Copyright 1984-2001 FileMaker, Inc. HBAM2016AUG95HPro 5.05@modified@lshale@A@A$andesiticandbasalticlavaflowsandmarineepiclasticrock@>bifurcation@ colluvial@deposts@;estuarinedeposits@6fan@'glacialandcolluvialdeposits@hypabyssalfelsicintrusiverocks@DENDbEt@!D%€ E(€A+D*E)€A,€+E1€4D4E3€>A:D9E8€H@= @@0}HBAM3016AUG95@wÃ![Ã!`Ã"`\Ã#1ÃDÃFÄ!BÄ'aÄ'nÄ'`Ä'qÄ'pÄ'1mmmDDDDDDDDDDHHHHHHHHHH:HHHHHHHHHHHHHHHHHHHH:HHHtonicrocksTVandQWRWandesitePWbasaltbeachXWYW\W]WcolluviumdepositsEWGWVWWWXWYWZW[W\W]W^WdriftFWfieldSWfloodAWfloodplainalluviumAVflood-plainVWWWZW[WgemukQWRWgemukgroupalteredmaficvolcanicsandsedimentaryrocksRVgemukgroupmaficvolcanicsandsedimentaryrocksQVglacialFWglacialdriftFVgraniticJWgraniticrocksJVgroupNWOWPWQWRWintrusiveKWintrusiverocksKVkuskokwimNWPWkuskokwimgroupandesitePVkuskokwimgroupsiltstoneNVlakeSWmaficLWQWRWTWmaficrocksLVnyacSWoldWWYW[W]W^Woldalluvialdeposits^VoldbeachdepositsYV]Voldflood-plaindepositsWV[VoutwashGWoutwashdepositsGVA105AUnit composed chiefly of silt, fine sand, and peat. Some gravel and coarse sand deposits occur locally along the tributary streams draining upland areas. The tidal flats and estuarine deposits consist of fluvial silt and sandy silt that have been reworked and redeposited by brackish-water tidal currents. Deposits form broad swaths along the Yukon and Kuskokwim Rivers and their major tributaries and include tidal flats and estuarine deposits along the shores of the Bering Sea and Norton SBound. The floodplain deposits are characterized physiographically by bars, oxbow lakes, meander scrolls, abandoned channels, and other evidence of recent floodplain building.CQfD QuaternaryE/Floodplain, tidal flats, and estuarine depositsFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.A35050F E4E Pro 3.0 - 4.0F!vv2(2( W#_Aw pxY~ 9/19/2006@ AGE DESCRIPTIONLABELNAMENSACLASS OVERPRINTSOURCESSYMBOLDAnsaclassB GA descriptionB GAlabelB GAageB GAnameB GAsourcesB GAsymbolB GA overprintB G A map labelB G$@ H Pro 5.0 - 5.5M1,,./: AM PM PMYyTtNnFfNALL OCOMSP^SundayMondayTuesday WednesdayThursdayFridaySaturdayJanuaryFebruaryMarchAprilMayJuneJulyAugust SeptemberOctoberNovemberDecemberQ1Q2Q3Q4 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter,  , X5{iD  jD{wHEkD { A $,.YesNo/,  , : AM PMB  C $,.YesNo/,  , : AM PMD  E $,.YesNo/,  , : AM PMF  G $,.YesNo/,  , : AM PMH  I $,.YesNo/,  , : AM PMJ   K $,.YesNo/,  , : AM PML  MN $,.YesNo/,  , : AM PMO $,.YesNo/,  , : AM PMP $,.YesNo/,  , : AM PMQR $,.YesNo/,  , : AM PM S $,.YesNo/,  , : AM PMT $,.YesNo/,  , : AM PMV  $,.YesNo/,  , : AM PMW  X  $,.YesNo/,  , : AM PMY    $,.YesNo/,  , : AM PM  BnsaclassDlabelFnameHageJ descriptionLsources A AWsymbolY overprint @BB0A$ $BC*     @@B s@A $,.YesNo/,  , : AM PMB $,.YesNo/,  , : AM PMC $,.YesNo/,  , : AM PM    70SunMonTueWedThuFriSatJanFebMarAprMayJunJulAugSepOctNovDec0Arial MS Sans Serif @2$A1$FPTH*SPATNAME WSPCFPTHA*Data-00:FHW Shared Folder Copy:nnsakey.FP5*NAMEA nnsakey.FP5 SPATAData-00:FHWSHA~1:nnsakey.FP5WSPCAD:\FHW Shared Folder Copy\A12RPTH RolyNAME WSPCNAMEA LYunits.fp5 RPTHA LYUNITS.FP5 RolyAWSPCAF:\FHW\Lower Yukon\!@A*FMRLFMRLAA3FMRLFMRLA AnnsakeyBunits`I?rrhyoliteWaWqWtWrocksdWWWWW$W`WaWkWlWmWnWoWpWqWW$W$WW$W$WWW$W$WWW$WWZWliteWrocksMWdWCWWWWWW$WZWZW$WZWZWZWZWZWZWZWZWSWZWZWZWZWZWZWZWZWZWZWZWZWZWZWZWW>WCWEWFWHWJWNWQWSWZWZWZWZWZWZWZWZWZWSWZWZWZWWSWZWZWZWZWZWZWSWZWZWZWQWSWZWZWZWZWZWWFWHWJWNWQWSWZWZWWSWZWZWWNWQWSWZWZWQWSWZWZWCWEWFWHWJWNWQWSWZWZWSWZWZWZWZWZWSWZWWWJWNWQWSWZWZWWZWZWZWZWZWZWWWWWWSWZWWWWWWWWWWWQWSWZWWWWlWvWwW}WJWKWLWvWWWWWWW W!W.W/W0W1W2W3W;W<WKWLW7+1:500000AWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWaAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWalaskaAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWandAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWfAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtW|CCfA~0'dD-wtkaptkadatkdqtkg_tki`mnotrmvhabundantcWalluvial[Walluvialcoluvialandglacialdriftdepositsundivided[ValteredWhWkWalteredmaficplutonicrockskVandAW_WdWWWWWWW!W[W\W_W`WaWbWcWdWeWfWgWhWiWmWnWoWpWqWrWsWtWtWWtWtWtWW!W!W!WW!W!W!W!W!W!W!W!W!W!W!WW!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!W!WW!WW!WW!WW!WW!WW!WW!WWW!WW!WW!WWW W!W!WW!WW!WW!WW!WW!WW!WW!W!W!WWWW W!W!W!W!W!W!W!W!WWWWW W!W!W!W!W!W!WW!W!W!W!W!W!W!WW!WW!W!W!W!W!W!W!W!W!WW!WW!W!W!WW!WWWW W!W!W W!W!W!WW6@CQbl$1!$B[\_`abcdefghijklmnopqrstÃ![Ã!`Ã"`\Ã#1ÃDÃFÄ!BÄ'aÄ'nÄ'`Ä'qÄ'pÄ'1mÄ'6Ä'FÄ'aoÄ'f_Ä'kÄ*TeÄ*fÄ12$Ä14tÄ2!Ä2cÄ2dÄ5rÄ5!sÄ5bÄ9ijÄ9lÄB1ÄDgÄEaÄE$ÄcFÄch O7 A BCDEFGHIretaceousandjurassicjvclateandmiddlejurassicjabmiddlejurassickksfkygdkygc!kygvckymekys  cretaceouskmucretaceoustomississippian tkd(%earlyteritiaryandlatestcretaceous tkatkg_tki`'$earlytertiaryandlatestcretaceous mzpzum$mesozoicandpaleozoic tbB latetertiary tkada!tertiaryandlatestcretaceouskgblateandearlycretaceous7y$AHighly disrupted assemblage of mafic to intermediate tuff, breccia, agglomerate, volcanic-rich conglomerate and graywacke, cherty tuff, chert, mudstone, and andesitic and basaltic pillow lava. Unit locally intruded by sills and dikes of diabase, diorite, and gabbro. Tuffs commonly are laumontitized. Some of the conglomerate beds east of the Yukon River in the Holy Cross quadrangle contain clasts of altered granitic rocks. Unit crops out in localities scattered in the Holy Cross quadranglBe and the northern part of the Russian Mission quadrangle. Unit also includes several small exposures along the faulted western boundary of the Yukon-Koyukuk basin in the Kwiguk quadrangle and in the adjoining St Michael quadrangle. Unit is assigned an Early Cretaceous to Jurassic age based on sparse isotopic and fossil data and on its stratigraphic position below the late Early Cretaceous sedimentary rocks of the Yukon-Koyukuk basin and above the Triassic rocks of the Angayucham-Tozitna 5€fFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000. €gA3380AUnit is composed chiefly of trondjhemite and tonalite plutonic bodies that locally have been metasomatized by potassium-rich fluids to a pink granite and granonodiorite. Unit also includes subordinate amounts of quartz diorite, diorite, and gabbro. Some of the plutonic bodies have been cataclastically deformed. Unit confined to the north-central part of the Holy Cross quadrangle where it intrudes a fault-bounded belt of undivided Koyukuk and Angayucham-Tozitna terranes (KMu). Unit is assBigned a Jurassic age based on data from the adjoining Unalakleet quadrangle where similar plutonic bodies yield K/Ar isotopic cooling ages that range from 173 to 130 Ma (Patton and Moll-Stalcup, 1996).CJtDJurassicassic" Ä'6666FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF2,JÄ3! 4BÄ3qsÄ41>Ä4A$MÄ5!5Ä5-Ä9rUÄDCÄEÄX!8ÄaFVÄc?ÄhGWÄt1@ÄtYÄu#Äzf[ÄzZÄ&XÄ6\Ä!^_ÄV]agglomeratetWalbiteIWalbiterhyoliteIValluvial^WgWrWGWOWdWalluvialfandepositsdValluvialsandandgravelOValluviumAW`WaWbWfWalteredRWTWW@WalteredbasaltdiabaseandsubordinatelimestoneValteredmaficplutonicrocksTVandQWRW`WeWfWlWtWxW{W}WW@WEWNWOWZWcWeWiWrWsWandesitePWrWsWandesitetodaciteflowsandtuffrVandesitic~Wandesiticvolcaniclasticrocks~VaplitetWbasalt+3zWW@WHIRqbasaltflowszVbasalticsWbasalticandesiteandandesitesVbasic_Wbasicintrusiverocks_VbeachXWYW\W]WhWiWEWbeachandlagoondepositsEVbeavernW#Rof`WhWmWnWoWtWpatterntWplutonickWpolymicteWaleeVhaleeVeVsWVsWVsWVsWVsWVsWVsWVsWVouter-fan W WoldWWoldflood-plaindepositsWVouter-fanW W W Woutwash-fandepositsoVdepositsoVoVsitsoVoVpeatcWpeatcWcWphyllite^peatcWphyllite^e^e^e^e^^^^^^eatcWphyllite^^^^^overbankbWpeatcWphyllite^^^^^^^^^^^tcWphyllite^^^'<graywackeW!WcWdWhWhighly!WhyabyssallWhyabyssalfelsicintrusiverockslVhypabyssalWaWqWtWintermediate`WmWnWoWintrudedtWintrusive`WlWmWnWoWistWkjvWkjvWWWWermediate`Wintrusive`W`W`Wve`W`WWWyssalWWWWWWsalWWWWintrusiverocksQVhypabyssalWWWWWFWWFWFWFWFWFWFWFWFWFWFWlfelsicintrusiverocksQVhypabyssalWWCWFWFWFWFWFWFWFWFWWFWFWFWFWFWFWFWFWFW0WCWFWFWFWFWFWWCWFWFWFWFWWCWFWFW0WCWFWFWCWFWFWWFWFWFWFWWWWWWWWW0WCWFWWWWWWWW0WCWFWW9WEWintrusiverhyodaciteanddacite`VintrusiverhyodacitedaciteandaplitetVintrusiverocksKVintrusives|WAWBWkjvW>Wkoyukuk4Wop1D QuaternaryEWind-blown depositsFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€A3120ATuffaceous marine sandstone, shale, and conglomerate. Minor basaltic and andesitic lava flows. Felsic pyroclastic rocks locally near base of unit. Unit rests conformably(?) on unit Jab and is conformably(?) overlain by unit KJb. Mollusks collected from this unit are of Late Jurassic (late Kimmeridgian to early Tithonian) age (table 2). Middle Jurassic (Bajocian) mollusks are reported by Box and others (1993) from this unit in the adjoining Bethel quadrangle south of the Russian MissiBon quadrangle.CJvcDLate and Middle JurassicE?Nyak Terrane, volcaniclastic conglomerate, sandstone, and shalehale ;;conglomerateWeWcontainingcWdaciteWaWqWtWdaciteandrhyolitelowsdomesash-flowtuffsandhypabyssalVqVdaciterhyoliteandesiteandbasaltlavaflowsandvolcaniclaVdebriscWdeformedhWdeltaicWfWdepositsAWqWW!W[W\WcWdWeWfWWWWdeltaicLWdepositsWWXWqWKWLWVWWWXWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWWYWYWWXWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWXWYWYWWYWYWYWYWYWYWYWYWYWYWKWLWVWWWXWYWYWYWVWWWXWYWYWYWYWYWYWYWYWYWYWWWWWWWWWWWWWWWYWWWWWWWWWWWWXWYWWWWdolomiteZWdomesWdriftFWW'W)W5W?WepiclasticWestuarinejWoWW*W6W WMU€_Coenite, monzonite, and quartz monzonite and a core of quartz syenite and porphyritic quartz monzonite. A large pluton located in the northwest corner of the Russian Mission quadrangle and extending into the eastern edge of the Marshall quadrangle locally displays a strong gneissic banding. Seven K/Ar cooling ages from this unit range from 70.9 to 60.9 Ma (table 1).KCTKgD$early Tertiary and latest CretaceousE-Granite, granodiorite, syenite, and monzoniteFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.AEEH `AK S AC@ DIN@F@AFO@$ACyF{1@oD€Fp€Fz€@TA%€@:B1€A)€@bCf€!Da€$B|€B@gA`€[@HA8€\AB€_AMC€`@UARF~€a@B€bAd€c@F]€dF}€e@(BF€fBF€gE5€hB€i@2€jA€k@mEK€m@B€n@Fj€oB€p@AC€q@Y€sA€t@AF6 @P00P0P0?/(scoriaceous_Wserpentinized$Waficrocks$Vficrocks$V$Vficrocks$VVks$VVzedulramaficrocks$VV$VVWserpentinizedulramaficrocks$V$VonUVserpentinized$Wserpentinizedulramaficrocks$V$VonUVserpentinized$Wserpentinizedulramaficrocks$V$V$V$V$Ventinizedulramaficrocks$V$V$Vserpentinizedulramaficrocks$V$Vcrocks$V$Vinizedulramaficrocks$V$Vs$V$VWserpentinizedulramaficrocks$VVVViltandpeatcVsiltdepositsEVsiltstoneNWlW WWWWWW Wsmall|W}W~WsubordinateW@Wsubvolcanic{WNWsurficialyWsurficialdepositsundifferentiatedyVsyenitezW{WWsyenitetomonzoniteandquartzmonzonite{VtalushterracePWfWiWterracealluviumfVterraneSWWWWterrnaeWtidalWtilleWklWmWnWWtillbeavercreekglaciationnVtillbifurcationcreekglaciationmVVZV!EAAHP LaserJet 5/5M PostScriptw odXXP?Rp_A+RdB|Custom page 1|CCCustom page 2|CCCustom page 3|CCfA~0'd€th Jby? to Jurassic?Jurassicic rockserocksdites0 ABCDEFGH $1!$B[\_`abcdefghijklmnopqrsthijklmnopqrstZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ $,.YesNo/,  , : AM PMO C,Z=/%=I,=/=/7turbidites!WcWdWulramafic$WundividedW[WaWdWfWvolcaniccWjWvolcanicclasitcWpWvolcaniclasticdWWWWaWhWwheretWwhitefishjWwhitefishlakevolcanicfieldjVVolcanicfieldjVjVjVVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVRVlomeratesandstoneandshaleRVRVhaleRVRVndshaleRVRVRVRVRVRVshaleRVRVRVRVRVRVRVneandshaleRVRVRVdstoneandshaleRVRVRVRVRVRVratesandstoneandshaleRVRValeRVRVRVRVRVRVRVRVVVVV7Wwind-blowndepositsqV7Vwind-depositedDWwind-depositedsiltDVwithbWyounghWnWDWyoungbeachdepostshVyoungflood-plaindepositsnVDVyoungerVWXWZW\WyoungerbeachdepositsXV\Vyoungerflood-plaindepositsVVZVyukon-koyukukW.W/W0W1W2W3W;W<W>bchertdWWhWcoluvial[WcomplexlyhWcomposition`WmWnWoWcones_Womposition`Wcones_Ws_Ws_Wcones_Ws_WWcones_Ws_WW W W WstW W Wcoarse-grainedgravel-richalluviumaVchalluviumaVaVvel-richalluviumaVaVaVmaVVVVVV2wAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWwilsonAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWyukonAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWsWtWtWtWtWtWtWtWtWtWtWtWtWtWtWtWtWWWWtWWtWtWtWtWtWtWtWtWtWtWWtWtWtWtWtWtWtWWWWWvWvWvWvWvWvWvWvWvWvWvWvW|CCCustom page 3|CCfA~0'd .Ä'FÄ'aoÄ'f_Ä'kÄ*TeÄ*fÄ12$Ä14tÄ2!Ä2cÄ2dÄ5rÄ5!sÄ5bÄ9ijÄ9lÄB1ÄDgÄEaÄE$ÄcFÄchwhhhh$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$^_ÄV]ą#agglomeratetWalbiteIWalbiterhyoliteIValluvial^WgWrWGWOWdWWalluvialcolluvialandglacialdriftdepositsundividedValluvialfandepositsdValluvialsandandgravelOValluviumAW`WaWbWfWalteredRWTWW@WWWalteredbasaltdiabaseandsubordinatelimestoneValteredmaficplutonicrocksTVVandQWRW`WeWfWlWtWxW{W}WW@WEWNWOWZWcWeWiWrWsWxW{W|W}W~WWWWW W WWWWWWWWWWWWWWWWW W!W&mudstonedWW!WcWdWnumeroustWnyakWWiWnyakterraneandesiticandbasalticlavaflowsandmarinevoVnyakterranebasaltandandesitelavaflowsiVnyakterranevolcaniclasticconglomeratesandstoneandshaleVXWnoncalcareousaWaWndstonenoncalcareousaWaWoncalcareousaWaWcareoussandstoneJVnoncalcareousaWWnoncalcareousaWWcalcareousaWWW->yandesiteWaWiWpWandesiteandbasaltflowsandvolcanicclasitcrocksVpVandesiticdWWWbasalticlavaflowsandmarinevolcaniclasticVVPWSWSWSW>WNWPWSWSWSWSWW"W4W>WNWPWSWSWSWWWbasalticlavaflowsandmarineepiclasticrockVandesiticandbasalticvolcaniclasticrockslavaflowschertV"V4V>Vandesiticvolcaniclasticrocks~Vangayucham-tozitna=WaplitetWargillitexWW%W=W>Wassemblage%W=Wbasalt+3zWW@WHIRqWWWW%W,8=W>WBCWHWbasaltflowszVbasalticsWWWW"W4W>WbasalticandandesiticlavaflowsnyacterraneVbasalticandesiteandandesitesVbasic_Wbasicintrusiverocks_VbasinW.W/W0W1W2W3W;W<WKWLWbeachXWYW\W]WhWiWEWW(W+WbeachandlagoondepositsEVbeachandlagoonaldepositsV(V+VbeavernWT:€AFluvial and shallow marine deltaic deposits of sandstone, siltstone, and shale. Locally crossbedded and ripple marked. Unit contains abundant plant debris and fresh- and brackish-water mollusks. Unit is widely exposed in a broad belt that extends from the northwestern Holy Cross quadrangle through the eastern Kwiguk quadrangle and into the northern edge of the Marshall quadrangle. A few scattered exposures also occur in the southeastern part of Holy Cross quadrangle. Shallow water marineBI mollusks of mid-Cretaceous age found in the Kwiguk quadrangle (table 2).7CKysD CretaceousE>Yukon-Koyukuk Basin, Deltaic Deposits, sandstone and siltstoneFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.<#lagoonal\WlakejWlaumontitizedcWlavaHW_WdWWWBWaWiWlimestoneWhWlowsWqWmafickWmarginaleWmarineWmonzonite_WWWVmarineWWWWSWSWSWSWSWSWSWSWSWSWSWSWSWWSWSWSWWSWSWSWSWSWnal.WKWYWmarineWSWSWranitoidrocksCVmarginal.WKWYWmarineWSWSWmarginal.WKWYWmarineWSWSWranitoidrocksCVmarginal.WKWYWmarineWSWSWitoidrocksCVmarginal.WKWYWmarineWSWSWmeta-igneousxWxWmetasandstonexWonexWxWxWWWxWmetasandstonexWxWxWWnexWWmarineWSWmeta-igneousxWmetasandstonexWxWxWxWxWonexWxWWYWmarineWSWmeta-igneousxWmetasandstonexWxWxWWWWandstonexWWW;6flatsAWfloodplainAWfloodplaintidalflatsandestuarinedepositsAVflowsHW_WdWWWWBWaWiWpWgabbrogWglacial[Wgranite_WbWrWsWgranitegranodioritesyeniteandmonzonite_Vgranodiorite_WbWrWsWgranodioriteandgranitebVrVsVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVWVW'W)W5W?WVWVWVWVWVWVVglacialeWWW'W)W5W?WVWVWVWVWVWVWW'W)W5W?WVWWWVVglacialeWWW'W)W5W?WVWWWWWWWWWWWyrocksglacialfWeWWW'W)W5W?WVWWWVWWglacialfWeWWW'W)W5W?WVWWWW}€eA1943APebble and cobble conglomerate interbedded with sandstone, siltstone, and shale. Conglomerate contains clasts of chert, greenstone, quartz, and schist in variable amounts. Sandstone varies from poorly-sorted graywacke turbidite to well-washed quartz-rich sandstone. Unit poorly exposed along the eastern and western margins of the Yukon-Koyukuk Basin. On the eastern margin unit crops out at scattered localities in the southern Holy Cross and northern Russian Mission quadrangles. Some congliable amounts. Sandstone varies from poorly-sorted graywacke turbidite to well-washed quartz-rich sandstone. Unit poorly exposed along the eastern and western margins of the Yukon-Koyukuk Basin. On the eastern margin unit crops out at scattered localities in the southern Holy Cross and northern Russian Mission quadrangles. Some congl1b€ADacite, rhyolite, and subordinate trachyandesite lava flows, sills, dikes, and interlayered tuffs, ash-flow tuffs, and breccias. Flows generally are porphyritic and composed of phenocrysts of plagioclase, sanidine, quartz, and biotite in a fine-grained felsic groundmass. Unit forms a large volcanic field in the southeastern part of the Holy Cross quadrangle and is widely distributed elsewhere in the Holy Cross and Russian Mission quadrangles as small bodies that intrude or are interlayereBd with andesite and basalt belonging to unit TKa. Most of these bodies are too small or too poorly known to be mapped separately.pCTKdD%early Teritiary and latest CretaceousEEDacite and rhyolite lows, domes, ash-flow tuffs, and hypabyssal rocksFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€A16351635^30pattonAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWpattonwwjrwilsonfhandlabaykainprepreconnaissancAVHV_VdVqVVVVVVV!V$VBV[V\V_V`VaVbVcVdVeVfVgVhViVjVkVlVmVnVoVpVqVrVsVtVprepAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWreconnaissanceAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWWmWnWoWpWqWrWsWtWtWtWWtWtWtWHWMWNWSWUW_WaWcWdWlWqWWCWyWWWWWW WWWWWW!W$WBW[W\WgeologicAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWgeologicalAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWtWtWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWinAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWinvestigationsdWWWWW!WbWcWdWeWfWgWiWrWsWjrdWWWWW!WbWcWdWeWfWgWiWrWsWtWkdWWWWW!WbWcWdWeWfWgWiWrWsWtWVLporphyriticWW_WpWqWporphyrydWpositiondWpotassium-richgWpredateqWprehnite-pumpellyitehWpresenceWcWpresentHWpresscWpresumed$WprimaryWprobable!Wprobably$WprocessedbWrWsWpyroclasticHWWpyroxeneWpWqacqWqfqWquadrangleHW_WdWWWWWW!W$WBW[W_W`WaWbWcWdWeWfWgWhWiWjWlWmWnWoWpWqWrWsWtWquadranglesHWW\WeWhWkWqWquartzWW_W`WeWgWmWnWoWqWWqWqWqWHWW_WgWpWrangingHWbWrecentAWrecently\Wreconnaissance$WredepositedAWregion`WmWnWoWregionaljWrelationshipsjWreplacementWreportedWcWrestsWreworkedAW[WrhyoliteWW`WaWjWlWmWnWoWpWqWrhyolitedaciteandlesseramountsoftrachyteandandesite`VmVnVoVridges\Wrim_W$ andYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYWYW"v"0.19HW1dWWBW_W`WaWbWhWmWnWoWpWrWsW10.48hW100qW101bWrWsW104bWrWsW120mabWrWsW128dW129bWrWsW130gW164dW173gW19.35BW1991_W1993W1996HWW$WgWpW2NW2NWW2NWW2NWW2NWWWW2NWWWW50.8W51.9W6.19BW60.4 W60.9yW63.6 W64.7MW65.2W67.0MW67.3 W70.9yW80.6UWaHWMWNWUWXW_WaWcWyW WWWW!WabandonedAWabundantaWlWWaccordingyWactiveXWadjoiningHWNWlWWageNWUW_WaWcW WWW!WagesHWMWUWyWWBWagglomeratesWalaskaNWalbian-cenomanianaWalkaliHWalluvialWWqWalluvialandcolluvialdepositsconsistmainlyofsiltsandyWValluviumWWalongAWXWaWlWalsoHWlWyWWamountsaWW WanMWyWandAWHWMWNWUWWWXW_WaWcWlWqWyWW WWWW!WBWandesiteMW WWWshaleWeWfWshallow`WmWnWoWshallowintrusiverocksofintermediateandsiliciccomposit`VmVnVoVshelfeWsilicic`WmWnWoWsiltstoneWeWfWslopeeWsmalltWsubmarine!WcWdWfWsyenite_WterranedWWWW$WgWhWiWtholeiitic_WtidalAWtkitWtonalitegWtrmvWtrondhjemitegWtuffWhWtuffsWqWWWW@W@W@W@W@W@W@W@W@W@W@W@W@WtillWlWWWWWtidalW*W6W@WtillWWWWtillbeavercreekglaciationnVnVtillbifurcationcreekglaciationmVmVmVVtionmVmVonmVVekglaciationmVmVmVmVglaciationmVmVnmVmVVVmVaciationmVmVbifurcationcreekglaciationmVmVmVrcationcreekglaciationmVmVmVmVVVillbifurcationcreekglaciationmVViationmVVkglaciationmVViationmVVglaciationmVVVVV P_ABUUX  $,.YesNo/,  , : AM PM3:)€BAndesitic and basaltic volcaniclastic rocks, lava flows, chert, and mudstone (KJv) and altered basalt, chert, chert breccia, argillite, tuff, volcaniclastic graywacke, and limestone (TrMv), undivided.CKMuDCretaceous to MississippianEAngayucham-Tozitna Terrane, andesitic and basaltic volcaniclastic rocks, lava flows, chert, and mudstone (KJv) and altered basalt, chert, chert breccia, argillite, tuff, volcaniclastic graywacke, and limestone (TrMv), undividedFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€A1625625N€iA2870BVariably altered basalt and andesite. Conformably(?) overlies unit Jab and unconformably(?) overlain by unit TJb. Unit confined to Kilbuck Mountains, southeastern Russian Mission quadrangle. Assigned an Early Cretaceous to latest Jurassic age.CKJbD%Early Cretaceous and/or Late JurassicE,Nyak Terrane, Basalt and andesite lava flowsFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€jA2870870. Assigned an Early Cretaceous to latest Jurassic age.CKJbD%Early Cretaceous and/or Late JurassicE,Nyak Terrane, Basalt and andesite lava flowsFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.ITJb€jA2870*regionAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWriverAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWsAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWscaleAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWscientificAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWserivesAWHW_WdWqWWWWWWWiWrWsW9XabundantWdWeWhWtWaccording_Wactive\WadjoiningHWdWWWdWfWgWpWaerial$Wage_WdWWWWW!W$W`WbWcWeWfWgWhWiWkWlWmWnWoWpWrWsWtWagesHWWBW_WaWbWgWpWrWsWagglomeratedWagglomeratesWpWalaskafWalbian-cenomanianeWalbiteWalkaliHWalluvialqW[Walluvialandcolluvialdepositsconsistmainlyofsiltsandy[Valluvium[WalongAWdW$W\WdWeWalsoHWdWW$W_WdWgWtWaltereddWWWaWeWfWiWjWkWlWalteredbasalticlavaflowsandsubordinatealteredandesitejValteredgabbroanddioritebodiescropsoutassmallscatterkVVVVWaWiWandAWHWNW_WdWqWWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWandesitedWWW`WaWhWiWjWW€gE3Koyukuk Terrane, Trondhjemite, tonalite, and gabbroFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€hA5280AUnit composed of a wide variety of mafic and intermediate volcanic and intrusive rocks including basalt, andesite, diabase, gabbro, and volcaniclastic rocks that are weakly metamorphosed to prehnite-pumpellyite and locally to greenschist facies assemblages. The volcanic and intrusive rocks are interbedded with varicolored radiolarian chert, chert breccia, chert pebble conglomerate, argillite, graywacke, and small limestone bodies. The chert, argillite, graywacke, and limestone are locallcall€tFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€wA5280ITrMvwind-blownqWwind-blowndepositsqVyoung_Wyoungscoriaceoustholeiiticbasaltlavaflowsandcones_Vyukon-koyukukW!WcWdWeWyukon-koyukukbasindeltaicdepositssandstoneandsiltstoneVyukon-koyukukbasinmarginalshelfandslopedepositspolymieVyukon-koyukukbasinsubmarinefandepositsgraywackesandstocVdVyukon-koyukukbasinsubmarinefandepositshighlycalcareous!Vbasinsubmarinefandepositshighlycalcareous!V!V!VWYWWWKWWWXWYWWWWXWYWWHB€[AAlluvial and colluvial deposits consist mainly of silt, sandy silt, and peat. Alluvium is chiefly fluvial in origin, but locally includes reworked windblown deposits. Alluvium deposits cover wide areas of the Yukon and Kuskokwim lowlands and delta plain. Colluvial deposits make up the bulk of the unconsolidated deposits on the uplands slopes. Colluvium includes glacial drift composed of sand, gravel, and boulder morainal and outwash deposits. Glacial drift is found at higher elevations inB the Russian and Kilbuck Mountains in the Russian Mission quadrangle and in the Askinuk Mountains in the Hooper Bay quadrangle.mCQacD QuaternaryE9Alluvial, coluvial, and glacial drift deposits, undividedFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€\A115115v42WeWfWhWtW2006!W3.25maHW349.27hW4.0bWrWsW40ar/39ar`WmWnWoW40ar39arbWrWsW42.9WpW50.8WpW51.9WpW6.19BW60.4`WmWnWoW60.9_W63.6`WmWnWoW64.7aW65.2WpW67.0aW67.3`WmWnWoW70.9_W80.6bWrWsWaHW_WdWWWWW!W$W\W_W`WaWbWcWeWfWgWhWlWmWnWoWpWqWrWsWtWabandonedAWabovedWabundantWWWalaskaNWalbian-cenomanianaWalkaliHWalluvialWWqWalluvialandcolluvialdepositsconsistmainlyofsiltsandyWValluviumWWalongAWXWaWdWlW$WalsoHWdWlWCWyWW$WaltereddWWWalthough$WamountsaWCWW WamphiboledWamphiboliteWanMWdWyWWandAWHWMWNWUWWWXW_WaWcWdWlWqWWCWyWWWWW WWWWW!W$WBWandesiteMWdWWW WWW%1 €A5235Fluvial and shallow marine deltaic deposits of sandstone, siltstone, and shale. Locally crossbedded and ripple marked. Unit contains abundant plant debris and fresh- and brackish-water mollusks. Unit is widely exposed in a broad belt that extends from the northwestern Holy Cross quadrangle through the eastern Kwiguk quadrangle and into the northern edge of the Marshall quadrangle. A few scattered exposures also occur in the southeastern part of Holy Cross quadrangle. Shallow water marineBI mollusks of mid-Cretaceous age found in the Kwiguk quadrangle (table 2).7CKysD CretaceousE>Yukon-Koyukuk Basin, Deltaic Deposits, sandstone and siltstoneFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€A5235'domesWqWdottWdotpatternwherekysisintrudedbynumeroussmallhypabysstVdrift[WestuarineAWfan!WcWdWfWfelsiclWfieldjWWWW@W@W@W@W@W@W6W@W@W@WWW6W@WWW&#koyukukdW$WgWkoyukukterraneandesiticandbasalticvolcaniclasticrocksdVkoyukukterraneserpentinizedulramaficrocks$VkoyukukterranetrondhjemitetonaliteandgabbrogVkuskokwimfWkuskokwimbasindeltaicandsubmarinefandepositsundividedfVkystWWWsandstonesiltstoneandshaleVVexucratersHWcretaceousdW!W`WcWeWfWiWmWnWoWcropsdWdWeWkWcrossdWWWW!W$W_W`WaWeWfWgWhWkWmWnWoWpWqWtWcross-beddedfWcrossbeddedWtWcrystallizationbWrWsWcurrentsAWdaciteWW`WaWjWlWmWnWoWpWqWtWdaciterhyoliteandsubordinatetrachyandesitelavaflowssiVqVdaciterhyoliteandesiteandbasaltlavaflowsandvolcaniclaVdatadWW_WaWdWgWpWdebrisWdWtWdeformedgWdeltaHW[WdWdeltaicWfWtWdeltaicandsubmarinefandepositsthedeltaicdepositsconsfVdepositsAWHWqWW[WfWtWdetailed_WdevitrifiedaWdiabasedWhWdike`WmWnWoWdikesdWW`WmWnWoWqWdioritedW_WgWkWdisplays_WWWWWWW_W_W_W$ angayucham-tozitnaWhWangayucham-tozitnaterraneandesiticandbasalticvolcaniclaVangayucham-tozitnaterranecomplexlydeformedassemblageofhVargilliteWhWash-flowWqWassemblagehWbasaltHW_WWWBWaWhWiWpWbasaltlavaflowsHVBVbasalticdWWWbasinW!WcWdWeWfWbeach\Wbeachandlagoonaldeposits\VbodiestWbrecciaWhWbytWcalcareous!WWW!W!W!WWhXWhXWhXWhXWhXWhXWhXWhXWhXWhXWhXWhXWhXWhXWWhXWhXWhXWhXWhXWhXWhXWhXWWbeachandlagoonaldeposits+V+V+V+V+V+V+V+V+V+V+V+V+V+VagoonaldepositsV(V+V+V+VVbeavernW(V+VbeavernWnWernWnWWWWV(V+VbeavernWnWnWnWsitsV(V+VbeavernWWVbeavernWWWvernWWWWWWWWW2sandstoneWW!WcWdWeWfWWstonesiltstoneandshalefVfVVWYWYWYWYWYWYWYWYWYWYWWYWYWYWYWWWWWlÄ'6@Ä'F@".2dv9abundant4alteredrhyoliteanddaciteporphyriesconfinedtoasingle@Xandesiteandbasaltlavaflowsandvolcaniclasticrockswide@_base@beach@beds@Jbut@Wcones@ecraters@=disrupted@xend@[fluvial@Sgroundmass@qinclude@intertongues!kisland@hkilbuck@Plocallytmapped@missionjQha@nspits@Itributaries@Ztwo@iwell-washed@rDand"-andesite@$andesiticandbasalticlavaflowsandmarineepiclasticrock@>bifurcation@ colluvial@deposts@;estuarinedeposits@6fan@'glacialandcolluvialdeposits@hypabyssalfelsicintrusiverocks@DE?BDCB~}NDbEt@!yBUT€@%€€@€@€ E(€ BYX€€f€A+D*E)€Dba€B^]€A,€!g€$€+E1€4D4E3€>A:D9E8€BR€H@=€RDCEB @@08M_€\A*Silt and sandy silt. Unit includes active offshore bars, spits, and beaches ridges and former beach ridges that have been recently stabilized by a thin vegetation cover. Scattered localities along the Norton Sound and Bering Sea coast in the St. Michael, Kwiguk, Black, and Hooper Bay quadrangles.*CQblD QuaternaryEBeach and lagoonal depositsFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€_A1655655IwstabilizedqW\Wstock_Wstocks_WstratigraphicdWstreamsAWstrong_Wstuart_WsubmarinefWsubordinateWaWeWfWgWjWqWsuggestjWsuggesting_WsuggestsdWswathsAWsyenite_WtabledWWWWBW_W`WaWbWeWfWhWmWnWoWpWrWsWtWtbaWterranedWbWrWsWterranesgWtertiaryaWjWkWlWthankWlWthatAWHWqWWWW\W_WbWdWfWgWhWpWqWrWsWtWtheAWHW_WdWqWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWhWhWhWhWhWhWWW!W_WdWeWfWtholeiiticHW_WthreeBWthroughWtidalAWtithonianWtjbiWtkaWaWtkadaWtkdWaWtkiWtoHWNWdWWWWW!W$W_W`WaWbWcWeWfWgWhWiWjWtonalitegWtooW`WtrachyandesiteWtrachyte`WtriassicdWhWrjabjtgjvckgbrskjbikjv$kksfkmukygdkygc!kygvckymekystmzpzum$qac[qbqbl\qfqtbqw1tbBtjbjtjiltjmkkBBBbBBBBBBBBBBBBBBBBBBBtbBBBBBBBbBBBBBBBBBBBBBBBBBBtbBbBbBbBbBtbBBtbBBbBBtbBBtbBBtbBBBBBBtbBBbBBbBBBBbBBtbBBtbBBtbBBtbBBbBBtbBBbBBbBBbBBbBBbBBbBBbBBbBBBbBBbBBbBBbBBBBbBBBBbBBBBbBBbBBBBbBBBBBBbBBBBbBBBbBBbBBbBBBBbBBBBtgrAArAAAgrAAgrAAArAAAAAAAAArAAAAAAgrAAAAgrAAAAAAAAAAAAtgrAAtgrAAAArAArAArAAAgrAAgrAArAAW WWWWWWWWWWWWWWWWW W!W D&  @BBA                       r]vegetationHW\WvesicularHWWBWpWvesiculartholeiiticandalkalibasaltlavaflowsconesandHVvolcanicHWdWWWdWhWqWvolcanic-richdWvolcaniclasticWWaWhWpWvolcano-plutonic_WwaterWtWweaklyhWwell-induratedcWwell-preservedeWwell-sortedfWwell-washedeWWortedNWWrtedNWWWwell-sortedNWNWortedNWNWWdNWdNWdNWdNW`8 €[A100lat-lying vesicular basalt yielding whole-rock K/Ar ages of 19.35 Ma and 6.19 Ma (table 1). Basalt flows located in Three small areas in the Russian Mission quadrangle: two on the Yukon River in the northwestern part of the quadrangle and one on the Owhat River in the northeastern part of the Russian Mission quadrangle.CCTbD late TertiaryEBasalt lava flowsFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€[A100nC*stHW_WdW!W\WcWdWeW^WdqW\WstockyWstocksyWstratigraphicdWstreamsAWstrongyWstuart_WsubmarineNWsubordinateSWCWWWsuggestSWsuggesting_WsuggestslWswathsAWsyeniteyWtableMWNWUWaWdWWyWW WWWBWtbMWterraneUWdWWterranesCWtertiaryMWSWWWthanWWthatAWHWNWUWlWqWWCWyWWWW\W]WtheAWHWMWNWSWUW_WaWcWdWlWqWWCWyWWWWW WWWWW!W$WBW[W\W]WtheirAW$WthermalWtheseNWWtheyqWthickqWthindWyW\WthinnerHW]WthisHWNWaWdWlWyWWW!WtholeiiticHW_W]WthreeBWthroughWtidalAWtithonianWtjbWtjmSWtkaMWWtkadMWtkdMWWtkiWtoHWMWNWSWUWaWcWdWWCWyWWWWW WWWW!W$W]WtonaliteCWtoo WWtrachyandesiteWtrachyte WtriassicdWWWbedsdWcWeWbeenAW\W_WgWbelongingHWWWpWqWbelowdWbeltW!W$WcWgWtWberingAW\WbethelWbetweenWbWpWrWsWbiotiteW_W`WbWmWnWoWqWrWsWbiotitegraniteandhornblende-biotitegranodioriteformingbVrVsVblack\WblowoutsqWbodiesqWWW$W_W`WgWhWkWmWnWoWpWqWtWbodydWhWlWborderhWborderingaWeWfWbothaWdWboulder[WboundarydWboxWbrackish-waterAWWtWbrecciaHWdWWWhWpWbrecciasWWqWbristolfWbroadAWHWqWW!WcWfWtWbuildingAWbulk[Wbundtzen_WWW_Wrosion_WestuarineAWevidenceAWexaminationyWexposedHWextendsHWfeetqWfewyWfieldHWyWfieldsHWqWfineAWHWflat-lyingBWflat-lyingvesicularbasaltyieldingwhole-rockk/aragesofBVflatsAWfloodplainAWqWflowsHW_WBWBWm€kEAltered mafic plutonic rocksFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€lA2885BAltered rhyolite and dacite porphyries confined to a single body in the Kilbuck Mountains, southeastern Russian Mission quadrangle. Age of unit is uncertain, but not older than Jurassic. May be as young as Tertiary.CTJiDearly Tertiary? to Jurassic?E Hyabyssal felsic intrusive rocksFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.QcsmodifiedqWmoll-stalcupHWW$WgWpWmollusksdWWWW!WcWfWtWmonzodiorite_Wmonzonite_Wmorainal[WmostW_W`WcWmWnWoWqWmottledcWmountainsW[W_W`WaWbWdWeWfWiWjWlWmWnWoWrWsWmuchqWmudstonedWWcWfWnames_WnearWWhWpWnearlyfWnoHWW!WcWpWnoncalcareous!WnorthW$WpWnorth-centralW$WgWpWnortheasternBW_W`WaWeWfWmWnWoWnortherndWWWaWeWpWtWnorthwest!W_WnorthwesternWBW_W`WhWmWnWoWtWnortonAW\WnotkWlWnumber_Wnumerous`WmWnWoWtWnyacbWrWsWoccurAWWeWtWoccurs`WmWnWoWofAWHW_WdWqWWWWWW!W!W!W!W!W!W!W!W!W!W!W!W!WtlyqWpartsNWpattonHWcWCWW!Wpb/u WpeatAWWWpebbleaWB€_AUnit is composed of plutonic rocks that have been assigned various petrographic names based largely on field inspection and examination of only a few thin sections. The most common rock type appears to be biotite granite, but other rock types include granodiorite, quartz diorite, syenite , quartz monzonite, monzonite, monzodiorite, and diorite. Unit forms the core of a domal volcano-plutonic complex in the Russian Mountains in the northeastern part of the Russian Mission quadrangle and a Bsimilar domal complex in the Fox Hills in the southeastern part of the Holy Cross quadrangle. Unit also composes two large plutonic bodies and a number of small stocks in the northwestern part of the Russian Mission quadrangle and one small stock in the Kilbuck Mountains at the southern edge of the Russian Mission quadrangle. The only detailed chemical data come from the domal complex in the Russian Mountains, which according to Bundtzen and Laird, (1991) is composed of an outer rim of sy^3labayAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWlowerAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWmapAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWWWWtWvWvWvWvWvWvWvWvWFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.htkilbuckW[W_WbWfWiWjWlWrWsWkimmeridgianWkjbWkjvWkWkmu$WgWkWknownWqWkoyukukgWkusilvak`WdWmWnWoWkuskokwimAWqWW[WfWpWkwigukHWdWW!W\W`WcWdWeWmWnWoWtWkygccWdWkygv!WdWkystWkys-fluvialtWlabay!WcWlaird_WlakesAWlaminatedfWlargeW_W`WbWmWnWoWqWrWsWlargely_WdWlate_WdWW!WaWcWfWlatestiWlaumontitecWlaumontitizeddWlavaHW_WdWWWWWWaWjWpWqWlayerscWleafeWlesser`WmWnWoWlimestoneWhWlithologicallycWlittleHWlocalitiesdW\WeWlocallyAWHWdWdWdWdWdWmetasandstonemetaconglomerateandsubordinateVmetavolcanicWmicaceouscWmicaeous!WmichaelHWXW_WaWcWlW!WmicrolitesWmid-cretaceousWmissionMWNWUWWWaWyWWWWBWL WmissionjWkWlWpWqWrWsWmississipianhWmississippianhWhWhWU~€`ARhyolite, dacite and lesser amounts of trachyte and andesite. Typical rock is composed of a fine-grained felsic groundmass with phenocrysts of plagioclase, quartz, biotite, and hornblende. Unit forms numerous large sills, dikes, and domes intruding Cretaceous sedimentary rocks in the northwestern Holy Cross quadrangle, in the northeastern Kwiguk quadrangle, and in the Kusilvak Mountains in the southwestern part of the Kwiguk quadrangle. A felsic to intermediate dike in the southern part B5of the Holy Cross quadrangle has a Pb/U zircon age of 63.6 Ma and a 40Ar/39Ar age of 67.3 Ma. A dike of similar composition from the same general region has a 40Ar/39Ar age of 60.4 Ma (table 1). Elsewhere the unit occurs as small isolated bodies most of which are too small to be shown separately on the map.#CTKiD$early Tertiary and latest CretaceousE?Shallow intrusive rocks of intermediate and silicic composition[qKfluvialAWW[WfluvialandshallowmarinedeltaicdepositsofsandstonesilVforbWrWsWformAWqWfWformedaWeWfWformer\WformingbWrWsWformsHWW_W`WbWmWnWoWqWrWsWfossildWfossils!WcWhWfoundW!W[WtWfour$Wfox_WaWeWfWfreshWtWfromHWdWWWW!W_W`WaWbWcWeWfWgWhWmWnWoWpWrWsWtWgabbrodW$WgWhWjWkWgavedWgeneral`WmWnWoWgenerallyWWpWqWglacial[Wgneissic_WgradefWgranite_WbWgWrWsWgraniticdWaWeWfWgranodiorite_WbWrWsWgranonodioritegWgravelAW[WgraywackedWWdWeWfWhWgreenschisthWgreenstoneeWground$WWWWW$W$W$WdcW!WinspectionyWinsufficientMWinterbeddedaW!WinterceptUWinterlayeredHWWWintermediate Wintertonguesz% €A2021desitic and basaltic lava flows and flow breccias. Tuffaceous sandstone and conglomerate containing abundant clasts of mafic and intermediate volcanic and intrusive rocks. Unit altered to low-grade metamorphic facies by variable replacement of primary minerals by chlorite, calcite, epidote, albite, and quartz. Unit confined to Kilbuck Mountains, southeastern Russian Mission quadrangle. Unit assigned a Middle Jurassic (Bajocian) age based on the presence of marine mollusks.CJabDMiddle JurassicEONyak Terrane, andesitic and basaltic lava flows and marine volcaniclastic rocksFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€A2021R €`A1602ite, monzonite, and quartz monzonite and a core of quartz syenite and porphyritic quartz monzonite. A large pluton located in the northwest corner of the Russian Mission quadrangle and extending into the eastern edge of the Marshall quadrangle locally displays a strong gneissic banding. Seven K/Ar cooling ages from this unit range from 70.9 to 60.9 Ma (table 1).KCTKgD$early Tertiary and latest CretaceousE-Granite, granodiorite, syenite, and monzoniteFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€`A1602s,(physiographicallyAWpillowdWpinkgWplagioclaseWW`WmWnWoWpWqWplainHW[WdWeWplantWtWpleistocene_Wpluton_WbWrWsWplutonic_WgWplutonsbWrWsWpoorlyWdWeWqWpoorly-sortedeWporphyrieslWte-pumpellyiteWpresencecWWpresentHWpresscWpresumed$WprimaryWprobable!Wprobably$WprocessedUWpyroclasticHWWpyroxeneWqacqWqfqWquadrangleHWMWNWSWUWWW_WaWcWdWlWWCWyWWWWW WWWW!W$WBWquadranglesHWXWaWWWWquartzaWCWyWW WWquartz-richNWaWradiolarianWrangeHWCWyWWrangingHWUWrecentAWrecentlyXWreconnaissanceW$WredepositedAWregion WregionalSWrelationshipsSWreplacementWreportedcWWrestsWreworkedAWWWrhyoliteMWSWW WWWrhyolitedaciteandlesseramountsoftrachyteandandesite VJebutW!W$W[W_WcWkWlWpWbyAWHW_WdWqWWWW$W\WgWiWpWcalcareousdW!WdWcalciteWcataclasticallygWcenomanian-turonianfWcentralWfWpWchannelsAWcharacteristics$WcharacterizedAWqWchemical_WchertdWWeWhWchertydWchieflyAWHW[WgWhWchloriteWcinderHWclastdWclastsdWWeWcoarseAWHWcoast\WcoastaleWcobbleeWcollectedHWWfWcolluvialqW[Wcolluvium[WcolumnarWpWcome_Wcommon_WcommonlydWWcWpWcomplex_WcomposeqWcomposedAWWW!W$W[W_W`WdWfWgWhWmWnWoWpWqWcomposes_Wcomposition`WmWnWoWconcordiabWrWsWWWWWdioriteyWdisplaysyWdissectedqWdistributedWdomalyWdomes WdrainingAWdriftWWduneqWdunesqWeasternyWeastwardHWedgeyWWelevationsWWelsewhere WW4_alteredrhyoliteanddaciteporphyriesconfinedtoasinglelValthough$Wamounts`WaWeWfWgWmWnWoWamphiboledWamphibolitehWandW_WaWiWandAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWandesitedWWW`WaWhWiWjWmWnWoWpWqWWqWqWqWW€q€rA2400ABiotite granite and hornblende-biotite granodiorite forming two large plutons that intrude the Nyac terrane in Kilbuck Mountains of the southern Russian Mission quadrangle and a large pluton that forms the Askinuk Mountains in the Hooper Bay quadrangle. Samples from plutons in the Kilbuck Mountains processed for isotopic ages yielded K/Ar and 40Ar39Ar cooling ages ranging from 101 to 120Ma and U/Pb zircon crystallization age of between 104 and 129 Ma (upper Concordia intercept). A singleBf sample from the Askinuk Mountains pluton yielded a biotite K/Ar cooling age of 80.64.0 Ma (table 1).TCKgDLate and Early CretaceousEGranodiorite and graniteFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€sA241010wiltributariesAWtributaryAWtrmvWtrondjhemitegWtroughfWtuffdWWaWtuffaceousWWcWtuffaceousmarinesandstoneshaleandconglomerateminorbasVtuffaceous-richcWtuffsdWWWpWqWturbiditeeWturbidites!WdWturbiditescomposedofhighlycalcareoussandstoneinterbedd!VturbiditicfWWWnedvyVunitsMWWunmodified_WupWWuplandAWuplandsWWupperUWvariousyWvegetationHWXWvesicularHWWBWvesiculartholeiiticandalkalibasaltlavaflowsconesandHVvolcanicHWWvolcaniclasticMWWvolcano-plutonicyWwaterWwesternHW_WwhereHWMWwhichHWyW Wwhole-rockHWBWwideWWwidelyWWWwilson!WwindblownWWwithHW WWW!WyieldHWWyieldedMWUW!WyieldingBWyoungMW_Wyoungscoriaceoustholeiiticbasaltlavaflowsandconesmap_VyoungerHWyukonAWWWqWWBWyukon-koyukuk!WzirconUW WxSendHWentirekWentirely$WepidoteWequivalentaWeWfWjWerosion_Werosional$WestuarineAWevidenceAWexamination_WexposedHWWWcWdWeWpWtWexposuresdWWeWfWtWextending_WcWextendsHWW!WfWtWextrusivejWfaciesWhWfanfWfault-bounded$WgWfaulteddWfeetqWfelsicWW`WmWnWoWqWfewW_WeWtWfieldHWW_WaWdWqWfieldsHWqWfineAWHWcWfWfine-grainedW`WmWnWoWqWfiveWpWflat-lyingBWflat-lyingvesicularbasaltyieldingwhole-rockk/aragesofBVflatsAWfloodplainAWqWflowWaWflowsHW_WWWWWWBWaWjWpWqWfluidsgWWWWWurippleWtWriverdWWBWdWpWriversAWqWWpWrock_W`WdWeWmWnWoWrocksdWWWWW$W_W`WaWeWfWhWjWmWnWoWpWrussiandWWWWWBW[W_WaWbWeWfWhWiWjWkWlWpWqWrWsWsame`WmWnWoWsamplebWrWsWsamplesHWWaWbWpWrWsWsandAW[WsandstoneWWW!WcWeWfWtWsandyAWqW[W\WsanidineWaWqWscattereddWW\WeWhWkWtWschisteWhWscoriaceous_WscrollsAWseaAW\Wsections_WsedimentarydW`WdWfWmWnWoWseparately_WW`WaWmWnWoWqWsequencesfWserpentinized$Wseven_WWWWW_W_W_W_W_WallerHWsomeAWaWcWWsoundAWXWsouth-centralcW!Wsoutheast!WsoutheasternaWcWlWyWWWWsouthernUWaWyW WsouthwesternlW WsparselW}€cFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€dA2180ASparse field data on this sedimentary rock unit suggests that this unit is composed largely of graywacke turbidites including both highly calcareous graywacke as in unit Kygc and graywacke containing abundant volcanic debris as in unit Kygv. Unit poorly exposed along the eastern margin of the Yukon River delta plain in the southeastern part of the St. Michael quadrangle and in the adjoining Kwiguk quadrangle. Unit also crops out in the Kusilvak Mountains in the southwestern part of the KwiB8guk quadrangle and in the adjoining Marshall quadrangle.&CKygD CretaceousEcYukon-Koyukuk Basin, submarine fan deposits, graywacke sandstone and mudstone turbidites, undividedividedN*ofAWHW_WdWqWWWWWWW!W$WBW[W\W_W`WaWbWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWrWsWtWWvWvWvWXandesiteandbasaltlavaflowsandvolcaniclasticrockswideVpVandesiticdWWWWWpWandesiticandbasalticlavaflowsandflowbrecciastuffaceoVandesiticandbasalticvolcaniclasticrockslavaflowschertVangayucham-tozitnadWgWappearance$WcWappears_WareAWHW_WdWqWWWW$W`WaWeWfWhWmWnWoWpWqWareadWWaWcWfWpWareasAWBW[WtWargilliteWhWasqWW$W`WaWdWjWkWlWmWnWoWqWashHWash-flowWqWaskinuk[WbWrWsWassemblagedWaWassemblages!WhWassigneddWW_WgWhWiWat[W_WeWaureoleaWeWfWavailableWpWbajocianWWbanding_WbarsAW\WbasaltHW_WWWWBWaWhWiWpWqWbasalticdWWWWWjWpWWWpWWfWbayHWNW[W\WbWfWbeW$W_W`WjWkWlWmWnWoWgHe€BACFlat-lying vesicular basalt yielding whole-rock K/Ar ages of 19.35 Ma and 6.19 Ma (table 1). Basalt flows located in Three small areas in the Russian Mission quadrangle: two on the Yukon River in the northwestern part of the quadrangle and one on the Owhat River in the northeastern part of the Russian Mission quadrangle.CCTbD late TertiaryEBasalt lava flowsFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.f|b€!D CretaceousEjYukon-Koyukuk Basin, submarine fan deposits, highly calcareous graywacke sandstone and mudstone turbiditesFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€$A3498AUnit presumed to be composed of partly serpentinized harzburgbite and dunite. May also include some gabbro. Unit confined to four small bodies distributed along the eastern side of a fault-bounded belt composed of units KMu and Jt in the north-central part of the Holy Cross quadrangle. Although the four bodies were mapped entirely by aerial reconnaissance, their appearance and erosional characteristics are similar to small bodies of ultramafic rocks which were mapped on the ground a shora shor)f€AAndesite and basalt lava flows and volcaniclastic rocks widely exposed in the central part of the Holy Cross quadrangle and in a small area in the north-central part of the Russian Mission quadrangle between the Yukon and Kuskokwim Rivers. Flows are generally porphyritic and composed of phenocrysts of plagioclase and pyroxene in a groundmass of plagioclase microlites. Some of the flows are columnar jointed and locally vesicular. Volcaniclastic rocks in this unit include breccia, tuffs, aBnd agglomerates. The andesitic and basaltic rocks commonly are interlayered with or intruded by small bodies of dacite and rhyolite belonging to units TKi and TKd. Two basalt samples from outcrops on the Yukon River near the northern edge of the map area yield K/Ar isotopic ages of 50.8 and 42.9 Ma (table 1). No other age data are available from the map area, but in the adjoining Unalakleet quadrangle to the north similar basaltic rocks yield five K/Ar isotopic ages that range from 65.2Lsof$WBW[W_W`WaWbWcWdWeWfWgWhWjWkWlWmWnWoWpWqWrWsWtWoffshore\Wold$WjWolderkWlWonHW_WdWWWW$WBW[W_W`WdWeWgWhWmWnWoWpWoneBW_WaWonly_WorHW_WWW!WjWkWpWqWorigin[WotherAWW_WaWpWothersWoutdWdWeWkWoutcropsWeWpWouter_Woutwash[WoverlainHWWiWoverlieqWoverliesiWowhatBWowingcWoxbowAWpaleozoic$WpartdWWWW!W$WBW_W`WaWcWdWeWfWgWmWnWoWpWqWtWpartlyqW$WpartsfWpattonHWW!W$WcWgWpWpb/u`WmWnWoWpeatAW[WpebbleeWhWpebbleandcobbleconglomerateinterbeddedwithsandstonesieVpelitichWpetrographic_WW_W_W_W_W€bABiotite granite and hornblende-biotite granodiorite forming two large plutons that intrude the Nyac terrane in Kilbuck Mountains of the southern Russian Mission quadrangle and a large pluton that forms the Askinuk Mountains in the Hooper Bay quadrangle. Samples from plutons in the Kilbuck Mountains processed for isotopic ages yielded K/Ar and 40Ar39Ar cooling ages ranging from 101 to 120Ma and U/Pb zircon crystallization age of between 104 and 129 Ma (upper Concordia intercept). A singleBf sample from the Askinuk Mountains pluton yielded a biotite K/Ar cooling age of 80.64.0 Ma (table 1).TCKgDLate and Early CretaceousEGranodiorite and graniteFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.W=aconesHW_WconfinedW$WaWeWfWgWiWjWlWconformablyWiWconglomeratedWWWeWhWconsistAW[WfWcontaindWeWcontainingWdWcontainsWeWtWcoolingdW_WbWgWhWrWsWcore_WcoresaWeWfWcorner!W_WaWcWcouldjWcoverHW[W\WWW\WW!WcropsaWdWlWWcrossMWNWaWdWWCWyWW WWWWW!W$Wcross-beddedNWcrossbeddedWcrystallizationUWcurrentsAWdaciteMWSWW WWWdaciterhyoliteandsubordinatetrachyandesitelavaflowssiVdaciterhyoliteandesiteandbasaltlavaflowsandvolcaniclMVdataMWdWlWWCWyWWdebrislWWdeformedCWdeltaHWlW[WdeltaicNWWdeltaicandsubmarinefandepositsthedeltaicdepositsconsNVdepositsAWHWNWqWW[W]WdetailedyWdevitrifiedMWdiabasedWWdike WdikesdW WWdioritedWCWyWWdisplaysyWba€C, to 51.9 Ma (Patton and Moll-Stalcup, 1996).CTKaD$early Tertiary and latest CretaceousE3Andesite and basalt flows and volcanicclasitc rocksFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€!A2102ATurbidites composed of highly calcareous sandstone interbedded with noncalcareous micaeous siltstone and shale. Unit is infolded with and locally intertongues with unit Kygv. Unit extends in a broad belt from the southeast corner of St. Michael quadrangle and the northwest corner of the Holy Cross quadrangle to the south-central part of the Kwiguk quadrangle. No fossils found in this unit, but elsewhere in the Yukon-Koyukuk Basin similar assemblages have yielded marine mollusks of probableBQ late Early or early Late Cretaceous age (Patton, Wilson, Labay, and Shew, 2006).?CKygcKygc|` €BA1004it presumed to be composed of partly serpentinized harzburgbite and dunite. May also include some gabbro. Unit confined to four small bodies distributed along the eastern side of a fault-bounded belt composed of units KMu and Jt in the north-central part of the Holy Cross quadrangle. Although the four bodies were mapped entirely by aerial reconnaissance, their appearance and erosional characteristics are similar to small bodies of ultramafic rocks which were mapped on the ground a shorBt distance to the north in the Unalakleet quadrangle (Patton and Moll-Stalcup, 1996). Unit probably Mesozoic in age, but may be as old as Paleozoic.CMzPzumDMesozoic and Paleozoic?E.Koyukuk Terrane, serpentinized ulramafic rocksFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€BA1004kP)island_Wisolated`WeWmWnWoWisotopicdWWaWbWgWhWpWrWsWitHWgWitsdWjabWiWkWjointedWpWjt$WjurassicdWWWgWiWjWkWlWjvckWk-arHWk/ardWWBW_WaWbWgWhWpWrWsWZtwoWBW_WaWbWpWrWsWtype_Wtypes_Wtypical`WmWnWoWu/pbbWrWsWultramafic$WunalakleetHWW$WgWpWuncertainkWlWunconformablyiWunconsolidated[WundividedWaWgWtWundividedareaswherenumeroussmallhypabyssalbodiesofrhtVunitAWHWdWqWWWWWW!W$W\W_W`WaWcWdWeWfWgWhWiWjWkWlWmWnWoWpWqWtWunitcomposedchieflyofsiltfinesandandpeatsomegravelAVunitcomposedofawidevarietyofmaficandintermediatevohVunitiscomposedchieflyoftrondjhemiteandtonaliteplutongVunitiscomposedofplutonicrocksthathavebeenassignedv_Vunitpresumedtobecomposedofpartlyserpentinizedharzbur$VunitsW$WaWkWpWunmodified_Wup[WuplandAWuplands[WupperbWrWsWWblyoverliesuniVvaricoloredhWvarieseWvarietyhWvarious_W€nFPatton, W.W., Jr., Wilson, F.H., and Labay, K.A. , in prep., Reconnaissance geologic map of the lower Yukon River Region, Alaska: U.S. Geological survey Scientific Investigations Serives Map SIM-xxxxx, scale 1:500,000.€oA1650ARhyolite, dacite and lesser amounts of trachyte and andesite. Typical rock is composed of a fine-grained felsic groundmass with phenocrysts of plagioclase, quartz, biotite, and hornblende. Unit forms numerous large sills, dikes, and domes intruding Cretaceous sedimentary rocks in the northwestern Holy Cross quadrangle, in the northeastern Kwiguk quadrangle, and in the Kusilvak Mountains in the southwestern part of the Kwiguk quadrangle. A felsic to intermediate dike in the southern part part h!intertongues!WcWintoHWW_WtWintrudeWbWqWrWsWtWintrudeddWWpWintrudesgWkWintruding`WmWnWoWintrusivedWWhWjWisHWdWWWW!W[W_W`WcWdWgWkWlWmWnWoWqWtW@A-modified@Lof$cphenocrysts@sphysiographically@Vporphyritic@,quartz-rich@ripple@\several@usouthern@spits@nst@Istabilized@Cthejwtributaries@Ztwo@ivalanginian@vegetation@Gwere@rDtka@and-andesite@$angayucham-tozitna@>chert@ conglomerate@domes@;flats@'graywacke@koyukuk@