U.S. DEPARTMENT OF THE INTERIOR Prepared in cooperation with the SCIENTIFIC INVESTIGATIONS MAP 3184 U.S. GEOLOGICAL SURVEY STATE OF VERMONT, VERMONT AGENCY OF NATURAL RESOURCES, BEDROCK GEOLOGIC MAP OF VERMONT MARCIA K. McNUTT, DIRECTOR VERMONT GEOLOGICAL SURVEY SHEET 3 OF 3 (FRONT) LAURENCE R. BECKER, STATE GEOLOGIST CORRELATION OF MAP UNITS (Some lesser units listed in the Description of Map Units may not be shown here. Asterisk indicates U-Pb zircon age.) NEW HAMPSHIRE PLUTONIC SUITE Zfc 2 OTHER DEVONIAN Carbonaceous albite schist member—Gray to medium-dark-gray, Y lga Ludlow Mountain aplitic gneiss (Middle Mesoproterozoic)—Light-gray to Owwu Sandy phyllite, granofels, and cherty phyllite (Upper Ordovician)—Gray and Belvidere Mountain Structural Complex (Cambrian and Neoproterozoic) Compton Formation (Lower Devonian) Oarq Coarsely porphyritic, greenish-gray, light-bluish-gray, or medium-bluish-gray GRANITES rusty-weathering, carbonaceous albite-chlorite-quartz-muscovite schist, contain- white, very fine grained microcline-plagioclase-quartz (±magnetite) aplitic gneiss; grayish-green rocks associated with Whipstock breccia on Whipstock Hill but of metarhyolite tuff, lapilli tuff, and tuff breccia. Quartz and plagioclase pheno- STAGE GRANITE BLACK FRENCH AND PLUTONS STAGE Brandon Lignite POND ing porphyroblasts of black albite. Unit resembles gray albitic granofels and contains sparing amounts of biotite, and secondary muscovite. Unit interpreted to uncertain correlation Zbu Ultramafic rocks—Brown to white-weathering, green, massive, moderately to Dco Metasandstone member—Light-gray to tan, micaceous, locally calcareous crysts commonly as large as 5 mm DIKES MOUNTAIN AGE UNCERTAIN 2 2 Tmb GRANITE GRANITE schist of the Hoosac Formation (Zhab) be border facies of Y lgg. Y ap is similar aplitic gneiss, but is not in contact with fully serpentinized dunite and peridotite and schistose serpentinite; metasandstone and slate or metamudstone in beds a few centimeters to tens of Lower 2 2 Miocene TERTIARY Dg Dfpg either Y lgg or Y phg. Exposed on Ludlow Mountain Owbl Graptoliferous slate (Upper Ordovician)—Black slate of Climacograptus rusty-weathering, medium-grained talc-carbonate rock and quartz-carbonate centimeters thick. Graded bedding common. Interpreted to be correlative with Oat Metamorphosed aphyric rhyolite tuff *364 Ma *365 Ma 365* Ma Zfqz 365 Ma 24 Ma 365 Ma Quartzite member—White quartzite and tan to light-gray, medium-grained bicornis Biozone on and west of Whipstock Hill, otherwise typical of slates of the (magnesite) rock the Gile Mountain Formation Dbmg BARRE EAST BETHEL 2 PLUTONS muscovite quartzite locally rich in magnetite. Resembles quartzite of the Tyson Y phg Proctor Hill granodiorite gneiss (Middle Mesoproterozoic)—Gray to pinkish- Walloomsac Formation shown as Ow Oam Medium-light-bluish-gray, medium-bluish-gray, medium-dark-gray, to medium- break in scale PLUTONS DERBY *368 Ma PLUTON Formation (Ztq) 2 gray, gneissoid magnetite-biotite-microcline-perthite granodiorite, and locally Zbc Coarse-grained amphibolite—Dark-gray, coarse-grained amphibolite and Dcoa Amphibolite member—Garnetiferous hornblende schist and minor dark-greenish-gray metasiltstone and phyllite, and medium-gray feldspathic Dbbg Dbqm Y pha WHITE MOUNTAIN IGNEOUS SUITE Ddbg microcline megacrystic gneissic granite, well-foliated and highly variable in compo- layered amphibolite composed of barroisite, epidote, garnet, actinolite, albite, hornblende amphibolite metawacke. Purple tinge common; coticule and magnetite locally abundant FAMENNIAN FAMENNIAN 2 (consisting of plutons and dike swarms Ddrz Zfs Schist member—Silvery-green to rusty-tan, fine-grained chlorite-quartz- sition, having aplitic and hornblende-rich reaction zones (Y pha) where in contact chlorite, sphene, sericite, biotite, and calcite VICTORY (Dbg) Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices of Jurassic to Early Cretaceous age) sericite (±garnet±chloritoid±allanite) schist and phyllite. Resembles green with calc-silicate rocks. Crosscuts all paragneiss units; is a thoroughly gneissic Di Ironbound Mountain Formation (Lower Devonian)—Medium-dark-gray to Oac Siliceous and argillaceous dolomite and calcareous pelite Upper Devonian Upper Devonian PLUTON (Dqm) WILLOUGHBY PLUTON CUTTINGSVILLE STOCK (Ddg) Dwmz phyllites of the Pinney Hollow Formation (Zph) and Mount Abraham Forma- rock. Correlated with the Ludlow Mountain granodiorite gneiss Zbf Fine-grained amphibolite—Bluish-gray, fine- to medium-grained albite-horn- grayish-black lustrous slate, phyllite, and schist containing sparse to moderately DIKES 100 Ma Opaw Pawlet Formation (Upper Ordovician)—Light-gray, tan-weathering, Dvbg (Dg) Dwwz Oap 375 Ma Kqs 375 Ma tion (Za) and chloritic phyllite (Ztg) of the Tyson Formation blende-epidote-actinolite (±garnet) amphibolite and quartz-bearing amphibolite abundant 1-mm to- 5-cm-thick beds of light-gray, fine-grained metasandstone and Dark-gray to grayish-black, rusty-weathering sulfidic slate and phyllite interlay- (Debg) mica-speckled, massive to thin-bedded quartz-plagioclase wacke interbedded with Kns Dwhz Y2cp NIAN NIAN Cole Pond tonalite gneiss (Middle Mesoproterozoic)—Gray to medium-dark- ered with felsic tuffs and minor sandy rocks; locally forms the base of the FRAS- FRAS- Oag metasiltstone, commonly pyritiferous and calcareous. Some graded beds. Grada- Kes Kab (Dedg) dark-gray carbonaceous slate. Contains distinctive autoclastic chips of gray slate, (Degr) gray, biotite-rich metatonalite gneiss, having irregular screens, and xenoliths of Zbg Mafic schist—Green, fine-grained schist composed of chlorite, actinolite, albite, tional contact with Dco above and Dir below. Interpreted to be correlative with the Ammonoosuc Volcanics 382 Ma 382 Ma fragments of dacitic to andesitic volcanics, and subangular clasts of dark-gray Kpd Kmd (Dwdg) BARBER HILL ASCUTNEY MOUNTAIN IGNEOUS COMPLEX CONNECTICUT VALLEY TROUGH Pinney Hollow Formation (Cambrian and Neoproterozoic) more mafic hornblende-biotite tonalite or diorite gneiss. U-Pb zircon SHRIMP age quartz and oligoclase. Interbedded black slates contain graptolites of the C. and epidote with biotite, calcite, sericite, quartz, sphene, pyrite, and magnetite; Meetinghouse Slate Member of the Gile Mountain Formation TIAN TIAN GIVE- GIVE- STOCK Kag Kgd Lower CRETACEOUS Zph of 1,321±9 Ma, no. 7 (Ratcliffe and others, 1991; Aleinikoff and others, 2011) bicornis Biozone (see Webby and others, 2004, fig. 2.1) (lower to middle includes homogeneous schistose greenstone, albitic greenstone, and massive Kas Kahg 387 Ma Kbh 387 Ma Phyllite member—Light-greenish-gray to lustrous pale-green chlorite- Mohawkian). Interpreted as uncomformable on rocks as old as the Hatch Hill banded greenstone Dih Halls Stream Grit Member (of Myers, 1964)—Lenticular masses of coarse- Washburn Brook Formation (Upper and Middle Ordovician) Kfd 2 Khf Kav BRONSON HILL AREA Zphc muscovite-quartz (±chloritoid±garnet±magnetite) phyllite. Chloritoid-rich rocks Y bv Bondville metadacite and trondhjemite gneiss (Middle Mesoproterozoic)— Formation and possibly the West Castleton Formation of the allochthon. Unit is grained quartzose volcaniclastic grit and cobble metaconglomerate commonly Owc CHESTER (Zphc) appear gritty owing to distributed porphyroblasts of chloritoid. Unit is Light-gray to whitish-gray, fine-grained biotite trondhjemitic gneiss, locally contain- indistinguishable from beds in the Austin Glen Graywacke (after Potter, 1972) Zbs Spangly schist—Silvery-blue, medium-grained tectonic mélange composed of with abundant dark-gray metapelitic matrix (diamictite) interlayered with Metamorphosed gray siltstone, quartzite, volcanogenic chert, and ironstone, all DOME NULHEGAN locally albitic and contains minor beds of quartzite ing abundant magnetite. U-Pb zircon SHRIMP age of 1,342 Ma, no. 6B (Ratcliffe (Oag) interpreted as synorogenic autochthonous rocks muscovite schist with minor amounts of chlorite, epidote, albite, and tourmaline; metasandstone, metapelite, and porphyritic metarhyolite. Grit contains suban- typically containing coticule and magnetite GRANITE PLUTON Middle Devonian EIFELIAN EIFELIAN 144 Ma Middle Devonian Y1rta and others, 1991; Aleinikoff and others, 2011) contains fragments and discontinuous lenses of greenstone, coarse-grained gular clasts of plagioclase and potassic feldspar as large as 2.5 cm across and SOUTH- CENTRAL- NORTH- SAWYER Dg SHAW MOUNTAIN, NORTHFIELD, WAITS RIVER EASTERN EASTERN EASTERN MOUNTAIN Dnqm (See DMU for Zphq Feldspathic quartz schist member—Light-gray to grayish-green, laminated, Omm Mount Merino Formation (Upper Ordovician)—Light-gray, powdery-weather- amphibolite, and talc phyllite larger clasts of dark-gray slate. Conglomerate contains rounded clasts of meta- Ows Metamorphosed sedimentary breccia interlayered with dark-gray slate and Upper *392 Ma unlisted symbols) 1 MONADNOCK AND GILE MOUNTAIN FORMATIONS VERMONT VERMONT VERMONT BELT gritty feldspathic chlorite-muscovite-plagioclase-quartz schist Y rt Rawsonville trondhjemite gneiss (Early Mesoproterozoic)—Chalky-white to ing, and red, green, and dark-gray, thinly bedded siliceous argillite and mudstone rhyolite, fine-grained granitoid, and rare marble, and angular clasts of dark-gray micaceous siltstone. Clasts include light-colored, fine-grained metasandstone MOUNTAIN 159 Ma Littleton Formation light-gray-weathering, medium- to coarse-grained biotite metatrondhjemite and Zbagn Albite gneiss—White, light-gray- and green-banded, fine- to medium-grained,