWksBWDWkugururokrWkunaUWWWkvgBWkyaniteYWlWlLWlackYWlagtWlakeYWtW}WHWlaminaeNWPWbWBWCWlaminatedBWNWPWSWaWcWeWoWsWW@WBWCWJWlaminationsKWlaminitedWlargeLWSWuWEWlarge-scaletWlargelyaWW@WlargerXWIWIblueFWUWcWeWJWblue-greennWbluecloudpWblueschistcWqWwWblueschist-faciesqWwWblumyWbodiesDWFWHWPWQWRWSW_WlWqW{W}WBWCWDWEWbodyEWKW|WbombardmenttWborder[W\WFWborniteJWbothCWLWPWVWWWXW^W_W`WcWgWhWqWtWuW{WBWCWDWGWIWKWbottomsDWboudinsPWBWCWbouldersDW~WboumaHWboundaryAWBWCWFWHWLWMWPW_WaWfWhWnWoWyW}WW@WBWCWDWGWKWboundedUWbowsherTWUWVWWWXWZW[W\WsWtWFWHWIWboxAWCWGWbrachiopod[W\WsWFWbrachiopodsCWIWJWUWVWXW[W\W^W_W`WbWdWeWfWgWjWsWtWuWDWFWGWHWIWJWbracketedKWphylliteFWGWHWIWWWbWiWkWAWphylliteandgraywackephyllitebeltHVphyllitecentralbeltandpartofnorthernthrustassemblageiVquartz-micaKWquartz-micaschistschistbeltKVquartz-richYWoWquartz-richconglomeratecentralbeltandpartofnortherntYVquartz-richmetasedimentaryrockscentralbeltandpartofnoVquartziteMWriverSWsWrocksCWEWIWJWTWUWZW[WaWdWeWfWhWjWlWmWoWpWqWrWtWuWyW|WW@WGWJWKWrocksofthekivivikcreeksequencecentralbeltandpartofUVrubyvWwWrubyschistrubyterranewVsandstoneAWBWGW^WAWschistKWLWMWNWPWQWRWnWvWwW@WBWCWEWdedarrigetch-igikpakthermalhighQVschistandparagneissarrigetch-igikpakthermalhighRVschistoseAWschistoselithicsandstoneandshalephyllitebeltAVsedimentaryTWrWtWuW~WsedimentaryrockscentralbeltandpartofnorthernthrustaTVsedimentaryrocksdoonerakantiformtVsequenceJWLWUWsWserpentiniteAWBWCWDW)DEGy and weakly foliated parts) display lower greenschist-facies minerals CDhf*D Late DevonianEXHunt Fork Shale, strongly foliated, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.t'D PaleozoicEandesiterWangayuchamAWCWDWFWGWangayukaqsraqeWqW}WJWangularVW^WanirakKWankeritePWBWCWantiformPWTWZWdWeWuWBWCWJWanyYWaphaniticLWapoonuWapparentlyQWdWBWCWappearRWsWappearanceKWQWoWapproximatelyQWSWar-aruWarcheanKWarchedKWarcticLWarcticLWWcticLWWWGrmountainsCWDWIWMWPWUWVWWWXWZW]W^W_W`WaWcWdWeWgWiWmWqWtW|W}WW@WBWCWDWGWHWIWJWmountains/amblerFWmovementAWmteWqW{W}WJWmuUW[W\WsWFWmuchVW[W\W^WeWFWJWmuddy`WHWmudstoneBWHWTW`WsWmullTWUWVWWWtWmulticrystallinenWmultipleKWcWmurphyHWmuscoviteKW{WmustPWBWCWSWmylonitic@Gnortheastern@occurs@old@zoliver@orange-weathering@nour@2pale@patton@#phengite@phylliteorslatesiltstonesandstonelimestoneandchertex@polycrystalline@present@Tpzbq@quartzconglomeratequartzitemetasandstonephylliteshalea@quartz-rich@Dquartzitic@redstone@represent@reworking@ sandstone@{schistose@ several@3shungnak@Nslate@Yslice@(spines@Qsteep@gstudied@surbrounded@surfaces@QQstudied@surbrounded@surfaces@QQQQJZ+E[Black phyllite and siliceous phyllite, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.,A8611ACoarse crystalline marble, orange dolomitic marble, quartz-mica schist, metaquartzite, calcareous schist, graphitic metaquartzite, and metabasite exposed in the eastern Survey Pass and western Wiseman quadrangles. Marble is the most common lithology; other lithologies are more common in the eastern part of the unit (Wiseman quadrangle), are locally gneissic, and are interlayered with the marbles. These non-marble lithologies correspond to the banded schist ("Pb") of Dillon and others (1986%KCuivalent to the "unnamed metagraywacke and metaconglomerate" of Moore and others (1997b). Stratigraphic relations of both belts unknowndCPzw_572D PaleozoicEKMetasedimentary rocks, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.HEs). Maximum quartz clast size in conglomerate is 3 cm in the Baird Mountains quadrangle (Karl and others, 1989b). Sandy layers differ from those in the Noatak Sandstone by being generally better sorted and coarser grained and by containing fewer non-chert lithic grains and no plagioclase; some quartz grains have quartz overgrowths interpreted as inherited from preexisting quartz-cemented sedimentary rocks (Nelson and Grybeck, 1980). Limy beds in parts of the unit transitional to the NoatakF Sandstone contain echinoderm debris, brachiopods, mollusks, cephalopods, and plant fragments. The most definitively dated fossil assemblages of the Kanayut in the map area, presumably from these transitional lithologies, are Late Devonian (Famennian?) in the Survey Pass and Wiseman quadrangles (Nelson and Grybeck, 1980; W. Brosg, unpublished fossil compilation, 1988). MDk was deposited in fluvial to very shallow marine settings. It also occurs as part of the Kivivik Creek sequence (unHGit JDk of this map) and the Endicott Group undivided (unit MDe of this map) in the Baird Mountains quadrangle (Karl and others, 1989b). MDk is equivalent to "MDk" of Karl and others (1989b), "Dk" of Mayfield and Tailleur (1978), "Dk" and "Dkq" of Nelson and Grybeck (1980)  CMDkD&Early Mississippian? and Late DevonianEJKanuyut Conglomerate, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.f+-ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000..A8661ADark green-weathering foliated mafic schist exposed in one area on the boundary between the Ambler River and Survey Pass quadrangles. Composed of green to blue-green amphibole, albite, epidote, quartz, and biotite. Grain size is variable. Epidote occurs in the matrix of the rock and as multicrystalline ovoids, some with relict garnet grains in their centers. Epidote ovoids are probably pseudomorphs after garnet. Amphibole is aligned in the foliation and biotite crosses it. Equivalent 4HAQuartzite, pebbly quartzite, conglomerate, and minor siltstone. MDk is exposed in a few small areas in the northwestern Baird Mountains quadrangle and the northeastern Ambler River quadrangle, and is widely distributed in northern Survey Pass quadrangle. In the northern Wiseman quadrangle, an overlay of crosses indicates an area where the Kanayut has not been differentiated from Noatak Sandstone (Dillon and others, 1986). The Kanayut was defined by Bowsher and Dutro (1957) in the ChandlBer Lake quadrangle north of map area; its age was modified by Nilsen and Moore (1982) and it is part of the Endicott Group (Tailleur and others, 1967). The Kanayut overlies the Noatak Sandstone; the contact is commonly gradational. Upper contact of MDk is rarely preserved in the map area, but the unit is locally overlain by the Kayak Shale of the Endicott Group in the Survey Pass quadrangle. The Kanayut consists of fine- to medium-grained, thin- to thick-bedded quartzite, pebbly quartzit%mn-richPWBWCWmobilityLWmoderateYWmoderately^WhWKWmodifiedHWmoldscWmolluscan[W\WFWmollusksAWBWUWVW_W`WeWDWHWJWmonoplacophoraneWJWmonzoniteyWmooreCWFWGWHWKWPWSWUW_WaWbWhWiWjWoWpWtWuWW@WAWBWCWDWEWGWHWKWmoreBWKWPWTWUW_WbWgWlWtWuW{WBWCWDWmorrowantWmosquitoEWmostIWLWQWVWYW[W\W^W`WdWeWgWlWsWtWFWHWJWmostlySWtWHWmounds`WmounttWmountainCWTW_WaWbWeWgWhWiWjWpW{WW@WDWGWJWKW'undifferentiatedHWKW]WundividedUWXW^WHWIWundulatoryTWtWunidentified_WDWuniformlyUWunitAWBWCWFWGWHWJWKWLWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWjWlWmWnWoWqWsWtWuW{W}WW@WAWBWCWDWEWFWGWHWJWunitsFWGWHWIWJWKWLWMWPWSWUWVWXWYW[W\W_WaWbWeWfWgWmWsWuWW@WAWBWCWDWEWFWIWJWunknownEWPWUWcWhWBWCWKWCWKWWWU1Eored epidote after garnet. Dolostone and marble occur along shear zones within the albite-epidote amphibolite facies rocks. Both the amphibolite facies and albite-epidote amphibolite facies rocks experienced a blueschist facies overprint detectable only in thin section (Till and others, 1988; Till and Snee, 1995). The blueschist-facies event yielded a 40Ar/39Ar age of 120 Ma (Till and Snee, 1995). Equivalent to unit "Psv" of Karl and others (1989) and parts of unit "mi" of Mayfield andF Tailleur (1978) CpCamD ProterozoicE\Metamorphic rocks of Mt. Angayukaqsraq, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.2A4951Al;harrisJWVW_W`WaWbWcWdWeWgWsWW@WDWJWharzburgiteDWhasCWKWLWPWQWTWUWYW[W\WaWcWdWgWoWtWW@WBWCWFWGWHWhaveAWCWFWHWIWJWKWLWPWUWYW[W\W`WbWcWdWgWpWtWuWwW{WBWCWFWGWHWheYWheartCWGWhemleyYWhenceWWhere[W\WeWsWFWJWheterogeneousPWSWaWmWW@WBWCWheterogeneousassemblageofinterlayeredcalcareousmaficanmVheterogeneousexpansesofcalcareoussiliceousandvolcaniclaVheterogeneousmixoffinelylaminatedmostlymyloniticlithoSVhettangianUWUWanUWWW9crestCWGWcrestalCWGWcretaceousAWBWDWnWzW{WcrinoidIWLWXWgWIWcrinoidaltWcrinoidsJW[W\WFWcriticalYWcropIWeWJWcrops[W\WgWFWcross-beddedUWcross-beddingcWHWcross-beds^Wcross-laminaeeWJWcross-laminated`Wcross-stratificationHWtWcrossesPWjWnWpWBWCWHWcrossiteFWcWcrustal{WcryptalgaldWcrystallinePWgWlWBWCWcrystallizationGWaWnWW@WAW1C plagioclase, hornblende, calcite, and garnet. Metapelitic rocks, commonly containing biotite and garnet, form light-green, well-layered outcrops rich in white mica, typically interlayered with metaquartzite on a scale of centimeters. Mineral assemblages record amphibolite-facies conditions (Till, 1989). Light-gray to tan-weathering metagranite and cream to brownish-green metagabbro occur as small bodies up to 100 m across that are volumetrically minor (Till, 1989; Karl and others, 1989a)D. U-Pb zircon ages from the granite indicate that it crystallized around 750 Ma (Karl and others, 1989a). White mica from a metapelite yielded a Late Proterozoic metamorphic age (680 Ma; Till and Snee, 1995). In the Baird Mountains quadrangle, some of the amphibolite-facies rocks were overprinted by an albite-epidote-amphibolite-facies event; these rocks are shown with a dashed overlay. Mafic outcrops in these areas are massive dark-blue to dark-bluish-green with small knots of olive-colr}/@ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.i]locatedDWSWlocationsDWlochkovianPWBWCWloneyDWlostgWlowAWCWFWGWLWYWtW{W~WAWGWlow-oxygenUWWWlowerJWQWRWTWUW^W_WcWeWjWtW{WDWHWJWlowestjWsWlpmcUWWWlreeCWGWludlovianbWgWmCWFW_W`WeWfWqWDWGWJWmaAWEWKWLWPWQWaWlWqWuWyW{W}WW@WBWCWmadeUW[W\WbW{WFWHWmaficAWBWCWFWHWKWLWPWRWUW_WaWeWmWnWpWqWW@WBWCWDWEWGWJWmafic-richPWmagmas{Wmagnetite}Wmagnetite-bearingQWmainlyTW`WcWeWsWtWHWJWmaiyumerakCWcWsWGWmajorKWPWQWRWVW_W{WBWCWDWmakePW`WsWBWCWmakeseWJWmametTWXWtWIWmanyKW{WmapAWBWCWFWGWHWIWJWKWTWUWWWXWZW[W\W^W_W`WaWbWdWeWgWrWsWtWwW}WW@WAWDWEWFWGWHWIWJWmappableNWmappedCWPWWW^W_WlWrW{WDWGWmappingKWmarbleIWJWKWLWNWPWQWSWVW`WaWcWdWeWfWgWhWjWlWmWoWpWqWrWW@WBWCWJWKWmarblesNWlWBWCWW/metamorphicrocksofmtangayukaqsraqcentralbeltandpartqVmetamorphicrocksoftheernielakeareacentralbeltandpalVmetasedimentary[WaWfWhWjWmWoWpWW@WKWmetasedimentaryandlessermetaigneousrockscentralbeltanaV@Vmetasedimentaryandlessermetaigneousrocksvolcanic-rockbVmetasedimentaryandmetavolcanicrocksundividedcentralbelmVmetasedimentaryrockscentralbeltandpartofnorthernthru[VhVKVmetasedimentaryrocksofbluecloudmountaincentralbeltandpVmetasedimentaryrocksofjessemountaincentralbeltandparjVmetavolcanicCWmWGWmigmatite:mosquitoEWmountainjWpWmountainsrWmtqWmudstoneBW-phyllite@schistandmarbleundividedarrigetch-igikpakthermalhigh@serpentiniteangayuchamterraneserpentiniteandyukon-koyuk@surficialsedimentarydepositsundivided@terrane@accompanying@>bedrock@ybenjamin@bleick@~data@wdumoulin@?geologic@Zheather@,in@[investigations@mooreAx&C)AA,E-B0D1 @B54 B6D7 B;DJ?! BLDKFJH[A#" @MAU$BZA&%AXA('AWCVE\G]I^K_M`AeDf)A+*AhEiBmDnFoArCsEtGuIvKwMxOyB}D~FHBACEBDFBACEACE(KAWeakly to moderately metamorphosed metasandstone, meta-argillite, phyllite, conglomerate, and rare marble exposed in two belts that straddle the northern part of the Wiseman/Chandalar quadangle boundary. The northern belt is composed of metasandstone and argillite; in its eastern part, metasandstone contains abundant detrital white mica that yielded a Late Ordovician 40Ar/39Ar cooling age (Moore and others, 1997b). The northern belt is equivalent to the Trembley Creek phyllite of Moore anBd others (1997b), and "Rocks of Whiteface Mountain" of Dillon and others (1986). The southern belt (shown with overlay) is composed of phyllite, metasandstone with volcanic clasts, argillite, sandstone, pebble conglomerate and rare marble. A bryozoan- and coral-rich marble in the southern belt yielded late Middle to Late Devonian conodonts (Table A-1, Wiseman quadrangle), suggesting that at least part of the southern belt may be equivalent to or correlate with Dmu. The southern belt is eqR1AAmphibolite, metaquartzite, calcareous schist, metapelite, and a few small bodies of metagranite and metagabbro, exposed in the northeastern Baird Mountains quadrangle around Mt. Angayukaqsraq and in the northeastern Ambler River quadrangle. Lithologies are interlayered on a scale of centimeters to meters, with pelite layers generally thicker than a meter and other lithologies in layers up to tens of meters thick (Till, 1989). Outcrops vary from massive to stepped, depending on the scale Bof interlayering. Amphibolite is dark-gray to black weathering, massive, and dotted with pink garnets up to 1.5 cm in diameter. Hornblende, plagioclase, sphene and quartz constitute the rest of the rock. Metaquartzite forms tan-, green-, and gray-weathering layers interlayered on a millimeter to centimeter scale with tan- and brown-weathering calcareous schist. The metaquartzite contains 15% white mica, biotite, garnet and calcite; the calcareous schist is composed of quartz, epidote,GBlow) and fault contact with metabasalt and metatuff; chert, basaltic tuff, and cherty tuff are present in sequences up to 60 m thick (Pallister and Carlson, 1988). Commonly, metamorphic minerals partially overprint primary igneous and sedimentary textures in the metabasalts and metagabbros, but some foliated and lineated metabasalts occur in the western Ambler River quadrangle (A.B. Till, unpublished data) and in the Angayucham Mountains. Mineral assemblages indicate the unit experienced Cprehnite-pumpellyite- to greenschist-facies metamorphism, with some exceptions. Barker and others (1988) reported albite-epidote-amphibolite-facies assemblages in metabasalt. A sliver of mafic schist in the Angayucham Mountains retains relict hornblende and garnet from an amphibolite-facies metamorphic assemblage, contains a foliation-forming greenschist-facies assemblage, and is cut by prehnite-bearing veins (Pallister and Carlson, 1988). Devonian, Mississippian, Triassic, and JurassiGDc radiolarians, conodonts, and megafossils have been collected from chert, cherty tuff, metalimestone layers, interpillow sediments, and fault slivers of carbonate rocks and chert (Pallister and Carlson, 1988; Jones and others, 1988). Conodonts of Late Silurian to Early Devonian age (Table A-1, Ambler River quadrangle) are the oldest fossils collected from the unit, and Early Jurassic radiolarians are the youngest (Pallister and Carlson, 1988; Jones and others, 1988). Pennsylvanian-PermiEan, Permian, and Early Permian radiolarians were collected near the southeast corner of the Wiseman quadrangle (Jones and others, 1988). At two localities, Early Mississippian conodonts have been collected from the same localities that also have yielded distinctly younger micro- and megafossils. At Twelvemile Mountain (Sheet 2), in the southeast Wiseman quadrangle, tightly dated late Early Mississippian (middle Osagean) conodonts, and Mississippian and Mississippian to Early Pennsylvanian crystallizedqWwW{Wcu{WcurrentseWJWcutCWGWcycles^WdWeWHWJWczmzspDWdLWTWtWJWdaKWdaciterWdaltoneWJWdarkHWNWPWTWUW`WcWeWnWtWBWCWJWdarkgreen-weatheringfoliatedmaficschistexposedinoneanVdark-blueqWdark-bluish-greenqWdark-brownSWdark-grayHWKWUWZW_WcWdWfWgWkWpWqWsWtWDWdark-graytoblackphylliteandbrown-weatheringlithicsandHVdark-graytoblackphylliteandcalcareousphyllitewithdarfVzn&oliverIWJWLWolivinexWomeWJWomarcWonAWCWFWHWKWLWNWSWTWUWXW_W`WaWbWcWdWeWfWmWnWqWrWsWtW{W|W}W~WW@WDWGWIWJWoncoidseWJWoneFWKWLWPWUWWWXWZW_W`WeWgWmWnWuW|WBWCWDWIWJWonlyNWUWeWgWqWJWooidseWJWopBWCWJWopaqueKWopceWJWopccPWcWdWeWgWmWopenKWTWtWorCWDWGWHWJWKWLWPWUWWWXWYW[W\W^W_W`WaWbWdWfWgWhWpWsWtWwW{WW@WAWBWCWDWFWGWHWIWKWorangeQWUW`WaWdWeWlWmWsWW@WJWTWoriginJWoriginalKW^W`WeWoriginally_WcWrWoriginatedLWorogenyCWorthoconebWorthogneissEWKWPWQWRWVW{W|W}WorthogneissesPWlW{WoseWosageanCWTWsWtWoscillationHWostracode[W\WostracodesVWXWdWotherCWKWLWNWPWRWUWWWXWaWgWlWqWuWothersAWBWCWDWEWFWGWHWIWJWKWLWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWlWmWoWpWqWrWsWtWuWwW{W}WGnortheasternAWEWVWXWZW^WaWbWdWeWfWgWiWqWtWuW{W}WW@WHWIWJWnorthernCWHWXW^W_WaWbWhWyWzWW@WDWGWHWIWKWnorthwestCW]WaWeWW@WGWJWnorthwesternUWWWXW`WaWdWeWfWgWiWtWW@WHWIWJWnorthwesternmostrWnotCWKWLWPWTWUWWWXWdWgWlWnWsWtWvW{WBWCWGWHWIWnotabletWnotablyUWnotedCWtWGWHWnotesNWeWgWBWCWJWnowLWnuggetPWEWnumerousUWnutirwikaWW@WoJWobservedPWBWCWobvious_WDWocceWJWoccurCWLWPWUW^WaWbWeWgWlWqWW@WBWCWEWGWHWJWoccurredwWoccurrenceNWXWoccurrencescWWWWW4AQuartzite, phyllite, siltstone, conglomerate, shale, sandstone, limestone, argillaceous limestone, dolomitic limestone, and cherty dolostone. The unit occurs in the Mount Doonerak area in northeastern Wiseman and northwestern Chandalar quadrangles, where it has been interpreted (Dillon and others, 1986) to unconformably overlie lower Paleozoic rocks (map unit SCvs). TrCs consists of the Kekiktuk Conglomerate (Brosg and others, 1962) and Kayak Shale (Bowsher and Dutro, 1957) of the EndicoBtt Group (Tailleur and others, 1967; Mississippian), the Lisburne Group (Schrader, 1902; Bowsher and Dutro, 1957; Carboniferous), the Echooka Formation (Keller and others, 1961) of the Sadlerochit Group (Leffingwell, 1919; Detterman and others, 1975; Triassic and Permian), and the Shublik Formation (Leffingwell, 1919) and Karen Creek Sandstone (Detterman and others, 1975; Triassic). The succession is similar to that of map unit JCs but differs in some aspects; it is part of unit TrCs of DT3Crk-gray, fine- to coarse-grained, commonly argillaceous limestone and lesser dolostone; beds are planar to irregular and bioturbated and rock types range from lime mudstone to bioclastic packstone. Conodonts denote an age of late Middle or early Late to late Late Devonian (late Givetian or Frasnian to Famennian); it also contains brachiopods of Late Devonian (possibly mid-Famennian) age (entries 8494-96 in Alaska Paleontological Database). Utukok is gray to brown limestone, sandy limestoneD, quartzose to calcareous sandstone, and subordinate siltstone and shale. Carbonate lithofacies include bioclastic wackestone, packstone, and grainstone; bioclasts are mainly pelmatozoan, brachiopod, bryozoan, and coral fragments, foraminifers, and algae. Age is Early Mississippian (Kinderhookian through middle Osagean) based on conodonts. Kogruk is light- to medium-gray-weathering, medium- to dark-gray, fine- to coarse-grained limestone and dolostone with locally abundant layers and nodul3Ees of black, gray, and white chert. Lithofacies include bioclastic wackestone and, in the upper part of the unit, spiculitic limestone. Conodonts, corals, and brachiopods indicate an age of late Early-Late Mississippian (late Osagean to late Meramecian-early Chesterian; see entries 5079-84 in Alaska Paleontological Database for details of coral identification and age). The top of the Kogruk is not exposed in the map area, but to the west, the Etivluk Group conformably overlies the Kogruk. F The MDer succession was deposited in a range of shallow-water, inner to middle shelf environments; the shallowest and most restricted depositional regimes prevailed during the late Middle Devonian. Strata are locally recrystallized, but conodont CAI values are generally 4 to 4.5 (Karl and others, 1989b), indicating temperatures of at least 190-250 C (Table A-2; Watts and others, 1994). MDer is part of a sequence exposed extensively outside this map area, where is it called the Eli RiverP3G sequence (Mayfield and others, 1988) or the "Eli River plate" (Young, 2004) of the Kelly River allochthon. Middle Devonian carbonate rocks correlate at least in part with youngest part of Baird Group; the Kogruk Formation correlates with unit "Ml" and parts of units "Mkl", "Mkkl", and "Mu". MDer is equivalent to the Maiyumerak sequence of Dumoulin and Harris (1992), who described in detail the lithofacies and biotas of these rocks  ICMDerDMississippian and DevonianE/Eli River sequence, Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.4A5004=:analyzedLW|WanastomosingFWancient{WandAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWand/orfWandalusitevWL(JHly equivalent to Middle Cambrian phyllite and metalimestone that crop out northwest of Snowden Mountain (here included in Pzm; Snowden Mountain unit of Dumoulin and Harris, 1994). Ordovician strata are roughly coeval with the older part of DOb, but formed in a deeper water setting. Fossils in OP_c are mainly cosmopolitan, but include some Siberian and Laurentian forms (Dumoulin and Harris, 1994; Dumoulin and others, 2002). Exposures that contain the Ordovician part of the section only are Ishown on the map with a vertical line overlay. OP_c includes map units PzP_cb and OCc of Karl and others (1989b) and CP_vc, CP_ic, Cc, and Opc of Till and Snee (1995) in the Baird Mountains quadrangle, part of map unit DSsk of Mayfield and Tailleur (1978) in the western Ambler River quadrangle, map unit Om of Toro (1998) in the central Survey Pass quadrangle, and informal units PzP_d and Os (Snowden Creek unit) of Dumoulin and Harris (1994) in the Wiseman and Chandalar quadrangles (SnowdenW5C, 1976). Three samples yielded Devonian ages (373-388 11-17 Ma); two samples yielded older ages, both with large errors. The older sample with the more potassic hornblende and better radiogenic yield is Ordovician (478 20 Ma), and was collected from the volcanic sequence (Dutro and others, 1976). Equal to units SCb and OCv of Dillon and others, (1986) and the Apoon assemblage of Julian and Oldow (1998)xCSCvsDSilurian to CambrianE1Volcanic and sedimentary rocks, Doonerak antiformATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.6A8601BQuartz-albite-oligoclase-biotite schist with staurolite and andalusite exposed in the southeastern Chandalar quadrangle, adjacent to rocks of the Schist belt. Age of metamorphism not known4Cillon and others (1986). Dutro and others (1976), Dillon and others (1986), Mull and others (1987), Adams (1991, 1994), and Adams and others (1997) provide additional data on these strata. The Kekiktuk is discontinuously present and consists of quartzite and minor pebble conglomerate with interlayers of phyllite, siltstone, and felsic volcaniclastic rocks and a basal conglomerate (Dillon and others, 1986; Mull and others, 1987). Coarser beds display horizontal and trough cross-stratificatiDon and small- to large-scale channels; conglomerate clasts are mainly chert and quartz but locally include green to dark-gray phyllite. These rocks were included in the basal sandstone member of the Kayak by Armstrong and others (1976) but noted by these authors to strongly resemble the Kekiktuk of the northeastern Brooks Range. The Kayak and Lisburne (Mount Doonerak composite section) were discussed by Armstrong and others (1976), Armstrong and Mamet (1978), and Dumoulin and others (19974E). The Kayak is black shale with interbeds of sandstone and siltstone near the base and limestone (crinoidal packstone) near the top. It contains conodonts and foraminifers of Early Mississippian (Kinderhookian and Osagean) age. Basal and upper contacts of the Kayak are gradational. The Lisburne is composed of three formations. The Wachsmuth Limestone is argillaceous limestone and cherty dolostone of Osagean age, formed in an open marine setting. The Alapah Limestone is dark, argillaceous,F coralline limestone (foreslope deposits?) overlain by light-gray, locally dolomitic limestone (shoal and open platform strata) of Late Mississippian age. The Wahoo Limestone is fossiliferous limestone of Pennsylvanian (mainly Morrowan) age that accumulated at least partly as a lag concentrate on a drowned carbonate platform. Post-Carboniferous stratigraphy was detailed by Adams (1991, 1994, Amawk Creek and Bombardment Creek sections) and summarized in Mull and others (1987) and Adams andX4G others (1997). The lower contact of the Echooka is sharp and undulatory and locally coated with several centimeters of red clay; basal beds contain probable phosphatic pebbles. The Echooka consists in ascending order of siltstone, sandstone, and silty dolostone (subunit A), light to dark gray silty shale with subordinate carbonate interbeds (subunit B1), and dark gray to black cherty shale with barite nodules (subunit D). The formation contains abundant burrows and trace fossils, as well Has brachiopods that indicate an early Early Permian (Wolfcampian) age for the lower part of subunit B1. Regional correlations suggest that the upper part of the Echooka in the Doonerak area is late Early to Late Permian (Leonardian to Guadalupian). The Echooka is overlain (disconformably?) by black, calcareous, sooty shale with phosphatic nodules and argillaceous gray to black limestone assigned to the Shublik Formation; this unit has produced pelecypods of Middle and (or) Late Triassic ag2#palemW|Wpalegray-greenmassivetogneissicgranitictodioriticort|Vpale-gray-weatheringLWpaleontologicalIWZW`WcWdWeWgWsWJWpaleontologically[W\WFWpaleontologistsLWpaleozoicDWIWSWVWYWaWlWtWW@WpallisterAWBWCWFWGWpalynoflorasHWpanelCWGWparagoniteKWparallelKWMWeWJWparautochthonousVWtWparisbWpartBWCWFWGWJWKWLWPWSWTWUWVWXWZW]W^W_W`WaWbWcWdWeWgWhWjWlWmWnWrWsWtWxWW@WAWBWCWDWGWHWIWJWKWpartiallyCWKWGWparticularlyRWpartlycWeWtWJWpartsAWCWGWHWIWJWNWPWQWYW]W_W`WaWcWdWeWfWgWiWkWlWmWoWqWsWtWW@WAWBWCWDWEWGWHWJWpartsoftheunitcontainingfelsictointermediatevolcanicVpassFWLWQWUWVWXWYW[W\W^W_WaWbWeWfWgWlWnWoW{W}WW@WDWEWFWHWIWJWpatrickLWQW{W|WpatternGWAWpatternsUW:/elisWeliriversequencenorthernthrustassemblagessVendicottVWXW]WIWendicottgroupundividedcentralbeltandpartofnorthernt]VernielWferriginuous@WfoliatedDWfork_WDWgraniticyW{W|W}Wgraniticorthogneiss{Vgraniticorthogniess}VgraniticrocksyV|VgraywackeHWgroupVWXW]WcWIWhammondSWhammondrivershearzonecentralbeltandpartofnortherntSVhighQWRWhillsJWhunt_WDWhuntforkshalecentralbeltandpartofnorthernthrustass_VhuntforkshalestronglyfoliatedcentralbeltandpartofnDVigneousrWigneousandsedimentaryrocksofthemaiyumerakmountainsnorVjessejWkanuyut\WFWHWkanuyutconglomeratecentralbeltandpartofnorthernthrus\VFVHVkayakVWXWIWkayakshaleofendicottgroupandlisburnegroupcentralbelXVIVkekiktukVWkekiktukconglomeratekayakshaleofendicottgroupandlisbVVkivivikUWlakelWlesseraWW@WlisburneVWXWIWlithicBWGWAWLJDte interlayers of phyllite and calcareous and chloritic schist. Carbonate layers contain locally abundant coated grains; preserved sedimentary structures include grading and parallel and cross-laminae and suggest deposition by turbidity currents. Subunit two is massive marble that grades upward into thin couplets of bioturbated metalimestone and laminated dolostone interpreted as shallowing-upward peritidal cycles. Protoconodonts, chancellorid sclerites, hyolithids, and steinkerns of monopElacophoran mollusks indicate a maximum age of Early Cambrian for the marble; acrotretid brachiopods and agnostid arthropods demonstrate Middle and Late Cambrian ages for the middle and upper parts of the subunit. A condensed Lower and Middle Ordovician section deposited in a shallowing-upward regime makes up the third subunit. Carbonaceous phyllite, with subordinate layers of radiolarian chert and fine-grained metalimestone, grades up into platform-margin carbonate turbidites and then into GFradiolarians were collected from carbonate and chert lenses. Bird (1977) identified Pennsylvanian(?) foraminifers from the same locality and noted that the rocks are lithologically similar to those of the Lisburne Group, a unit widely distributed to the north (in the Northern thrust assemblages). At Heart Mountain (Sheet 2), in the southwest Wiseman quadrangle, both Early Mississippian conodonts and Permian foraminifers, bryozoans, and brachiopods were identified (Table A-1; Patton and MGiller, 1973). These contrasting ages could reflect structural juxtaposition of rocks of different ages, reworking of older fossils into younger strata, or problems in correlating age ranges of different fossil groups. The thermal indices of conodont collections in this unit are commonly high (CAI=5), though some are low (CAI=2-3). The basalts are tholeiitic, and fall into "within-plate" fields on trace element discrimination diagrams; LREE elements are enriched relative to chondrites iOfincludingLWNWPWUWVW[W\WbWcWuWBWCWFWinclusionVWinclusionsKWincorrectlypWp7DPaleozoic to Proterozoic?ERuby schist, Ruby terraneATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.8A350BFlat-lying, vesicular olivine basalt flows exposed in the southeastern part of the Chandalar quadrangle. Thought to be about 300 meters thick (Brosg and Reiser, 1964)CQTbDQuaternary? or Tertiary?EBasaltATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.9A2492{5reworkingCWGWrhyoliteaWW@WrhythmicPWBWCWribbonVWrichAWPWYWkWqWBWCWrichmondiandWridges~WriftedLWrip-upHWrippleHWripplescWriverCWDWFWIWJWLWMWNWPWSWTWUWVWYW[W\W^W_W`WaWbWcWdWeWgWiWkWmWnWqWsW{W}WW@WBWCWDWFWGWHWJWrockCWEWNWPWUWaWmWnWqWrWsWW@WBWCWGWrocksAWBWCWDWEWFWHWIWJWKWLWNWPWRWSWTWUWVWXWYWZW[W\W`WaWbWcWdWeWgWhWjWlWmWqWrWsWtWuWvWzW{W|W}WW@WBWCWEWFWGWHWIWJWKWroeskeEWwWroughlycWeWJWroundedKWVWrubble~WrubyAWJWwWyWzWrugoseJWrutileKWPWBWCWryherdbWsFWsableZWrWsWsadlerochitVWtWsameCWPWBWCWGWsampleLWgWuW|WsampledNWsamplesUW[W\WgWuW{WFWsand`W~WW{3lschistoseGWKW_WjWAWDWEWschistosevarietiesareequivalenttounitsdmwanddpmofbAVschistsKWPWYWwWBWCWschmidtLWUWWWcWschraderTWUWVWWWXWZW[W\WsWtWFWIWscleriteseWJWscvstWsecondPWsecondary{WsectionSWTWUW^WaWcWdWeWgWpWqWrWtWW@WJWsectionsTWUW`WtWsedimentUWsedimentaryAWCWHWPWUWVW^W_WaWbWdWeWgWuWW@WBWCWDWGWHWJWsedimentationaWW@Wsedimentologically[W\WFWsedimentsCWGWseeKWLWTWUW^WsWseenHWsegregationMWsegregationsKWsemipeliticKWsemischistose[W\W^WFWHWseparate^W{WseparatedKWseparatelyUWWWsequenceCWDWLWPWUW^W`WcWeWpWsWuWBWCWGWHWJWsequencesCWHWbWuWGWsericite{W}WserpentiniteDWFWsetsuWsettingTWUWbWeWgWtWJWsettingsHWTWUWWW^WcWdWgWHWO+xinternalPWBWCWinternallyCWGWinterpillowCWGWinterpretationVWinterpretedJWTWVW[W\WeWtWFWHWJWintertidaleWJWintervalaWcWtWW@WintervalsJWWW[W\W^W`WcWeWFWJWintoCWKWUWWW`WeWuWGWJWintrafolialKWVWintroductionKWLWintrudedUWlWBWCWintrusiveAWBWKWNWaW{WintrusivesW@WinvolvesFWintrusiveAWBWKWNWaW{WintrusivesW@WinvolvesFWWFWWad;Dgneisses (Nelson and others, 1993). Strontium isotope compositions are unrealistically low for some of the orthogneiss samples, indicating that the Rb -Sr systems in these rocks have been disturbed and do not provide useful petrogenetic information (Nelson and others, 1993). Metafelsite in unit Dmu and the Kiwalik Mountain orthogneiss, Seward Peninsula, are similar in age to the more precisely dated granitic orthogneisses in this unit (Aleinikoff and others, 1993; Till and others, 1986; ETill and others, 2006). Thermobarometric analysis of phengite and feldspars in eight separate bodies of granitic orthogneiss in the Schist belt yielded temperatures ranging from 372 to 427C and pressures of 7 to 11.3 kb, thought to represent conditions of Jurassic high-pressure metamorphism (Patrick, 1995). These samples all had secondary populations of phengite that yielded lower pressure estimates and are thought to have crystallized during exhumation of the belt. Five samples from grGHn some basalts and gabbros, but show little to no enrichment in other rocks (Barker and others, 1988; Pallister and others, 1989). Based on these characteristics, the mafic rocks are thought to have been parts of oceanic plateaus or islands. In the Angayucham Mountains, where the unit has been mapped in detail, Hitzman and others (1982) and Pallister and Carlson (1988) recognized that several distinct subunits can be distinguished within the package, although the subunits are lithlogicalIly similar and each is internally imbricated. Pallister and Carlson (1988) initially distinguished three subunits on the basis of slight variations in metamorphic minerals and minor element chemistry, but the packages also can be distinguished by age. Jurassic radiolarians were collected from the southernmost subunit and Triassic radiolarians from the central subunit. Along the northern boundary of the central subunit and in the northern subunit, Triassic, Mississippian, and Devonian rad)XEBR, quartz, calcite, and sphene, though exposures in the central Chandalar quadrangle adjacent to unit Dg contain hornblende, garnet, and biotite. Equivalent to unit "Dgs" and parts of unit "Dgh" of Brosg and Reiser (1964), parts of "Dv" of Nelson and Grybeck (1980), and parts of the "Nugget Creek greenschist" of Moore and others (1997b)@CPzsgD PaleozoicEMafic schist, Schist beltATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.D+quartzconglomeratequartzitemetasandstonephylliteshalea[V\VFVquartz-albite-oligocvWquartz-albite-oligocschistwithstauroliteandandalusiteevVquartz-carbonate`Wquartz-cementedHWquartz-chertVWquartz-chloritegWquartz-micaHWKWPWlWBWCWquartz-muscoviteKWicaHWKWPWlWBWCWquartz-muscoviteKWWlhostPWmWBWCWhostsJWPWcWhowardUWhoweverLWUWVWYWgWtWhughesAWFWIWhummockyHWhuntKWUW]W^W_WaWpWW@WDWhyaloclasticCWGWhydrothermalJWhyolithidseWJWhypabyssalaWW@WiLWicJWichnofossilsLWidentificationsWidentifiedCWPWYWBWCWGWifKWYWigikpak{WigneousCWFWLWGWimbricateCWGWimbricatedCWGWimmediatelyUWimpurePWaWbWeWjWpWW@WBWCWJWinAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWzW{W|W}WW@WAWBWCWDWEWFWGWHWIWJWKWincludeKWNWUWVWXWZW^W`WbWcWdWeWjWlWpWrWsWtWuWHWIWJWincludedGWKWLWUWXWYW[W\W^W_W`WaWbWeWtW}WW@WAWDWFWIWJWincludesCWIWJWNWSWUWXW[W\W`WaWbWcWdWeWgWmWuWW@WFWGWIWJWWIWJWWWTpolycrystallineKWpooriWpoorlyAWLWSW[W\W^W`WjWFWpopulationLWpopulationsKW{WporphyriesLWaWW@WporphyriticaWW@Wporphyroblastic{WporphyroblastsPW}Wportion_WDWpositionCWGWpossibleIWLWPWYWZW[W\WaWgWW@WBWCWFWpossiblyCWcWlWsWGWpost-carboniferousTWXWtWIWpost-earlyjWpost-middleLWpotassicuWpowdermilkcWpre-devonianjWpreciseIW{Wprecisely{WprecludesUWpredominantXWIWpredominantlyBWlWpredominateCWBWCWGWpredominatesNWpreexistingHWpreferred{Wprehnite-bearingCWGWprehnite-pumpellyiteAWCWGWpresenceJWLWXWeWtWIWJW(diverseeWJWdividedKWuWdkHWdkqHWdl_W`WaWgWW@WDWdlsaWW@WdmmWdmuUWZW_W`WaWcWfWhW{WW@WDWKWdmwGWAWdnUW]W^W_WDWdnl`WdnuUWaWW@WdoCWUW{WGWdobUW`WaWcWdWeWfWgWmWW@WJWdocaWcWdWfWgWmWW@WmWW@WW=C 6 Ma (Karl and others, 1989a); the granodiorite and related granitic rocks are too small to show on the map and were included in unit pCamhCpCgD ProterozoicEGranitic orthogniessATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.>A100BFrost-rived rubble on slopes and broad low ridges; glacially deposited sand, gravel, and boulders; fluvial gravel and sand; terrace deposits; wetlandsCQsD QuaternaryE)Surficial sedimentary deposits, undividedATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.e >c=AMetagranitic rocks of several Proterozoic ages exposed in southern Baird Mountains and western Wiseman quadrangles. In the Schist belt in the Baird Mountains quadrangle, a light-gray, medium- to fine-grained, foliated to gneissic metamorphosed granite sits within an exposure of unit DpCsc (Karl and Aleinikoff, 1990). The orthogneiss contains cm-sized albite porphyroblasts, pink K-feldspar, quartz, biotite, chlorite, sericite, magnetite, calcite, sphene, and zircon. Karl and Aleinikoff (1B990) reported a U-Pb zircon age of 705 35 Ma. In the Central belt, two bodies of Proterozoic metagranitic rocks span the boundary of the Survey Pass and Wiseman quadrangles. The Ernie Lake pluton yielded an age of 971 5 Ma (McClelland and others, 2006); the nearby Sixtymile River orthogneiss yielded discordant zircons likely of a similar age (Dillon and others, 1980). Granodiorite at Mt. Angayukaqsraq, in the northeastern Baird Mountains quadrangle, yielded a U-Pb zircon age of 750  AGreenish-gray, yellowish-green, olive green or greenish-black serpentinite, minor basaltic rocks, harzburgite tectonite, and nephrite jade exposed in the southern Ambler River and adjacent Shungnak quadrangles. In the Cosmos Hills, fault-bounded serpentinite bodies up to 130-m-thick and 8-km-long sit structurally above Paleozoic and older metasedimentary rocks of the Schist belt and below metabasalts of the Angayucham terrane (JDab) and Cretaceous metasedimentary rocks (Ks) (Hitzman and otBhers, 1982; Loney and Himmelberg, 1985). In the Jade Mountains, in the southwestern Ambler River quadrangle, serpentinite is mixed with subordinate basaltic rocks, dunite, peridotite, and nephrite jade (Mayfield and Tailleur, 1978), and is located adjacent to a thick sequence of basalts of the Angayucham terrane (JDab). Nephrite jade is found as boulders in stream bottoms in several locations in the area and in outcrop in the Jade Mountains (Loney and Himmelberg, 1985). Equivalent to CzMz1surficialsedimentarydepositsundivided~VA5133AMetamorphosed pillow basalt, hyaloclastic breccia, basaltic tuff, diabase, microgabbro, radiolarian and tuffaceous chert, minor metalimestone, and rare mafic schist in an imbricate package exposed along the southern boundary of the map area. The package varies significantly in breadth (north-south) along its exposure length; the area of broadest exposure is 8 km across (Pallister and others, 1989). Basalt and diabase predominate. Metachert occurs in both depositional (bedded and interpilsed along the southern boundary of the map area. The package varies significantly in breadth (north-south) along its exposure length; the area of broadest exposure is 8 km across (Pallister and others, 1989). Basalt and diabase predominate. Metachert occurs in both depositional (bedded and interpily~benjaminAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWbrooksAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WconodontAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WdataAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW$ATectonic assemblage of meter to kilometer-scale fault slivers of pillow basalt, mafic schist, metagabbro, metalimestone, metachert, metamorphosed lithic sandstone, phyllite, and rare serpentinite exposed in low hills in the south central and southwestern part of the map area. Metamorphic grade varies from slice to slice and ranges from pumpellyite to greenschist facies; relict igneous clinopyroxene is present in some metagabbros. One sliver of mafic schist on the Baird Mountains/Ambler RiBver quadrangle boundary contains abundant blue amphibole, probably crossite (S.M. Karl, unpublished data). The age of the unit is based on the likely time of fault juxtaposition of the tectonic slivers. Metachert yielded Mississippian radiolarians; metalimestone bodies near the contact between this unit and the adjacent Angayucham terrane (JDab) yielded Middle and Late Devonian and Ordovician conodonts (Pallister and Carlson, 1988; Table A-1, Ambler River, Hughes, and Survey Pass quadran}AByielded Late Devonian plant fossils and spores that are of Middle or Late Devonian and probable Early Devonian age (Brosg and Reiser, 2000). May be correlative to parts of unit Pzpg. Area with overlay pattern is schistose, due to crystallization of micas at low metamorphic grade, and contains quartz veins. Schistose varieties are equivalent to units "Dmw" and "Dpm" of Brosg and Reiser (2000). Dps is part of the Venetie terrane of Brosg and Reiser (2000), and was included in the SlatC-e Creek subterrane by Moore and others (1994) CDpsDDevonianE3Schistose lithic sandstone and shale, Phyllite beltATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.BA86076CPzpCbsDPaleozoic to Proterozoic?EBiotite schist, Ruby terraneATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.7A9325ABiotite-bearing pelitic schist with subordinate metaquartzite, exposed in the southern Chandalar quadrangle. May have crystallized at upper greenschist or amphibolite facies (Dusel-Bacon and others, 1989). Equivalent to schists of the Ruby geanticline, south of the map area, where the earliest documented metamorphic episode occurred under blueschist-facies conditions (Sheet 1, Figure 2; Patton and others, 1994). The Ruby blueschist episode was similar in grade, deformational style, and tBaiming to the blueschist-facies metamorphism recorded in the Schist belt (Roeske and others, 1995)OCPzpCsrKCgles). Pallister and Carlson (1988) suggested that the unit is derived from the adjacent units to the south (JDab) and north (Pzpg), and that contacts with those units are structurally gradational. Some of the carbonate rocks are too old to have been derived from JDab, and may have affinities with units some distance to the north. In the Wiseman quadrangle, the contact between the Angayucham terrane and the phyllite and graywacke unit (Pzpg) is a zone of anastomosing faults that involves DZa broad variety of lithologies and matrix-supported mlange (Moore and others, 1997b; Gottschalk and others, 1998), and probably an eastward extension of KJm. Equivalent to "KJm" of Patton and others (2005), "KJm" of Pallister and Carlson (1988), "MzPzm" of Karl and others (1989b) and part of the Slate Creek terrane of Moore and others (1997b)$CKJmDCretaceous to JurassicEMelange, Phyllite belt 4GJiolarians and conodonts were collected from fault-bounded lenses of chert and carbonate rock. The Angayucham terrane is thought to comprise parts of a collapsed ocean basin that were emplaced in a high structural position during the Brooks Range orogeny. Metabasalts of the terrane along the southern flank of the Brooks Range, the "Narvak panel" of Patton and Box (1989) are typically correlated with basalts of the "Copter Peak allochthon", which are exposed in the crest of the range (MooKre and others, 1994), also in a high structural position. The Maiyumerak sequence (MzDm), in the northwest corner of the map area, contains similar lithologies, but includes basalts with island-arc chemical affinities, unlike metabasalts along the southern or crestal parts of the range (Karl, 1992); we do not consider MzDm part of the Angayucham terrane. The Angayucham terrane is thought to be correlative with the Tozitna terrane and possibly the Innoko terrane in central Alaska (Patton \ tillAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWtillabdumoulinjaharrisagmooretebleickheatheranAVBVCVDVEVFVGVHVIVJVKVLVMVNVPVQVRVSVTVUVVVWVXVYVZV[V\V]V^V_V`VaVbVcVdVeVfVgVhViVjVkVlVmVnVoVpVqVrVsVtVuVvVwVxVyVzV{V|V}V~VV@VAVBVCVDVEVFVGVHVIVJVKVuAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWxofAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWpressAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWrangeAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWsAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWWrWsWtWuWvWwWxWyWzW{W|W}W~WW@W7J Bte" layers and lenses are characteristic and show rare flow banding, breccia textures, and possible welded shard textures (Hitzman and others, 1986). Metabasites occur as pods and lenses; exposures in the Ambler River quadrangle retain remnant pillow structures (Hitzman and others, 1986). Near the Ambler River - Survey Pass quadrangle boundary, where it has been studied in the most detail, the unit is thought to be 700-1,850 meters thick (Hitzman and others, 1986); there, massive sulfideC deposits are associated with the metarhyolites, including the world-class Arctic deposit (Schmidt, 1986). U-Pb zircon ages from metarhyolite layers in the Ambler sequence range from 378-386 Ma; the sample from the Arctic deposit yielded a bimodal igneous zircon population with ages about 378 and 405 Ma (McClelland and others, 2006; Raterman and others, 2006). The significance of the older population of zircons is not understood. The Ambler metarhyolites are, based on these ages, Middle #M ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000. A8602AjBlack-weathering, fine- to medium-grained black metaquartzite exposed along the contact between units Dsq and DpCsc near the boundary between the Baird Mountains and Ambler River quadrangle. Locally may contain small amounts of mica and show segregation of quartz and graphite in layers parallel to foliation. Equivalent to Pzbq of Mayfield and Tailleur (1978)jCPzbqD Paleozoic?EBlack quartzite, Schist belt[" Hhistory. One sample of metafelsite from the Ambler sequence was included in a suite analyzed for feldspar and phengite thermobarometry, and yielded a temperature of 376C and pressure of 10.3 kb, thought to represent conditions of high-pressure metamorphism of the Schist belt (Patrick, 1995). Relict primary volcanic textures in some of the metarhyolite porphyries in the sequence are thought to have been preserved as a result of low fluid-rock ratios and limited element mobility during meIotamorphism, rather than an indication that the sequence escaped metamorphism and deformation (Schmidt, 1986). Equivalent to "metamafic igneous rocks", "megacrystic felsic schist", and "felsic schist" of Mayfield and Tailleur (1978); "mafic volcanic rocks" and "felsic schist" of Nelson and Grybeck (1980); and "Ambler metavolcanic rocks" of Dillon and others (1986)CDaDDevonianEAmbler sequence, Schist belt&_+ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A8605ALight-gray-, brown- and locally orange-weathering, lithologically heterogeneous mix of marble and carbonate-rich, quartz-rich, and mafic schist derived from metasedimentary and metaigneous protoliths; one of two major units that extends along the length of the Schist belt. Within the unit, lithologies are interlayered at scales varying from millimeters to 10's of meters. Calcareous schist, albitic schist, marble, and metaquartzite (massive, mica-poor varieties of pelitic schist) are commOR+/ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.0A8604ALight-, medium-, and dark-gray phyllite, dark-gray to black metaquartzite, dark-gray and grayish-brown calcareous phyllite, and reddish-brown-weathering impure marble exposed in fault-bounded lenses along the Schist belt-Central belt contact in the Wiseman quadrangle. Lithologic layering is visible in outcrop where it crosses foliation; locally, lithologic layering is transposed by foliation, which is defined by fine-grained mica. In thin section, lithologic layering and relict clasts arM$zBitic schist and dolostone, and are undated. Medium-dark-gray, fine-crystalline, medium-bedded metalimestone with relict corals, stromatoporoids, spines, and echinoderm debris yielded conodonts of Early (middle Emsian)-Middle Devonian age (Table A-1, Ambler River quadrangle). Other undated lithologies (all sampled for, but barren of conodonts) include medium-light-gray dolostone with fine, wispy laminae; dark cherty metalimestone intercalated with quartzite; and dark gray to black, locally CGsooty metalimestone and marble. Local garnet-epidote skarn in marble adjacent to granite (Dg) indicates intrusive relation between pluton and some parts of Pzsm, but other Pzsm lithologies, including the Devonian metalimestone, may be in fault contact with the skarn-bearing marbles (J. Dumoulin, unpublished field notes, 1986)#CPzsmD PaleozoicEMarble of the Schist beltWN+st and marble" of Brosg and Reiser (1964) ACDpCscDDevonian to ProterozoicECalcareous schist, Schist beltATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A7360AGray marble, orange dolomitic marble, magnetite-bearing chlorite schist, and pelitic schist exposed in the central Survey Pass quadrangle. Lithologies are interlayered and isoclinally folded, and the unit has a bedded appearance due to layers of resistant marble. Adjacent to the Arrigetch pluton, the unit contains calc-silicate skarn (Nelson and Grybeck, 1980). Mineral assemblages from most of the unit stabilized at albite-epidote-amphibolite facies (Dusel-Bacon and others, 1989; Nelson JJ Mountain area). Additional data on lithofacies and biotas of this unit are found in Carter and Tailleur (1984), Dumoulin and Harris (1987), Table A-1 (Ambler River, Baird Mountains, Chandalar, and Survey Pass quadrangles), and the Alaska Paleontological DatabaseeCOpCcD!Middle Ordovician to Proterozoic?E{Older carbonate rocks of the Nanielik antiform, Central belt and part of Northern thrust assemblages, Ordovician rocks onlyATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.KA6927EA7000AGreen and greenish-gray, schistose to massive, irregularly-shaped bodies and lenses of metamorphosed mafic rocks in units Dsq and DpCsc large enough to show at the scale of the map occur in the Survey Pass and Chandalar quadrangles. Relict pillow structure is reported in the central Survey Pass quadrangle and adjacent to unit Dg in the Chandalar quadrangle (Nelson and Grybeck, 1980; Brosg and Reiser, 1964). Rocks of the unit are typically composed of albite, chlorite, actinolite, epidoted greenish-gray, schistose to massive, irregularly-shaped bodies and lenses of metamorphosed mafic rocks in units Dsq and DpCsc large enough to show at the scale of the map occur in the Survey Pass and Chandalar quadrangles. Relict pillow structure is reported in the central Survey Pass quadrangle and adjacent to unit Dg in the Chandalar quadrangle (Nelson and Grybeck, 1980; Brosg and Reiser, 1964). Rocks of the unit are typically composed of albite, chlorite, actinolite, epidote`/;Bned and broken. Protolith rocks may range in age from Proterozoic to Paleozoic, but no age control is available. Age of unit is based on likely age of tectonic event that created the shear zone, which encompasses a zone of deformation between the Schist and Central belts. Equivalent to "Hammond River phyllonite" of Moore and others (1997b); westernmost extent of the unit is approximately locatedCKhsD Cretaceous?ENHammond River shear zone, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A5003`APelitic schist, metaquartzite, mafic schist and other lithologies; gneissic textures are particularly common where the unit is adjacent to metaplutonic rocks. Mafic rocks within the unit contain assemblages stable in the albite-epidote-amphibolite facies (Dusel-Bacon and others, 1989; Vogl, 2002); exposures west of the major orthogneiss bodies appear to be lower in grade (Nelson and Grybeck, 1980; Toro, 1998). Metasedimentary rocks contain biotite throughout the unit, and garnet adjacentB to the granitic orthogneiss bodies of Dg (Nelson and Grybeck, 1980; Toro, 1998). Equivalent to "Pzsgn" of Nelson and Grybeck (1980), and "Pzqm" and "Pzs" of Toro (1998)CDpCgnDDevonian to Proterozoic?E5Schist and paragneiss, Arrigetch-Igikpak thermal highZ[heatherAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWinvestigationsAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWjAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWmapAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWmooreAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvW]Gof@ scale@scientific@_v^sim@8t@\ AK S B @CAABD FHJLB$A(AA&C)AA,E-B0D1 @B54 B6D7 B;DJ?! BLDKFJH[A#" @MAU$BZA&%AXA('AWCVE\G]I^K_M`AeDf)A+*AhEiBmDnFoA/.ArCsEtGuIvKwMxOy0B}D~FH1BA32ACE4BDF5BA76ACEA:9ACEA<y~oOcause rocks are generally foliated and contain minerals consistent with lower greenschist facies metamorphism, and CAIs are uniformly 5-5.5 (Table A-1, Baird Mountains quadrangle)CJDkDJurassic to DevonianEYRocks of the Kivivik Creek sequence, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6305*hASandstone, shale, argillaceous limestone, limestone, dolostone, mudstone, chert and siltstone in north-central Wiseman quadrangle. The unit conformably overlies the Kanayut Conglomerate (Bowsher and Dutro, 1957) of the Endicott Group (Tailleur and others, 1967). JCs consists of the Kayak Shale (Bowsher and Dutro, 1957) of the Endicott Group (Lower Mississippian), the Lisburne Group (Schrader, 1902; Bowsher and Dutro, 1957; Carboniferous), and the Siksikpuk Formation (Patton, 1957; PermianB) and Otuk Formation (Mull and others, 1982; Triassic and Jurassic) of the Etivluk Group (Mull and others, 1982). The succession is similar to that of map unit TrCs of the Doonerak antiform, but differs in some aspects; it is part of unit TrCs of Dillon and others (1986). Dillon and others (1986), Adams (1991, 1994), and Adams and others (1997) provide more information on this succession. The Carboniferous rocks were described in detail and dated on the basis of foraminifers by Armstrong 1+ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6200ABlack carbonaceous metachert and siliceous phyllite exposed in a small area in the northwestern Baird Mountains quadrangle. Local layers of black carbonaceous metalimestone contain conodonts of Devonian-Mississippian age (Table A-1). The unit likely formed in low-oxygen slope and (or) basin settings. Massive iron sulfide intervals with elevated silver and other metal values were documented by Karl and others (1985), Schmidt and Allegro (1988), and Zayatz and others (1988). Karl and others0B (1989b) mapped basal depositional contacts with both the Noatak Sandstone and the Kayak Shale. At one locality (Karl and others, 1989b), Mcp is overlain by an outcrop of chert and argillite of the Etivluk Group (Mull and others, 1982) that is too small to show separately at the scale of our map. Mcp is lithologically similar to, and likely correlative with, the Kuna Formation (Mull and others, 1982) of the Lisburne Group (Schrader, 1902; Bowsher and Dutro, 1957). New studies (e.g., DumouC7lin and others, 2004) indicate that the Kuna is of Mississippian age and does not extend into the Pennsylvanian; hence, we infer a Mississippian age for Mcp. Mcp is equivalent to map unit lPMc of Karl and others (1989b) in the northwestern Baird Mountains quadrangle; it is also present in unit JDk of this mapCMcpD MississippianE_Carbonaceous chert and siliceous phyllite, Central belt and part of Northern thrust assemblagesDnite (Plate 2, Dillon and others, 1980). However, Reed and Hemley (1966) identified the mica pyrophyllite in exposures of Kekiktuk Conglomerate in the northeast Brooks Range. Pyrophyllite forms in rocks unusually rich in silica and aluminum at low metamorphic grades, and at temperatures and pressures above 400C and about 3kb, it reacts to form kyanite (Spear, 1993). Vogl (2003) reported kyanite - pyrophyllite and kyanite - chloritoid assemblages in exposures of Kekiktuk Conglomerate in Ethe central Survey Pass quadrangle. He considered the kyanite to be metamorphic and estimated pressures and temperatures of 300-400C and pressures between 3 and 6 kb. Thus, in rocks rich in Si and Al, kyanite is stable at greenschist facies and moderate pressures; kyanite in conglomerates of this unit may have formed at conditions consistent with the low metamorphic grade of the surrounding rocks. Equivalent to parts of unit Mc of Mayfield and Tailleur (1978), parts of Mke? and Mk? of NeB quadrangle Mkl includes map units Mk (part) and Ml of Nelson and Grybeck (1980) and overlies the Kanayut Conglomerate of the Endicott Group. In both quadrangles, Kayak Shale (Bowsher and Dutro, 1957) of the Endicott Group (Tailleur and others, 1967) is volumetrically predominant and consists of black phyllite or slate interlayered with brown to orange-weathering fossiliferous siltstone, sandstone, and limestone. Limy layers in the Survey Pass quadrangle contain ostracodes, brachiopods, brCyozoans, and echinoderm debris of probable Early Mississippian age, as well as latest Devonian-earliest Mississippian (late Famennian-Kinderhookian) conodonts with CAI values of 4 to 5.5 (Table A-1). The Lisburne Group (Schrader, 1902; Bowsher and Dutro, 1957) is gray limestone to metalimestone with layers and nodules of black and gray chert. It contains locally abundant fossils that include crinoid, bryozoan, and coralline debris, brachiopods, gastropods, and sponge spicules, as well as L6/ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.7ALight- to medium-gray weathering, dark-gray metalimestone and dolostone with locally abundant layers and lenses of black chert, exposed at one locality in the Nanielik antiform, northeastern Baird Mountains quadrangle. The unit contains conodonts of Late Mississippian (latest Meramecian to early Chesterian) age (Karl and others, 1989b) and megafossils, commonly silicified, that include Meramecian-early Chesterian lithostrotionid corals (entries 5682, 5683 in Alaska Paleontological DatabaBse) and possible stromatolites. Ml is correlative in age and facies with the Kogruk Formation (Sable and Dutro, 1961) of the Lisburne Group (Schrader, 1902; Bowsher and Dutro, 1957). Carbonate rocks of Ml are spatially related to metasiliciclastic strata (map unit Dmu of this map, map unit Pzqs of Karl and others, 1989b) that consist of quartz metaconglomerate, metasandstone, and siliceous phyllite. The nature of the contact between the siliciclastic and carbonate rocks is uncertain. Ml i:4Eer rocks (units Pzm and Spl of this map) (Mayfield and Tailleur, 1978; Nelson and Grybeck 1980). Mu also occurs along the eastern border of Survey Pass quadrangle, where it consists of rocks tentatively assigned to the Kekiktuk and Kayak (Nelson and Grybeck, 1980) that have yielded no diagnostic fossils, and in a small area near the western border of Wiseman quadrangle, where Lisburne(?) metalimestone contains gastropods, molluscan and echinoderm debris, possible bryozoan, pelecypod, brachF;iopod, and ostracode fragments, and foraminifers of Mississippian(?) age (J. Dutro and A. Armstrong, unpublished fossil reports, 1980, 1981). Although the exposures in this unit may be correlative to those included in the unit Mkkl, they are relatively poorly characterized sedimentologically and paleontologically CMuD MississippianEKMetasedimentary rocks, Central belt and part of Northern thrust assemblages56Cs equivalent to map unit Mc of Till and Snee (1995) and the eastern part of map unit Mko of Karl and others (1989b) in the Baird Mountains quadrangle rCMlD MississippianEECarbonate rocks, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6365^\simAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWsiwiecAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWsouthernAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWsurveyAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWWkWlWmWnWoWpWqWrWsWtWuWvW<AQuartz conglomerate, quartzite, metasandstone, phyllite, shale, and metalimestone in the Ambler River, Survey Pass, and Wiseman quadrangles. Includes metasiliciclastic and metacarbonate strata in Ambler River and Survey Pass quadrangles, most with few to no age constraints, assigned to various Mississippian units by Mayfield and Tailleur (1978) and Nelson and Grybeck (1980). In east-central Ambler River quadrangle, consists of undated quartz conglomerate that contains minor interlayers ofB coarse-grained quartzite and red and green phyllite (map unit Mc of Mayfield and Tailleur, 1978). Clasts are stretched and made of quartz, varicolored chert, quartzite, and gray slate. Here the unit resembles Kekiktuk Conglomerate of Brosg and others (1962). Along eastern border of Ambler River quadrangle, this unit comprises a depositional succession of, in ascending order, Kekiktuk Conglomerate, Kayak Shale (Bowsher and Dutro, 1957), and Lisburne Group (Schrader, 1902; Bowsher and Dutr6Co, 1957) that consists of map units Mke, Mk, and Ml of Mayfield and Tailleur (1978); the succession is lithologically like that of our map unit Mkkl (which crops out ~10 km to the south) but has no reported age control. A similar succession, included in this unit, occurs in adjacent west-central Survey Pass quadrangle (map units Mke, Mk, Ml, and Mu of Nelson and Grybeck, 1980). These rocks have produced a few fossils, including crinoids, brachiopods, corals, and foraminifers, of Early and DLate Mississippian ages (Brosg and Pessel, 1977). The Kekiktuk in this area consists of semischistose metasandstone and metaconglomerate with minor interlayers of red, green, and gray phyllite (Nelson and Grybeck, 1980). Coarser layers contain quartz clasts as much as 2 cm in diameter; some intervals are calcareous and (or) feldspathic. Radiating clusters of chloritoid grew across foliation planes in some samples. Mu in all three of these areas is interpreted to depositionally overlie old+ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.A6900AMetasandstone, metasiltstone, and subordinate phyllite exposed in the northern Baird Mountains, Ambler River, and Survey Pass quadrangles; part of Endicott Group (Tailleur and others, 1967). The unit was established by Smith (1913); Dutro (1952) designated the type section in the Misheguk Mountains quadrangle north of map area (see also Nilsen and others, 1985). Dn is mapped as a separate unit in the north-central Baird Mountains quadrangle (unit Dn of Karl and others, 1989b), northeastern9Co, 1957) that consists of map units Mke, Mk, and Ml of Mayfield and Tailleur (1978); the succession is lithologically like that of our map unit Mkkl (which crops out ~10 km to the south) but has no reported age control. A similar succession, included in this unit, occurs in adjacent west-central Survey Pass quadrangle (map units Mke, Mk, Ml, and Mu of Nelson and Grybeck, 1980). These rocks have produced a few fossils, including crinoids, brachiopods, corals, and foraminifers, of Early and DLate Mississippian ages (Brosg and Pessel, 1977). The Kekiktuk in this area consists of semischistose metasandstone and metaconglomerate with minor interlayers of red, green, and gray phyllite (Nelson and Grybeck, 1980). Coarser layers contain quartz clasts as much as 2 cm in diameter; some intervals are calcareous and (or) feldspathic. Radiating clusters of chloritoid grew across foliation planes in some samples. Mu in all three of these areas is interpreted to depositionally overlie oldamountsBWMWPW^WBWCWamphiboleFWcWeWnWJWamphiboliteqWwWamphibolitemetaquartzitecalcareousschistmetapeliteandaqVamphibolite-faciesCWEWqWGWanAWCWFWKWLWNWPWTWWW_W`WbWcWdWeWgWqWsWtW{W}WBWCWDWGWHWJWanalysis{WyaccompanyingAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWalaskaAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWandAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWbAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWuWvWwWxWyWzW{W|W}W~WW@WwZdumoulinAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWeAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWgAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWharrisAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWDoriginal sedimentary structures are commonly preserved. In the Baird Mountains quadrangle, these include meter-thick intervals of planar and trough cross-beds and, near the top of the unit, coarsening-upward cycles of pebbly beds; pebbles are quartz or argillite and as much as 1 cm in diameter (Karl and others, 1989b). Metasandstone is typically calcareous and (or) ferruginous, thin- to medium-bedded, and fine- to medium-grained. The most detailed petrographic descriptions of metasandstoneE are from the Survey Pass quadrangle, where it consists of poorly to moderately well sorted, angular to subrounded quartz and chert (together generally ~80%), plagioclase feldspar (5 to 15%), fine-grained foliated lithic grains (as much as 20%), and minor amounts of iron oxide, tourmaline, and zircon. Fossils are abundant in some calcareous beds and include brachiopods, echinoderms, gastropods, pelecypods, plant debris, and trace fossils; the most tightly dated assemblages in the map area LC Chapman and others (1964). Limestone layers contain Late Devonian (late Frasnian to early Famennian) brachiopods, mollusks, and echinoderms (Dillon and others, 1986; Brosg and Reiser, 1964). Middle to Late Devonian conodonts were collected in the east-central Wiseman quadrangle (Table A-1). In the Phillip Smith quadrangle, north of the map area, conodonts from the limestones are middle to late Frasnian (Late Devonian; Dumoulin and Harris, 1994). A single Middle Devonian conodont colleDction on Wiseman/Survey Pass quadrangle boundary is unusually old for the unit; the conodonts may be reworked, or may indicate there is an unidentified expanse of Dmu included in the unit. The portion of unit shown with overlay is more strongly foliated and sedimentary structures are less obvious. The "Dietrich River phyllite" and part of the "Dusty Mountain phyllite" of Moore and others (1997b) are included in this more schistose part of the unit. Mafic bodies in the unit (both strongl#ABeige- to orange-weathering, laminated, partly argillaceous to silty metalimestone and light- to dark-gray, flaggy-bedded to massive metalimestone, marble, and dolostone. DOb is part of the Nakolik River sequence of Karl and others (1989b). The Baird Group was established by Tailleur and others (1967), but was restricted by Dumoulin and Harris (1994) to the carbonate succession of the west-central Baird Mountains quadrangle; broadly coeval carbonate strata of the eastern Baird Mountains qBuadrangle and Middle and Late Devonian carbonate rocks of the Maiyumerak Mountains were excluded. Conodonts constrain the age, depositional settings, and biogeographic affinities of this unit (Karl and others, 1989b; Dumoulin and Harris, 1987, 1994; Table A-1, Baird Mountains quadrangle; Alaska Paleontological Database). Older rocks are exposed mainly in the south and younger strata to the north. Lower and upper contacts of DOb are faults, but the unit was likely depositionally overlain byE+#ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.$A6980AVery light- to dark-gray- (locally orange-) weathering, gray to black, commonly massive dolostone and lesser metalimestone and marble exposed in the Nanielik antiform (northeastern Baird Mountains and northwestern Ambler River quadrangles) and in the northwestern Chandalar quadrangle. DOc was first described in the Nanielik antiform (Sheep Creek section of Dumoulin and Harris, 1987) and later recognized to the east (Dumoulin and Harris, 1994). Meter- to decimeter-scale color banding is ch$EfYounger carbonate rocks of the Nanielik antiform, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.%A7740ADolostone, metalimestone, marble and subordinate quartzose metasedimentary rocks, carbonate conglomerate, and metabasite exposed in the in the Nanielik antiform (northeastern Baird Mountains and northwestern Ambler River quadrangles), central Survey Pass quadrangle, and along the Dalton Highway in the Wiseman and Chandalar quadrangles. The unit was first described in the Nanielik antiform (Mt. Angayukaqsraq section of Dumoulin and Harris, 1987) and later recognized to the east (Dumoulin aC#E, chloritic metasandstone. DOb hosts several mineral occurrences, including the Omar copper prospect in Devonian (Emsian) dolostone (Folger and Schmidt, 1986; Folger, 1988) and the Powdermilk Pb-Zn-Ag prospect in Ordovician(?) dolostone (Schmidt and Folger, 1986). DOb includes local occurrences of metabasaltic rocks of unknown age that are especially abundant in western exposures. These rocks contain fine-grained blue amphibole (crossite) at multiple localities, indicating that the Baird GFCroup has experienced blueschist facies metamorphism. The unit has similarities in lithofacies and biofacies to parts of OpCc and DOc, as well as coeval strata of the York Mountains on Seward Peninsula. Conodont assemblages have both Laurentian and Siberian affinities (Dumoulin and Harris, 1994; Dumoulin and others, 2002)  CDObDDevonian to OrdovicianEABaird Group, Central belt and part of Northern thrust assemblages;&ADark-gray to black phyllite and calcareous phyllite with dark-gray to orange-weathering marble and dolostone layers up to 50 m thick are exposed in the northeastern Survey Pass and northwestern Wiseman quadrangles. In the Wiseman quadrangle, the unit is thought to be depositionally overlain by unit Dmu. Brachiopods from a marble lens near the Wiseman-Survey Pass boundary yielded a Middle Devonian or Frasnian age (W.P. Brosg, written commun., 1988). Based on this very limited data, PzbsB may overlap the age of upper parts of units DOb and Doc and/or it may be a facies equivalent of the older parts of Dmu. Equivalent to "MDcp" of Nelson and Grybeck (1980), and "Dbs" of Dillon and others (1986)CPzbsD PaleozoicEQBlack metasedimentary rocks, Central belt and part of Northern thrust assemblages%Dte interlayers of phyllite and calcareous and chloritic schist. Carbonate layers contain locally abundant coated grains; preserved sedimentary structures include grading and parallel and cross-laminae and suggest deposition by turbidity currents. Subunit two is massive marble that grades upward into thin couplets of bioturbated metalimestone and laminated dolostone interpreted as shallowing-upward peritidal cycles. Protoconodonts, chancellorid sclerites, hyolithids, and steinkerns of monopElacophoran mollusks indicate a maximum age of Early Cambrian for the marble; acrotretid brachiopods and agnostid arthropods demonstrate Middle and Late Cambrian ages for the middle and upper parts of the subunit. A condensed Lower and Middle Ordovician section deposited in a shallowing-upward regime makes up the third subunit. Carbonaceous phyllite, with subordinate layers of radiolarian chert and fine-grained metalimestone, grades up into platform-margin carbonate turbidites and then into}[(ATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.)A5560APhyllite, fine-grained schist, and phyllonite of the Central belt that underlie areas of poor exposure in the northeastern Baird Mountains quadrangle, western Ambler River quadrangle, and northwestern Chandalar quadrangle. Locally contains minor lenses of metalimestone and metaconglomerate. Equivalent to parts of Pzqs of Karl and others (1989b), parts of uqm of Mayfield and Tailleur (1978), and Dusty Mountain phyllite of Moore and others (1997b)CPzpD Paleozoic?E>Phyllite, Central belt and part of Northern thrust assemblages'Bstudied in sufficient detail to allow assignment to carbonate units such as DOc. Thoroughly recrystallized parts of this unit may be equivalents of units such as OpCc, DOc, DOb, and (or) Dl that have lost their distinctive lithologic and faunal features through metamorphism and (or) deformation. Existing fossil data and regional relationships suggest that most Pzm is Cambrian through Mississippian in age. Pzm occurs in the southwestern, central, and northeastern parts of the Baird MountainCs quadrangle. Most outcrops contain no fossils or relict sedimentary features, but a belt in the central part of the quadrangle (marble of Klery Creek, Pzkm, of Karl and others, 1989b) is in part of Devonian and Mississippian age. This marble contains subordinate interlayers of quartz-chlorite schist, mica schist, and black carbonaceous quartzite, and has produced Late Silurian-Early Devonian conodonts, silicified two-hole crinoid columnals of late Early-early Middle Devonian (late Emsian}*B]of the unit. They also collected poorly preserved brachiopods, thought to be post-Early Ordovician, and coral fragments from the lowest part of the unit. Equivalent to the Jesse Mountain phyllite of Moore and others (1997b), thrust nappe N6 of Oldow and others (1998), and part of "black slate, phyllite, and limestone" of Dillon and others (1986)KCPzjD PaleozoicE]Metasedimentary rocks of Jesse Mountain, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.+A7325BGray to dark-gray carbonaceous phyllite, locally silica rich, exposed in the Central belt in the western Ambler River quadrangle. Equivalent to parts of Pzbs of Mayfield and Tailleur (1978)CPzbD Paleozoic?z+IATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.JA7741ADolostone, metalimestone, marble and subordinate quartzose metasedimentary rocks, carbonate conglomerate, and metabasite exposed in the in the Nanielik antiform (northeastern Baird Mountains and northwestern Ambler River quadrangles), central Survey Pass quadrangle, and along the Dalton Highway in the Wiseman and Chandalar quadrangles. The unit was first described in the Nanielik antiform (Mt. Angayukaqsraq section of Dumoulin and Harris, 1987) and later recognized to the east (Dumoulin aJF middle to inner platform bioclastic supportstones; graptolites and conodonts indicate an age of Arenig to Caradoc for this subunit. The stratigraphic succession of O_Pc is most complete and lithologies are most diverse in the Baird Mountains and western Ambler River quadrangles. There, the close spatial relationship of the unit with Proterozoic metamorphic rocks (P_am) is thought to reflect an original depositional relationship. Conglomerate and metabasite intervals in older rocks and thGe lower two subunits of younger strata are known only in the Baird Mountains. The presence of OP_c as a fault-bounded sequence in the Akiak antiform (western Ambler River quadrangle) is documented in Dumoulin (1988) and Dumoulin (unpublished field notes, 1986, 1987). Older rocks in unit OP_c may correlate with parts of DP_sc in the schist belt (Dumoulin, 1988) and the Katakturuk Dolomite (Dutro, 1970; Blodgett and others, 1986) in the northeastern Brooks Range. The Cambrian subunit is partZf,E^Metamorphic rocks of the Ernie Lake area, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.-A8655AHeterogeneous assemblage of interlayered calcareous, mafic, and siliceous rocks exposed in the central Baird Mountains, Ambler River, and Wiseman quadrangles. Includes black quartzite, meta-argillite, and marble; white quartzite; green, buff, and black phyllite and calcareous phyllite; orange-weathering dolostone, orange weathering chloritic marble, chloritic dolomitic marble, gray marble, medium- and dark-green mafic metavolcanic rocks; pale green and orange calcareous schist, and gray-gim,?JNg and Reiser (1964); and units "Dbsg" and "Dbls" of Brosg and Reiser (2000) CDmuDMiddle and Late DevonianEMetasedimentary and lesser metaigneous rocks, volcanic-rock bearing subunit, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.%&/ARelatively homogeneous assemblage dominated by light greenish-gray fine-grained schist, typically accompanied by minor layers of metaconglomerate, marble, and calcareous schist. Exposed in the southern Central belt in the western Survey Pass quadrangle and straddling the Wiseman/Chandalar quadrangle boundary. In the eastern exposure of the unit, the schist has a laminated appearance and contains a marble that yielded a conodont of Ordovician to Triassic age (Moore and others, 1997b; TableB A-1, Chandalar quadrangle). Equivalent to "Pzclq" and parts of "DSsk" and "DSso" of Nelson and Grybeck (1980) and the "Vi Creek schist" of Moore and others (1997b)CPzpCqsDPaleozoic to Proterozoic?EWQuartz-rich metasedimentary rocks, Central belt and part of Northern thrust assemblages& CA8608 The calcareous schist unit is equivalent to the "Kogoluktuk schist" of Hitzman and others (1982, 1986), "calcareous schist and marble of the Kallarichuk Hills" of Karl and others (1989b), parts of the Pzuc, Pzcq, and Pzcs units of Mayfield and Tailleur (1978); parts of the Pzsch, Pzca, DSso and DSsk units of Nelson and Grybeck (1980), the "calcareous schist" unit of Dillon and others (1986), the "Emma Creek schist", "unnamed calcareous schist", "Midnight Dome schist", and the "calcareoN2us schist and marble" of Brosg and Reiser (1964) HCDpCscDDevonian to ProterozoicE3Calcareous schist, albite-rich subunit, Schist beltATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.CA8608(gspinesNWspl[W\WbWgWFWspongePWTWVWXWBWCWIWsporesGWAWsr{WstabilizedQWstableRWYWstarvedTWstaurolitevWaurolitevWWvWW%N0Be recognizable; metamorphic minerals include white mica, chlorite, stilpnomelane (?), and very fine-grained garnet or albite. No protolith age control is available; the protolith may have been a sequence of turbidites. Equivalent to "Hunt Fork schist" of Brosg and Reiser (1964) and Bluecloud Mountain schist of Moore and others (1997b) who incorrectly described it as mafic schistoCPzpCbDPaleozoic to Proterozoic?EaMetasedimentary rocks of Bluecloud Mountain, Central belt and part of Northern thrust assemblagesATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.1A9300DADark-gray to black phyllite and lesser gray-green phyllite with thin layers of siliceous or calcareous metasiltstone, lithic wacke, metasandstone, and minor layers of fossiliferous metalimestone exposed along the length of the northern boundary of the map. Locally massive mafic sills and dikes up to 10 m thick are common. One locality of pillow lava was reported in the Baird Mountains quadrangle (Karl and others, 1989b). A basal conglomerate containing clasts of quartz, chert, siltstone,B slate, and a few limestone and dolostone pebbles was mapped in Wiseman and Chandalar quadrangles (Dillon and others, 1986; Brosg and Reiser, 1964) . In excess of 300 m thick, the unit depositionally overlies parts of units Dl, Dmu, and Pzm. The Hunt Fork Shale is depositionally overlain by the Noatak Sandstone (Dn) and Kanayut Conglomerate (MDk), and with those units constitutes a major part of the Endicott Group (Tailleur and others, 1967). Originally designated the Hunt Fork Shale bye3ADolostone, limestone, argillaceous or sandy limestone, sandstone, and limestone and dolostone with chert that make up the Eli River sequence of Karl and others (1989b). MDer consists of unnamed Middle Devonian carbonate rocks (here excluded from the Baird Group of Tailleur and others, 1967), Eli Limestone of Tailleur and others, 1967 (also excluded from the Baird Group), and Utukok and Kogruk Formations (Sable and Dutro, 1961) of Lisburne Group (Schrader, 1902; Bowsher and Dutro, 1957); aBll contacts within this succession appear conformable. Unnamed lowest unit is light- to medium-gray-weathering, medium- to dark-gray dolostone and lesser limestone. Lithofacies include laminated mudstone with fenestral fabric, sheet and desiccation cracks, and evaporite laths; stromatoporoid wackestone; and peloidal grainstone. Conodonts indicate an age of Eifelian-Givetian (Middle Devonian). Base of the unit is not exposed. Eli Limestoneis yellow-brown to orange weathering, medium- to dae2ABasalt, limestone, and two belts of mlange exposed in the northwesternmost part of the map area. Four northeast-southwest trending belts defined by Karl and others (1989b) and revised in Karl (1992) include, from east to west: matrix supported mlange with meter-decameter-size blocks of pillow basalt, dolostone, marble, phyllite, argillite, quartz wacke, and gabbro; the Kugururok Limestone (Sable and Dutro, 1961), which is Middle to Late Devonian based on conodont and megafossil ages (KBarl and others, 1989b), and contains sandstone layers, volcanic lithic grains, and feldspar grains; a thick section of massive to pillowed basalt with minor andesite, dacite, tuff, and volcanic breccia, thought to be Triassic; and a matrix-free mlange with meter to kilometer sized blocks of quartz wacke, argillite, bedded chert, limestone, and volcaniclastic rocks (Karl and others, 1989b; Karl, 1992). Blocks of carbonate rock and chert in the matrix-supported mlange yielded fossils thatXW4K`, the nearest coeval strata in the EMA; the most notable contrast is the presence of somewhat deeper water facies in parts of both the Carboniferous and Permian successions in JCs. However, Lisburne Group facies in TrCs are generally similar to coeval rocks exposed to the northeast in the central Chandler Lake quadrangle (Dumoulin and others, 1997) CTrCsDTriassic to CarboniferousE$Sedimentary rocks, Doonerak antiformATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.5A6720V5AVolcanic rocks, volcaniclastic rocks, and clastic sedimentary rocks exposed in the core of the Doonerak antiform, northeastern Wiseman quadrangle. The unit can be divided into at least two lithologic sequences, one dominated by volcanic rocks, the other by sedimentary rocks (Dillon and others, 1986; Moore and others, 1994; Julian and Oldow, 1998). The thick volcanic sequence includes flows and pyroclastic rocks with island-arc chemical affinities (Julian and Oldow, 1998). Sedimentary roBcks include phyllite, slate, sandstone, fine-grained conglomerate, and lenses of limestone, including carbonate conglomerate. Middle Cambrian microfossils, brachiopods and trilobites, Ordovician conodonts, and Silurian graptolites and conodonts have been recovered from the sedimentary rocks (Dutro and others, 1984; Repetski and others, 1987). Cambrian fossils have Siberian affinities (Dutro and others, 1984). K-Ar and Ar-Ar ages from five dikes yielded two sets of ages (Dutro and othersV4Ie, as well as Late Triassic conodonts (Dutro and others, 1976; Mull and others, 1987; Adams, 1991; Table A-1, Wiseman quadrangle). The Shublik is gradationally overlain by a thin interval of dark-gray to black siltstone and very fine grained sandstone correlated with the Karen Creek Sandstone by Mull (1982) and Mull and others (1987). The upper contact of the Karen Creek is not exposed in the map area. CAI values of conodonts from TrCs mostly range from 4.5 to 6, but may be as low as 3 to J4 locally (Table A-1, Wiseman quadrangle). Various workers (e.g., Dutro and others, 1976; Mull, 1982; Mull and others, 1987; Adams and others, 1997) have suggested that the general stratigraphy of TrCs is more like that of coeval parautochthonous rocks in the northeastern Brooks Range (outside of this map area) than that of equivalent strata in the central part of the range that have been assigned to the Endicott Mountains allochthon (EMA; Moore and others, 1994). TrCs does differ from JCs`CKe part of the Central belt. In the western exposure of the calcareous schist unit, at the Akiak antiform, similar stromatolites are part of a fault-bounded lens of the OP_c unit within the calcareous schist; there, they occur as part of a lithologic sequence similar to that found in OP_c. Metamorphic assemblages in the calcareous schist unit show that it experienced the same early high-pressure/low-temperature metamorphic and deformational history as the quartz-mica schist (Dsq; GottschaLlk, 1990; Little and others, 1994; Dinklage, 1998). Chloritoid, glaucophane, pseudomorphs after glaucophane and pseudomorphs after lawsonite are present in pelitic and mafic layers in the unit (Little and others, 1994; Dinklage, 1998; Till, A., unpublished data). Some calcareous lithologies contain pseudomorphs after glaucophane and lawsonite as well, but more typically consist of calcite, quartz, albite, chlorite, white mica, and ankerite, with lesser garnet, epidote, sphene, and rutile?,geologicAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWgeologicalAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWharrisAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKW,inAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WjAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWmapAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WmooreAWBWCWDWEWFWGWHWIWJWKWLWMWNWOWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@W8tAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWtheAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKW-still@>B`C`LIQKO4AK S B @C@gAABDFHJL ACf@$A(AA&C)AA,E-B0D1 @B54 B6D7 B;DJ?! BLDKFJH[A#" @MAU$BZA&%AXA('AWCVE\G]I^K_M`AeDf)A+*AhEiBmDnFoA/.ArCsEtGuIvKwMxOy0B}D~FH1BA32ACE4BDF5BA76ACEA:9ACEA<_8^scientificvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKW^scientificAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWuWfYCInian (Lochkovian) conodonts were recovered from a dark gray fine-grained dolostone lens in the same area (Moore and others, 1997a). In the Baird Mountains quadrangle, conodonts of Middle Ordovician to Middle Devonian and Silurian to Mississippian age have been identified. All but one of the Late Devonian granitic orthogneisses (Dg) within the Schist belt are associated with DP_sc; this may indicate that the protolith of DP_sc was host to Late Devonian plutonism. Skarns around orthogneissJes in the Chandalar quadrangle occur within the calcareous schist unit (Newberry and others, 1997). At one locality in the Ambler River quadrangle, undated stromatolites occur near the probable boundary with the Central belt (Hitzman and others, 1982). A dolostone breccia exposed nearby yielded Ordovician to Early Devonian conodonts (Table A-1, Ambler River quadrangle). As the contact has not been mapped well in this area, it is possible that the dolostone breccia and the stromatolites ar; ;Bd calcite are also present in many of the plutons. Remnants of intrusive contact relations are locally preserved. Exposures of skarn have been mapped at the contacts and within the orthogneiss bodies. Skarns at the contacts of some of the plutons are mineralized (Sn or Cu; Newberry and others, 1997). The first isotopic dates on the plutons were done by the K-Ar method and yielded middle Cretaceous ages (Turner and others, 1979). A Devonian U-Pb zircon age for a group of metaplutonic bCodies in the southern and northeastern Brooks Range was determined assuming the bodies were comagmatic (Dillon and others, 1980). More precise U-Pb zircon dates on individual orthogneiss bodies are Middle Devonian (390-396 Ma; Aleinikoff and others, 1993). Toro and others (2002) give a preferred age of 375-395 Ma for orthogneiss at Mt. Igikpak in the central Survey Pass quadrangle. Neodymium isotopic data indicate an ancient crustal component in the magmas that formed the Devonian ortho1990KWPW}WBWCW1991JWTWtW1992CWLWrWsWGW1993YWaW{WW@W1994CWGWHWKWPWQWTWVW_W`WaWbWcWdWeWgWsWtWuWwWW@WAWBWCWDWGWJW1995LWZWdWeWqWwW{W|WJWdL<APale gray-green, massive to gneissic granitic to dioritic orthogneiss exposed in the Schist belt in the southern Baird Mountains quadrangle. This body was one of several metagranitic rocks from the Schist belt analyzed to evaluate the temperature and pressure conditions of Jurassic metamorphism. Results of phengite and feldspar thermobarometry on a sample from this body yielded 432C, 10.2 kb (Patrick, 1995). No direct age control; may be correlative with pCgCPzpCgDPaleozoic to Proterozoic?EGranitic rocksATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.=A9060 cX;Fanitic orthogneiss in the Central belt were collected from three major bodies in the eastern Ambler River and central Survey Pass quadrangles and yielded temperatures ranging from 327 to 416C and pressures of 3 to 8.9 kb (Patrick, 1995)  CDgDDevonianEGranitic orthogneissATill, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data: U.S. Geological Survey Scientific Investigations Map SIM-????, scale 1:500,000.I?A7 B!DJF[H#A" AMB&A$B_D^F]H\JVLWN'BA+A`B*A/ChEoGnAmCtEuGvIwKxMyO.A~CsEGA0B1AB3DABD2FA5C7AC:E6A4@A9CbedrockAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKW|KMIDangle (B. Mamet, unpublished fossil report, 1983), and middle Late Mississippian (late Meramecian-early Chesterian) conodonts in the Survey Pass quadrangle (Nelson and Grybeck, 1980). The Shublik Formation (Triassic) and Siksikpuk Formation (Permian), undivided, were reported to overlie the Lisburne Group in two small areas of the north-central and northeastern Survey Pass quadrangle (Nelson and Grybeck, 1980). These authors described the Siksikpuk as black slate and orange-weathering blacEk chert and the Shublik as pink-weathering limestone but presented no age data to confirm the presence of post-Carboniferous strata. These rocks are not differentiated on this map and are included in MklCMklD MississippianEfKayak Shale of Endicott Group and Lisburne Group, Central belt and part of Northern thrust assemblages  ABCDEF ABCDEF   !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKP_ABUUX  $,.YesNo/,  , : AM PMO $,.YesNo/,  , : AM PMOzIBeck (1980) and overlies the Kanayut Conglomerate of the Endicott Group. In both quadrangles, Kayak Shale (Bowsher and Dutro, 1957) of the Endicott Group (Tailleur and others, 1967) is volumetrically predominant and consists of black phyllite or slate interlayered with brown to orange-weathering fossiliferous siltstone, sandstone, and limestone. Limy layers in the Survey Pass quadrangle contain ostracodes, brachiopods, bryozoans, and echinoderm debris of probable Early Mississippian age, asC well as latest Devonian-earliest Mississippian (late Famennian-Kinderhookian) conodonts with CAI values of 4 to 5.5 (Table A-1). The Lisburne Group (Schrader, 1902; Bowsher and Dutro, 1957) is gray limestone to metalimestone with layers and nodules of black and gray chert. It contains locally abundant fossils that include crinoid, bryozoan, and coralline debris, brachiopods, gastropods, and sponge spicules, as well as Late Mississippian endothyrid foraminifers in the Baird Mountains quadrAA7200ASchistose varieties are equivalent to units "Dmw" and "Dpm" of Brosg and Reiser (2000). Dominantly gray-green lithic sandstone, lesser brown quartz sandstone, and black shale and silty shale exposed in the western Christian quadrangle (Brosg and Reiser, 2000). Sandstones are fine- to medium-grained and thin- to medium-bedded. Black shale forms up to 50 percent of the unit and occurs in layers up to 15 meters thick. The unit may be 1200 meters thick. Localities east of the map area exposed in the western Christian quadrangle (Brosg and Reiser, 2000). Sandstones are fine- to medium-grained and thin- to medium-bedded. Black shale forms up to 50 percent of the unit and occurs in layers up to 15 meters thick. The unit may be 1200 meters thick. Localities east of the map area wbleickAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWbrooksAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWconodontAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWdataAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW[xinvestigationsAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWjAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWmapAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKWmooreAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@W _scaleAWBWCWDWEWFWGWHWIWJWKWLWMWNWPWQWRWSWTWUWVWWWXWYWZW[W\W]W^W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWuWvWwWxWyWzW{W|W}W~WW@WAWBWCWDWEWFWGWHWIWJWKW<= Cvaried in character in more micaceous lithologies. Evidence for multiple foliation surfaces, such as intrafolial isoclinal folds, are common in outcrop. Sheath folds and more open, asymmetrical folds are also present. Clots of polycrystalline quartz give a knotty appearance in some structurally complex outcrops. Thin, laterally extensive centimeter-scale quartz and mica segregations give some outcrops a banded appearance. Very strongly foliated outcrops typically display fine, millimeteDr-scale planar laminations of mica and quartz. At map scales, the dominant foliation is typically broadly arched or folded around axes that are subparallel to the east-west trend of the Schist belt. Gottschalk (1990), Little and others (1994), Law and others (1994), and Dinklage (1998) contain detailed structural descriptions of this and associated Schist belt units. No fossils have been collected from the quartz-mica schist but protolith age can be partially bracketed by the ages of de'+wBand Grybeck, 1980; Vogl, 2002); exposures southwest of the major orthogneiss bodies are apparently lower in grade (Nelson and Grybeck, 1980). Albite-epidote-amphibolite facies metamorphism peaked at approximately 105 Ma (Patrick and others, 1994; Vogl and others, 2002). Equivalent to "Pzmsm" and parts of unit "DSsk" of Nelson and Grybeck (1980); equivalent to "Pzqm" and "Pzs" of Toro (1998). May be a metamorphically upgraded equivalent to parts of unit DpCscCDpCsmDDevonian to Proterozoic?E