MARCIA K.McNUTT, DIRECTOR U.S. GEOLOGICALSURVEY U.S. DEPARTMENT OFTHEINTERIOR Kmd Jmsy

Kahg CAMBRIAN ORDOVICIAN SILURIAN DEVONIAN Jd PRECAMBRIAN Tmb Jmg Jme Kbh Kgd Kpd Kag Kab Kav Kqs Kns Kas Kes Khf Kfd Early Middle Late Mesoproterozoic Mesoproterozoic Mesoproterozoic Neoproterozoic Lower Cambrian Middle Cambrian Upper Cambrian Lower Ordovician Middle Ordovician Upper Ordovician Lower Silurian Upper Silurian Lower Devonian Middle Devonian Upper Devonian White MountainIgneousSuite(EarlyCretaceousandJurassic)

1400 Ma 1350 Ma 1300 Ma 1200 Ma 1100 Ma 1000 Ma 900 Ma 571 Ma 544 Ma 495 Ma 485 Ma 470 Ma 464 Ma 458 Ma 453 Ma 449 Ma 441 Ma 428 Ma 419 Ma 418 Ma 413.5 Ma 409 Ma 394 Ma 387 Ma 382 Ma 375 Ma 365 Ma Ma (FolandandFaul,1977) plutons, apartialringdike,andscreens ofvolcanicrocks. K-Aragesof122to120 Ascutney Mountain igneous complex (EarlyCretaceous)—Consistsoftwo syenite core, a fine-grained quartz syenite border, and associated trachyte dikes ( A small,0.5-km-long,northwest-trending stock consisting ofacoarse-grainedalkali Barber Hillstock(EarlyCretaceous) Ma (FolandandFaul,1977) Composite stockofquartzsyenite,syenitegranite,andessexite.K-Arage175±4 Monadnock Mountainpluton(MiddleJurassic) 1980) isochron ontrachytedikesof125±5Ma(McHoneandCorneille, andStump,1971)Rb/Srwhole-rock K-Ar biotiteageof114±2Ma(Armstrong be MiddleJurassic(McHone,1992) EarlyCretaceous, butsome may Dikes ofWhiteMountainIgneousSuite—Largely Ascutney Mountainstock 103±4 and 99±2 Ma (Armstrong andStump,1971) 103±4 and99±2Ma(Armstrong ite, andspessartite.Average offiveK-Arages101Ma;rangebetween essexite, andmonzodiorite.Associateddikesofmonchiquite,camptonite,boston- dikes consistingofaugiteandhastingsitesyenite,nephelinesodalite Cuttingsville stock(EarlyCretaceous)—Compositeandintrusivebreccia kaolin, hematiteochre, andlignite workingsfor concealedbutknownfrom historicunderground east. Depositlargely between theDunhamDolostoneonwestandCheshire Quartziteonthe fault into kaolin perhaps by karst collapse along a concealed west-dipping normal kaolin, residual hematite,andochre depositsnearBrandon.Lignitewasletdown and dismembered ligniteoccurringaselongatedisrupteddepositsinunderlying silt,sandandgravelslumped Brandon Lignite(lowerMiocene)—Organic bostonite, camptonite,aplite,andpegmatite Dikes associatedwithMonadnockMountainpluton—Granite,syenite,quartz abundant, poorlydefinedareas ofdiorite.Includestwoareas ofsyenite( centers definedbyweaklydevelopedigneousfoliation.Gabbro isintrudedby intrusive and western) A composite gabbro-diorite stock having two (eastern Little Ascutneystock Y Y Y Y Y 3A 3C 3B Z 2 1 Hornblende graniteoccurringassmallintrusivemassesin Hornblende Medium- tocoarse-grainedbiotite-microperthite-orthoclase-albite granite autoclasts offelsicalkalicandfine-grainedmaficrocks Andesite brecciacontainingxenolithsofMesoproterozoic gneissand Essexite (alkaligabbro) Quartz syenite Nepheline andsodalitesyenite,hornblendesyenite and Athensdomes well outsidetheAscutneyMountainstocksinsaddlebetweenChester within theplutonsandinadjacentcountryrocks. Onepaisanitedikeoccurs Paisanite dike—Fine-grainedsyeniticsimilartospheruliticdikesfound andbiotitediorite gabbro infiltratedbyhornblende Gabbro anddiorite—Medium-tocoarse-grainedaugite-hornblende-biotite quartz syenite andesinegabbroic rock gradinginto Essexite—Pyroxene-biotite-hornblende Granite andscapolite quartz-wollastonite, plagioclase,grossular garnet, cordierite, pleonaste,andcorundum;calcareous pelitescontaindiopside, containandalusite,sillimanite, aluminous rocks oftheWaits RiverFormation in structuralcontinuitywithrocks outsidethecontactaureole. Locally schists of the country rock. Shown only around main Ascutney Mountainstock consistingofrecognizable butaltered Hornfels—Dense, compacthornfels the edifice having trachytic flow structure and layering. Interpreted as volcanicrocks of Trachytic torhyolitictuffs,andbreccias containingfragmentsofvolcanicrocks Ascutney stock minor fayalite,augite,andquartz;occursasapartialringdikeintheLittle syenite;contains Syenite-porphyrite tosericite-perthite-hornblende-biotite —Greenish-gray to pink hornblende-biotite quartzsyenite Quartz syenite—Greenish-gray topinkhornblende-biotite CROIXIAN IBEXIAN WHITEROCKIAN MOHAWKIAN CINCINNATIAN 1–51 refer touranium-lead(U-Pb)zircon agesampleslistedintable1onthe Minerals thatare variablypresent are showninparentheses with±.Nos.

[Minerals are listedinorder ofincreasing andapproximate abundance. DRESBACH FRANCONIAN TREMPEALEAUAN CHAZY BLACK RIVER TRENTON EDENIAN MAYSVILLIAN RICHMONDIAN ˆ

— GIVE- FRAS- TREMADOCIAN ARENIGIAN LLANVIRNIAN CARADOCIAN ASHGILLIAN LLANDOVERY WENLOCK LUDLOW PRÍDOLÍ LOCHKOVIAN PRAGIAN EMSIAN EIFELIAN FAMENNIAN Hornblende-biotite-microperthite granite,gradationalintoquartzsyenite Hornblende-biotite-microperthite TIAN NIAN STAGE Y 2 cs back ofthissheetandshownonthegeologicmaps] DESCRIPTION OFMAPUNITS ADIRONDACKS INVERMONTANDTHEWHITEHALL,N.Y., AREA

Y Beekmantown Group 2 ? hgn Ogmw Ofcrp Ohc Otl ADIRONDACK LOWLANDSAND LAKE CHAMPLAINLOWLANDS Y 2 qz O w Ogm Ofcw Ogf Ofa pt Oh ti Y 2 Ofh bpg ? Ofcpi Omi O wl PARAGNEISS Oo Ogml Ofcs Ohl Y 2 ? cs Ocgu Osp Obku Y 2 bmg Oha Obr Ogf Oib ? (Ocbrp) Odp Ocp Opi Kas Ov Ochd Ob VERMONTVALLEY SEQUENCEAND Kas Otl MIDDLEBURY SYNCLINORIUM ) Kfd Y 3A ). gd Ocbrp INTRUSIVE ROCKS Ohc Ogf Oh Ofh Omi du Ocu sp m w Oo Ob d c Os Y Y 2 3A Ocbu bt ? ? ? Y phg Ocbe Zdi 3C ca Ocw cb Ohl p Y Dwmz 2 Dbqm Dmbg Dnqm Dwwz Dwdg Dwhz Dnwz Dbbg Dnbg Ddbg Dvbg Dabg Dedg Debg Dkbg Degr ba Ddrz Dniz Dhg Dbg Dst Y 3A Oil Oilc Ocu gb Oi New HampshirePlutonicSuite sp du w Ob Os c ? Owbl (1992)—Plutons identifiedonmap Igneous rocksoftheNortheastKingdombatholithAyuso andArth Cuttingsville stock Mountain, alongU.S.Route4southwestofProctor, andimmediatelywestofthe dikes occurontheeastsideofMonadnockMountain,3.2kmwestLittleAscutney orstrike-slip.Notablefaulted minor faultsthatare eithernortheast-trending normal andchilled,butlocallytheyare offsetby Range. Commonlydikesare nondeformed plutons atMountAscutneyandCuttingsvilleextendingwestward intotheTaconic offoidalfelsic,mafic,andlamprophyre dikesassociatedwith Early Cretaceous swarm ofConnecticutValley margin lamprophyre atwestern trough; and(3)asouthern of with BarberHillstocknearLakeChamplainandextendingeastward toswarm associated associated withMonadnockMountainpluton;(2)EarlyCretaceous swarms (1)probable MiddleJurassicdikesofsyenitediabase,andlamprophyre swarms: reporting; however,uneven owingtononuniform three generalareas containdike measured; spotlocationsfrom literature withoutstrikesare notshown.Distribution elsewhere, felsicdikesare notshownseparately.Orientationgivesstrikeofdikes Other plutonsoftheNewHampshirePlutonicSuite trachyte dikes.Onlyfelsicdikesnearintrusivecentersare distinguishedas monchiquite andgranitic,rhyolite,trachytefoidalfelsicdikes;spherulitic of olivine-augitediabase,lamprophyre, calciteamygdaloidalmaficdikes;alkalibasalt, dikesofdiabase,<1mto3thick,consisting Predominantly maficandintermediate m Ow d and similar to the predominantly lighter-colored granitic rocks of southern Vermontand similartothepredominantly lighter-colored graniticrocks ofsouthern biotite quartzmonzonite,locally orbicular; commercially knownas“Bethel white” dikes labelled Binary andbiotitegranitegranodiorite,undifferentiated—Includessmall granodiorite ( muscovite porphyriticgranodioriteandminortonalite( Derby pluton—Light-gray,medium-tocoarse-grained,massive,epidote-biotite- gabbro andquartzdiorite( main zone( peraluminousleucogranite.Variesmiarolitic garnet-muscovite from apegmatitic Willoughby pluton—Light-graytopink,medium-verycoarsegrained,massive, bodies—Contains phenocrystsofeuhedralandembayedquartz,micro- Porphyritic, light-gray, hypabyssalbiotitegraniteandtonaliteinsill-like Stiles Pondpluton—Gray,medium-grained,nonfoliatedbiotite-muscovitetonalite (four generaldesignatorsare used: Devonian intrusiverocks rite, undifferentiated; East Bethel plutons— (SHRIMP) ageof368±4Ma,no.47(Aleinikoffandothers,2011) biotite granodiorite.U-Pbzircon Sensitive High ResolutionIonMicroprobe East Barreplutons—Gray,homogeneous,fine-tomedium-grainedmuscovite- rocks oftheEastBarre plutons muscovite granite.Hasdistinctlymore potassiumfeldsparandislightergraythan Knox Mountainpluton—Light-gray,medium-grained,quartz-richbiotite- rock unit abundant dikes and sills of granite. Underlying color and symbol identify country and Overprint pattern—Showsareas ofintricatelymixedcountryrock, hornfels, granite; accessoriesincludeapatite,sphene,pyrite,andmagnetite grained hypidiomorphic,granular, biotite-muscovite-microcline-plagioclase Maidstone pluton—Almost-whitetodark-gray,locallypink,medium-coarse- well asbiotitegranodiorite quartzmonzonitelikethatintheNulheganpluton,as zone ofbiotite-hornblende more melanocratic tonaliteandaneastern, granite andminorhornblende-biotite zoneofmedium-tofine-grainedbiotite-muscovite Victory pluton—Awestern magnetite-microcline-perthite-biotite granite Newark pluton—Pinkish-graytocream-colored, medium-tocoarse-grained granite andpegmatite,undifferentiated Averill pluton—Gray topink,medium-coarse-grainedgarnet-muscovite-biotite and Arth,1992) seriate toporphyriticgranodioriteandgranite( Echo Pondpluton—Light-graytopink,medium-coarse-grained,massive, Arth, 1992) divided into a western zone ( divided into a western monzodiorite,minorgranodiorite,andgranite biotite-clotted, hornblende-quartz Nulhegan pluton—Light-graytodark-gray,medium-coarse-grained,massive, (±pyroxene) gabbro anddiorite quartz-biotite-hornblende West Charlestonpluton—Dark-gray,medium-tocoarse-grained,massive, nite ( hydrothermally altered zone ( hydrothermally small dikes.Only Owl Dnqm psc pdo ST. ALBANS Ohg O g c pq ). Rb/Srwhole-rock ageof390±14Ma(Ayuso andArth,1992) AREA psc pc pq Dwmz du Oml Ddrz Dg p O sk O sks O skl Dbg ). Rb/Srwhole-rock isochron ageof370±17Ma(Ayuso and ca psh ) to biotitic granodioritic western zone( ) tobiotiticgranodioriticwestern pdo Dqm and Very light-bluish-graytowhite,medium-grained,muscovite- Zdph Dedg , quartzmonzonite; O sw Dg Zd SOUTHERN GREEN Zdb Dnwz Dwhz are shownintheDescriptionofMapUnits) Zdb Zdc Dalton Formation Zdq MOUNTAINS ), andinnerzoneofgranite( Zdm ), inner zone ( Dbg, ). Rb/Sr whole-rock age of 376±9 Ma (Ayuso Zdc binaryandbiotitegranitegranodio- Zd BARBER HILL Zds CUTTINGSVILLE STOCK STOCK Zdfq Zd MONADNOCK Kns Zdq MOUNTAIN Kbh Ddg Zds PLUTON Jmsy Dniz Debg Jmg , dioriteandgabbro; and Jme Kqs Kes ), andcore of quartz monzo- ) andouterzoneofquartz Ddbg Zh ASCUTNEY MOUNTAIN IGNEOUSCOMPLEX Degr ), witharimzoneof Kab WHITE MOUNTAIN IGNEOUSSUITE Dwwz Zhs Kgd (consisting ofplutonsanddikeswarms ) of JurassictoEarlyCretaceous age) Zhgt break inscale Zhab Zhq ), toinner Zhq Kag Zhbs Hoosac Formation Kas Zhs Brandon Lignite Eastern flankoftheGreenMountainmassif Dg Kfd Khf break inscale , Zhtm Kahg Zhc ; Tmb Zhd Zhab Zhabc Zhrab OF GREENMOUNTAIN MASSIF Zhtm and easterndomes Kav Zhgab Zhc Zhtm COVER ROCKSEAST Dbmg Ofcrp Ofcpi Obku Ochd Ocgu Odp Oha Ocp Osp Obr Ogf Opi Oib Dg Oo Ov Dd Zhcgt ? ? Kfd Devonian graniticrocksofsouthernVermont Beekmantown Group(MiddleOrdoviciantoUpperCambrian) Chazy Group(UpperandMiddleOrdovician) Formation Plymouth Ztc ( granite,minorpegmatite,andaplitedikes whitish-gray, garnet-biotite-muscovite Black MountainplutonoftheGuilforddome—Weakly foliated,light-grayto bluish-gray, fine-grained,foliatedandlineated gray, fine-grainedpoorlyfossiliferous limestone Orwell Limestone(UpperOrdovician)—Dove-gray-weathering,blacktodark- beds; upperbedsfossiliferous withblackchert dolostone, sandyandlight-graylimestone;verticalburrows inbasal Black RiverGroup,undivided(UpperOrdovician)—Thin-beddedto massive weathering shalylimestonebedsrichinfragmentsofthetrilobiteCryptolithus bedded dark-graytoblackgranularlimestone;locally grades upward into sooty- Glens FallsLimestone(UpperOrdovician)—Dark-bluish-gray-weathering,thinly bioclastic limestone,bluish-graycalcareous shale,andlaminatedshale Cumberland HeadFormation(UpperOrdovician)—Interbedded graded beds ofbluish-graylimestone Stony PointFormation(UpperOrdovician)—Dark-graycalcareous shalewith ous bedsofcrossbedded andgradeddolomiticsiltstone Iberville Formation(UpperOrdovician)—Dark-gray shale with thin discontinu- sandstone, andchertwithinbedsofblackshale Hathaway Formation(UpperOrdovician)—Clastsoflimestone,dolostone, Biotite metadiorite in unit (±muscovite) cline withCarlsbadtwinning(ingranite),plagioclase,andeuhedralbiotite Whitehall, N.Y., toOrwell,Vt.LaterallyequivalentProvidence IslandDolostone Fort CassinFormation(MiddleandLowerOrdovician)—Shownlocallyfrom north ofOrwell) equivalenttotheBridportMemberofChipmanFormation, limestone (largely contains thinlayersoffossiliferous bluish-gray “beeswax-scored” surfaces; weathering, massivetothick-bedded,fine-graineddark-graydolostone;has Providence IslandDolostone(MiddleandLowerOrdovician)—Light-buff-tan- Beekmantown Group,undivided(MiddleOrdoviciantoUpperCambrian)— sandstone andfossiliferous limestone Day PointFormation (Middle Ordovician)—Gray,thin-beddedto massive ous limestone Crown PointFormation(MiddleOrdovician)—Gray,massivelybeddedfossilifer- Valcour Formation(UpperOrdovician) massively beddedfossiliferous limestoneandcalcareous sandstone Chazy Group, undivided (Upper and Middle Ordovician)—Dark- tolight-gray, cut Valley trough westoftheConnecti- dikes ofgranite,trondhjemite, andquartzmonzonitelargely of theBethelarea anddikesintheChesterAthensdomes;alsoresemble small (Aleinikoff andothers,2011).Thesecloselyresemble undatedwhitegranodiorites south of Plymouth has a U-Pb zircon SHRIMP age of365±5 Ma, no. 49 SHRIMP ageofabout380to390Ma(Aleinikoffandothers,2011);asimilardike Plymouth. Thelattercontainsinheritedzircon withrimshavinganimprecise to Northfield,includingtheLibertyHilllocalityandgranodioritestockeastof orbicular, thatintrudecoverrocks eastoftheGreen Mountainmassiffrom Jamaica to medium-grainedbiotite-muscovitequartzmonzoniteandgranodiorite,locally fine- small stocksofverylightgraytowhite,muscovite-rich,locallygarnet-bearing, well-foliated dikesontheeastandwestflanksofdomes;alsogranite crosscutting nonfoliateddikeswithinthecore ofthedomesandasfolded quartz monzoniteandgranodiorite,granitepegmatite,aplitewhichoccuras Aleinikoff, USGS,writtencommun.,2002);andwhitish-graymuscovite-rich no. 46(Aleinikoffandothers,2011),from rimsonProterozoic-age cores (J.N. granodiorite atGassettsquarry,havingaU-Pbzircon SHRIMPageof392±6Ma, the ConnecticutValley trough—Light-gray to white, garnet-muscovite-biotite Granite andtrondhjemitedikesofChesterAthensdomeswest intercept ageof364±4Ma,no.48(Aleinikoffandothers,2011) limestones, fossiliferous limestones,anddolostones DIKES Ztrg Dg (west oftheOrwellandChamplainthrusts) Adirondack lowlandsandLakeChamplain ROCKS OFTHELAURENTIANMARGIN commun., 2004) upper IbexianconodontssouthwestofRootPond(J.E.Repetski,USGS,written Interbeddedlimestonescontain several positionsintheFortCassinFormation. but herein extendedtoincludethinlensesofquartzitethatoccurinterbeddedat limestone. Namedforoccurrences nearRootPondintheBensonquadrangle, orangey-tan- and beige-weathering dolostone and thin bedsoffossiliferous tannish-white, well-beddedandvitreous steel-grayquartziteinterbeddedwith Root PondQuartziteMember(MiddleandLowerOrdovician)—Light-grayto pfq pd Kpd Jd ). Rb/Srmuscoviteageof383±7Ma(Naylor, 1971)andaU-Pbzircon upper- Ztbs Tyson Formation Y Y 1,2 1,2 Kmd bg Ztd be Y West Bridgewater 2 Ztg LAURENTIAN MARGIN rgt unconformity ? unconformity Ztc Ztgr Formation Ztab Y Ztq 2 Y rss 2 Ztc Owb wg Y Ztq 1 ? Y rs Y 2 159 Ma 144 Ma 100 Ma 24 Ma 2 rs wxg Monastery Formation Y 2 Zmt Y wxd Y Y Dgq 2 2 ? ? wxs 2 wxcs wxq Middle Upper Lower Miocene Lower northeast of St. Johnsbury— Zfb Ocu unconfomity Zmp Zmq Y Y Zpw 1,2 — 1,2 Zps

Zfq Zfd be sp du w bg Os Dark- tolight-grayfossiliferous limestone c JURASSIC CRETACEOUS TERTIARY Zfco m d Zmmt Zmf Y Zpwd Zpc 2 bgt Fairfield Pond Zwb Formation O sw du

Pinnacle Formation c Zfp Y Y Zpw Zpc Zpc 1 2 q q Zps West Bridgewater unconformity ? unconformity Medium-light- Y Zpvc Zungs MOUNTAIN ANTICLINORIUM 3A Zpva Formation Zpvf Zunql COVER ROCKSOFGREEN Formation Zpu Underhill bga Y Y Owb Zpv 1 2 Zun a a Zunw Gray Zung Y Y 2 2 Formation Tibbit Hill hg lq Y Zth 3A ? ? fg Y Y 2 2 dm m Fayston Formations ? Hazens Notchand Zfqz Y 2 O wl Ogm cs Y Ogmw Y Zfs Y Y Ofcw O w Y Y 3A Ofcs Y Y Zfa Zfw pt Ofa 2 3A 3A Zfq ti 2 2 2 hgn 2 Ogml Y phg ba qz cs bt Zdi gd gb 3C Y 2 p Zfc Zhn myu Zhnn Zf ? Zhng Paragneiss Intrusive Rocks bedded pebblyquartzite,crossbedded vitreous quartzite,andlocalconglomerate Potsdam Sandstone(UpperCambrian)—Light-gray,tan,anddark-gray,well- quartzite weathering quartzose dolostone, pebbly dolomitic quartzite,and interbedded Ticonderoga Formation(UpperCambrian)—Light-gray,yellowish-gray-tobuff- containing layersofgraylimestone( light-gray andpinkish-gray,coarse-graineddolostonechertydolostone, quartzite ( Biotite gneiss ofuncertainorigin weathering fossiliferous limestone( medium- to thick-bedded dolostone, locallycherty;containslensoflight-gray- Great MeadowsFormation(LowerOrdovician)—Light-gray,medium-grained, limestone andbuff-weatheringdolostone State)—Medium- to dark-gray and mottled, medium- to thick-bedded dolomitic Fort AnnFormation(LowerOrdovician)(ShownonlyinNewYork schist, and dark-gray diopside-hornblende (actinolite)-plagioclasecalc-silicategneiss schist, anddark-graydiopside-hornblende to light-graydiopside-phlogopite-scapolite-calcitemarble,phlogopite-tremolite-talc Marble andcalc-silicate gneiss (Middle Mesoproterozoic)—Medium-dark-gray Hague Gneissandonewithinbiotite-quartz-plagioclasegneiss( beds asmuch10mthick.Occursintwolayers,onewithinorattachedtothe quartzitein quartziteandmagnetite-biotite-garnet well-layered magnetite-garnet Quartzite (MiddleMesoproterozoic)—Light-tantoyellowish-gray,massive sillimanite-feldspar gneissosityolderthantheregional Ottawanfoliation lenses, layersorpodsofquartzite,marble,calc-silicaterock. Containsacoarse plagioclase-quartz schist orgneiss,locallycontainingmappableanddiscontinuous - (large)-sillimanite-biotite-orthoclase green torusty-sulfidic-weathering,garnet Hague GneissofAlling(1918)(MiddleMesoproterozoic)—Yellowish-grayish- rock ( (?) ofplagioclase.Containsmappableandfoldedscreens ofmarble,calc-silicate plagioclase asmuch1.5cmlong,recrystallized from pre-Ottawan phenocrysts polycrystallineaggregates of granitegneiss.Haslarge and garnet-hornblende gneiss andpyroxene-bearing charnockitic grained magnetite-garnet-hornblende Mesoproterozoic)—Rusty-grayish-brown- tobrown-weathering, knubblycoarse- Pharaoh MountainGneissofWienerandothers(1984)(LatetoMiddle phenocrysts(augen)alignedinoldrelict flow(?)foliation deformed perthite augengranodioriticgneiss,locallymassivebutwellfoliated.Contains - Mesoproterozoic)—Light-gray topinkish-gray,garnet-biotite-plagioclase-micro Granodioritic augengneissandquartzmonzonite(Late dioritic gneiss;similarrock mappedintheChittendenIntrusiveSuiteVermont (±olivine)gabbro and Metagabbro (LateMesoproterozoic)—Garnet-hornblende ductileshearzones normal Ottawan foliationandlocallyfillsnarrow, northeast-trending, steeplydipping granitepegmatite,<1mto10thick.Crosscuts magnetite-biotite (±tourmaline) Pegmatite dikes(Late Mesoproterozoic)—Pinkish-gray tolight-gray,unfoliated, subvertical northeast-trending discontinuouszoneinthecenterofBaldMountain ocellar basaltictomedium-grainedaugite-plagioclasediabasicdikes,occurringasa Diabase dikes(Neoproterozoic)—Dark-graytogreenish-gray, very fine grained, Whitehall Formation(LowerOrdovicianandUpperCambrian)— 1328±32 Ma(McLellandandChiarenzelli, 1990) interpreted asintrusiveintosomeparagneissunitsthatare here olderthan quartzite,andcalc-silicategneissonsouthendofAustinHill.Unit garnet-feldspar schist,dark-gray lenses andscreens ofrustysulfidicgarnet-biotite-feldspar-quartz west ofAustinHillonthesideSouthBay,Whitehall,N.Y. Contains 1329±37 Ma(McLellandandChiarenzelli, 1990)obtainedfrom exposure 1.5km IonizationMassSpectrometry (TIMS)ageof paragneiss. U-Pbzircon Thermal screens of into white,fine-grainedtrondhjemitic aplitenearcontactswithlarger tonalite gneisshavingscreens, dikes,orsillsofmore maficgneiss.Passeslaterally Mesoproterozoic)—Predominantly chalky-white-weathering, massive biotite into aquartzosefaciesof Hague Gneiss.Thelatterisrichinmicrocline andpassesthrough interbedding dacks inVermont andintheWhitehall,N.Y., area Neoproterozoic andMesoproterozoicrocksoftheAdiron- to thequartziteofRootPondQuartziteMember( and crossbedded, calcareous anddolomiticsiltstonequartziteinbedssimilar Ward SiltstoneMember(LowerOrdovician)—Light-tantogray,thinlybedded commun., 2004) School House, in the Bensonquadrangle(J.E. Repetski, USGS,written upper IbexiantolowerWhiterockian conodontsatthetypelocalitynearSciota grained, anddark-gray,fossiliferous, andplatybluish-graylimestone.Contains Sciota LimestoneMember(MiddleandLowerOrdovician)—Light-gray,fine- surface texture surface laminated quartziteanddolostone;sandybedsweathertoawoody-grained Winchell Creek Member—Tan-weathering, gray, well-bedded andcrossbedded Pinney Hollow Zphb Zphq Formation Zphf 571 Ma TACONIC ALLOCHTHON(GIDDINGSBROOK, SUNSET LAKE,ANDSUDBURY SLICES)AND Y Zph * 2 cs Zphw Zphw Zpha Zpha Y ROCKS OFTHEBENNINGTONAREA t ), maficdiopside-hypersthenegneiss,andinterbeddedsillimanite-garne tonalite 2 qz Early Mesoproterozoic or GREEN MOUNTAIN MASSIF Cavendish Formation Neoproterozoic inpart ). Interpreted as largely intrusive but may contain some charnockitic intrusive but may contain some charnockitic ). Interpreted as largely Opaw AND EASTERNDOMES:

MOUNT HOLLY COMPLEX unconformities (Some lesserunitslistedintheDescriptionofMapUnitsmaynotbeshownhere. AsteriskindicatesU-Pbzircon age.) (age problematic) ? Y Y 1 gneiss 1 cg cfs ? co wcu Zbp ( Znb) Zbb wcnb Znr Y 2 bpg ------unconformity------Zmpq Y Y 1? 1 cs ( cm Y ( Znm) 2 Zbm Omm bt wc Opo Oir Ogml ? ) Ocwl hh d Zbmg and Zbv ls Zzh ) Znr ) wcbb Zbk ls eb Y Rocks atDevilsDen ls ? mafic d dm (age problematic) Y Y ? ? DORSET MOUNTAIN ANDMOUNTEQUINOXAREA cms

Bull Formation and Nassau Formation MOUNT EQUINOXAND mfs ? Znw Ofcrp ARLINGTON AREA gneiss Zngq Y ? q ) CORRELATION OFMAPUNITS Zngs TACONIC ALLOCHTHON (syn- andpost-emplacement) Y 1326 Ma Y 2 Zngq ( bpg 2 ? Y mig * Zbms 2 Predominantly Zbq ba ) beneaththe ) (Middle Oag Y 1309 Ma 2 Y lga 2 * lgg

Netop Formation DORSET MOUNTAIN AREA

? Austin Glen Graywacke Zd after Potter (1972) Y Znw 1342 Ma 2 Y pha Y CONGLOMERATE 2 SOUTH LONDONDERRY IGNEOUSSUITE 2 * phg bv Zngs BRECCIA FORBES Zn Green Mountainmassif Znab ? AND Znq OF THEGREENMOUNTAIN ANDLINCOLNMOUNTAIN HILL Y (Owm) Y Ocbrp Ocbu Ocgu Owbl Ofh Ocbe Znq Ocw Odp Omi 2 Ocp Owl Osp Ohc Oilc Ogf Ohl Ow 2 Ob Oo Otl Oh Ov Oil bmg Oi bpg Y 1 Y ? tg Y Zngq 3A 2 ? lg gb Chazy Group(UpperandMiddleOrdovician) MASSIFS ANDEASTERNDOMES 1321 Ma Y 1367 Ma INTRUSIVE ROCKS Potter (1972)( varieties nearandonWhipstockHillconstitutetheBreccia Memberof thrust southofMiddlebury thinly bedded and well-foliated dolomitic limestone, shown above the Champlain Middlebury Limestone(MiddleOrdovician)—Buff-streaked, dark-bluish-gray, with difficulty,especiallyinthearea westoftheSudburyslice dark-gray fine-grainedlimestone.Distinguishedfrom theMiddleburyLimestone Orwell Limestone(UpperOrdovician)—Dove-gray-weathering,blackand Middle Ordovician)—ShownlocallywestoftheTaconic allochthon Chazy, BlackRiver, andTrenton Limestones,undifferentiated(Upperand in fragmentsofthetrilobiteCryptolithus grading locallyupward intosooty-weatheringshalylimestonescontainingbedsrich bedded, dark-graytoblackgranularlimestones,andgraylimestone, Glens Falls Limestone (Upper Ordovician)—Dark-bluish-gray-weathering, thinly paragneisses olderthanthetonaliticgneiss( tonalitic gneissandthePharaohMountainGneissisinterpreted as quartz schistandgraysulfidicsillimanitequartzite.Occursasscreens within - cm thick, tremolite-pyroxene gneiss, and biotite-rich,rusty-weatheringgarnet quartzite,2to5 commonly containingbedsofdark-grayvitreous magnetite-garnet gneiss, fine-grained, magnetite-garnet-hornblende-biotite-diopside-plagioclase Mafic gneiss(MiddletoEarlyMesoproterozoic)—Dark-grayblack, Member, andapolymictlimestoneconglomerate( ville Formation above.Containsbasallimestonemember( ville Formation Walloomsac Formation(UpperOrdovician)—SamedescriptionastheHorton- side oftheTaconic allochthonsouthtoBennington (mapped southofWings Point) Chipman Formation(MiddleOrdovician) bedded sandstoneandfossiliferous limestone Day PointFormation(MiddleOrdovician)—Gray,thinlybeddedtomassively erous limestone Crown PointFormation(MiddleOrdovician)—Gray,massivelybeddedfossilif- Valcour Formation massive fossiliferous limestoneandcalcareous sandstone Chazy Group,undivided(UpperandMiddleOrdovician)—Dark-tolight-gray, above. Containsbasallimestone( Ira Formation (Upper Ordovician)—Same descriptionasHortonvilleFormation beds ofbluish-graylimestone Stony PointFormation(UpperOrdovician)—Dark-graycalcareous shaleand limestone ( Near basecontainsbluish-gray,granular, smooth-weatheringfossiliferous of graytotanquartzite.GradesintolimyshalestheStonyPointFormation. limestone and minor beds phyllite containing thin beds of bluish-gray argillaceous Hortonville Formation(UpperOrdovician)—Dark-graysiliceousshaleand gneiss ( irregularly distributed within unit. Unit may be in part older than the tonalitic gneiss gneiss andmore maficbiotite-hornblende-pyroxene-quartz-plagioclase Light-greenish-gray topinkish-gray,well-foliatedandwell-layered quartz-rich Biotite-quartz-plagioclase gneiss(MiddletoEarlyMesoproterozoic)— slice members oftheChipmanFormation Taconic mayincludeunmapped Range,rocks mapped asBascomFormation Vermontor calcitemarbleandcalcareous sandstone.Insouthern eastofthe to buff-weatheringdolostoneandbluish-graygraymottleddolomiticlimestone Bascom Formation(MiddleandLowerOrdovician)—Interbeddedorangey-tan- carbonaceous highly graptoliferous phyllite ( ( 2 Ohc * (above theOrwellandChamplainthrusts) Vermont Valley sequenceandMiddleburysynclinorium Y Owbl Y cp Whipstock Breccia of theWalloomsac * 1348 Ma 1 3A rt (largely tectonic) (largely Bridport Member—Thickly bedded,“beeswax-scored,” orangey-beige- positions withintheBeldensMember and thindolomiticlayers,locallycrossbedded; mayoccuraslensesatseveral Weybridge Member—Light-graytocream-colored fine-grained calcite marble, Burchards Member—Light-bluish-graymottleddolomiticlimestone calcite marble limestone, orangey-buff-weathering dolostone,and reddish-streaked (hematite) Beldens Member—Light-graytocreamy-white-weathering fine-grained ering, yellowish-graytolight-bluish-graydolostone,dark-gray to Providence IslandDolostone( eastward intothe Beldens Memberwithadditionoflimestonebeds.Equivalent aphanitic dolostone,andminorbedsofbluish-graylimestone.Transitions la ). UnitmappedwestoftheTaconic allochthon,andnorthwestoftheSudbury * Y 1121 Ma,1119Ma Formation CHITTENDEN INTRUSIVESUITE 2 STRATTON MOUNTAIN ap Y Y 2 1 Y bt 1393 Ma Y rta Owwu IGNEOUS SUITE 3A Y Ohl * 3C 1221 Ma ) 1 * ma Ow dg p Y Y 1370 Ma * ) andlocallyapolymictlimestonedolostone-clastconglomerate 3A 2 Oww gg g Oww 1037 Ma 1372 Ma (Upper ) * Y Y Y 1 1244 Ma 3B * fg * 3A Y p Y 2 pg * CARDINAL BROOKINTRUSIVESUITE ch 1 East Hoosick fga Chester andAthensdomes Basalt at Ordovician) ------unconformity------Y Obvb 3C Y 962 Ma Y cbsa 1149 Ma 3C 1383 Ma Y 3B Y * 3A cbs 1 g * * bm mb Oil Ofcpi Ottauquechee Formation ), locallyreferred toastheWhippleMarble Y 965 Ma 3C — Za ocf * ) cbsr Zap Dark- tolight-grayfossiliferous limestone Y Y oa 3A 1 Y bmp gg 2 Owbl bt oa Y Y o DSwi 3C 3C ) opw oq cbhr SHAW MOUNTAIN, NORTHFIELD, WAITS RIVER bsa Oilc ). Tectonically shredded, silty obq TRANSITIONAL MARGIN ROCKS Y om 3A Ss ). Unitmappedalongeast of ma Y 955 Ma AND GILEMOUNTAIN FORMATIONS DSwac 3C 945, ? cbbh * Dga * 409 Ma Owl DSn Dgr fine-grained to ) andablack DSw DSnl Scv Dga weath- Zj DSws Dgqs Zjg DSwq DSnq Zsd DSwc DSwc OF THENEWPORT CENTERAREA Zsa Zsa Zsg Sv Dga Dga DSwa Zs CRAM HILLFORMATION Zsbg Stowe Formation Ochcv DSwb Ocha ( Zsg) CONNECTICUT VALLEY TROUGH ( Zsg) Zsa Dga Zsa Dgq DSwv unconformity Ochpq Ochfv Zmmt Zsgt Zdph Dga Zmp Zmq Zdfq Zdm Zmf Zdb Zdq Zds Zdc spl sp Zd du Ochu Ocu m Ochsb Ochcv w cb ca c d Os Ochfg Ochuc Zswa DSwqc DSwb DSwgs Zsws Zswa cian are afterFortey(2000). usage of Davidson (1998) rather than that of Plumb (1991). Chronostratigraphic subdivisions in the Ordovi- the muchmore functionalboundarybetweenNeoproterozoic andMesoproterozoic of900Mafollowingthe 1:2,000,000). Becauselateorogenic activityoftheGrenville orogeny isyoungerthan1,000Maweadopt on the1998geologicmapofGrenville province (GeologicalSurveyofCanadaMap1947A,scale Subdivisions andsymbologyoftheMesoproterozoic onthismapfollowthetimescaleusedbyTony Davidson Cram HillFormation VERMONT EASTERN (DSwb) Och SOUTH- Ochp Dl Sf muscovite-quartz phylliteneartop( massive topoorlybeddedvitreous quartzite,containinglayersofdark-graybiotite- Cheshire Quartzite(LowerCambrian)—Light-gray-totannish-gray-weathering, dolostone-breccia andconglomerateoccurnearRutland Contains distinctivesmallpebblesandgrainsofwell-rounded quartz;minorbedsof light-gray, pinkish-gray-weathering,andmassivetopoorlybeddeddolostone. Dunham Dolostone(LowerCambrian)—Buff-andpink-mottledmassive,or Vermontin southern dolostone, andreddish-brown-weathering dolomiticquartzite.Unitdiscontinuous thick-bedded sandstone,orangey-gray-andbuff-weatheringwell-bedded Monkton Quartzite(MiddleCambrian)—Reddish-brown, pebbly,thin-to beds ofblue-quartz-pebbleconglomerateandquartzite beige, cream, andbuff,withgreen, red, orgrayphyllite,siliceouspartings,andthin Winooski Dolostone(MiddleCambrian)—Well-bedded dolostoneweathering Vermontand crossbedded sandydolostone.Unitdiscontinuousinsouthern Danby Formation(UpperCambrian)—Thin,light-graybedsofvitreous quartzite Marble dolostone andbeneaththecalciticmarblesofoverlyingShelburne and totheeastwithrocks oftheHoosacFormation) tothenorthwithrocks oftheTyson Formation (unit interfingers Dalton Formation(LowerCambrianandNeoproterozoic) Moosalamoo Formation(LowerCambrianandNeoproterozoic) weathering, gray to brown argillaceous quartzitemember( weathering, graytobrown argillaceous Locally containslight-bluish-graytowhitish-graycalcitemarble( calcitic dolostonecontainingwhitequartzknotsneartop;unitlocallybrecciated. light-gray, massivecalciticdolostonegradingupward intodarker, more fissile Clarendon SpringsFormation(UpperCambrian)—Steel-gray-weathering, dolostoneandgraylimestonebeds marble. Locallycontainsintermediate bluish-gray-streaked calcitemarbleandmassivewhite-green-streaked calcite Shelburne Marble(LowerOrdovician)—Predominantly light-gray-towhite-and Marble appear assandyzoneswithinrocks mappedastheShelburne VermontIn southern eastoftheTaconic Range,unitisnotrecognized andmay sandstone, gradingupward intodolomiticlimestoneormottledmarble. Cutting Dolostone(LowerOrdovician)—Gray,thinlybeddeddolomitic massif Mountain massifandnorthwesternflankoftheGreen Lower CambrianandNeoproterozoiccoverrocksoftheLincoln Tillotson Peak STRUCTURAL COMPLEXES quartzite. Resembles dark phyllite of the Moosalamoo Formation ( quartzite. ResemblesdarkphylliteoftheMoosalamooFormation phyllitecontainingthinbedsoflaminated tourmaline-biotite-muscovite-quartz Dark phyllite member—Dark-gray togray,rusty-weathering,well-laminated blue-quartz-pebble quartzite Quartzite member—Tan towhitish-grayvitreous quartziteandminor feldspathic quartzite tan-weathering flaggyfeldspathicquartzite,quartzphyllite,and Dalton Formation,undivided—Heterogeneous unitconsistingofrusty-to latter resembles similar rocks of the Dalton Formation ( latter resembles similarrocks oftheDaltonFormation albite-quartz granofelsandflaser-bedded tantograyfeldspathicquartzite;the Feldspathic quartziteandgranofelsmember—Gray to dark-gray, biotite- former resembles albitic rocks of the Hoosac Formation ( resembles albiticrocks oftheHoosacFormation former eastern flank of the southern Green Mountainmassif;similarinappearance to flankofthesouthern eastern muscovite-biotite-quartz schistandfeldspathicquartzite.Occurson - Lustrous quartzschistmember—Dark-graytosilvery-gray,tourmaline phyllitic quartzite quartziteandinterbedded thin-bedded, flaggy,tourmaline-muscovite-feldspar Feldspathic quartzitemember—Light-tantogray-weathering,massive which itisinpartcorrelative quartz-pebble wacketoconglomerate.Occursatornearbaseofunit schistose quartzconglomerate.Locallydark-graybiotite-muscovite-blue- coarse- tofine-grainedquartz-pebble-cobble,quartzconglomerateand Conglomerate member—Commonly tan-toyellowish-tan-weathering, Zhs magnetite quartzite.Directly overliesdolostonesoftheForestdale Formation base containsmagnetite-cementedquartz-pebbleconglomerateandbedded weathering, well-laminated,magnetite-studdedchloriticmetasiltstone;near Magnetite metasiltstonemember—Grayish-brown- topale-green- metawacke splintery sulfidictonon-sulfidicquartzphylliteandpebblygrittybiotite Gray phylliteandmetawackemember—Dark-gray,sooty-weathering, feldspathic quartziteandquartzconglomerate Quartzite member—Light-tan to gray, vitreous andnon-vitreous quartzite and Dolostone member—Buff,sandy,massivedolostoneaslensin the Green MountainmassifintheSouthWallingford area flankof biotite-muscovite-quartz phyllite,andquartzitemappedalongwestern - Phyllite member—Rusty-tantogray,thinlylayered phyllite,tourmaline Complex Ztagn Ztm Ztp 407 Ma Omw Ombb DSw of the Hoosac Formation exposedtotheeast oftheHoosacFormation Omhb units completely Ochfg Ochic fault bounded Ochq Omc VERMONT CENTRAL- Dgmr Omc Dgq EASTERN Ochs Omwhb Dgqs Belvidere Mountain Dgm * Dga Norman L.Hatch,Jr., Ochv Dgmc Ochfv Zbs Complex Zbu Ochu Zbagn Zbg ROWE –HAWLEY ZONE Omp Omwh Dih Dgqs Zbf DSfr DSfra VERMONT Zbc EASTERN NORTH- Oma Dir Di Omfs Dia Di cb Dco Dih lower structurallevel Omc Dir ); locallycontainsamappablebrown- Dcoa Omwhv Ombq Zrrgt Moretown Formation Zrs Omfv Omq Zrr Zra Zrr Omwhg ca Zhab Zdfq Partridge Formation Oma ) Oma Cooper Hill Omfs MOUNTAIN (many unitsfaultbounded) Zra Omb Member Oma Omwhb SAWYER Formation Oar Zrch ), whereas the Zrc ) Littleton Zdph * BELT BEDROCK GEOLOGIC MAPOFVERMONT spl) ROWE SCHIST 407 Ma Zmp Ssm Omp Op Dlr Sc Omfv Omfv 1 Svf Oaa Nicholas M.Ratcliffe, * within

), with Omgt Douglas W. Rankin, Omb EARLY TO LATE TACONIAN ACCRETED TERRANE Zu higher structurallevel Omp Zrfb Zra Zra Oma Omq Omp Zrs Omfgc Oma Omfq Zrgs Omq Oma Zra Zpw Zpva Zpcg Zpvc O sks O sw Zpvf Zfco O skl Zpu Zpq Zpv O sk Zpc Zps Zth Zfb Zfq Zfd O g Ohg Oml p Zpwd Ombq GRANITE Ochfg DIKES Cram HillFormation 365 Ma Ochfs Ochq Dg Forestdale Formation(LowerCambrianandNeoproterozoic) dolostone withthinsandstonebeds interbedded dolostoneandsandstonebreccia inadolostonematrix;andmassive Parker Slate(Cambrian)—Blackarenaceous slatewithdolomitehorizons; byothersintheHighgatearea Saxe Brook Formation slate withthinorangedolostonebeds;includesmassivedolostonesmappedas Skeels CornersSlate(LowerOrdovicianandCambrian)—Laminatedblack dolostone andblackquartzite graphitic, quartzosephylliteandschist,withtan-weatheringlayerspodsofgray Sweetsburg Formation(LowerOrdovicianandCambrian?)—Blacktogray, gray quartzosedolostone breccia composedofangularclastsdolostone,sandstone,andchertinabuffto Gorge Formation(LowerOrdovicianandCambrian)—Dolomite,dolomite dolostone clastsinasandylimestonematrix slate withlocallensesofconglomeratecomposedlimestone,sandstone,and Highgate Formation(LowerOrdovician)—Bandedlimestoneandcalcareous Morses LineSlate(Ordovician)—Medium-graytoblackcalcareous slate Pinnacle Formation(CambrianandNeoproterozoic) the Pinnacle Formation. Volcanicsthe PinnacleFormation. are alkalictotransitionalmetabasalts metawacke, andbasaltictuffaceousmetasedimentaryrocks, allsimilartorocks of chlorite (±actinolite); and interbedded phyllitic grits, feldspathic quartzite, chloritic metabasalt flows,pillowbasalt,vesicularbasaltcomposedofalbite,epidote, minor metasedimentaryrocks consistingofmassive,fine-grained,dark-green Tibbit metabasalt and HillFormation(CambrianandNeoproterozoic)—Largely * Cambrian toMiddleOrdovicianrocksoftheSt.Albansarea ULTRAMAFIC ROCKS (tectonically intercalated) Dolostone member—Upperpartof quartz sandmatrix Sandy matrixconglomeratemember—Limestoneandsandstoneclastsina in alimestonematrix,interbeddedwithsandstone Limestone matrixconglomeratemember—Limestoneandsandstoneclasts dolostone; metasandstone; lowerpartof weathering quartz-pebbledolostoneanddolomiticcrossbedded feldspathic -cobble conglomerate( metawacke isinterlayered withlensesofquartz,feldspar, andgneiss-pebbleto and localthinconglomeratichorizonsare present. Feldspathicbiotitephyllitic feldspar-quartz schist,phyllite,andmetagraywacke.Quartziscommonlyblue, Pinnacle Formation,undivided—Gray,foliatedmuscovite-chlorite-biotite- blue- andgray-mottledsulfidicdolostone ceous phyllite,interbeddeddolostoneboulderconglomeratetobreccia, and Phyllite anddolostonebrecciamember—Dark-graytosooty-blackcarbona- feldspathic grittyquartzite Quartzite member—Grayish-tantolight-grayvitreous quartziteandwhite quartz-rich dolostone( coarse- tomedium-grainedclasticwacke,beige-weatheringdolostone,and pebbly phyllite, wacke and feldspathic quartzite; heterogeneous unit consists of bedded muscovite-biotite-chloritemetawacke,conglomerate,andblue-quartz Metawacke member—Gray-tolight-brownish-gray-weathering, massiveto -cobble conglomerate metawacke interlayered withlensesofquartz,feldspar, andgneiss-pebbleto Light-gray phylliticconglomeratemember—Feldspathicbiotite 1.5 cmindiameter fine-grained greenstone withremnant plagioclasefeldsparphenocrystsupto Feldspathic greenstonemember—Olive-drab-weathering,dark-green, ded withcalcareous metagraywacke greenstone withlaminaeandsplotchesofcalcareous material;locallyinterbed- Calcareous greenstonemember—Rusty-weatheringandpitted,dark-green hornblende epidote-chlorite greenstone withdark-green porphyroblasts ofactinolitic Amphibolitic greenstonemember— Calcite-biotite-sphene-albite-actinolite- epidote-albite-chlorite (±actinolite)greenstones carbonate - Metabasalt andvolcaniclasticrocks,undifferentiated—Largely magnetite-calcite-chlorite-muscovite-biotite-feldspar schist ing quartzitebouldersas supported quartz-andgneiss-cobbletoboulderconglomerate,locallycontain- Cobble andboulderconglomeratemember—Poorlysorted,matrix- feldspar conglomerateandquartzite Quartzite and quartz-pebble conglomerate member—Light-gray quartz- magnetite chlorite-muscovite-quartz schist,andphylliteorpebblyphyllite,locallyrichin quartz-sericite-chlorite-albite metawacke,graytograyish-green magnetite- Metawacke andphyllitemember—Light-gray,medium-grained,massive Ochq Och MOUNTAIN GRANITE (serpentinite) Ochic BLACK * Zu Dbmg 364 Ma Zutc Zsp VERNON DOME NEW HAMPSHIREPLUTONICSUITE CORE ROCKS Ocha Ocha 483 Ma 1 Ochv

425 Ma 1 OF THE Zfco 1 U.S. GeologicalSurvey, Snd INTRUSIVE NEWPORT COMPLEX Obqd * * RolfeS.Stanley, BarryL.Doolan, CHESTER LAKE MEMPHREMAGOGINTRUSIVESUITE VICTORY GRANITE PLUTON DOME * Dvbg 392 Ma is boulderandcobbledolostoneconglomerate ROCKS OFTHENORTH RIVERIGNEOUSSUITE Dg FAIRLEE QUARTZ VOLCANIC ARCINTRUSIVEAND Sng AND MAFICROCKS, IN PART VOLCANIC MONZONITE Zpwd PLUTONS LAYERED FELSIC Zpc BARRE * large * HIGHLAND- Dbbg Onr 368 Ma PLUTONIC Dfqm 410 Ma

442-444 Ma CROFT OF THEROWE–HAWLEY ZONE SUITE 450 Ma ) STATE OFVERMONT, VERMONTAGENCYOFNATURAL RESOURCES, NULHEGAN 421 Ma Ohi Sbg ) BRAINTREE as Ol PLUTON Zfd INTRUSIVE * * COMPLEX * Dnqm Onbm GRANITE 3 FRENCH EAST BETHEL *

POND m 365 Ma PLUTONS Dfpg largely cream- tobeige-weatheringmassive largely in 419 Ma Dbqm Sbd Zfd BRANCH BROOK KINSMAN QUARTZ MONZONITE * diameter, DIKE ANDSILL Oogt BETHLEHEM GNEISSAND COMPLEX ? Onbs PLUTONIC SUITE Onbwm 2 consists oforangey-tan-tobrown- OTHER DEVONIAN University ofVermont, AGE UNCERTAIN OLIVERIAN * Onbw AND PLUTONS INTRUSIVE COMPLEX Dbgn 407 Ma Scd unlisted symbols) 412,414 Ma in GRANITES (See DMUfor Oobg COMERFORD a (Dwdg) ? Dr (Dedg) (Debg) (Dqm) (Degr) * (Ddg) (Dbg) (Dg) matrix LAURENCE R.BECKER,STATE GEOLOGIST Cartography byLinda M.Masonic 2 419 Ma 2 Scm INTRUSIVE * * 486 Ma Dkq

VERMONT GEOLOGICALSURVEY Ont

ROCKS Oohg * 496 Ma of gray-weathering 471 Ma 502 Ma Marjorie H.Gale, Jonathan Kim, Onnt Onb WILLOUGHBY PLUTON ? * * * Ontw Prepared incooperationwiththe Scg With contributionsby Dm PLUTON DERBY Dwmz Dwwz Dwhz Ddbg Ddrz JOSLIN TURN PLUTON 469 Ma Partridge Formation 3 Oj * Vermont GeologicalSurvey, 2011 Opa By Op Opr Opr AMMONOOSUC VOLCANICS BRONSON HILLAREA Zungs Oarq Zunql Zunw Oaa Zung Zhnn Zhng Owbg Zwb Oat Zun Zhn pdo Clough Quartzite Zfw psh Oaa Littleton Formation psc Zfp Zfa Owb O alp pq pc ps Zf 3 OF BILLINGS(1935) Dla CharlotteJ.Mehrtens, LITTLETON Oam FITCH- AREA Sc Oam 3 Dl Dlr Srr O ali Sf PeterJ.Thompson, * Oar 492 Ma O als O al light-green, quartz-sericite-chlorite(±magnetite±biotite)phylliteandfoliatedquartzite ( granofels, quartz-granulechlorite(±biotite)metawacke( contains dolomite. Local lenses of white to pale-gray quartzite, quartz-albite muscovite-chlorite schistandphyllite,commonlywithalbitemagnetite;locally Underhill Formation(CambrianandNeoproterozoic)—Silvery-green quartz- massive andspecularhematiteneartopatSheldon colored massivedolomiteanddolomiticsandstone,containingprominent zoneof White Brook Formation (Cambrian and Neoproterozoic)—Buff tocream- Fairfield Bolton (Ratcliffeandothers,1999;Thompson2002) mid-Whiterockian atWest BridgewaterandWhiterockian atBuelsGore andWest silicic phyllite.DolostonecontainsMiddleOrdovician conodonts(Ibexianto upper part,rhythmically layered gray quartzite, limestone breccia and laminated and gray-and-white-mottleddolostone,thinbedsofankeriticquartzite,and,in biotite-muscovite-quartz phyllite;containspodsandthinbedsofmedium-dark-gray Black to dark-gray, sulfidictononsulfidic, carbonaceous, fine-grained, well-foliated West BridgewaterFormation(MiddleOrdovician) Fayston Formation(LowerCambrianandNeoproterozoic) Hazens NotchFormation(CambrianandNeoproterozoic) Zungs north oftheLincolnMountainmassif Ordovician, Cambrian,andNeoproterozoiccoverrocks Oarq Oaa Oap Oac uncertain.) Mappedonlyinthearea westofGranville bluish-gray dolostone.(Correlation withWest BridgewaterFormation green chlorite-muscovite-quartz-knotted albitic phyllite, containing pods of Dark-gray andgreenphyllitemember—Interbeddeddark-graygrayish- Dolostone member—Massivebedsofwhitetobuffdolostone green albitic granofels of the Hoosac Formation ( green albitic granofels of the Hoosac Formation orange dolostoneinablackarenaceous matrix Dark conglomeratemember—Conglomerate consisting of round clasts of withsandydolostonecontainingclasts interfingered Sandy dolostonemember—Sandycontaininglimestoneclasts, and sandstoneclastsinacalcareous sandymatrix Calcareous sandyconglomeratemember—Conglomeratewithdolostone in ashalymatrix Conglomerate member—Conglomeratewithdolostoneand sandstone clasts Sandstone member—Thin-tothick-beddedcalcareous coarse-grainedsandstone grained quartz-albite-biotitegneiss Foliated metawacke member—Salt-and-pepper-colored, medium- to coarse- albite-chlorite (±magnetite±epidote)greenstone oramphibolite Greenstone member—Dark-green, pitted-weathering,foliatedcarbonate- Hollow Formation andwith the schistsofPinney lated withrocks oftheTyson Formation albite-muscovite-quartz schist.TheFaystonsouthofMount Abraham isinterca- - silvery-dark-gray torusty-weathering,medium-grainedchlorite-tourmaline coarse-grained pyrite-magnetite-biotite-albite-quartzschistandgneiss; unmapped light-gray,thinquartzites;salt-and-pepper-colored, medium-to porphyroblasts; resembles albitic schists of the Tyson Formation ( porphyroblasts; resembles albiticschistsoftheTyson Formation schistwithwhitealbite albite-chlorite-muscovite-quartz (±garnet±magnetite) Albite schistmember—Silvery-green tograyish-green, medium-grained quartz schist Schist member—Rusty-weathering,non-graphitic,sulfidicchlorite-muscovite- biotite, magnetite,andsphene actinolite,albite,chlorite,epidote, containing varyingamountsofhornblende, chlorite, albite,carbonate,epidote,amphibole,andsphene;amphibolite foliated maficschisttomassivegreenstone containingvaryingamountsof Greenstone andamphibolitemember—Dark-green, pitted-weathering, graphite androcks identicaltoFaystonFormation foliated quartziteare common.Unitincludesrusty-weatheringschistwithout euhedralpyrite,andbedsofdark-gray gneiss; blackalbiteporphyroblasts, large schistand dark-rusty-brown graphiticbiotite-muscovite-chlorite-quartz(±garnet) Hazens NotchFormation,undivided—Schist,gneiss,andquartzite; mite)-laminated schist fine-grained, well-foliatedmyloniticalbite-chlorite-muscovite-quartz(±dolo- Quartz-laminated schistmember—Light-graytotanandrusty-weathering, biotite-albite-amphibole amphibolite albite-amphibole schist; dark-green, coarse-grained, weakly foliated epidote- amphibolite; light-todark-green, fine-tomedium-grainedepidote-chlorite epidote greenstone andmassivemagnetite-albite-amphibole-biotite-epidote Greenstone andamphibolitemember—Thinlybeddedcarbonate-albite- Oaa O alm Oarq 4 ) 1 Wesleyan University, Pond Oa Formation Ows Owc ALLOCHTHONS AND OTHER PIERMONT ------unconformity------Sg Sr (Cambrian Src * Deceased.

and 3 ˆ 2 GIVE- FRAS- andGregoryJ.Walsh JohnN.Aleinikoff, TREMADOCIAN ARENIGIAN LLANVIRNIAN CARADOCIAN ASHGILLIAN LLANDOVERY WENLOCK LUDLOW PRÍDOLÍ LOCHKOVIAN PRAGIAN EMSIAN EIFELIAN FAMENNIAN STAGE TIAN NIAN Neoproterozoic)—Light-gray

DRESBACH FRANCONIAN TREMPEALEAUAN CHAZY BLACK RIVER TRENTON EDENIAN MAYSVILLIAN RICHMONDIAN Zhgab Y Y Zunw Y Y Y Z 3A 1 3C 2 3B CROIXIAN IBEXIAN WHITEROCKIAN MOHAWKIAN CINCINNATIAN

), and garnet schist ), andgarnet 413.5 Ma ). Locally contains 1400 Ma 1350 Ma 1300 Ma 1200 Ma 1100 Ma 1000 Ma 900 Ma 571 Ma 544 Ma 495 Ma 485 Ma 470 Ma 464 Ma 458 Ma 453 Ma 449 Ma 441 Ma 428 Ma 419 Ma 418 Ma 409 Ma 394 Ma 387 Ma 382 Ma 375 Ma 365 Ma

Early Middle Late Neoproterozoic Lower Cambrian Middle Cambrian Upper Cambrian Lower Ordovician Middle Ordovician Upper Ordovician Lower Silurian Upper Silurian Lower Devonian Middle Devonian Upper Devonian Mesoproterozoic Mesoproterozoic Mesoproterozoic Ztab PRECAMBRIAN CAMBRIAN ORDOVICIAN SILURIAN DEVONIAN ) and to 1 Y Zhgab Y Y Zhabc Y Zhrab andJ.GregoryMcHone Zhcgt Zphw Zhtm Y Y Y Y Zhab Zmt Y Y Zhbs Zphb Zphq Zpha Zhgt Y Ztab Y Y Y Ztbs Zphf Ztgr Ztrg Zfqz Zph Zhq Zhd 3C Y Y Zhs Zhc Y 3C 3C Ztd Ztq Ztg pfq Y 3C Y Y Ztc Y Y Y Y Zfs Zfc Zh pd Y 3C 3C 2 3A 3A 3A Zt 2 3A 3A 3A 2 3A 3A myu 2 2 3A 3B 3B 3C 2 cbbh mig 2 cbsa cbhr Zmtg cbsr lgg gg bsa Zphc ap cbs ch mb ma ma lg Zd gb pg gg fg 1 la g p p g

Mount HollyComplexintrusiverocks(Mesoproterozoic) (1,393±9 Mato1,309±6Ma) South LondonderryIgneousSuite(MiddleandEarlyMesoproterozoic) (1,149±8 Mato1,119±3Ma) Chittenden IntrusiveSuite(LateMesoproterozoic) (965±4 Mato945±7Ma) Cardinal BrookIntrusiveSuite(Neoproterozoic) Migmatitic andmyloniticrocksofuncertainorigin (1,244±8 Mato1,221±4Ma) Stratton MountainIntrusiveSuite(MiddleMesoproterozoic) Interpreted asintrusivegraniticrock olderthan and pinkish-gray, medium- to coarse-grainedmicrocline-perthite granitic gneiss. geneous unitconsistingofmedium-grainedbiotite-microcline-plagioclase gneiss Pinney HollowFormation(CambrianandNeoproterozoic) Pinkish-gray Albitic biotite granite and pegmatite at Baker Brook (Mesoproterozoic)— character highly interpretive basedoncrosscutting ofgneissosityandweaklydeformed microcline-perthite aplitictopegmatiticgranite( a myloniticaugengneiss.Whitetopinkish-gray,medium-grainedplagioclase- is perthite orporphyriticrapakivigraniteandpegmatiticgranite;where deformed Somerset ReservoirGranite—Light-pinkish-gray-weathering,biotite-microcline- no. 20(revised from KarabinosandAleinikoff,1990) dikes.U-Pbzircon upper-intercept ageof962±1Ma, border faciesorthininternal magnetite-studded white aplite, and kyanite-tourmaline pegmatite. magnetite-studded whiteaplite,andkyanite-tourmaline granodiorite, medium- tofine-grainedgarnet-biotite-microcline-perthite Ludlow Mountaingranodioritegneiss(MiddleMesoproterozoic)—Light-gray, passes locallyintomore equigranulargraniticgneiss( coarse-grained biotite-microcline megacrysticgraniteandmonzograniticgneiss; Microcline-augen graniteandmonzogranitegneiss—Graytowhitish-gray, at BrandonGap;similarrock mappedintheAdirondacks contact that crosscuts paragneissunits. Unit alsoin Lincoln Mountain massif and xene) gabbro anddioriteatRobinsonHillinShrewsbury; exhibitsfine-grainedchill (±pyro- Hornblende gabbro-diorite(Mesoproterozoic)—Biotite-hornblende muscovite-biotite-microcline-plagioclase apliticgranite( rite andferromonzonite. Afine-grainedfaciesconsistingofwhite-weathering, ferrodio- Unit includeslesserirregular dikesandsegregations ofhornblende-biotite perthite havingrimsofplagioclasethatcontaininclusionsbiotiteandgarnet. megacrystsofmicrocline plagioclase-microcline rapakivigranite;containslarge Stamford Granite—Light-graytomedium-gray,verycoarsegrainedbiotite- epidote retrograded metadiabasicdikes;commonlyhaverelict diabasictexture Mafic dikes—Medium-tocoarse-grained,foliated,actinolite-chlorite-calcite- Suite ( 0.5-cm clotsofmuscovitepossiblyafterberyl.Intrudesquartzite,lustrous Hill slicenearSouthWallingford ismappedas feldspathic mylonite and mylonitic gneiss mapped near Brandon Gap; in the Pine Mylonitic gneiss(ageuncertain)—Highly schistose, biotite-muscovite (±chlorite) South LondonderryIgneousSuite.Ageofmigmatizationisyoungerthan1,326Ma Y anintegralpartof in theChesterdome,andWeston where itappearstoform matite-veined biotite-plagioclasegneiss.Occursprominently inJamaica,Andover yellowish-gray, Migmatitic gneiss(MiddleMesoproterozoic)—Light-grayandpinkish-grayto Y Aplitic gneiss—Light-gray towhite,fine-grainedapliticgraniteasborder of Londonderry IgneousSuite and others,2011)obtainedfrom Londonderry.Unitintrudesrocks ofSouth zircon TIMSageof1,221±4Ma,no.12(Ratcliffeandothers,1991;Aleinikoff part of the Green Mountain massif. U-Pb migmatitic, occurring in the southern dioritic andaplitebiotiticmicrocline-rich gneisses,highlygneissicandlocally Biotite-granitic gneiss—Aheterogeneous unitconsistingofgraniticandgrano- augen asmuch4cminlength medium-grained, biotite-quartz-plagioclase-microcline gneiss;containsmicrocline Microcline augengneissofLincolnMountainmassif—Light-tomedium-gray, Green Mountains Mountain IntrusiveSuiteofthecentralandsouthern tain massif. Not distinguishable with certainty from older granitoids of the Stratton part of the Green Moun- with 1,149- to 1,120-Ma augen gneisses, in the northern biotite-microcline megacrystictoeven-grainedgranitegneisscloselyassociated Granitic gneissofChittendenIntrusiveSuite(?)—Light-gray,coarse-grained, Granulose albiticgneiss(Mesoproterozoic?)— containing abundantrose-colored zircon alsoisconfinedtothePineHillslice 16 (Aleinikoffandothers,2011).Undatedlight-graybiotitegranitegneiss ed byabundantrose-colored zircon; U-Pbzircon SHRIMPageof1,037±6Ma,no. parts of the Green Mountain massif. Assignment of individual pegmatites to andeast-central Mount HollyComplex,andespeciallyprominent inthenorthern pegmatitecommoninmetapeliticrocks ofthe bodies. Albiticgarnet-muscovite (±garnet±tourmaline±magnetite) Pegmatite (Mesoproterozoic)—Light-gray to pinkish-gray, biotite-muscovite ite andmetawacke schist,andlayersofdark-graybiotiticquartz- slabby quartz-richmuscovite(±garnet) dark-gray tomedium-light-gray-weathering,white-plagioclase-studdedschist,gray Hoosac Formation,undivided—Heterogeneous unitconsistingmainlyof Hoosac Formation(LowerCambrianandNeoproterozoic) Plymouth Formation(Cambrian) 1,309±6 Ma,no.9(Aleinikoffandothers,2011) extensive areas ofbiotitepegmatoidgraniticgneiss( south and the Underhill Formation tothenorth south andtheUnderhillFormation tothe Hancock andRiptoninpartaslateralequivalentoftheTyson Formation chlorite-muscovite-albite granofelsandphyllite.Unitmappedin laminated magnetite-actinolite-chlorite feldspathicwacke,and,nearbase,grayish-green biotite-quartz granofels, well-bedded light-graytosteel-graybiotite,minor epidote- Granitic Ma, no.11(Ratcliffeandothers,1991;Aleinikoff2011) Mountain; truncatesstructure inoldergneisses.U-Pbzircon TIMSageof1,244±8 intrusivemassonCollegeHillinJamaicaandwestofStratton asinglelarge Forms migmatitic border exhibitingdecreasing concentrationofmicrocline megacrysts. laterpegmatite;gradesoutward intoa lineated, andsaturatedwithlessdeformed biotite-microcline-perthite granodioriticgneissandpegmatite.Strongly deformed, College HillGraniteGneiss—Light-gray to medium-dark-gray, porphyritic muscovite-quartz schist,bedsofgrittyfeldspathicquartzite( - consisting ofcoarse-grained,gray-torusty-brown-weathering garnet-biotite Monastery Formation(CambrianandNeoproterozoic)—Heterogeneous unit and along the eastern margin oftheGreen MountainmassifeastofRutland margin and alongtheeastern central Green Mountainmassiffrom PlymouthtoShrewsbury, onRobinsonHill, albitic micropegmatite, tononlayered albiticgranulosewhitegneiss.Occursin biotite-quartz-plagioclase gneisshavingcentimeter-thick veinsofgarnet-bearing 1,120-Ma periodofgraniticintrusions.Unitshowsallgradationsfrom pinkish-gray are common.Highlyaltered rock isperhapsmetasomaticandrelated to1,170- original amphibole,pyroxene,spots ofankeriteandclotschloriteafter orgarnet magnetite-biotite (chlorite)-muscovite-albite-quartzgneiss, veined withmagnetite; lineated, light-tannish-graytograyish-green, medium-grained,granulose,epidote- Mesoproterozoic suggests affinitywithmetamorphicandigneouseventsassociatedtheMiddle U-Pb zircon SHRIMP ageof1,326±4Ma, no. 8 (Aleinikoff and others,2011), Mountain massifasunit limbofLincoln ity incountryrocks andmayextendnorthward alongeastern ated withminorexposures ofmetadioritetotonaliticgneisses;crosscuts agneissos- SHRIMP ageof1,149±8Ma,no.13(Aleinikoffandothers,2011).Unitisassoci- dark-gray, biotite-magnetite-microcline-plagioclase augengneiss.U-Pbzircon Microcline-magnetite augen gneiss at BrandonGap—Pinkish-graytomedium- Chittenden ReservoirbyKarabinosandAleinikoff(1990) CenterandonTelegraph onsamplesnearSherburne determined Hilleastof U-Pb zircon ages of 1,119±3.3 Ma (no. 15) and 1,121±1.4 Ma (no. 14) aluminous altered rocks nowcontainrestites ofchloritoidandabundantsericite. gneisses are locally albitizedand enriched in magnetite; enclaves of highly bearing. Enclavesofmetasedimentaryunitsinthesegranitesandassociated (Karabinos andAleinikoff,1990) U-Pb zircon upper-intercept agesof 945±7 Ma,no.17,and955±518 intercalated withrocks oftheMountHollyComplexandHoosacFormation. andtectonically margins, andwestern well asinfaultsliversalongtheeastern Complex. Restricted to the Chester and Athens domes, occurring in the core as intrusive breccia containing xenolithsof gneissic unitsof the Mount Holly ovoidalrelict microcline withrapakivirimsand augen gneiss;locallyhaslarge grained tomedium-grainedandmyloniticbiotite-plagioclase-quartz-microcline Bull HillGneissofRichardson(1931)—Light-pinkish-graytogray,verycoarse preserved. UnitoccursintheRaypondaandSadawgadomes microcline megacrystic granite and augen gneiss; rapakivi texture locally Harriman ReservoirGranite—Light-graytopinkish-gray,biotite-plagioclase- no. 19(KarabinosandAleinikoff,1990) rocks and irregular border facies. U-Pb zircon upper-intercept age of 965±4 Ma, (shown on the eastern and western flanksoftheGreen Mountainmassif) andwestern (shown ontheeastern Tyson Formation(LowerCambrianandNeoproterozoic) Y and LincolnMountainmassifseasterndomes Neoproterozoic andMesoproterozoicrocksoftheGreenMountain Eastern flankoftheGreenMountainmassifandeasterndomes 1,2 2 1 gg rs bg ( phyllite.Chloritoid-richrocks muscovite-quartz (±chloritoid±garnet±magnetite) Phyllite member—Light-greenish-gray tolustrous pale-green chlorite- volcaniclastic wacke.Occursaslensesatmultiplestratigraphiclevels.Lower plagioclase ankeriticgreenstone; gradesintoepidote-quartz-plagioclase amphiboliteandgrayish-green epidote- plagioclase (±garnet±epidote) Turkey- MountainMetabasaltMember—Dark-green toblack,hornblende lenses ofwhitelaminatedquartziteasbedsanddiscoidalboudins weathering, biotite-muscovite-plagioclase-quartz schist and phyllite, containing Biotite phyllite member—Coal-black, lustrous, rusty-tonon-rusty- maybecorrelative Cavendish Formation lacks amphibolite.AluminousschistsatDevilsDenandaluminousrocks ofthe but muscovite-quartz (±paragonite)schist;resembles PinneyHollowFormation - Garnet schistmember—Lustrous, green, ilmenite-chlorite-chloritoid-garnet rusty-brown-weathering biotite-richquartzschistanddarkbiotite-albite Albite schistmember—Dark-graytoblack,locallycarbonaceous, ( Formation and whitish-grayvitreous quartzite.SimilartodolostoneoftheForestdale tan-weathering dolostoneaslensesinphyllite.Containsbedsofbluish-gray weathering dolostone,bedsofpebblyquartzandpink-toorange- massive, gray-,beige-, and pinkish-gray- Dolostone member—Largely ( Formation quartzite andphylliticquartzite.ResemblesfeldspathicoftheDalton gray- andbrownish-gray- totan-weatheringflaggybiotite-muscovitefeldspathic Feldspathic quartzitemember—Thinly laminated but massive-appearing, and withsimilarbedsintheupperpartofForestdale Formation with boulderandconglomeratebedsoftheDunhamDolostonenearRutland dark-gray phyllitic dolostone andlimestone in upper part. Correlative in part upward intomore thinlybeddedbluish-grayandbuffdolostonebreccia; bluish-gray-weathering mottleddolostonebreccia andconglomerate,passing Dolostone member—Light-gray- to beige-weathering massive dolostone and ( phyllites ofthePinneyHollowFormation schist andphyllite.Resembles green sericite (±garnet±chloritoid±allanite) Schist member—Silvery-green torusty-tan,fine-grainedchlorite-quartz- ite, Aleinikoff, 1999).Containspurplish-grayfeldspathicquartzite volcaniclastic rock. U-Pbzircon ageof571±5Ma,no.21(Walsh and calcite-muscovite-quartz-albite metarhyoliticgneissorschist;isavolcanic Metafelsite member—White topale-green, laminatedtomassiveepidote- and volcanicmetawacke massive but well-foliated metabasalt to well-bedded basaltic volcaniclastic rock chlorite-magnetite-plagioclase (albite)greenstone. Showsallgradationsfrom (±quartz)amphibolite,epidoteandankeritic- biotite-hornblende Amphibolite andgreenstonemember—Dark-greenblack plagioclase- to schist of the Hoosac Formation ( schist oftheHoosacFormation ing porphyroblasts of black albite. Unit resembles gray albitic granofels and rusty-weathering, carbonaceousalbite-chlorite-quartz-muscoviteschist,contain- Carbonaceous albiteschistmember—Graytomedium-dark-gray, dark-medium-gray blue-quartzbiotitequartziteandschist biotite-muscovite-quartz conglomerateandpebblymuscovitequartzite, Conglomerate and quartzite member—Light-grayish-tan-weathering, of albiticgranofelsaspseudoconglomerate containing bouldersofpegmatiteandgraniticgneiss,disarticulatedbeds member ( schist, commonlyinterbeddedwithoradjacenttoamphiboliteandgreenstone Black phyllitemember—Dark-graytoblack,sulfidicbiotite-plagioclase-quartz conglomeratic andrichinepidote blue-quartz-pebble chlorite-biotite-plagioclase-quartzmetawacke;locally Metawacke member—Silvery-gray,“pinstriped,”coarse-tomedium-grained, gritty feldspathicchlorite-muscovite-plagioclase-quartzschist Feldspathic quartzschistmember—Light-graytograyish-green, laminated, locally albiticandcontainsminorbedsofquartzite Quartzite member beds ingrayalbiticgranofelsmember( medium- tofine-grainedphlogopite-quartz-dolomitemarble.Occursasthin Dolomite marble member—Light-gray-, cream- orpinkish-gray-weathering, ridge basalt(MORB)-typemetabasalts layers are transitional andalkalicmetabasalts;higherunitsare typicalmidocean pebble conglomerate.OccursatbaseandinlowerpartoftheTyson Formation conglomeratic metawacke,andlocallyadolomite-cementedfeldspathicquartz- (±albite)-quartz-pebble, -cobble,and-boulderconglomerate,feldspathic Conglomerate member—Massivetowell-beddedchlorite-biotite ( Formation ite, locallyinterbeddedwithdolostone.SimilartoquartziteintheForestdale to thin-beddedquartzite,magnetiteandbiotitefeldspathicquartz- Quartzite member—Graytoverylightgray,vitreous andnonvitreous, massive metawacke. Albiticbiotite-(chlorite)-quartzgranofelsandwackelocallypresent but more thinly bedded and contains less member of the Pinnacle Formation chlorite-quartz-pebble phyllite;albiticmetawackeissimilarto Quartz-pebble phylliteandwackemember—Graytograyish-green, biotite- muscovite-quartz phylliteandminorbedsofpebbly-quartzmetawacke Quartz phyllitemember—Rusty-weathering,graytograyish-green, chlorite- Chlorite-muscovite ( green albiticgranofelsoftheHoosacFormation chlorite-(biotite)-muscovite-albite-quartz granofelsandschist.Similartograyor Albitic magnetitegranofelsmember—Grayandgreenish-gray, magnetite- Tyson Formation,undivided—Phylliteandmetawacke. spangles ofmuscoviteandweathered-out pitsofdolomiteorankerite dark-gray, blackalbite-biotite-quartzschistandgranofels,markedbylarge Albite schistandgranofelsmember—Rusty-weathering,medium-to to bluish-graylaminatedquartzite biotite massive, coarse-grainedbiotite-whitealbite-quartzgranofelslike Albite granofels andgneiss-boulder conglomerate member—Light-gray, gneissic aspect locally isamedium-gray,finergrained,more biotite-richalbiticquartzschistof massive tothicklybeddedmedium-grainedbiotite-whitealbite-quartzgranofels; Albite-quartz granofelsmember—Light-gray- to whitish-gray-weathering, gray, chlorite-magnetite-white-albite-spotted-quartzgranofelsandschist Chlorite albiteschistandgranofelsmember—Pale-green tolight-greenish- tion ( above theForestdale Formation ( Formation muscovite quartzite locally rich in magnetite. Resembles quartzite of the Tyson Quartzite member—Whitequartziteandtantolight-gray,medium-grained associated with schist; schist and feldspathic garnet garnet-biotite-muscovite-plagioclase-quartz Garnet biotiteschistmember—Medium-dark-graytolustrous silvery-gray biotite-quartz schistandsteel-graymuscoviticquartzite - Schist member—Lustrous, dark-gray to silvery-gray tourmaline-muscovite ( grained thanthemetawackeandphyllitememberofPinnacleFormation to butfiner contains bedsofpebblymetawackeandmagnetitephyllite.Similar lowish-greenish-gray, chlorite-muscovite-quartzphylliteandschist;locally Zphc ), andcalc-silicaterocks onLudlowMountain.U-Pbzircon SHRIMPageof orasthindikessillsinparagneissunits Zps , butalsolocallyappearstobeintrusive.Amixedrock ofuncertainorigin.

commonly Za gneiss )

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muscovite ) andchloriticphyllite( garnet-biotite-albite Zpha Zfd Zfq Ztq Zdfq massive, medium-grainedplagioclasegraniticgneiss,andmig- of

Ludlow Mountain occuring Lincoln Zhs ); locallyisasilvery-graysulfidicbiotitephyllite ) ) ) ) and similar quartzite of the Moosalamoo Formation ( ) andsimilar quartzite of the Moosalamoo Formation

quartzite, — phyllite Y memberwhichitlaterallyreplaces Light-gray-, yellowish-gray-todark-dull-gray-weathering, 3A

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Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Obvb Y Y Y Y Y Oww 2 2 Y Y Y Y Y Y Y 2 Y Y 3A Y Y Y Y Y 1 2 2 2 ? rs Ofh Y Y Y Y 1? 2 Yur 1,2 phg Y ? 1,2 Y wxcs 2 ? 1 1 2 1 2 2 c ms 2 bmp 2 m fs 1 1 wxd wxg wxq 1 1 2 wxs 2 2 2 1 d m 1 2 1 Y dm Y bm fga 1 2 wg c 1 2 lga rss ? rgt 2 bga hg c g dg c m rt c s cp bv cs m fg tg lq rs q q q bg a a be 2 pha 1 fs bgt rta uncertain; abundant interfingering ofunitsandstratigraphicduplicationlikely) uncertain; abundantinterfingering (includes possiblefelsicmetavolcanicrocks andvolcaniclasticrocks; relative age Mount HollyComplexparagneiss(MiddletoEarlyMesoproterozoic) Formation andrelatedrocks Aluminous schistsandgneissesoftheWashington GneissandWilcox of the Cavendish Formation, asdochloritic-muscoviticretrograded of theCavendishFormation, Felchville Gneiss(EarlyMesoproterozoic) Mills tonaliticgneissexposedonthenortheastflankofChesterdome Plagioclase-phenocrystic tonalitegneiss—Coarse-grainedfaciesoftheBaileys (Ratcliffe andothers,1991;Aleinikoff2011) Pond andRawsonvillegneisses.U-Pbzircon SHRIMPageof1,383±13Ma,no.2 in MountHolly,ratherthancoarsergraineddioriticgneissassociatedwiththeCole amphibolites associatedwithcalc-silicaterocks ofthetypeMountHollyComplex coarse biotite.Containsnumerous lensesoffine-grainedamphibolitesimilarto gray-weathering, medium-grainedbiotite-quartz-plagioclasegneissfleckedwith Baileys Millstonaliticgneiss(EarlyMesoproterozoic)—Light-graytowhitish- SHRIMP ageof1,393±9Ma,no.1(Aleinikoffandothers,2011) Londonderry area, where itisinterpreted asmetagabbro andhasaU-Pbzircon (±quartz) dioritic gneiss and gabbroic gneiss mapped in the hornblende-plagioclase Hornblende dioritegneiss(EarlyMesoproterozoic)—Coarse-grained Cavendish Formation(EarlyMesoproterozoic) quartz gneiss, occurring as a sliver in the Shelburne Marble,SouthWallingford quartz gneiss,occurringasasliverintheShelburne Retrograde gneiss (Mesoproterozoic)—Mylonitic chlorite-biotite-microcline- granofels and other rocks of the Wilcox Formation granofels andotherrocks oftheWilcox Formation muscovite-rich, chlorite-spotted,chloritoid-bearingquartzphyllitesandgarnet be youngerthantheFelchvilleGneiss(Karabinosandothers,1999).Retrograded between 1,290and934MasuggestsomeofthemarbleCavendishmay dish. Zircons from aquartzitelensindolomitemarbleatlocality4havePb-Pbages volcanics, andcoarsepebble-to-cobbleconglomerate,allabsentfrom theCaven- lacks pegmatiteandcontainsdistinctivewell-beddedalbiticgranofels,mafic also striking and cannot be altogether dismissed;however, theHoosac Formation are within theMountHollyComplex.Similaritiestorocks oftheHoosacFormation Cavendish to aluminous and feldspathic schists, calc-silicate rocks, and quartzites (1961) assedimentarywildflysch gray toyellowish-grayslate,quartzwacke,andlimestone;interpreted byZen wildflysch depositsisinpartquestionable compositional layering.Unitsare retained althoughinterpretation assedimentary down-plunge lineationparalleltoreclined hingelinesofminorfoldsfoliationand and related foldingcommonlyisalatestrain-slipcleavagecharacterizedbystrong carbonate-quartz-sulfide veinsratherthanclasticsedimentaryrocks. Thecleavage insitubydisruptionofthintothickbeds,laminae,and tectonic breccias formed Whipstock. Here andatmanylocalitiestheForbesHillWhipstockbreccias are oftheallochthonandinBenningtonarea atthetype margin and northern Ordovician) (Zen,1961;Potter, 1972;Fisher, 1985).Exposednearthewestern tary breccias, depositedinfront oftheadvancingTaconic allochthon(Upper slate, wacke,andpunky-weatheringbluish-graylimestone,interpreted assedimen- tions occuraslocalareas ofblackslaterichininclusionsquartzite,greenish-gray - Wildflysch-like conglomerates within theHortonville,Ira,andWalloomsac Forma insitu;containsabundantpseudo-pebbles a tectonicbreccia formed Whipstock BrecciaintheWalloomsac Formation(UpperOrdovician)—Largely Vesicular (Upper Ordovician)— Forbes HillconglomerateandbrecciaintheIraHortonvilleFormations volcaniclastic andclasticsediments.Areas of and marbleswhichlocallyare mappable.Associationsuggestsanaccumulationof quartzites,andcalc-silicates minor amphibolites,rusty-weatheringgarnetiferous light-gray more plagioclase-andquartz-richgneiss,containslayers, volcanics andvolcaniclasticrocks. Unitvariesfrom verydarkgraybiotiticgneissto plagioclase andisolatedigneousquartzgrainsprobably are metadacitic and little potash feldspar.garnet, Plagioclase-rich layers contain epidote-crowded and plagioclase gneissescontainingvariableamountsofmagnetite,hornblende, gneiss andquartzite( (small)-quartz-biotite overprint). Unitlocallyincludessteel-gray-weathering,garnet (red dot phyllonitic retrograde varieties contain chloritoid-chlorite and relict garnet lustrous yellowish-grayish-green locally containingabundantchloritizedgarnet; gneissandrustyschist, weathering, garnet-muscovite-biotite-quartz-plagioclase Quartz schistandgneiss(MiddleMesoproterozoic)—Dark-tan-torusty-tan- Washington Gneiss(MiddleMesoproterozoic) (1) on the basis of Mesoproterozoic age is here favored for the Cavendish Formation less extensivebelt,containingsimilarrocks, occursnearStarHill.AnEarly beltoccursatCavendishandonHawksMountain,a Chester dome;thelarger isrestricted totwobeltsofrocks withinthe “CavendishFormation” The term Formation isstriking Formation terozoic ageisfavored. Neverthelesstheresemblance torocks oftheTyson Complex andare transitionalintorocks oftheMountHollyComplex,aMesopro- are structurallycompatiblewithGrenvillian orolderfoldsintheMountHolly varieties oftheparagneissesMountHollyComplex.Becausetheserocks andretrograde and minorquartzitewhichresemble rocks oftheTyson Formation, schist, dolomite marble muscovite schist, chloritoid-chlorite-muscovite(±garnet) (Mesoproterozoic?)—Near DevilsDenandMosesPondincludesalbiticbiotite- Problematic rocks at Devils Den in Weston and Danby areas Holly Complexcontainabundantpegmatite gneiss and schist in the Mount spotted, chlorite-muscovite-rich retrograded garnet talc-tremolite rock, diopsidequartzite,calc-silicategneiss,andlustrous chlorite- of theMountHollyComplexinGreen Mountainmassif.Dolomitemarble, and aplite ( light-gray-weathering, medium-tocoarse-grainedbiotitemetatrondhjemite and Rawsonville trondhjemitegneiss(EarlyMesoproterozoic)—Chalky-whiteto and others,1991;Aleinikoff2011) ing abundantmagnetite.U-Pbzircon SHRIMPageof1,342Ma,no.6B(Ratcliffe Light-gray towhitish-gray,fine-grainedbiotitetrondhjemitic gneiss,locallycontain- Bondville metadaciteandtrondhjemitegneiss(MiddleMesoproterozoic)— of 1,321±9Ma,no.7(Ratcliffeandothers,1991;Aleinikoff2011) tonaliteordioritegneiss.U-Pbzircon SHRIMPage more mafichornblende-biotite gray, biotite-richmetatonalitegneiss,havingirregular screens, and xenoliths of Cole Pondtonalitegneiss(MiddleMesoproterozoic)—Grayto medium-dark- rock. Correlated withtheLudlowMountaingranodioritegneiss with calc-silicaterocks. Crosscuts allparagneissunits;isathoroughly gneissic widespread, heterogeneous unitofwell-layered, predominantly biotite-quartz- Biotite-quartz-plagioclase gneiss(MiddleandEarlyMesoproterozoic)—A Contains thinbeltsofamphiboliteandcalc-silicategneiss biotite,andfinelaminaeofquartzplagioclase. abundant smallgarnets, brown-weathering, sulfidic muscovite-biotite-magnetite gneiss or schist marked by Garnet-biotite gneiss(Middle Mesoproterozoic)—Dark-gray- torusty-grayish- dioritic-appearinggneiss coarse-grained hornblende Hornblende-plagioclase gneiss(MiddleMesoproterozoic)—Medium-to the EarlyandMiddleMesoproterozoic-age rocks oftheMountHollyComplex includes bothmeta-igneousandmetasedimentaryrocks intercalated throughout rocks and as lenses within biotite-quartz-plagioclase paragneiss. Unit probably amphibolite.Occurswithbeltsofcalc-silicate grained hornblende-plagioclase and medium- amphibolite, locally garnetiferous, quartz-hornblende-plagioclase Amphibolite (MiddleMesoproterozoic)—Dark-grayish-green, fine-grained plagioclase gneiss,tremolite-phlogopite schist,anddiopsidequartzite calcite-diopside knottedrock; andrusty-weathering,beigescapolite-quartz- - rock orpale-green diopsiderock; hornblende dark-green hornblende-diopside Calc-silicate rock(MiddleMesoproterozoic)—Heterogeneous unitconsistsof calc-silicate rock beds or pods less than 5 m thick, interbeddedwithorpassinglaterally into other and medium-grainedcalcite-diopsidemarblecalcite-diopside-talcin Calcite marble(MiddleMesoproterozoic)—Light-bluish-gray and white, coarse- tremolite-talc marbleandtremolite-talc schist Center,Sherburne Weston, andinthePineHillslice;iscommonlyassociatedwith weather salmonpinktobeige.UnitoccursonWest MountaininChittenden, coarse-grained dolomite-phlogopite-scapolite marble; pyritiferous varieties Dolomite marble(MiddleMesoproterozoic)—Light-graytoyellowish-gray, be border faciesof contains sparingamountsofbiotite,andsecondarymuscovite.Unitinterpreted to white, veryfinegrainedmicrocline-plagioclase-quartz (±magnetite)apliticgneiss; Ludlow Mountain aplitic gneiss (Middle Mesoproterozoic)—Light-gray to either calc-silicate gneiss,andmarbles,mappedseparately quartzite, Adirondacks. Locallycontainsmappablequartzite,garnet of theeastern feldspathicquartzgneisses garnet-rich is theretrograde equivalentofcharnockitic schist;probably biotite-muscovite (±chloritoid)schistandretrograde coarse-garnet Wilcox Formation(MiddleMesoproterozoic)—Lustrous torusty-weathering calc-silicate rock nearKillington rusty-weathering carbonaceoustographiticschistassociatedwithquartziteand Carbonaceous sulfidicschist(MiddleMesoproterozoic)—Dark-gray, minor amphiboliteolderthanpartoftheSouthLondonderryIgneousSuite Quartz schist(EarlyMesoproterozoic)—Rusty-weatheringsulfidicand ated withdiopside-bearingquartzite abundant epidoteandlocally magnetite, and frosted round grains of quartz associ- Mesoproterozoic)—Light-pale-yellowish-green tograyquartzitegneisscontaining Biotite-epidote-quartz gneiss and epidotic quartzite (MiddleandEarly be correlative upper partsmaybeMiddleMesoproterozoic. Rocksmappedas 1,350-Ma intrusive rocks range down into the Early Mesoproterozoic, whereas the Mountain massifandinthePineHillarea aluminous rocks now seen throughout the Mount Holly Complex of the Green interpreted tobeanAcadianremetamorphosed product oftheretrograde andkyanite-bearingGassettsSchistMemberis tion. Thecoarsegarnet-staurolite- - Chittenden andare identicalbutlower-grade correlatives oftheCavendishForma more aluminous,lessquartzofeldspathicrocks are mappedas of Green Mountainmassif.Distinctivequartzribbingdecreases northward where part rusty-weathering layers of sulfidiccalc-silicate rock. Exposed in southernmost quartziteand rusty-weathering blue-quartz-ribbedquartzschist;andgarnet (±sillimanite)schist; weathering, graphiticgarnet-plagioclase-biotite-quartz sition, having aplitic and hornblende-rich reaction zones( sition, havingapliticandhornblende-rich microcline megacrysticgneissicgranite,well-foliatedandhighlyvariableincompo- gray, gneissoidmagnetite-biotite-microcline-perthite granodiorite,andlocally Proctor Hillgranodioritegneiss(MiddleMesoproterozoic)—Graytopinkish- trondhjemite facies( Weston; probably correlative withtheBaileysMillstonaliticgneissorFelchville tonalitegneissexposedonTormentweathering, biotite(±hornblende) Hillin Tonalite gneiss(EarlyMesoproterozoic)—Medium-gray-tolight-gray- Mountain; U-Pbzircon ageof1,348±3Ma,no.6(Ratcliffeandothers,1991) 3 (Ratcliffeandothers,1991;Aleinikoff2011)from crest ofBromley Formation; levels; maybeEarlyMesoproterozoic inpart( biotite-quartz-plagioclase paragneiss.Unitprobably occursatvariousstratigraphic associated withaluminousschistsandcalc-silicaterocks orinterbeddedwithin quartzite and schistose quartzite rusty-brown or gray, thinly layered garnet-biotite Quartzite, undifferentiated(MiddletoEarlyMesoproterozoic)—Tan to gneiss oftheSouthLondonderryIgneousSuite no. 10(Aleinikoffandothers,2011),suggestderivationfrom trondhjemitic Forest. U-Pbagesofdetritalzircons rangefrom 1,359±32Mato1,261±62Ma, retrograde phyllite.OccursasathickunitonLudlowMountain,inOkemoState quartzite and aluminous sericite-muscovite-tourmaline brown garnet-muscovitic vitreousmeters thick,interlayered quartziteinbedsseveral withrusty-grayish- Okemo Quartzite(MiddleMesoproterozoic)—Light-tantowhitish-gray,massive Altered rocksadjacenttotheChittendenIntrusiveSuite descriptive purposes(seeZen,1961,1964,1967). describing geographicareas andstratigraphicdistinctionsare retained here for structural stackingsequenceandboundariesare indefinite,thenamesare usefulfor uncertain andisnotshownonthismap;there maybenodistinction.Althoughthe and distinctionbetweentheBird MountainandGiddingsBrook slicesisparticularly the identificationofprimaryemplacementrelations. Forexample,theboundary imbricate thrustfaults, thus complicating both theinferred stackingsequence and The structural boundaries among the slices are commonly late post-emplacement Neoproterozoic rocks andtoexhibitdifferent faciesfrom thoseofthelowerslices. Cambrianand Mountain andDorsetslicesare inferred tocontainlargely contain thecompletestratigraphicrangewhereas thehigherandmore easterlyBird slices, slices,theSunsetLake,GiddingsBrook, andNorthPetersburg lowermost Potter, 1972)containrocks ranging in age from Neoproterozoic to Ordovician. The Five structuralslicesoftheTaconic allochthoninVermont (Zen,1961,1972; THE TACONIC ALLOCHTHON contains magnetitegrainsasmuch1cmindiameter the LincolnMountainmassifadark-graybiotite-microcline-chlorite-spotted gneiss 1,150-Ma intrusiveaugengneissesoftheChittendenIntrusiveSuite( containing chloritized biotite and garnet. Occursasaltered varietiesof containing chloritizedbiotiteandgarnet. gray, albite-andmagnetite-studdedgranulosebiotite-quartz-plagioclasegneiss, Albite-magnetite-studded gneiss(LateMesoproterozoic)—Grayorgreenish- garnet amphibolite( garnet original highly poikiloblastic garnet. Nearthecontactswith original highlypoikiloblasticgarnet. as inclusionsinalbite,orabundanttotallyretrograded chlorite-sericiteclotsafter muscovite and biotite, and abundant clinozoisite. Locally contains fresh garnet platesof albitecrystals,conspicuouslarge ance andbytheabundanceoflarge distinguished from Biotite-muscovite-plagioclase-quartz schist—Ahighlyheterogeneous unit, gradational Y structural baseandhassharpcontactwithstructurallyoverlyingquartzite( road atDevilsDen.Gradesintochlorite-biotite(±actinolite)-carbonateschist and fine-grainedphlogopite-chlorite-dolomitemarbleexposedincliffseastofthe Dolomite marble—Beigetopinkish-gray-weathering,pyrite-bearing,medium- schist and garnet-bearing feldspathicgneissthatcontainspegmatite schist andgarnet-bearing ite at Devils Den. Grades into structurally overlying biotite-muscovite feldspathic Quartzite—Light-gray topinkish-gray,magnetite-muscovite-plagioclasequartz- muscovite-quartz-plagioclase quartzite( grained schist occur.- Unit is interbedded near its base with either garnet veins and highly albitic, very coarse of granitic gneiss, plagioclase-tourmaline determined byahigherabundanceofbiotite(commonlychloritized)andalbitein determined large subhedral garnets. Thecontactwithadjacent subhedralgarnets. large commonly occursinthefine-grainedsericiticmatrixbutlocallyisfoundwithin coarse muscoviteandbiotite.Robustgrainsofrutileare abundant.Chloritoid anhedralquartzandgrainsof thatcontainedlarge from thebreakdown ofgarnet muscovite. Rockishighlyretrograded andcontainsabundantchloritederived schist).Albiticvarietiestendtocontainmore biotiteandless muscovite-garnet in composition(from ultrafine-grainedphylloniticschisttomedium-grained biotite-albite-muscovite-quartz schist.Unitishighlyvariablebothintexture and schistand lustrous muscovite-chlorite-quartz(±garnet±chloritoid±ilmenite) Muscovite-chlorite-garnet schist—Light-silvery-green tograyish-green, Complex andcontainingpegmatite( the presence of deformed pegmatite thepresence ofdeformed ? 2011). Similarfine-grainedmagnetiteapliticgneissesexposedintheGreen U-Pb zircon SHRIMP age of 1,372±11 Ma, no. 4 (Aleinikoff and others, paragneisses oftheChester dome; containsxenolithsofmore maficgneiss. trondhjemitic gneissandaplitic trondhjemite, intricatelyintrusiveinto layered Felchville apliticfacies—Light-graytowhitish-gray,fine-grained, magnetite and calc-silicaterocks are identicaltounits( massesofgranitepegmatiteandinterlayered apliticgneiss.Marble and larger diopside quartzite,andschistosebluish-graymarble.Containspods,stringers, white talc-tremolite (±dolomite)-calc-silicateschist;andminorquartzite, rocks; coarse-grained dark-green diopside(±hornblende±zoisite)-calc-silicate dolomite-calcite marble;phlogopite-diopside-scapolite-calcite-dolomite phlogopite-tremolite-dolomite-quartz-(±talc) marble; greenish actinolite- coarse-grained calcitemarble;beigetogray,medium- Marble andcalc-silicatemember—Highlyvariableunit.Includeswhite, Athens domes and lacksamphibolitescommonintheHoosacflankingChester mylonite gneiss.Unitlesswell-beddedthangranofelsoftheHoosacFormation quartz granofels and gneiss, and porphyroclastic plagioclase-augen-biotite massive grayish-green chlorite-spotted,magnetite-studded,biotite-plagioclase- rusty-weathering, Feldspathic schistandgranofelsmember—Light-graytomedium-dark-gray, Gneiss (ofAlling,1918)( schist.Resemblesaretrograde varietyoftheHague quartzite andlarge-garnet chlorite-chloritoid ormuscovite-chlorite-biotite-clinozoisiteretrograde schistose Garnetiferous quartziteandquartzschistmember—Lustrous muscovite- quartzgneiss ite andfeldspathicretrograde-garnet Quartzite member—Tan, quartz- yellowish-gray-weatheringgarnet-muscovite plagioclase paragneissmember( oftheMountHollyComplex( of theWilcox Formation schist or gneiss granofels and garnet-quartz-feldspar garnet-plagioclase-quartz crystals.Unitcloselyresembles retrograded chlorite-spotted,biotite- garnet chloriteclotsappeartoreplace earlierlarge plagioclase granofelsinwhichlarge (small)- schist. Passeslocallyintogreenish, chlorite-spotted,magnetite-garnet (large)-plagioclase-quartz and warty-textured, dark-gray,biotite-rich garnet schist (large)-plagioclase-biotite-muscovite-quartz staurolite (±kyanite)-garnet Gassetts SchistMember—Lustrous, yellowish-grayish-green, ilmenite- SHRIMP ageof1,370±11Ma,no.5(Aleinikoffandothers,2011) ritic gneiss;intrudesparagneissunitsoftheChesterdome.U-Pbzircon magnetite-biotite-microcline-quartz-plagioclase metatrondhjemite togranodio- Felchville trondhjemitefacies—Light-graytowhitish-gray-weathering, Mountain massifare associatedwithtonaliticgneissesonTorment Hill,Weston dolomite marble Dolomite marblemember—Beige-weatheringtowhitish-gray,fine-grained tremolite schist calcite marbleandcalcite-diopsidedolomitictalc-phlogopite- rock, lensesofbluish-graytogray,medium-coarse-grained hornblende Calc-silicate gneissandmarblemember—Dark-green, massive, diopside- Green Mountain massif and eastern domes Green Mountainmassifandeastern mfs Y 1 Y fga Y near 2 1 lgg rta

) basalt withintheCavendishand perhaps ). Dated sample with U-Pb zircon SHRIMP age of 1,367±16 Ma, no. or Y Y ?

cms 2 breccia atEastHoosick(UpperOrdovician) phg intrusive Y Y Y Y . Thecontactwith white-plagioclase-spotted biotite-quartz-plagioclasegranofels, 2 . ExposedonLudlowMountain 1 Black slatecontainingangulartoirregular chipsofgreenish- lgg ? 2 fg cms Y bgt ) oftheChesterdome,butundated 2 . a ) ) orcalc-silicaterock ( Y byitsgenerallyrusty-weathering,nonlustrous appear- 2 Y ap 2 hgn issimilarapliticgneiss,butnotincontactwith ) nearWhitehall,N.Y. (2) Y Y 1,2 themarkedresemblance ofmembersthe 3C bg ( Y Y p 2 3C q ) ) Y

- ) orafine-grained,blackhornblende p of theMountHollyComplex 2 rs ) Y andareas ofFelchvilleGneiss ( Y oftheMountHollyComplexis 1 Y q 3C 1,2 ) Y p Y bg 2 ( ) 2 Y onBlueRidgeMountainin cs cs — 2 associatedwith1,400-to wxs ) withinthebiotite-quartz- ), alloftheMountHolly Dark-rusty-grayish-brown- Y Y ? ) mfs Y closelyresemble those 2 pha 2 wsx Y Y — isgradationaland 1 2 ) where incontact fga In Y rs ) 1,2 the , abundantsills bg Y 2 Walloomsac rs maynotall Y Y members 1,2 3A bg ma Y near ? ( Y q ); in 1 ) fg

Zngs Zbms Zmpq Zbmg Ztagn ( wcbb wcnb Zswa Zsws Znab Zsbg Zsgp ( Zrrgt Owwu ls Zbm Zrch Zrgs Zsgt opw Znw Zap Zngq Zbv Opaw Zbq Zrfb wcu Omm Ztm Znq obq Zbb Zbp Zsg Zsd ocq ls Owbl Zbk wc Zsa Zzh Znr Za om Ztp Zra Zjg Zrc Zrs ocf Zrr Zn oq Opo hh oa Oag eb Zs co of Zj Oir o Znm) Znb) d Mountain nearBennington) (includes DorsetMountainproperandMountEquinox,southwardtoWest Rocks oftheDorsetMountainslice Rocks oftheGiddingsBrook,SunsetLake,andBirdMountainslices of garnet, omphacite,glaucophane,epidote,quartz,albite,andwhitemica of garnet, locally. Eclogiteoccurslocally,delimitedbygreen, medium-grainedlayersandpods coticuleoccur chlorite withminormagnetite,pyrite,andapatite.Quartzgarnet composed ofamphibole(glaucophane,barroisite, andactinolite),epidote,garnet, unit. Dark-bluish-gray, fine-tomedium-grained,massive to foliatedblueschist Tillotson PeakStructuralComplex(Cambrian)—Maficschistandamphibolite part correlative with the green phyllite member of the Netop Formation ( part correlative withthegreen phyllitememberoftheNetopFormation probably in into thegreen slateoftheMettaweefaciesinBullFormation, abundant chloritoid.UnderliestheBird MountainGrit(ofDale,1900)andgrades to thinly bedded. Has rare thin beds of white vitreous quartzite and contains nantly green, purpleandpurplish-red, chloritichematiticslateandphyllite,massive structural duplicationbythrustfaultingandfolding are uncertain owing to extensive Ottauquechee and Pinney Hollow Formations althoughstructuralcontinuityandcorrelations withthe Hollow Formations, tion) are inasimilarstructuralpositionasrocks oftheOttauquecheeandPinney - structuralpositions(abovetheHoosacForma Units inthemiddleandlowermost tothe north. These upper units are continuous with rocks oftheStowe Formation amphibolites, schists, and feldspathicschistsof the RoweSchist of Massachusetts. Vermont partiscontinuouswith Mapped insouthern where theuppermost Rowe Schist(CambrianandNeoproterozoic?) Distinctive chloritestreaks and1-cmrustyneedlesofaltered kyaniteare common (Lower CambrianandNeoproterozoic)—Includesbasalticvolcanics( Rensselaer GraywackeMemberoftheNassauFormationPotter(1972) the DorsetMountainslice ( members:greenish-gray laminatedalbite-metasiltstone mappable informal medium-gray andgrayish-green phylliteandmetasiltstone.Includesthefollowing Netop Formation(CambrianandNeoproterozoic)—Predominantly light-to Mountain, althoughlensesofwhitishquartziteare present the distinctivelensesandpodsofbluish-graydolostoneNetoponDorset tan-weathering tolocallymappablegray-weatheringdolomiticquartzite( bedded limestone( Carbonate (Cambrian and Neoproterozoic?)—Pods,lenses,orzonesofthinly tion, andprobably are notallcorrelative dolomitic quartzite( metasiltstone, locallycontaininglight-gray,medium-tothick-beddedquartziteand Neoproterozoic)—Medium- todark-graycarbonaceousphyllite,grayslate,and Carbonaceous phylliteandsiltstone(LowerCambrian Whiterockian (Berry,1961) the base,interbeddedwithdarkslate.Containsgraptolitesrangingfrom Ibexianto and metasiltstonelocallyabundantthinbedsofmicriticblacklimestonenear phyllite. Hasdistinctivebeds,1cmtoseveralcentimetersthick,ofsiliceousargillite gray-weathering, andpale-green andgray,thinlybeddedtolaminatedslate Poultney Formation (Middle and Lower Ordovician)—Dull-white andwhitish- ContainsgraptolitesoftheC.bicornis Biozone(Berry,1961) Merino Formation. white-weathering, red andbluish-blackchertylayerscharacteristicoftheMount weathering, well-beddedandvariegated slate; containsminorcentimeter-thick, Indian RiverSlate(UpperOrdovician)—Deep-maroon andbluish-green- distinguished from theIndianRiverSlatebyabundanceofchertysiliceouslayers andmudstone ing, andred, green, anddark-gray,thinlybeddedsiliceousargillite Mount MerinoFormation(UpperOrdovician)—Light-gray,powdery-weather- gneiss atthebaseofBelvidere MountainStructuralComplex Gneiss is similar to 10 cm thick alsocontain chlorite pseudomorphs after garnet. plagioclase andpolycrystallinequartzporphyroblasts. Green, chloriticlayers2to well-layered epidote-white Albite gneiss—White, light-gray- and green-banded, medium-grained, lenses ofcoticule localcentimeter-thick quartz, chlorite(±garnet±albite±glaucophane±chloritoid); Pelitic schist—Silvery-gray,medium-grainedcomposedofwhitemica, Ottauquechee Formation(Cambrian) ( as theNorthBrittainConglomeratememberofWest CastletonFormation age from Neoproterozoic toLateCambrian.Includesnamedunitsshownlocally Theserocks locallycontainLowerCambrianfossils,butmayrangein Formation. andHatchHill West CastletonFormation, slate faciesintheBullFormation, Biddie Mount AbrahamFormation(CambrianandNeoproterozoic)—Lustrous, (ofPotter,Member oftheNassauFormation 1972)intheBenningtonarea ( resembles instratigraphicpositionandlithologytheRensselaerGraywacke Zion HillQuartziteMember, wellexposedinandaround Bird Mountain.Unit purple andgreen slatechips.Interpreted asacoarse-grainedvariantofpartthe fragmental plagioclase,phosphaticnodules,fragmentsofgrayquartzite,and pebble conglomerate, and purplish-gray hematitic lithic wacke. Unitisrich in Dark-gray togreenish-gray andwhitish-gray,massivechlorite-quartzwacke, Bird MountainGritofDale(1900)(LowerCambrianandNeoproterozoic)— (Cambrian) West CastletonandHatch Hill(?) Formations,undifferentiated ( indistinguishable from bedsintheAustinGlenGraywacke(afterPotter, 1972) oftheallochthon.Unitis andpossiblytheWest CastletonFormation Formation onrocks asoldtheHatchHill Mohawkian). Interpreted asuncomformable bicornis Biozone (see Webby and others, 2004, fig. 2.1) (lower to middle quartz andoligoclase.InterbeddedblackslatescontaingraptolitesoftheC. fragments of dacitic to andesitic volcanics, and subangular clastsof dark-gray dark-gray carbonaceousslate.Contains distinctive autoclasticchipsof gray slate, mica-speckled, massivetothin-beddedquartz-plagioclasewackeinterbeddedwith Pawlet Formation(UpperOrdovician)—Light-gray,tan-weathering, shownas Walloomsac Formation bicornis BiozoneonandwestofWhipstockHill,otherwisetypicalslatesthe Graptoliferous slate(UpperOrdovician)—BlackofClimacograptus uncertain correlation grayish-green rocks associatedwithWhipstockbreccia onWhipstockHillbutof cherty phyllite(UpperOrdovician)—Grayand Sandy phyllite,granofels,and Neoproterozoic butmayextendlowerandintothe West CastletonandHatchHillFormations, maybeinpartequivalentageandfaciestopartsofthe The NetopFormation and theCastletonConglomerate(ofShumakerThompson,1967)( fine-grained limestone,limestoneconglomerate,andboudins( fine-grained slateandphyllite,interbeddedwiththinlylaminatedbluish-black West CastletonFormation(Middleand LowerCambrian)—Dark-graytoblack, bluish-gray dolomiticquartzite rusty-weathering, splintery-fractured pyriticslateandphylliteinterbedded Hatch HillFormation(UpperCambrian)—Dark-graytoblack,sooty- Thompson (1967) Townships,Mountains inPawletand Tinmouth afterusageofShumakerand Bull Formation(LowerCambrianandNeoproterozoic) in theBullFormation black slateoftheBrowns Pondisinterpreted asalensoftheMettaweeslatefacies Shown only in theGranville, N.Y., area. Locally purpleand green slateabove and thin limestone breccia in part equivalent to the West Castleton Formation. Cambrian)—Gray to black slate, punky-weathering calcitic wacke and mudstone, Browns PondFormationofRowleyandothers(1979)(Lower Formations, undifferentiated ( Formations, within theblackslateandgrayphylliteofWest CastletonandHatchHill(?) resembling theEagleBridgeQuartzitemayoccuratseveralstratigraphicpositions dark-blue toblackquartz,daciticrock fragments,andabundantplagioclase.Beds dolomitic quartzwackeandquartzitedistinguishedbysmallpebblesgrainsof Eagle BridgeQuartzite(LowerCambrian)—Dull-gray,pitted,andbluish-gray whichisshownseparatelywhere mapped the Browns PondFormation, green phylliteandsooty-punky-weatheringcalciticquartzwackelimestoneof gray-weathering, bluish-gray quartzite. Unit is interbedded near the base with schist and phyllite, locally with minor garnet andmagnetiteporphyroblasts ( schist andphyllite,locallywithminorgarnet green tobluish-gray,fine-medium-grained,whitemica-chloritoid-quartz-chlorite Stowe Formation(CambrianandNeoproterozoic?) Jay PeakFormation(CambrianandNeoproterozoic) Znab wcnb Oag ultramafic inclusions,volcanic-arcintrusives,andvolcanicrocks Eastern allochthonoussequence,oceanicandaccretionaryrealm, ROWE-HAWLEY ZONE EARLY TOLATE TACONIAN ACCRETEDTERRANEOFTHE in west-to-easttectonicstackingsequence metavolcanic rocksandtectonicinclusionsofultramaficdescribed east oftheGreenMountains—Riftanddriftstagemetasedimentary Ordovician, Cambrian,andNeoproterozoicallochthonouscoversequence ROCKS OFTHEROWE-HAWLEY ZONE larger ultramaficbodies( larger chlorite-muscovite-quartz phylliteandschist,highlytectonicallylaminatednear Chlorite phyllite member—Pale-green todark-green, lustrous, magnetite- compositions have transitionalbasalttoMORBcompositions;greenstones haveMORB biotitic feldspathicvolcaniclastic rock andfeldspathicquartzite. Amphibolites greenish-gray, chlorite-plagioclase-ankeritegreenstone andinterlayered gray black, Amphibolite andgreenstonemember—Predominantly verydarkgreen to chloritic greenstone (±quartz) amphiboliteandrusty-pale-green, punky-weatheringankeritic- Amphibolite and greenstone member—Dark-green plagioclase-hornblende sandy muscovite-plagioclase-quartzschistandtanquartzite Schist andquartzitemember—Light-graytotan,rusty-weathering,laminated quartz schistandinterbeddedtan,gray,bluish-grayquartzite carbonaceous, medium-tocoarse-grainedchlorite-plagioclase-muscovite- Carbonaceous albiteschistmember—Tan- todark-gray-weathering, coticule, locallyrichlygarnetiferous chlorite-muscovite-albite-quartz schistorphylliteandgranofels;contains Feldspathic schistandgranofelsmember—Graygrayish-green, biotite- phyllite quartzite. Bedsare asthick30morare thinandinterbeddedwithblack Black quartzitemember—Dark-bluish-graytoblack,fine-grainedvitreous schistcharacterizedbycoarsemuscoviteporphyroblasts muscovite (±garnet) Coarse-muscovite schistmember—Silvery-green albite-chlorite-quartz- phyllite havingsiliciclaminae.Includesblackquartzitesnotmappedseparately carbonaceous tohighlygraphitic,fine-grainedsulfidicbiotite-muscovite-quartz Carbonaceous phyllitemember—Predominantly dark-graytoblack, conglomerate, and thin bedsof chloritic wacke, all shown as Locally containsbedsofgrayish-green vitreous quartziteandquartz-pebble chlorite±chloritoid-muscovite-quartz phylliteand greenish-gray metasiltstone. Chlorite phyllitemember—Light-green to gray, lustrous, laterally grades into the BomoseenGraywackeMember.laterally gradesinto Alsoshownas with above the and Westquartzite. Castleton Unit Formation interfingers limestone andpodsofpinkish-graytocream-white dolostone,andminor bedded andmottledphyllite.Locallycontainsboudinsthinbedsof pale-lustrous-green chlorite-muscovite-quartzphyllite;andgreen andpurple, Mettawee slatefacies(Neoproterozoic)—Predominantly greenish-gray to ofPotter,Nassau Formation 1972) occurrence in containing thinbedsofdark-bluish-grayvitreous quartzite.Restrictedtominor weathering, sulfidic,graphiticbiotite-muscovite-plagioclase-quartzschist, Graphitic schist and quartzite member—Dark-gray- tosooty-gray- gneiss, and symbol( facies. IntheMt.Anthonyarea isshownas withandgradeslaterallyintotheMettaweeslate 1900). Unitinterfingers (ofPotter,Nassau Formation 1972),andtheBird MountainGrit(ofDale, Resembles finergrainedpartsoftheRensselaerGraywackeMember containing coarsedetritalmuscovite,biotite,andautoclasticslatechips. olive-green tograymicaceousquartz-feldspargraywackeandsiltstone,locally light-gray-weathering, medium- and fine-grained, massive to thickly bedded, Bomoseen GraywackeMember(Neoproterozoic)—Pale-reddish-brown to areas ofcarbonate-cementedquartzite vitreous quartzite as much as 6 m thick, containing deeply weathered ovoidal Mud PondQuartziteMember(LowerCambrian)—Buff-togray-weathering Member oftheBullFormation) part equivalenttorocks oftheMettaweeslatefaciesandZionHillQuartzite grained, Amphibolite member—Dark-green toblack,massive,medium-coarse- exposed intheWorcester Mountains spangly muscoviteandelongatedknotsofquartzlayerspinkishcoticule, containscharacteristic muscovite-quartz schist(±garnet±kyanite±chloritoid); Kyanite schistmember—Silvery-blue,medium-tocoarse-grainedchlorite- and interbeddedamphibolite coarse-grained garnet-biotite-plagioclase-quartz schist coarse-grained garnet-biotite-plagioclase-quartz Garnet-biotite feldspathicschistmember—Dark-grayish-brown-weathering, non-carbonaceous, well-foliatedchlorite-quartz-muscovite(±plagioclase)schist Chlorite schistmember—Rusty-gray-toyellowish-brown-weathering, lustrous, carbonaceous schist( exceptforminorlayersof ceous andatypicaloftheOttauquecheeFormation schist,withminorfeldspathicbiotitegneiss.Unitnoncarbona- (±garnet)-quartz schist,andsplinterychlorite-chloritoid-muscovite-plagioclase garnet slabby, well-foliated,quartz-richmuscovite-biotite-plagioclase-quartzschist, Cooper HillMember—Dark-grayorgreen, dull-gray-andrusty-weathering, Chester andAthensdomes( Vermontschist member of the Rowe Schist in southern and around the ( andbiotite-fleckedschist quartz phylliteandschist.Locallyrichlygarnetiferous -knotted, magnetite-chlorite(biotite)-albite(plagioclase)-sericite(muscovite)- well-foliated, silvery-green, grayish-green, andbright-green, quartz-ribbedand Schist andphyllitemember—Predominantly fine-grained,lustrous, and justnorthoftheLowell-Westfield townline Conglomerate andbreccia occurlocallyatThe Knob (northwestofLakeEden) metawacke iscommon;quartzgrainsrangeinsizefrom 0.5mmtocm. fragments inafine-grainedmatrixofquartz,sericite,andchlorite.Feldspathic to angular grains of quartz, blue quartz, albite, and traces of detrital rock Metawacke member—Tan tograyphylliticmetawackecomposedofrounded ous quartzite,andpodsofbrecciated dolostone.ExposedatPlymouthFiveCorners keritic greenstone, ankeriticordolomiticmuscovitequartzite,bluish-graycalcare- Carbonate-bearing quartzitemember—Heterogeneous unitconsistingofan- perhaps equivalenttothe Wacke restricted toonehorizon not lar quartziteswithintheMettaweeslatefaciesinBullFormation, commonly 5to10m thick butisas much as65mthick;occurs many lenticu- locally containsquartz-pebbleconglomerateandwackenearthebase.Unit Light-greenish-gray towhitish-gray-weathering,massivevitreous quartzite; Zion HillQuartziteMember(LowerCambrianandNeoproterozoic)— plagioclase-biotite (chlorite)-quartz-muscovite schist. Comparable to garnet plagioclase-biotite (chlorite)-quartz-muscoviteschist.Comparabletogarnet (large)- Large-garnet schistmember—Silvery-green tograyish-green, garnet interbedded feldspathicquartzite( ankerite-magnetite-albite-epidote (plagioclase) feldspathic greenstone and amphibolite, and light-grayish-green, rusty-weathering, carbonate-pitted amphibolite,epidote-hornblende-plagioclase-quartz plagioclase (±garnet) biotite- Amphibolite andgreenstonemember—Dark-green hornblende-rich of the Ottauquechee Formation ( of theOttauquecheeFormation rusty-weathering blackquartzosephyllite,similartodarkcarbonaceousphyllites Carbonaceous phyllitemember—Interlayered grayish-green and Sericite schistmember—Quartz-sericitephylliteand Ottauquechee Formation butatadifferent structuralorstratigraphiclevel Ottauquechee Formation near theMassachusettsStateline.Closelyresembles rocks typicalofthe and within amphibolite atastructurally high position within the Rowe Schist ering, Biotite-plagioclase schistandgneissmember—Gray and light-gray-weath- elsewhere coarse cross-biotite. Typical ofrocks withintheStoweFormation and garnets schist,distinguishedbylarge muscovite-plagioclase-quartz-garnet Garnet schistmember—Mainlyyellowish-green, lustrous, biotite-chlorite- farthernorth Stowe Formation (Mettawee Member of the Nassau Formation ofPotter,(Mettawee MemberoftheNassauFormation 1972) Greenstone member—Green, carbonate-albite-epidote-chloritegreenstone green chloriticphylliticlayers;locallyalbitic with phyllite or schist and quartzite; white quartzofeldspathic layers alternate Schist member—Light-grayish-green, fine-grained,chlorite-muscovite-quartz meta-intrusive. ExposedintheWorcester Mountains Zsgt ) interpreted assynorogenic autochthonousrocks ), anddark-grayphyllite containing bluish-graydolostoneand ), the Bebe Limestone Member of the West Castleton Formation ( ), theBebeLimestoneMemberofWest CastletonFormation Knob medium-tocoarse-grainedbiotite-plagioclase-sericite-quartzschistand ) athighergrades;areas richinmetadiabasedikesshownbyoverprint finely commonly —Black slateandgrayphylliteexposedonWoodlawn andTinmouth member—Bluish-gray, fine-grainedmetawackeandmetasiltstone, layered Formation Zsd foliated Zrch ls Zbq ), dolostone( ) flecked with large cross-biotite. Locally flecked withlarge albite-epidote-hornblende , alongthebaseofmajoramphiboliteabove Zrc ). Unit resembles rocks of the Netop Formation butlacks ). Unitresembles rocks oftheNetopFormation biotite-plagioclase mica-quartz-albite (±garnet±magnetite) gneiss with mica-quartz-albite (±garnet±magnetite) (Lower Zu Bomoseen GraywackeMemberoftheBullFormation ) wcu Zrgs ). Unittypicaloflustrous chloriticschistsofthe d Ow ), andlimestoneconglomerateintheMettawee - ), andnearthebaseofPoultneyForma Cambrian o Zsg ) ) ). Locallyamaficbasalticmetawacke amphibolite and Znb amphibolite; Neoproterozoic)—Predomi- (BomoseenMemberofthe to contains coarsegarnet dark-green

Zngq ls possibly ) ofwhitish- Zbv co (unit is in Zngs wcbb to silvery- Zrch Znq Zap Znm ) ) Znr is light- ) of ). ), ). a , )

Onbwm Omwhg Omwhq Omwhb Zbagn Omwhv Omfgc Omwh Omhfs Ochpq Ochsb Ochuc Dgmg Onbm Ombq Ombb Omhb Dgmu Ochcv Onbw Zutc Ochfg Dgmc Ochfv Ochfs Omgt Omfq Dgmr Ochic Omfv Zbg Zbu Ontw Omfs Omw Onbs Zbs Zbc Zsp Dgqs Ochu Ochq Ochp Ochv Ocha Ochs Onnt Ontd Omd Omb Zbf Omp Omq Dgm Oma Omc Omr Onb Zu Dgq Dga Och Onr Ont Dgr Belvidere MountainStructuralComplex(CambrianandNeoproterozoic) Metasedimentary hostrocksoftheNorthRiverIgneousSuite ofMassachusetts rocks oftheHawleyFormation Coextensiveinpartwithigneous rocks oftheMoretown andCramHillFormations. metadacitic tuffs.Correlative withextrusivedaciticmetavolcanicandmeta-andesitic occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and 471.4±3.7 Ma)—Collectionofmetatonalite,metatrondhjemite, andmetabasalt North RiverIgneousSuite(OrdovicianandLateCambrian)(502±4Mato Suite oftheRowe-Hawleyzone Volcanic-arc intrusiveandvolcanicrocksoftheNorthRiverIgneous faultsymbollocallyomitted) Ottauquechee, Stowe,Rowe,andMoretown Formations; (occur astectonicsliversandolistolithsinblockswithintheHazensNotch, Ultramafic rocks(CambrianandNeoproterozoic) Fine chlorite, sphene,sericite,biotite,andcalcite actinolite,albite, layered amphibolitecomposedofbarroisite, epidote,garnet, Coarse-grained amphibolite—Dark-gray,coarse-grainedand (magnesite) rock rusty-weathering, medium-grainedtalc-carbonaterock andquartz-carbonate fully serpentinized dunite and peridotite and schistose serpentinite; Ultramafic rocks—Brown towhite-weathering,green, massive,moderatelyto ( plagioclase amphibolite,andmetadiabasedikes;locallycalledRugerHillfacies - metatrondhjemite, garnet-hornblende unit consistingofbiotiteandhornblende Mixed felsicandmaficrocks—Heterogeneous composite intrusive well-layered Bartonsville 24 (Aleinikoffandothers,2011),from 4kmnorthwestofBrockways Mills,near tonalite gneiss,withminoramphibolite.U-Pbzircon TIMSageof486±3Ma,no. Tonalite gneiss—Medium-grayish-green, medium-grainedhornblende-biotite others, 1998) 2011); U-Pbzircon ageof471.4±3.7MasouthBethel,no.26(Karabinosand SHRIMP ageof496±8ManorthProctorsville, no.23(Aleinikoffandothers, base, andmetapyroxenite assmallstocks,inclusions,anddikes.U-Pbzircon metadia- muscovite-quartz-plagioclase trondhjemite; includesrare hornblendite, tonalite and biotite- whitish-weathering, massive to gneissic hornblende-biotite Barnard Gneissproper(ofRichardson,1924)—Predominantly light-grayto Gile MountainFormation(LowerDevonian) Moretown Formation(LowerOrdoviciantoCambrian?) Intrusive ComplexandnearBrattleboro cobble toboulderconglomerate,andgreenstone. MappednorthoftheBraintree quartzite, grayish-green tolight-yellowish-green sericitephyllite(felsictuffs)and dark-gray metasiltstoneandquartzite, thicker beds of dark-bluish-gray vitreous quartz-chlorite-(biotite)-muscovite phyllite;contains1-to2-cm-thickbedsof Cram HillFormation,undivided—Predominantly dark-gray to grayish-green Whetstone HillMemberoftheMoretown Formation) isinpartcorrelative with partoftheCramHillFormation (western Cram HillFormation(Middle?andEarlyOrdovician) it intrudes metavolcanics ( athick,sill-likeintrusiveextendingnorthward from SouthNewfane,where Forms and muscovite-biotitemetatrondhjemite andmetatonalite. hornblende-biotite Newfane tonalite—Light-graytocream-weathering, massivetogneissic, Branch Brookdikeandsillcomplex coextensive withtrondhjemite intheHawleyFormation lensnearMassachusettsStatelineis metatrondhjemite andmetatonalite;southern West HalifaxTrondhjemite —Cream-colored, light-gray-towhitish-gray-weath Serpentinite—Brown-weathering, dark-green serpentinite talc-carbonate schistandtalc-cabonate-richrocks Talc-carbonate schist—Cream-colored tolight-bluish-gray,brown-weathering, carbonate (magnesite)rock serpentinite; rusty-weathering,medium-grainedtalc-carbonaterock andquartz- massive, moderatelytofullyserpentinizedduniteandperidotiteschistose Meta-ultramafic rocks,undifferentiated—Brown towhite-weathering,green, PeakStructuralComplex Gneiss issimilartogneissatthebaseofTillotson are definedbyvariationsintheamountofquartz,albite,whitemica,andchlorite. plagioclase and polycrystalline quartz porphyroblasts. The 0.5- to 2-cm-thick layers gneiss;contains well-layered epidote-whitemica-quartz-albite(±garnet±magnetite) Albite gneiss—White,light-gray-andgreen-banded, fine-tomedium-grained, amphibolite, andtalcphyllite contains fragmentsanddiscontinuouslensesofgreenstone, coarse-grained muscovite schistwithminoramountsof chlorite, epidote,albite, and tourmaline; Spangly schist—Silvery-blue,medium-grainedtectonicmélangecomposedof banded greenstone includes homogeneousschistosegreenstone, albiticgreenstone, andmassive and epidotewithbiotite,calcite,sericite,quartz,sphene,pyrite,magnetite; Mafic schist—Green, fine-grainedschistcomposedofchlorite,actinolite,albite, t) amphiboliteandquartz-bearing blende-epidote-actinolite (±garne ing, g f524M,n.2 Aenkf n tes 01 age of502±4Ma,no.22(Aleinikoffandothers,2011) with metasediments of the Cram Hill Formation ( with metasedimentsoftheCramHillFormation intrusive. Resembleswell-layered undated felsic and mafic volcanicsintercalated thickness rangesfrom 5cmto1m.Unitmaybeinpartmetavolcanicaswell Chester dome;similarto muscovite-biotite-quartz-plagioclase metatrondhjemite ontheeastflankof Metatrondhjemite and metatonalite—Light-gray towhitish-gray,coarse-grained (in partcorrelative withtheSt.DanielGroup ofQuébec) Cram HillFormationoftheNewportCenterarea Onr CONNECTICUT VALLEY TROUGH Whetstone HillMemberoftheMoretownFormation with sandstone,pelite,andporphyriticrhyolite( conglomerate, commonlyhavingabundantdark-graypeliticmatrixinterlayered Grit—Lenticular masses of metamorphosed quartzose volcaniclastic grit and 2009) plagioclase. U-Pbzircon ageof407.0±3.3Ma,no.45(RankinandTucker, withquartz),andsaussuritized microcline (someingranophyricintergrowths apatite; grainsizeabout 0.05 mm. Relict phenocrysts of embayed quartz, to anaggregate ofquartz,microcline, plagioclase,biotite,muscovite,and metafelsite schistorgranofelsnearMaidstoneLake.Groundmass recrystallized Felsic metavolcanicmember—Very light gray, fine-grained porphyritic metasiltstone, 1mmtocmthick to moderatelyabundantbedsoflight-gray,fine-grainedmetasandstoneand Meetinghouse SlateMember—Dark-grayslateandphyllitecontainingsparse with dark-graygraphiticslate,phyllite,orschist micaceous quartziteafewcentimeterstotensofthick,interbedded Quartzite andmetapelitemember—Graytolight-gray,fine-grained Gile MountainFormation,undivided—Shownincross sectiononly rusty-weathering amphibolite, coticule, and vitreous quartzite ( splintery-fractured, biotitic sulfidic quartz schist. Containslayers of schist,carbonaceousandgray, biotite-muscovite-quartz (±garnet) Carbonaceous andsulfidicschistmember—Rusty-weathering,dark-gray “pinstriped” granofelsandfeldspathicbiotitequartzite weathering, chlorite-biotite-plagioclase-quartzgranofelsandtectonically “Pinstriped” granofelsmember—Light-graytopale-green, whitish-gray- sericite-chlorite-quartz schistwithpyrite Quartz schistmember—Bluish-black,rusty-weathering,fine-grainedalbite- and schist fine-grained massive to thinly bedded quartzite intercalated with green phyllite Harlow Bridgequartzitemember—Buff-weathering, tan to green, and vitreous quartziteinterbeddedwithgrayphylliteandschist Interbedded quartziteandphyllitemember—Light-graylaminated sills boudinaged, massive to foliated, dark-green metamorphosed mafic dikes and quartzofeldspathic granofelsanddark-grayphyllite.Containsnumer chlorite-sericite-quartz phylliticquartziteinterlayered withlight-greenish-gray Granofels andphyllitemember—Light-graytotan,fine-grainedalbite- breccia. Similartothevolcanicagglomerate( agglomerate, andgrayish-green fragmentalmetadaciticandmeta-andesite meta-andesite, gray-totan-weatheringblue-quartzphenocrysticmetadacitic stratigraphic levels.Includesdark-grayandwhitelayered metadaciteand Felsic andintermediatemetavolcanicmember—Occursatdifferent gray-weathering dolostone rusty-weathering amphibolite,coticule,andpodsoforangey-graytopinkish- quartzite, weathering siliceousironstone, magnetitequartzite,garnet Ironstone, quartzite,andcoticulemember—Dark-gray-tosooty-black- in core ofSpringHillsyncline granofels; hascoarsespanglesofmuscoviteandlocallyiskyaniterich.Mapped schistand rusty-weathering garnet-biotite-muscovite-quartz-plagioclase Feldspathic schistandgranofelsmember—Medium-dark-graytodark-gray, richathighermetamorphicgrade coticule. Locallyhornblende ankerite-epidote greenstone, ankerite-spottedfeldspathicgranofels,and and grayish-green chlorite-plagioclase-quartz granofels; contains thinlayersof Granofels member—Dark-medium-graybiotite-plagioclase-quartzgranofels South amphibolite nonporphyritic ilmenite-epidote-chlorite-plagioclase-hornblende Williamsville facies—Dark-graytoblack,poorlylayered, porphyriticand andabundantphenocrystsofplagioclase hornblende amphibolite, ilmenite-sphene-chlorite-hornblende-plagioclase Whitneyville facies—Light-green tomedium-green, massive,epidote- Member ( withtheUmbrella Hill Conglomerate pillows; interfingers with deformed massive carbonate-biotite-quartz-sphene-chlorite-actinolite-epidotegreenstone Coburn HillMetabasaltMember—Light-green, fine-tomedium-grained, Group ofQuébec Coburn HillMetabasaltMember( Coburn siltstone, phyllite, quartzite, and dark-gray slate breccia interbedded with phyllitewithclastsof carbonaceous garnet-pyrite-sericite-chlorite-quartz and slateconglomeratemember( quartz granofels;interpreted asmetabasalticandvolcaniclasticrocks - amphiboliteandhornblende-plagioclase Amphibolite member—Hornblende decrease inthicknessofquartzitebeds granofels; is alateralvariantof rusty-weathering, sulfidic biotite-muscovite-plagioclase-quartz schist and Black sulfidiccarbonaceousschistfacies—Dark-gray,sooty-and dark-gray quartzite,coticule,andironstone, locallymappedseparately phylliteandcarbonaceousphyllite;containslayersof garnet-biotite-muscovite Phyllite facies—Predominantly medium-dark-gray to lustrous-tan, fine-grained muscovite-chlorite-quartz phyllite chlorite-biotite feldspathicmetasiltstoneandpale-greenish-yellow-weathering Metasiltstone facies—Pale-greenish-gray, finelylaminated,magnetite- meta-andesitic breccia; mayoccuratseverallevels metadacitic volcanic breccia, agglomerate, and grayish-green fragmental Metavolcanic facies—Pale-tannish-gray-topurplish-gray-weathering,phyllitic quartzite, andcoticule Coticule andquartzitefacies—Dark-graytolight-gray,vitreous magnetite amphibolite anddark-grayquartzite 5 mthick;gradationalto noncarbonaceous quartz-micaschistandfeldspathicquartziteinbeds50cmto Thick-bedded micaceousfeldspathicquartzitemember—Brown togray, zircons yieldaU-Pbageof409±5Ma,no.51(McWilliams andothers,2010) containing bedsofmicaceousquartzite;locallythicklybedded.Detritalvolcanic or schistinbeds10to25cmthick;anddark-graymicaceousphyllite micaceous quartzitetodark-graymuscovite-quartz-biotitecarbonaceousphyllite Rhythmically gradedmember—Light-tomedium-gray,fine-grained Phyllite-chip conglomerateandslatemember Moretown Formation ( “dioritic”amphibolite amphibolite;andhornblende-spotted (±garnet±epidote) ankeritic greenstone; black,fine-grained hornblende-plagioclase Amphibolite andgreenstonemember—Includes light-pale-green chloritic phylliteandschist.OccurswestofMontpelier tite-muscovite-quartz (±garnet) Carbonaceous schistmember—Dark-gray,fine-grained carbonaceous bio- granofels andbiotite-hornblende-plagioclase of hornblende, green chlorite-muscovite-biotite-plagioclase-quartzschist,conspicuoussprays Hornblende fasciculeschistandgranofelsmember—Light-graytograyish- Omfs Hill Hill.PaperschistfabricoccurslocallyonthewestsideofCoburn Coburn granofels; thinlayersoffelsite,conglomerate,andbreccia occurinthevicinityof grained quartz-sericite-chlorite-albitephyllite,quartzite,andflintysulfidic HillMetabasaltMember( with Coburn northofAlbany.Interbedded stratigraphic levelsintheCramHillFormation atUmbrella Hill;occursatdifferent able withtheunderlyingStoweFormation - conglomerate, andtantograyphyllite.Occursaslenses,locallyunconform Umbrella HillConglomerate Member—Quartz-pebble andphyllitic-fragment schist. Similartophyllitefacies( (small)-biotite-muscovitephylliteand medium-dark-gray, fine-grainedgarnet Carbonaceous schistmember—Light-grayish-brown- totan-weathering, ered with thin bedsofrusty-weathering,pearly-white,fine-grainedgranofels.Interlay- Phyllite member—Graytosilvery-green, sericite-chlorite-quartzphyllitewith Quartzite amphibolite, associatedwithironstone, coticule,andminorpodsofdolostone chlorite-actinolite greenstone andbeddedandesitictobasaltictuff Amphibolite andgreenstonemember—Light-greenish-gray, feldspathic Hillarea complex andintheCoburn River IgneousSuiteandatscattered localitiesnorthoftheBraintree intrusive metatuff. Abundantscreens andlayersoccurwithinmaficrocks oftheNorth quartz-phenocrystic phylliticmetatuffandwhitishpyritiferous soda-rhyolite Felsic volcanicmember—Light-graytowhitish-gray,fine-grainedsericite- no. 25(Aleinikoffandothers,2011) has a U-Pb zircon SHRIMP age of 483±3 Ma, within the Cram Hill Formation Asimilarfelsiclayerinterlayered Hill MemberoftheMoretown Formation. andesitic metavolcanicandmetavolcaniclasticrocks, similarto Felsic metavolcanicmember—Gray,purplish-gray, and light-gray dacitic to ultramafic rocks inRoxbury tremolite-epidote-zoisite granofelstogneiss.Associatedwithgreenstone and to medium-grained, variably foliated calcite-quartz-albite-mariposite-actinolite- Mariposite-bearing metarodingitemember—Bright-green andwhite,fine- —Greenish-gray feldspathic garnet schist;gradesinto Garnet schistmember—Greenish-gray feldspathicgarnet Phyllite of the Ottauquechee Formation ( of theOttauquecheeFormation much as10mthickbutcommonlylessthan1thick.Resemblesquartzites Quartzite member—Dark-graytosteel-bluish-grayvitreous quartziteinbedsas garnetiferous variant( garnetiferous chlorite-muscovite feldspathicschistandschistosegranofels.Localrichly Chlorite schistmember—Pale-greenish-gray, lustrous andnonlustrous quartziteandcoticule small-garnet quartz granofelsandschistcontainingabundantfinelayersofpinkish-gray Granofels and coticule member—Grayish-green, chlorite-biotite-plagioclase- biotite-muscovite feldspathicquartziteandmuscoviticquartzschist Feldspathic quartzitemember—Light-grayish-brown- totan-weathering ( Proctorsville southward tonearTownshend containsabundantultramaficrocks nent zonethatextendsfrom thenorthendofChesterdomeandnear of theMeetinghouseSlateMember( with abundantdark-gray,pyritic,andcalcareous metapelitematrixatthebase Quartz-pebble metaconglomeratemember—Thin lens of metadiamictite (ofMyers,1964)tothenorth Mountain Formation dark-gray slate.Correlative withHallsStream GritMemberoftheIronbound rounded clastsofrhyolite,fine-grainedgranitoid,andangular metadacite. Similarinparttothemixedgneissfacies( cant calciteandpyriteinterlayered felsiclayersofmetatrondhjemite or amphibolite,locallycontainingsignifi- grained hornblende-chlorite-plagioclase phyllite andschistsimilarto paperymuscovite quartzite andinterbeddedcarbonaceous,small-garnet splintery-fractured, dark-graytosteel-graybiotite-quartz-feldspathicschistand Gray quartzschistmember—Rusty-grayish-brown-weathering, locally and associatedslabby,rusty-weatheringamphibolitecoticule gray-weathering, quartz-pebbleand-cobbleconglomerate,feldspathicquartzite coarse-grained Omd Zu ) in the Spring Hill syncline (Ratcliffe and Armstrong, 2001).Layering ) intheSpringHillsyncline(RatcliffeandArmstrong, - - grained amphibolite—Bluish-gray,fine-tomedium-grainedalbite-horn ) ) Pond and Ochuc Ochuc and facies—Light- todark-grayandsteel-blueapple-green, fine- quartzite chlorite-biotite-muscovite-quartz-plagioclase ) andwithphyllite-chipconglomerate( and quartz-pebble Ochsb Omgt Onb Ochv member—Light-gray totan,rusty-weathering,fine- , ) of the Cram Hill Formation. U-Pb zircon SHRIMP ) of the Cram Hill Formation. ) Onnt atthecontacts. Dgqs Ochs , and obq Omwh Ochsb Omwh Ochcv through interbeddingofphyllitebedsand Dgm Ontw ) Ochcv conglomerate ) intheWhetstoneHillMemberof ) northofAlbany ). Unitcorrelative withtheSt.Daniel . Contains layersof rusty-weathering ), southofBradford Mapped locallyintheAlbanyarea ) andphyllite-chipconglomerate Ochv Omwhv Dgmr ) ). Conglomeratecontains Onbm Ochsb ) withintheWhetstone

member—Tan- (±garnet ±hornblende) (±garnet ) ) marked Ombq Omwhv —Dark-gray, ). A promi- by coarse ous er- to DSwb/Dl Scc Opa DSwgs DSwqc DSwac DSwq DSwb DSwv DSwa DSwc DSws DSfra DSnq Obqd Oobg Oohg Dfqm DSwf DSwt Dbgn DSwi Dcoa Oogt DSnl Dfpg DSw DSfr Ssm Scm DSn Dco Oaa Snd Sng Sbd Sbg Dkq Src Scg Scd Opr Scv Oar Dih Ohi Dm Dia Dla Svf Op Srr Dir Dlr Oa Sg Sv Ss Sr Sc Dr Di Ol Oj Dl Sf Scq Lake MemphremagogIntrusiveSuite(LateSilurian) (425±3 Mato418.5±2Ma) (a sheeteddiketopegmatiticdioritecomplex) Comerford IntrusiveComplex Stratified rocksoftheBronsonHillarchandSawyerMountainbelt Oliverian PlutonicSuite(LateOrdovician) range from granitetodioritelesseramountsofgabbro plutons exposednorthwestoftheAmmonoosucfault.Compositions Epizonal tomesozonal,foliatedandmetamorphosed(greenschist facies) Highlandcroft PlutonicSuite(EarlySiluriantoMiddleOrdovician) Braintree IntrusiveComplex Newport IntrusiveComplex tional contactwith metasiltstone, commonlypyritiferous andcalcareous. Somegradedbeds.Grada- abundant 1-mm to- 5-cm-thick beds of light-gray, fine-grained metasandstone and grayish-black lustrous slate,phyllite,andschistcontainingsparsetomoderately Ironbound MountainFormation(LowerDevonian)—Medium-dark-gray to Compton Formation(LowerDevonian) Nonfoliated tofoliatedpegmatiticmetatonalitemetagabbro 418.5±2.0 Ma,no.35(Rankinandothers,2007) Mountain) are, respectively, 419.8±2.6Ma,no.33;419.3±1.334;and quarry,LeightonHill,andPeaked titic metadioritefrom three bodies(Comerford metatonalite; apliticandmetadiabase.U-Pbzircon agesofpegma- Foliated tononfoliated,fine-grainedpegmatiticmetagabbro, metadiorite,and Shown asoverprint Abundant, foliatedtoweaklyfoliated,metatholeiiticmaficdikes;somesheeted. (Taconian) inhostrocks postdatesdominantfoliation intheMoretown Formation cordierite hornfels - Ma, no. 36 (Black and others, 2004). Narrow zone of garnet-biotite-plagioclase and coarse-grainedquartzmonzodiorite.HasaU-Pbzircon TIMsageof419±0.39 dioriteandquartzdiorite, and sillsoffine-tomedium-grainedhornblende-biotite Metadiorite to metamonzodiorite—Medium-gray-weathering,porphyriticdikes U-Pb zircon ageof418±1Ma,no.37(AleinikoffandKarabinos,1990) Aleinikoff, 2003) Tucker, 2009); and U-Pb sphene ageof 443±3 Ma,no. 31 (Moench and 30 (MoenchandAleinikoff,2003),444.1±2.1Ma,no.29(Rankin U-Pbzircon agesof442±4Ma,no. Contact aureole isintheAlbeeFormation. and lesseramountsofgabbro. Where present, potassiumfeldsparismicrocline. granite;locallydiorite Lost Nationgranite—Foliatedbiotiteand(or)hornblende Meetinghouse Slate Member of the Gile Mountain Formation Meetinghouse SlateMemberoftheGileMountainFormation calc-silicate lensesandlayers schistandmicaceous quartz-feldspar granofels;some garnet-staurolite-kyanite Greenvale CoveFormation(LowerSilurian)—Thin-beddedmuscovite-biotite- schist ( Ammonoosuc Volcanics ofBillings(1935)(UpperandMiddleOrdovician) and tuffs,amphibolite( rusty-weathering sulfidicslateandphylliteinterlayered withfelsicvolcanicrocks Partridge Formation(UpperOrdovician)—Dark-graytograyish-black, Vermont neartheVernon dome interlayered withlight-gray,fine-grainedmicaceousquartzite;insoutheastern Littleton Formation(LowerDevonian)—Medium-dark- to dark-gray slate granite andgneissicgranite,apliteoftheLebanondome Biotite granite—Pink, medium-grained muscovite-biotite-microcline-perthite blende-andesine metagabbro Hornblende metagabbro—Dark-green, coarse-grained,well-foliatedhorn- Highlandcroft GranodioriteofBillings(1935,1937) Biotite-quartz dioritegneissofVernon dome(LateOrdovician)—Light- IntrusiveComplex( xenoliths ofdikestheComerford tain intrusiveintothe Albee Formation(EarlyDevonian)—Somecontain Dikes andsillsofporphyriticnonporphyriticmetarhyoliteHuntMoun- bole, epidote,chlorite,andcalcite composed mainlyofsecondarymineralssuchassaussuritizedplagioclase,amphi- Moulton Diorite(EarlyDevonian)—Dark-gray,medium-grainedmetadiorite U-Pb zircon ageof410±5Ma,no.42(MoenchandAleinikoff,2003) weakly foliated,coarse-grainedtoporphyriticbiotitegraniteoftheFairleepluton. Fairlee QuartzMonzonite(EarlyDevonian)—Greenish-gray, pink-tinged, commun., 2008) Ashuelot pluton.U-Pbzircon ageof403±2Ma(R.D.Tucker, USGS,written coarse-grained, potassium-feldspar-megacrystic, biotite granodiorite gneiss of the Kinsman Quartz Monzonite ofBillings (1955) (Early Devonian)—Medium- to and others,1992)atBellowsFalls inNewHampshire. U-Pbzircon ageof407±5Ma,no.43(Kohn ley Formation sillimanite-andalusiteandcordierite; intrudesrocks oftheRange- contains garnet, to porphyritic,muscovite-biotite-microcline-plagioclase metaquartzmonzonite; Bethlehem Gneiss (Early Devonian)—Medium- tocoarse-grained,equigranular by 3cm.U-Pbzircon ageof364±5Ma,no.50(MoenchandAleinikoff,2003) as 2 coarse-grained biotite granite; phenocrysts of potassiumfeldsparare aslarge French Pond Granite (Late Devonian)—Pink togray,nonfoliated,porphyritic present. Separatemappableunitsofquartzconglomerate( common inthegranofels;granuleandpebblemetaconglomeratelocallyare staurolite, andkyanite.Calc-silicatelenses containing porphyroblasts ofgarnet, rusty-weathering quartz-feldspar micaceous granofels and dark-gray mica schist Rangeley Formation (Lower Silurian)—Interlayered, commonly with associatedmetadiorites. Unmapped dikeof 421±7 Ma,no.38(Aleinikoffandothers,2011).Hasmutuallyintrusivecontacts biotite-mesoperthite granodioriteandgranitehavingaU-Pbzircon SHRIMPageof Nevis pluton—Yellowish-gray tolight-gray,medium-coarse-grainedmagnetite- Biotite-bearing metagranodiorite,metagranite,andmeta-apliteoftheMount Ma, no.39(Aleinikoffandothers,2011) U-Pbzircon SHRIMPageof425±3 UnitintrudesCramHillFormation. surface. Numerous crosscutting quartz-feldsparveinletsshowinrelief ontheweathering tan-weathering, medium- to coarse-grainedtrondhjemite withxenoliths of diabase. others, 1995) andothers,1997;Moench and 414±4 Ma,no.40,and412±2 41 (Lyons ate; onSkitchewaugMountain,upperquartzite( diorite withxenolithsofgreen phylliteandtrondhjemite; andmassive, consisting ofmassive to foliated,light-gray grayish-green, chalky-weathering Diorite and trondhjemite—Metamorphosed diorite,trondhjemite, anddiabase, plagioclase, perthite,microcline, biotite,andsericite grained, equigranulartoporphyriticfoliatedgranodioritecomposedofquartz, Granodiorite—Tan tolight-bluish-gray,brown-weathering, medium-tocoarse- Clough Quartzite(LowerSilurian)— strongly foliatedfelsite Felsic metavolcanicrocks—Includesvolcanicdebrisflow,laminatedtuff,and Valley andBronson Hillsequencesandcorrelative withFrontenac Formation quartz andfelsite)toward base.Interpreted astransitionalbetweenConnecticut punky weathering.Gradedgritandconglomeratebeds(havingcobble-sizeclastsof calcareous, fine-tomedium-grained,feldspar-rich metasandstone;somebeds dark-gray, pyritic,locallycalcareous phylliteandlight-gray,locallypyritic Sawyer MountainFormation(DevonianandSilurian)—Greenish-gray to N.H.,area inChesterfield, Madrid andSmallsFallsFormations ate andpolymictconglomeratewithcalcareous matrix.Locallyequivalentto limestone, calcareous sandstone,siltstone,andpelite.Somelimestoneconglomer- Fitch Formation(LowerDevonianandUpperSilurian)—Metamorphosed in theBradford area U-Pb zircon ageof469±1.5Ma,no.27(MoenchandAleinikoff,2003) ofquartzandplagioclase. epidote, sericite,andcalcite.Granophyricintergrowths clase, biotite,magnetite,pyrite,andapatite;secondarymineralsincludechlorite, weakly foliatedmetamorphosedtonalite.Primarymineralsincludequartz,plagio- Joslin Turn Tonalite—Greenish-gray tolight-brownish-gray, medium-grained, andothers,1986) zircon ageof450±5Ma,no.28(Lyons U-Pb overlainbytheCloughQuartziteandFitchFormation. Nonconformably biotite(chloritealteration),andsecondarycalcitesericite. hornblende, rite, andtonalitecontainingquartz,microcline, saussuritizedplagioclase, dark-greenish-gray, medium-grained,foliatedmetamorphosedgranite,granodio- as 5mthick pebble to-granulephyllite,andsteel-graytanvitreous quartziteinbedsasmuch beds 0.5to1mthick;andyellowish-graylight-grayphylliticquartzite,quartz- white quartzasmuch2.5cmindiameteratotanquartzitematrix, quartz-pebble conglomerateandconglomeraticquartzite,havingclastsofmilky- Shaw Mountain Formation (Upper to Lower Silurian)—White toyellowish-gray dome consistsofasmuch5percent bedsofpunkylimestone abundant dark-grayphyllitematrixthatresembles phylliteoftheLittletonFormation gneiss; forms sillsinoverlyingAmmonoosucVolcanicsgneiss; forms dioriteandtrondhjemite well-foliated subporphyriticbiotite(±hornblende)-quartz Waits RiverFormation(LowerDevonian andUpperSilurian) to 4mthick;calc-silicatelenseslocallypresent dark-gray metapelite. Metasandstone beds commonly are rusty weathering and up micaceous, andfeldspathicmetasandstonesinterlayered withsubordinate Frontenac Formation(DevonianandSilurian)—Thick-bedded,ankeritic, and maficrocks ( granofels ( limestone ( quartz-feldspar gritorquartzitenearbase.Containsonlyminorbedsofquartzose to centimeter-thick bedsofgrayquartziteandmetasiltstone,thicker biotite-muscovite-quartzschist;containsmillimeter- silicic phyllite,andgarnet-rich silvery-gray, lustrous, fine-grainedcarbonaceousquartz-muscovitephylliteand Northfield Formation(LowerDevonianandUpperSilurian)—Dark-grayto BRONSON HILLARCHINTRUSIVEROCKS Piermont andotherallochthons INTRUSIVE ROCKS(SILURIAN) hornblende amphibolite hornblende schistandminor hornblende Amphibolite member—Garnetiferous the GileMountainFormation centimeters thick. Graded bedding common. Interpreted to be correlative with metasandstone andslateormetamudstoneinbedsafewcentimeterstotensof Metasandstone member—Light-graytotan,micaceous,locallycalcareous with few centimeterstoaboutameter;typicallytheyare 10to30cmthick.Contact or phyllite;somerocks are calcareous. Gradedsetsrangeinthicknessfrom a micaceous metasandstonesthatgradeupward intosubordinate dark-grayslate Rhythmically gradedmember—Light-tomedium-gray,fine-grained quartz granofels;interpreted asmetabasaltandmaficvolcaniclasticrock - amphibolite and hornblende-plagioclase Amphibolite member—Hornblende slate rhyolite, fine-grainedgranitoid,andrare marble,andangularclastsofdark-gray clastsofdark-grayslate.Conglomeratecontainsrounded clastsofmeta- larger as2.5cmacross and gular clastsofplagioclaseandpotassicfeldsparaslarge metasandstone, metapelite, andporphyriticmetarhyolite.Gritcontainssuban- with abundantdark-graymetapeliticmatrix(diamictite)interlayered with grained quartzosevolcaniclasticgritandcobblemetaconglomeratecommonly Halls StreamGritMember(ofMyers,1964)—Lenticularmassesofcoarse- Granodioritic toquartz dioritic gneissicborder phase of Metamorphosed maficvolcanicrocks and Tucker, 2000) microcline phenocrysts.U-Pbzircon ageof407.5±3.9Ma,no.44(Rankin tuff, andlithictuffcommonlywithafewpercent millimeter-size quartzand laminated, aphanitictoveryfinegrainedgranofelsschistormetatuff,welded Metarhyolite—White-weathering, medium-todark-gray,foliatedand underlying volcanicandintrusiverocks intheCramHillFormation the Chesterdome.Interpreted asrecycled volcaniclasticrocks derivedfrom the onthenorthendof phyllite, occurringatthebaseofWaits RiverFormation (<10 m thick) unit of interbedded quartzite, amphibolite, felsic granofels, and Basal volcaniclasticandmetasedimentarymember—Heterogeneous, thin southofSpringfield Formation, metawacke and gray quartzite and conglomerate at base of the Northfield Quartzite, grit,andconglomeratemember—Dark-grayquartz-pebble mapped as Littleton Formation ( mapped asLittletonFormation shown southeast of Springfield; in part correlative with staurolite-grade rocks coaly-black, fine-grainedplagioclase-muscovite-quartzschistandmetawacke, Muscovite porphyroblastic carbonaceous schistmember—Dark-grayto amphibolite hornblende schistandminor hornblende Amphibolite member—Garnetiferous contains plagioclaseand(or)altered maficphenocrysts basaltic tuff, crystal tuff, and tuff breccia; minor pillow lava. Commonly Dark-greenish-gray tomedium-bluish-graymetamorphosedandesiticand waxy sheenonfoliationsurfaces clase and,insomeplaces,quartzphenocrysts.Generallystrongly foliatedwith tuff, tuffbreccia, andlava.Generallyporphyriticwith5to20percent plagio- Greenish-gray, light-bluish-gray,ormedium-bluish-graymetarhyolitetuff,lapilli siltstone, graywacke,volcanicconglomerate,andrare limestone lava. Sedimentaryprotoliths includedark-graysulfidicshale,ironstone, dominate (tufftotuffbreccia), butincludesparsemaficpillowlavaandfelsic rocks. Compositionsrangefrom basalttosodicrhyolite.Fragmentalrocks metamorphosedvolcanic,volcaniclastic,andsedimentary and interfingering Ammonoosuc Volcanics, undivided—Aheterogeneous unitofinterlayered DSws, and DSwv DSwb/Dl amphibolite percent plagioclaseand,insomeplaces,quartzphenocrystsandminor rhyolite tuff,lapillituffbreccia, andlava.Generallyporphyriticwith5to20 Metarhyolite—Greenish-gray, light-bluish-gray,ormedium-bluish-graymeta- not shownonthemap.InCorrelation, units (of Trask, 1980).ShownonlydiagrammaticallyinCorrelation ofMapUnits; (ofDoll,[1945])andPutneyVolcanicsMember ofMemphremagog Formation Volcanic andvolcaniclasticrocks—MappedwithStandingPondAmphibolite are absent,andnearRandolph Formation Shown south of the Pomfret dome where rocks typicalof the Gile Mountain thin beds of quartzite and only sparse layers of punky-weathering limestone. carbonaceous chlorite-biotite-muscovite-quartzslate,phyllite,orschist;contains Slate andphyllitemember—Predominantly dark-tolight-gray,lustrous, polymict schistosequartzconglomerate,associatedwith muscovite-quartz schistandquartzconglomeratedark-graycarbonaceous, Quartz-cobble andschistosemetaconglomeratemember—Light-gray and southofSpringfield;containsdetritalzircon havingGrenvillian provenance bedded quartziteinbeds2to10cmthick,exposednorthoftheChesterdome Quartzite andfeldspathicquartzitemember—Light-graytotan,thinly in partvolcaniclasticandlocallyinterbeddedwithamphibolite Crow HillMemberofHall(1959)—Grayquartziteandfeldspathicquartzite, biotite (chlorite)-plagioclase-quartzschistandgranofels Volcaniclastic rockmember—Silvery-grayish-green to light-gray, muscovite- epidote-chlorite greenstone amphibolite;actinolite- granofels; finelyfoliatedhornblende-plagioclase gneissand Mafic member—Massive,coarse-grainedhornblende-plagioclase schist schistandhornblende-fascicule (large)-muscovite-biotite-hornblende Garbenschiefer member—Rusty-brown to silvery-gray, coarse-grained,garnet 1990) of 423±4Ma,no.32(AleinikoffandKarabinos,1990;Hueberothers, dike cuttingtheStandingPondVolcanics, thatyieldedaU-Pbzircon TIMSage or metatuff.InSpringfield,containsadatedmetafelsitelayerinterpreted asa muscovite-plagioclase-quartz schistandfragmentalquartz-plagioclasegranofels Felsic volcanic member—Light-gray tograyish-green, chlorite-biotite- metasomatic rich limestoneinbedsrangingfrom 10cmtomthick abundant bedsofpunky-brown-weathering, dark-bluish-graymicaceousquartz- phyllitecontaining lustrous, carbonaceousmuscovite-biotite-quartz(±garnet) Carbonaceous phylliteandlimestonemember—Dark-graytosilvery-gray, thick bedsofcalcareous granofels.UnitoccursonlyinMassachusetts Calcareous granofelsmember—Carbonaceousphyllitecontainingmeter- Formation tofelsicvolcanicrocks; alsolocallyoccursintheNorthfield and intermediate metaconglomerate containingpebblestocobblesoflimestone,pelite,granite, Irasburg Conglomerate(member)—Gray-tobluish-graypolymictlimestone laminated calcareous metasandstoneandphyllite bedded calcareous metasandstone,quartzosemetalimestone,andfissile, Ayers Cliff Member—Gray- to bluish-gray, fine- to medium-grained, thinly Srr Di are locallyshownas ) occurinFallMountainnappenearBellowsFalls gradational Scc DSnl )

) are mapped.Locallycontainsquartz-cobbleconglomeratewith DSwv ); transition zone into Waits River Formation westoftheGuilford ); transitionzoneintoWaits RiverFormation Onbm Dco southeast ofSpringfield aboveand ) oftheNorthRiverIgneousSuiteatBridgewaterhasa Opa Sv ) Dl ; onthemaptheyare shownindividually Dir isequatedwith below.Interpreted tobecorrelative with the Dl Quartzite and quartz-cobble metaconglomer- Quartzite and ) flankingtheVernon dome(shownas Scq Sbg ) andlowerconglomerate DSwb —Medium-greenish-gray to DSwf in the layered, mixed felsic Scd andmaybeolderthan Oobg ). U-Pbzircon agesof Src , DSwgs ) andrustysulfidic DSwb , perhaps inpart , , DSwa DSwb/Dl , gray,

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Rankin,USGS,unpub.data,2011) U-Pb zircon SHRIMPageof492.5±7.8Mafrom aporphyritictonalitesillabout2 sulfidic (eitherpyriteorpyrrhotite)andrustyweathering.“Pinstriping”iscommon. structures are locally obvious. Tourmaline is a sporadic accessory mineral. May be calc-silicate nodules.Generallysharplybedded,butgradedbedsaswellslump light-gray togreenish-gray todark-grayphyllite. Lesser amounts of quartzite.Rare white-weathering, fine-grainedfeldspathicmetasandstoneandmetasiltstone, Albee Formation(OrdovicianandCambrian)—Light-graytogreenish-gray, Washburn BrookFormation(Upperand MiddleOrdovician) Edited byJamesR.Estabrook Digital cartographybyLindaM.Masonic GIS databasecompiledbyGregoryJ.WalshandMarjorieH.Gale Investigations Map3184,3sheets,scale1:100,000. 2011, Bedrock geologic map of Vermont: U.S. Geological Survey Scientific Ratcliffe, N.M., Stanley,R.S., Gale, M.H.,Thompson,P.J.,andWalsh,G.J., Suggested citation: on thismap. Charles RatteforinitiatingStatesupportandDianeConradcontinued work The Vermont Geological Survey would like to thank former State Geologists rusty weathering Commonlysulfidicand channeling and,inplaces,soft-sedimentdeformation. ing). Abruptly graded beds <1 cmto30 cm thickare locally common asis fine-grained micaceousandfeldspathicmetasandstone(typicallyribbyweather- Scarritt Member—Dark-grayslateinterlayered withthinbedsoflight-gray, Magnetite-rich areas—Shownasanoverprint Iron-formation member—Ironstone, magnetite-richrock andcoticule ing. Indistinguishablefrom theScarrittMember, butcrops outinsmallareas Dark-gray slateandphyllitemember—Commonlysulfidicrustyweather- greenish-gray slate Matrix consistsoffine-grainedmetasandstone,metasiltstone,ordark-gray coticule-bearing metasiltstoneandchertaswellsparsequartzpebbles. dark-grayorgreenish-gray slate,and and metasiltstoneoftheAlbeeFormation, micaceous siltstone.Clastsincludelight-colored, fine-grainedmetasandstone Metamorphosed sedimentarybreccia interlayered withdark-grayslateand typically containingcoticuleandmagnetite Metamorphosed gray siltstone, quartzite, volcanogenic chert, and ironstone, all Ammonoosuc Volcanics thebaseof ered withfelsictuffsandminorsandyrocks; locallyforms Dark-gray tograyish-black,rusty-weatheringsulfidicslateandphylliteinterlay- dolomiteandcalcareous pelite Siliceous andargillaceous metawacke. Purpletingecommon;coticuleandmagnetitelocallyabundant dark-greenish-gray metasiltstoneandphyllite,medium-grayfeldspathic Medium-light-bluish-gray, medium-bluish-gray,medium-dark-gray,tomedium- Metamorphosed aphyricrhyolitetuff as5mm crysts commonlyaslarge metarhyolite tuff, lapilli tuff, and tuff breccia. Quartz and plagioclase pheno- Coarsely porphyritic, greenish-gray, light-bluish-gray, or medium-bluish-gray in Detenbeck, J.C., ed., The geology of the Lake Champlain basinand in Fortey,R.A.,Harper,D.A.T.,Ingham,J.K.,Owen,A.W.,Parkes,M.A., in Bartholomew,M.J., ed., TheGrenvilleeventin the Appalachians and in Perkins,G.H.,17thReportoftheStateGeologistonmineral in Jacobs,E.C.,24thReportoftheStateGeologistonmineral ´ purposes onlyanddoesnotimplyendorsement bytheU.S.Government Any useoftrade,product,orfirmnames inthispublicationisfordescriptive World WideWeb: http://www.usgs.gov; Telephone 1-888-ASK-USGS For productandorderinginformation: Services, Box25286,DenverFederalCenter, Denver, CO80225 This map is available for sale by U.S. Geological Survey, Information in Sohl,N.F.,andWright,W.B.,Changesstratigraphic SCIENTIFIC INVESTIGATIONS MAP3184 206 BEDROCK GEOLOGICMAPOFVERMONT Pb/ REFERENCES CITED 238 in Friedman, G.M., ed., Guidebook [for field trips];Joint U microprobegeochronologybythemonitoringofa in Webby, B.D., Paris, Florentin, Droser, SHEET 3OF(FRONT) Provisional zirconand of Slack, J.F.,ed.,