Dark-gray to silvery-gray, lustrous, carbonaceous muscovite-biotite-quartz (±garnet) phyllite containing abundant beds of punky-brown-weathering, dark-bluish-gray micaceous quartz-rich limestone in beds ranging from 10 cm to 10 m thick. Part of the Connecticut Valley Trough.
Gray to light-gray, fine-grained micaceous quartzite a few centimeters to tens of centimeters thick, interbedded with dark-gray graphitic slate, phyllite, or schist. Part of the Connecticut Valley Trough.
Light-gray to pale-green, whitish-gray-weathering, chlorite-biotite-plagioclase-quartz granofels and tectonically “pinstriped” granofels and feldspathic biotite quartzite. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Schist, gneiss, and quartzite; dark-rusty-brown graphitic biotite-muscovite-chlorite-quartz (±garnet) schist and gneiss; black albite porphyroblasts, large euhedral pyrite, and beds of dark-gray foliated quartzite are common. Unit includes rusty-weathering schist without graphite and rocks identical to Fayston Formation. Cover rocks north of the Lincoln Mountain massif.
A widespread, heterogeneous unit of well-layered, predominantly biotite-quartz-plagioclase gneisses containing variable amounts of magnetite, hornblende, and garnet, and little potash feldspar. Plagioclase-rich layers contain epidote-crowded plagioclase and isolated igneous quartz grains and probably are metadacitic volcanics and volcaniclastic rocks. Unit varies from very dark gray biotitic gneiss to light-gray more plagioclase- and quartz-rich gneiss, contains quartz-rich layers, minor amphibolites, rusty-weathering garnetiferous quartzites, and calc-silicates and marbles which locally are mappable. Association suggests an accumulation of volcaniclastic and clastic sediments. Areas of Y1,2bg associated with 1,400- to 1,350-Ma intrusive rocks range down into the Early Mesoproterozoic, whereas the upper parts may be Middle Mesoproterozoic. Rocks mapped as Y1,2bg may not all be correlative. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Gray, foliated muscovite-chlorite-biotite-feldspar-quartz schist, phyllite, and metagraywacke. Quartz is commonly blue, and local thin conglomeratic horizons are present. Feldspathic biotite phyllitic metawacke is interlayered with lenses of quartz, feldspar, and gneiss-pebble to -cobble conglomerate (CZpc). Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Predominantly dark-gray to black, carbonaceous to highly graphitic, fine-grained sulfidic biotite-muscovite-quartz phyllite having silicic laminae. Includes black quartzites not mapped separately. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Light-gray to greenish-gray, white-weathering, fine-grained feldspathic metasandstone and metasiltstone, and light-gray to greenish-gray to dark-gray phyllite. Lesser amounts of quartzite. Rare calc-silicate nodules. Generally sharply bedded, but graded beds as well as slump structures are locally obvious. Tourmaline is a sporadic accessory mineral. May be sulfidic (either pyrite or pyrrhotite) and rusty weathering. “Pinstriping” is common. U-Pb zircon SHRIMP age of 492.5±7.8 Ma from a porphyritic tonalite sill about 2 km east of West Bath, N.H. (D.W. Rankin, USGS, unpub. data, 2011). Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Predominantly greenish-gray to pale-lustrous-green chlorite-muscovite-quartz phyllite; and green and purple, bedded and mottled phyllite. Locally contains boudins and thin beds of limestone and pods of pinkish-gray to cream-white dolostone, and minor quartzite. Unit interfingers with the West Castleton Formation above and laterally grades into the Bomoseen Graywacke Member. Also shown as CZnm (Mettawee Member of the Nassau Formation of Potter, 1972). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Brown to gray, noncarbonaceous quartz-mica schist and feldspathic quartzite in beds 50 cm to 5 m thick; gradational to Dgqs through interbedding of phyllite beds and decrease in thickness of quartzite beds. Part of the Connecticut Valley Trough.
Light- to medium-gray, fine-grained micaceous quartzite to dark-gray muscovite-quartz-biotite carbonaceous phyllite or schist in beds 10 to 25 cm thick; and dark-gray micaceous phyllite or schist containing beds of micaceous quartzite; locally thickly bedded. Detrital volcanic zircons yield a U-Pb age of 409±5 Ma, no. 51 (McWilliams and others, 2010). Part of the Connecticut Valley Trough.
Predominantly fine-grained, lustrous, well-foliated, silvery-green, grayish-green, and bright-green, quartz-ribbed and -knotted, magnetite-chlorite (biotite)-albite (plagioclase)-sericite (muscovite)-quartz phyllite and schist. Locally richly garnetiferous and biotite-flecked schist (CZsgt) at higher grades. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Silvery-green quartz-muscovite-chlorite schist and phyllite, commonly with albite and magnetite; locally contains dolomite. Cover rocks north of the Lincoln Mountain massif.
Light-gray- to tannish-gray-weathering, massive to poorly bedded vitreous quartzite. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Light-gray to light-green, quartz-sericite-chlorite (±magnetite±biotite) phyllite and foliated quartzite. Cover rocks north of the Lincoln Mountain massif.
Buff- and pink-mottled and massive, or light-gray, pinkish-gray-weathering, and massive to poorly bedded dolostone. Contains distinctive small pebbles and grains of well-rounded quartz; minor beds of dolostone-breccia and conglomerate occur near Rutland. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Dark-gray calcareous shale with beds of bluish-gray limestone. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts). Also part of the Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Silvery-green to grayish-green, medium-grained albite-chlorite-muscovite-quartz (±garnet±magnetite) schist with white albite porphyroblasts; resembles albitic schists of the Tyson Formation (CZtab) and green albitic granofels of the Hoosac Formation (CZhgab). Locally contains unmapped light-gray, thin quartzites; salt-and-pepper-colored, medium- to coarse-grained pyrite-magnetite-biotite-albite-quartz schist and gneiss; and silvery-dark-gray to rusty-weathering, medium-grained chlorite-tourmaline-albite-muscovite-quartz schist. The Fayston south of Mount Abraham is interca-lated with rocks of the Tyson Formation and with the schists of the Pinney Hollow Formation. Cover rocks north of the Lincoln Mountain massif.
Predominantly dark- to light-gray, lustrous, carbonaceous chlorite-biotite-muscovite-quartz slate, phyllite, or schist; contains thin beds of quartzite and only sparse layers of punky-weathering limestone. Shown south of the Pomfret dome where rocks typical of the Gile Mountain Formation are absent, and near Randolph. Part of the Connecticut Valley Trough.
Gray to pink, medium- to coarse-grained garnet-muscovite-biotite granite and pegmatite, undifferentiated. Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Light-greenish-gray to lustrous pale-green chlorite-muscovite-quartz (±chloritoid±garnet±magnetite) phyllite. Unit is locally albitic and contains minor beds of quartzite. Cover rocks of Green Mountain anticlinorium.
Interbedded orangey-tan- to buff-weathering dolostone and bluish-gray to gray mottled dolomitic limestone or calcite marble and calcareous sandstone. In southern Vermont east of the Taconic Range, rocks mapped as Bascom Formation may include unmapped members of the Chipman Formation. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Well-bedded dolostone weathering beige, cream, and buff, with green, red, or gray phyllite, siliceous partings, and thin beds of blue-quartz-pebble conglomerate and quartzite. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Dark-gray to silvery-gray, lustrous, fine-grained carbonaceous quartz-muscovite phyllite and silicic phyllite, and garnet-rich biotite-muscovite-quartz schist; contains millimeter- to centimeter-thick beds of gray quartzite and metasiltstone, and thicker beds of quartz-feldspar grit or quartzite near base. Transition zone into Waits River Formation west of the Guilford dome consists of as much as 5 percent beds of punky limestone. Part of the Connecticut Valley Trough.
Dark-tan- to rusty-tan-weathering, garnet-muscovite-biotite-quartz-plagioclase gneiss and rusty schist, locally containing abundant chloritized garnet; lustrous yellowish-grayish-green phyllonitic retrograde varieties contain chloritoid-chlorite and relict garnet (red dot overprint). Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
A heterogeneous unit consisting of granitic and granodioritic and aplite biotitic microcline-rich gneisses, highly gneissic and locally migmatitic, occurring in the southern part of the Green Mountain massif. U-Pb zircon TIMS age of 1,221±4 Ma, no. 12 (Ratcliffe and others, 1991; Aleinikoff and others, 2011) obtained from Londonderry. Unit intrudes rocks of South Londonderry Igneous Suite. Stratton Mountain Intrusive Suite (Middle Mesoproterozoic) (1,244±8 Ma to 1,221±4 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Dark-gray shale with thin discontinuous beds of crossbedded and graded dolomitic siltstone. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Steel-gray-weathering, light-gray, massive calcitic dolostone grading upward into darker, more fissile calcitic dolostone containing white quartz knots near top; unit locally brecciated. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Reddish-brown, pebbly, thin- to thick-bedded sandstone, orangey-gray- and buff-weathering well-bedded dolostone, and reddish-brown-weathering dolomitic quartzite. Unit discontinuous in southern Vermont. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Light-green to gray, lustrous, chlorite±chloritoid-muscovite-quartz phyllite and greenish-gray metasiltstone. Rocks of the Dorset Mountain slice (includes Dorset Mountain proper and Mount Equinox, southward to West Mountain near Bennington). Part of the Taconic Allochthon.
Light-gray, medium-grained, quartz-rich biotite-muscovite granite. Has distinctly more potassium feldspar and is lighter gray than rocks of the East Barre plutons. Part of other plutons of the New Hampshire Plutonic Suite.
Predominantly light-gray- to white- and bluish-gray-streaked calcite marble and massive white- and green-streaked calcite marble. Locally contains intermediate dolostone and gray limestone beds. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Light-gray- to whitish-gray-weathering, massive to thickly bedded medium-grained biotite-white albite-quartz granofels; locally is a medium-gray, finer grained, more biotite-rich albitic quartz schist of gneissic aspect. Eastern flank of the Green Mountain massif and eastern domes.
Laminated black slate with thin orange dolostone beds; includes massive dolostones mapped as Saxe Brook Formation by others in the Highgate area. Cover rocks of the Saint Albans area.
Light-grayish-green, fine-grained, chlorite-muscovite-quartz phyllite or schist and quartzite; white quartzofeldspathic layers alternate with green chloritic phyllitic layers; locally albitic. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Dark-bluish-gray-weathering, thinly bedded dark-gray to black granular limestone; locally grades upward into sooty- weathering shaly limestone beds rich in fragments of the trilobite Cryptolithus. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts). Also part of the Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Dark-gray siliceous shale and phyllite containing thin beds of bluish-gray argillaceous limestone and minor beds of gray to tan quartzite. Grades into limy shales of the Stony Point Formation. Unit mapped west of the Taconic allochthon, and northwest of the Sudbury slice. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Gray- to light-brownish-gray-weathering, massive to bedded muscovite-biotite-chlorite metawacke, conglomerate, and blue-quartz pebbly phyllite, wacke and feldspathic quartzite. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Light-gray to whitish-gray, fine-grained biotite trondhjemitic gneiss, locally containing abundant magnetite. U-Pb zircon SHRIMP age of 1,342 Ma, no. 6B (Ratcliffe and others, 1991; Aleinikoff and others, 2011). South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Thick-bedded, ankeritic, micaceous, and feldspathic metasandstones interlayered with subordinate dark-gray metapelite. Metasandstone beds commonly are rusty weathering and up to 4 m thick; calc-silicate lenses locally present. Part of the Connecticut Valley Trough.
Almost-white to dark-gray, locally pink, medium- to coarse-grained hypidiomorphic, granular, biotite-muscovite-microcline-plagioclase granite; accessories include apatite, sphene, pyrite, and magnetite. Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Binary and biotite granite and granodiorite, undifferentiated. Includes small dikes labeled Dg. Part of the New Hampshire Plutonic Suite.
Chalky-white to light-gray-weathering, medium- to coarse-grained biotite metatrondhjemite and aplite (Y1rta). Dated sample with U-Pb zircon SHRIMP age of 1,367±16 Ma, no. 3 (Ratcliffe and others, 1991; Aleinikoff and others, 2011) from crest of Bromley Mountain; U-Pb zircon age of 1,348±3 Ma, no. 6 (Ratcliffe and others, 1991). South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-gray to dark-gray, medium- to coarse-grained, massive, biotite-clotted, hornblende-quartz monzodiorite, minor granodiorite, and granite. Rb/Sr whole-rock age of 390±14 Ma (Ayuso and Arth, 1992). Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Buff-streaked, dark-bluish-gray, thinly bedded and well-foliated dolomitic limestone, shown above the Champlain thrust south of Middlebury. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Interlayered grayish-green and rusty-weathering black quartzose phyllite, similar to dark carbonaceous phyllites of the Ottauquechee Formation (Co). Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Dark-gray to black, fine-grained slate and phyllite, interbedded with thinly laminated bluish-black fine-grained limestone, limestone conglomerate. Unit is interbedded near the base with green phyllite and sooty-punky-weathering calcitic quartz wacke and limestone of the Browns Pond Formation, which is shown separately where mapped. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Gray- to bluish-gray, fine- to medium-grained, thinly bedded calcareous metasandstone, quartzose metalimestone, and fissile, laminated calcareous metasandstone and phyllite. Part of the Connecticut Valley Trough.
Medium-gray to black calcareous slate. Cover rocks of the Saint Albans area.
Dark-gray slate and phyllite containing sparse to moderately abundant beds of light-gray, fine-grained metasandstone and metasiltstone, 1 mm to 1 cm thick. Part of the Connecticut Valley Trough.
Largely metabasalt and minor metasedimentary rocks consisting of massive, fine-grained, dark-green metabasalt flows, pillow basalt, vesicular basalt composed of albite, epidote, chlorite (±actinolite); and interbedded phyllitic grits, feldspathic quartzite, chloritic metawacke, and basaltic tuffaceous metasedimentary rocks, all similar to rocks of the Pinnacle Formation. Volcanics are alkalic to transitional metabasalts. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Gray, thinly bedded dolomitic sandstone, grading upward into dolomitic limestone or mottled dolomitic marble. In southern Vermont east of the Taconic Range, unit is not recognized and may appear as sandy zones within rocks mapped as the Shelburne Marble. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
A western zone of medium- to fine-grained biotite-muscovite granite and minor hornblende-biotite tonalite and an eastern, more melanocratic zone of biotite-hornblende quartz monzonite like that in the Nulhegan pluton, as well as biotite granodiorite. Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Medium-dark-gray to grayish-black lustrous slate, phyllite, and schist containing sparse to moderately abundant 1-mm to- 5-cm-thick beds of light-gray, fine-grained metasandstone and metasiltstone, commonly pyritiferous and calcareous. Some graded beds. Gradational contact with Dco above and Dir below. Interpreted to be correlative with the Meetinghouse Slate Member of the Gile Mountain Formation. Part of the Connecticut Valley Trough.
Light-gray to pink, medium- to very coarse grained, massive, miarolitic garnet-muscovite peraluminous leucogranite. Pegmatitic main zone. Rb/Sr whole-rock age of 376±9 Ma (Ayuso and Arth, 1992). Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Thin, light-gray beds of vitreous quartzite and crossbedded sandy dolostone. Unit discontinuous in southern Vermont. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Same description as Hortonville Formation - Dark-gray siliceous shale and phyllite containing thin beds of bluish-gray argillaceous limestone and minor beds of gray to tan quartzite. Grades into limy shales of the Stony Point Formation. Tectonically shredded, silty varieties near and on Whipstock Hill constitute the Whipstock Breccia Member of Potter (1972) (Oww). Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Light-gray to whitish-gray-weathering, medium-grained biotite-quartz-plagioclase gneiss flecked with coarse biotite. Contains numerous lenses of fine-grained amphibolite similar to amphibolites associated with calc-silicate rocks of the type Mount Holly Complex in Mount Holly, rather than coarser grained dioritic gneiss associated with the Cole Pond and Rawsonville gneisses. U-Pb zircon SHRIMP age of 1,383±13 Ma, no. 2 (Ratcliffe and others, 1991; Aleinikoff and others, 2011). South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Lustrous, silvery-green to bluish-gray, fine- to medium-grained, white mica-chloritoid-quartz-chlorite schist and phyllite, locally with minor garnet and magnetite porphyroblasts (CZap). Distinctive chlorite streaks and 1-cm rusty needles of altered kyanite are common. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Light-gray, medium-grained, massive quartz-sericite-chlorite-albite metawacke, gray to grayish-green magnetite-chlorite-muscovite-quartz schist, and phyllite or pebbly phyllite, locally rich in magnetite. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Light-gray to pink, medium- to coarse-grained, massive, seriate to porphyritic granodiorite and granite. Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Pale-greenish-gray, lustrous and nonlustrous chlorite-muscovite feldspathic schist and schistose granofels. Local richly garnetiferous variant (Omgt). Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Interbedded feldspathic quartzite within unit CZsa. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Dull-white and whitish-gray-weathering, and pale-green and gray, thinly bedded to laminated slate and phyllite. Has distinctive beds, 1 cm to several centimeters thick, of siliceous argillite and metasiltstone and locally abundant thin beds of micritic black limestone near the base, interbedded with dark slate. Contains graptolites ranging from Ibexian to Whiterockian (Berry, 1961). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Medium- to dark-gray carbonaceous phyllite, gray slate, and metasiltstone, locally containing light-gray, medium- to thick-bedded quartzite and dolomitic quartzite (CZbq). Unit resembles rocks of the Netop Formation but lacks the distinctive lenses and pods of bluish-gray dolostone of the Netop on Dorset Mountain, although lenses of whitish quartzite are present. Rocks of the Dorset Mountain slice (includes Dorset Mountain proper and Mount Equinox, southward to West Mountain near Bennington). Part of the Taconic Allochthon.
Dark-gray to coaly-black, fine-grained plagioclase-muscovite-quartz schist and metawacke, shown southeast of Springfield; in part correlative with staurolite-grade rocks mapped as Littleton Formation (Dl) flanking the Vernon dome (shown as DSwb/Dl). Part of the Connecticut Valley Trough.
Light-gray to tan, micaceous, locally calcareous metasandstone and slate or metamudstone in beds a few centimeters to tens of centimeters thick. Graded bedding common. Interpreted to be correlative with the Gile Mountain Formation. Part of the Connecticut Valley Trough.
Light-pinkish-gray to gray, very coarse grained to medium-grained and mylonitic biotite-plagioclase-quartz-microcline augen gneiss; locally has large ovoidal relict microcline with rapakivi rims and intrusive breccia containing xenoliths of gneissic units of the Mount Holly Complex. Restricted to the Chester and Athens domes, occurring in the core as well as in fault slivers along the eastern and western margins, and tectonically intercalated with rocks of the Mount Holly Complex and the Hoosac Formation. U-Pb zircon upper-intercept ages of 945±7 Ma, no. 17, and 955±5 Ma, no. 18 (Karabinos and Aleinikoff, 1990). Cardinal Brook Intrusive Suite (965±4 Ma to 945±7 Ma). Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Heterogeneous unit consisting of rusty- to tan-weathering flaggy feldspathic quartzite, tan-weathering quartz phyllite, and feldspathic quartzite. Unit interfingers to the north with rocks of the Tyson Formation and to the east with rocks of the Hoosac Formation. Cover rocks of the Southern Green Mountains.
Light-gray to creamy-white-weathering fine-grained limestone, orangey-buff-weathering dolostone, and reddish-streaked (hematite) calcite marble. Chipman Formation (mapped south of Wings Point). Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Dark-rusty-grayish-brown-weathering, graphitic garnet-plagioclase-biotite-quartz (±sillimanite) schist; rusty-weathering blue-quartz-ribbed quartz schist; and garnet quartzite and rusty-weathering layers of sulfidic calc-silicate rock. Exposed in southernmost part of Green Mountain massif. Distinctive quartz ribbing decreases northward where more aluminous, less quartzofeldspathic rocks are mapped as Y2rs. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Same description as Hortonville Formation - Dark-gray siliceous shale and phyllite containing thin beds of bluish-gray argillaceous limestone and minor beds of gray to tan quartzite. Grades into limy shales of the Stony Point Formation. Unit mapped along east side of the Taconic allochthon south to Bennington. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Light-gray and pinkish-gray to yellowish-gray, massive, medium-grained plagioclase granitic gneiss, and migmatite-veined biotite-plagioclase gneiss. Occurs prominently in Jamaica, in Andover in the Chester dome, and in Weston where it appears to form an integral part of Y1,2bg, but also locally appears to be intrusive. A mixed rock of uncertain origin. U-Pb zircon SHRIMP age of 1,326±4 Ma, no. 8 (Aleinikoff and others, 2011), suggests affinity with metamorphic and igneous events associated with the Middle Mesoproterozoic Ludlow Mountain and Proctor Hill granodiorite gneisses of the South Londonderry Igneous Suite. Age of migmatization is younger than 1,326 Ma. Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Dark-greenish-gray to medium-bluish-gray metamorphosed andesitic and basaltic tuff, crystal tuff, and tuff breccia; minor pillow lava. Commonly contains plagioclase and (or) altered mafic phenocrysts. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Black slate and gray phyllite exposed on Woodlawn and Tinmouth Mountains in Pawlet and Tinmouth Townships, after usage of Shumaker and Thompson (1967). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Locally contains a mappable brown-weathering, gray to brown argillaceous quartzite member. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Rusty-weathering, dark-gray biotite-muscovite-quartz (±garnet) schist, carbonaceous schist, and gray, splintery-fractured, biotitic sulfidic quartz schist. Contains layers of rusty-weathering amphibolite, coticule, and vitreous quartzite (Ombq). A prominent zone that extends from the north end of the Chester dome and near Proctorsville southward to near Townshend contains abundant ultramafic rocks (CZu). Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Silvery-blue, medium- to coarse-grained chlorite-muscovite-quartz schist (±garnet±kyanite±chloritoid); contains characteristic spangly muscovite and elongated knots of quartz and layers of pinkish coticule, exposed in the Worcester Mountains. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Light-gray to tan, fine-grained albite-chlorite-sericite-quartz phyllitic quartzite interlayered with light-greenish-gray quartzofeldspathic granofels and dark-gray phyllite. Contains numerous boudinaged, massive to foliated, dark-green metamorphosed mafic dikes and sills. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Hetero-geneous unit consisting of medium-grained biotite-microcline-plagioclase gneiss and pinkish-gray, medium- to coarse-grained microcline-perthite granitic gneiss. Interpreted as intrusive granitic rock older than Y3 rocks of Chittenden Intrusive Suite. Stratton Mountain Intrusive Suite (Middle Mesoproterozoic) (1,244±8 Ma to 1,221±4 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Thickly bedded, “beeswax-scored,” orangey-beige-weathering, yellowish-gray to light-bluish-gray dolostone, dark-gray fine-grained to aphanitic dolostone, and minor beds of bluish-gray limestone. Transitions eastward into the Beldens Member with addition of limestone beds. Equivalent to Providence Island Dolostone (Ofcpi). Chipman Formation (mapped south of Wings Point). Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Light-gray to pinkish-gray, biotite-plagioclase-microcline megacrystic granite and augen gneiss; rapakivi texture locally preserved. Unit occurs in the Rayponda and Sadawga domes. Cardinal Brook Intrusive Suite (965±4 Ma to 945±7 Ma). Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Dark-gray to grayish-black, rusty-weathering sulfidic slate and phyllite interlayered with felsic volcanic rocks and tuffs, and amphibolite (Opa). Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Predominantly very dark green to black, finely foliated biotite-plagioclase amphibolite to dark-green to light- greenish-gray, chlorite-plagioclase-ankerite greenstone and interlayered gray biotitic feldspathic volcaniclastic rock and feldspathic quartzite. Amphibolites have transitional basalt to MORB compositions; greenstones have MORB compositions. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks. Rowe Schist: Mapped in southern Vermont where the uppermost part is continuous with amphibolites, schists, and feldspathic schists of the Rowe Schist of Massachusetts. These upper units are continuous with rocks of the Stowe Formation to the north. Units in the middle and lowermost structural positions (above the Hoosac Formation) are in a similar structural position as rocks of the Ottauquechee and Pinney Hollow Formations, although structural continuity and correlations with the Ottauquechee and Pinney Hollow Formations are uncertain owing to extensive structural duplication by thrust faulting and folding.
Massive, coarse-grained hornblende-plagioclase gneiss and granofels; finely foliated hornblende-plagioclase amphibolite; actinolite-epidote-chlorite greenstone. Part of the Connecticut Valley Trough.
Light-gray to grayish-green chlorite-muscovite-biotite-plagioclase-quartz schist, conspicuous sprays of hornblende, and biotite-hornblende-plagioclase granofels. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Quartz monzonite. Rb/Sr whole-rock age of 390±14 Ma (Ayuso and Arth, 1992). Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Pale-reddish-brown to light-gray-weathering, medium- and fine-grained, massive to thickly bedded, olive-green to gray micaceous quartz-feldspar graywacke and siltstone, locally containing coarse detrital muscovite, biotite, and autoclastic slate chips. Resembles finer grained parts of the Rensselaer Graywacke Member of the Nassau Formation (of Potter, 1972), and the Bird Mountain Grit (of Dale, 1900). Unit interfingers with and grades laterally into the Mettawee slate facies. In the Mt. Anthony area is shown as CZnb (Bomoseen Member of the Nassau Formation of Potter, 1972). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Gray to grayish-green, biotite-chlorite-quartz-pebble phyllite; albitic metawacke is similar to metawacke member of the Pinnacle Formation but more thinly bedded and contains less metawacke. Albitic biotite-(chlorite)-quartz granofels and wacke locally present. Eastern and western flank of the Green Mountain massif.
Black to dark-gray, sulfidic to nonsulfidic, carbonaceous, fine-grained, well-foliated biotite-muscovite-quartz phyllite; contains pods and thin beds of medium-dark-gray and gray-and-white-mottled dolostone, thin beds of ankeritic quartzite, and, in upper part, rhythmically layered gray quartzite, limestone breccia and laminated silicic phyllite. Dolostone contains Middle Ordovician conodonts (Ibexian to mid-Whiterockian at West Bridgewater and Whiterockian at Buels Gore and West Bolton (Ratcliffe and others, 1999; Thompson and others, 2002). Cover rocks north of the Lincoln Mountain massif.
Black arenaceous slate with dolomite horizons; interbedded dolostone and sandstone breccia in a dolostone matrix; and massive dolostone with thin sandstone beds. Cover rocks of the Saint Albans area.
Pale-green to dark-green, lustrous, magnetite-chlorite-muscovite-quartz phyllite and schist, highly tectonically laminated near larger ultramafic bodies (CZu). Unit typical of lustrous chloritic schists of the Stowe Formation farther north. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks. Rowe Schist: Mapped in southern Vermont where the uppermost part is continuous with amphibolites, schists, and feldspathic schists of the Rowe Schist of Massachusetts. These upper units are continuous with rocks of the Stowe Formation to the north. Units in the middle and lowermost structural positions (above the Hoosac Formation) are in a similar structural position as rocks of the Ottauquechee and Pinney Hollow Formations, although structural continuity and correlations with the Ottauquechee and Pinney Hollow Formations are uncertain owing to extensive structural duplication by thrust faulting and folding.
Predominantly medium-dark-gray to lustrous-tan, fine-grained garnet-biotite-muscovite phyllite and carbonaceous phyllite; contains layers of dark-gray quartzite, coticule, and ironstone, locally mapped separately. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Part of unit CZs local areas rich in metadiabase dikes. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Predominantly dark-gray to grayish-green quartz-chlorite-(biotite)-muscovite phyllite; contains 1- to 2-cm-thick beds of dark-gray metasiltstone and quartzite, and thicker beds of dark-bluish-gray vitreous quartzite, grayish-green to light-yellowish-green sericite phyllite (felsic tuffs) and cobble to boulder conglomerate, and greenstone. Mapped north of the Braintree Intrusive Complex and near Brattleboro. Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Coal-black, lustrous, rusty- to non-rusty-weathering, biotite-muscovite-plagioclase-quartz schist and phyllite, containing lenses of white laminated quartzite as beds and discoidal boudins. Eastern flank of the Green Mountain massif and eastern domes.
Light-gray, tan-weathering, mica-speckled, massive to thin-bedded quartz-plagioclase wacke interbedded with dark-gray carbonaceous slate. Contains distinctive autoclastic chips of gray slate, fragments of dacitic to andesitic volcanics, and subangular clasts of dark-gray quartz and oligoclase. Interbedded black slates contain graptolites of the C. bicornis Biozone (see Webby and others, 2004, fig. 2.1) (lower to middle Mohawkian). Interpreted as uncomformable on rocks as old as the Hatch Hill Formation and possibly the West Castleton Formation of the allochthon. Unit is indistinguishable from beds in the Austin Glen Graywacke (after Potter, 1972) (Oag) interpreted as synorogenic autochthonous rocks. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Light-gray to medium-gray, very coarse grained biotite-plagioclase-microcline rapakivi granite; contains large megacrysts of microcline perthite having rims of plagioclase that contain inclusions of biotite and garnet. Unit includes lesser irregular dikes and segregations of hornblende-biotite ferrodiorite and ferromonzonite. U-Pb zircon upper-intercept age of 962±1 Ma, no. 20 (revised from Karabinos and Aleinikoff, 1990). Cardinal Brook Intrusive Suite (965±4 Ma to 945±7 Ma). Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Includes light-pale-green chloritic ankeritic greenstone; black, and fine-grained hornblende-plagioclase (±garnet±epidote) amphibolite. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-gray, medium- to coarse-grained, massive, epidote-biotite-muscovite porphyritic granodiorite and minor tonalite. Rb/Sr whole-rock isochron age of 370±17 Ma (Ayuso and Arth, 1992). Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Dark-gray slate interlayered with thin beds of light-gray, fine-grained micaceous and feldspathic metasandstone (typically ribby weathering). Abruptly graded beds <1 cm to 30 cm thick are locally common as is channeling and, in places, soft-sediment deformation. Commonly sulfidic and rusty weathering. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Predominantly greenish-gray to pale-lustrous-green chlorite-muscovite-quartz phyllite; and green and purple, bedded and mottled phyllite. Locally contains boudins and thin beds of limestone and pods of pinkish-gray to cream-white dolostone, and minor quartzite. Unit interfingers with the West Castleton Formation above and laterally grades into the Bomoseen Graywacke Member. Also shown as CZnm (Mettawee Member of the Nassau Formation of Potter, 1972). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Dark-green to black plagioclase-biotite-hornblende (±quartz) amphibolite, epidote amphibolite, and ankeritic-chlorite-magnetite-plagioclase (albite) greenstone. Shows all gradations from massive but well-foliated metabasalt to well-bedded basaltic volcaniclastic rock and volcanic metawacke. Cover rocks of Green Mountain anticlinorium.
Predominantly green, purple and purplish-red, chloritic hematitic slate and phyllite, massive to thinly bedded. Has rare thin beds of white vitreous quartzite and contains abundant chloritoid. Underlies the Bird Mountain Grit (of Dale, 1900) and grades into the green slate of the Mettawee slate facies in the Bull Formation, probably in part correlative with the green phyllite member of the Netop Formation (CZngs) of the Dorset Mountain slice. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Pinkish-gray to cream-colored, medium- to coarse-grained magnetite-microcline-perthite-biotite granite. Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Gray to pinkish-gray, gneissoid magnetite-biotite-microcline-perthite granodiorite, and locally microcline megacrystic gneissic granite, well-foliated and highly variable in composition, having aplitic and hornblende-rich reaction zones (Y2pha) where in contact with calc-silicate rocks. Crosscuts all paragneiss units; is a thoroughly gneissic rock. Correlated with the Ludlow Mountain granodiorite gneiss. South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Rusty-weathering, medium- to dark-gray, black albite-biotite-quartz schist and granofels, marked by large spangles of muscovite and weathered-out pits of dolomite or ankerite. Eastern flank of the Green Mountain massif and eastern domes.
Dark-green to black, massive, medium- to coarse-grained, layered albite-epidote-hornblende amphibolite; possibly is a meta-intrusive. Exposed in the Worcester Mountains. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Foliated biotite and (or) hornblende granite; locally diorite and lesser amounts of gabbro. Where present, potassium feldspar is microcline. Contact aureole is in the Albee Formation. U-Pb zircon ages of 442±4 Ma, no. 30 (Moench and Aleinikoff, 2003), and 444.1±2.1 Ma, no. 29 (Rankin and Tucker, 2009); and U-Pb sphene age of 443±3 Ma, no. 31 (Moench and Aleinikoff, 2003). Part of the Highlandcroft Plutonic Suite: Epizonal to mesozonal, foliated and metamorphosed (greenschist facies) plutons exposed northwest of the Ammonoosuc fault. Compositions range from granite to diorite to lesser amounts of gabbro. Part of the Bronson Hill arch intrusive rocks.
Medium- to coarse-grained hornblende dioritic-appearing gneiss. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Greenish-gray feldspathic garnet schist; grades into Omfs. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Upper part of CZfd consists of orangey-tan- to brown-weathering quartz-pebble dolostone and dolomitic crossbedded feldspathic metasandstone; lower part of CZfd largely cream- to beige-weathering massive dolostone. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Light-gray to whitish-gray, fine-grained, magnetite trondhjemitic gneiss and aplitic trondhjemite, intricately intrusive into layered paragneisses of the Chester dome; contains xenoliths of more mafic gneiss. U-Pb zircon SHRIMP age of 1,372±11 Ma, no. 4 (Aleinikoff and others, 2011). Similar fine-grained magnetite aplitic gneisses exposed in the Green Mountain massif are associated with tonalitic gneisses on Torment Hill, Weston. South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Lustrous, green, ilmenite-chlorite-chloritoid-garnet-muscovite-quartz (±paragonite) schist; resembles Pinney Hollow Formation but lacks amphibolite. Aluminous schists at Devils Den and aluminous rocks of the Cavendish Formation may be correlative. Eastern flank of the Green Mountain massif and eastern domes.
Gray, massively bedded fossiliferous limestone. Part of the Chazy Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts). Also part of the Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Predominantly light-gray to whitish-weathering, massive to gneissic hornblende-biotite tonalite and biotite-muscovite-quartz-plagioclase trondhjemite; includes rare hornblendite, metadiabase, and metapyroxenite as small stocks, inclusions, and dikes. U-Pb zircon SHRIMP age of 496±8 Ma north of Proctorsville, no. 23 (Aleinikoff and others, 2011); U-Pb zircon age of 471.4±3.7 Ma south of Bethel, no. 26 (Karabinos and others, 1998). North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Rusty-grayish-brown-weathering, locally splintery-fractured, dark-gray to steel-gray biotite-quartz-feldspathic schist and quartzite and interbedded carbonaceous, small-garnet papery muscovite phyllite and schist similar to Ochs. Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Tan to rusty-brown or gray, thinly layered garnet-biotite quartzite and schistose quartzite associated with aluminous schists and calc-silicate rocks or interbedded within biotite-quartz-plagioclase paragneiss. Unit probably occurs at various stratigraphic levels; may be Early Mesoproterozoic in part (Y1q). Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-gray to dark-gray, medium- to coarse-grained, massive, biotite-clotted, hornblende-quartz monzodiorite, minor granodiorite, and granite. Rb/Sr whole-rock age of 390±14 Ma (Ayuso and Arth, 1992). Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Dove-gray-weathering, black to dark- gray, fine-grained poorly fossiliferous limestone. Distinguished from the Middlebury Limestone with difficulty, especially in the area west of the Sudbury slice. Part of the Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts). Rocks of the Laurentian Margin. Also part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Light-gray to cream-colored fine-grained calcite marble, and thin dolomitic layers, locally crossbedded; may occur as lenses at several positions within the Beldens Member. Chipman Formation (mapped south of Wings Point). Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Dark-green to black, hornblende-plagioclase (±garnet±epidote) amphibolite and grayish-green epidote-plagioclase ankeritic greenstone; grades into epidote-quartz-plagioclase volcaniclastic wacke. Occurs as lenses at multiple stratigraphic levels. Lower layers are transitional and alkalic metabasalts; higher units are typical midocean ridge basalt (MORB)-type metabasalts. Eastern flank of the Green Mountain massif and eastern domes.
Dark-grayish-green, fine-grained quartz-hornblende-plagioclase amphibolite, locally garnetiferous, and medium-grained hornblende-plagioclase amphibolite. Occurs with belts of calc-silicate rocks and as lenses within biotite-quartz-plagioclase paragneiss. Unit probably includes both meta-igneous and metasedimentary rocks intercalated throughout the Early and Middle Mesoproterozoic-age rocks of the Mount Holly Complex. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-gray laminated quartzite and vitreous quartzite interbedded with gray phyllite and schist. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light- to dark-gray and steel-blue to apple-green, fine- grained hornblende-chlorite-plagioclase amphibolite, locally containing significant calcite and pyrite and interlayered felsic layers of metatrondhjemite or metadacite. Similar in part to the mixed gneiss facies (Onbm). North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Brown to white-weathering, green, massive, moderately to fully serpentinized dunite and peridotite and schistose serpentinite; rusty-weathering, medium-grained talc-carbonate rock and quartz-carbonate (magnesite) rock. Part of Ultramafic rocks: occur as tectonic slivers and olistoliths in blocks within the Hazens Notch, Ottauquechee, Stowe, Rowe, and Moretown Formations. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Silvery-grayish-green to light-gray, muscovite-biotite (chlorite)-plagioclase-quartz schist and granofels. Part of the Connecticut Valley Trough.
Predominantly light-gray and pinkish-gray, coarse-grained dolostone and cherty dolostone. Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Heterogeneous unit consisting of coarse-grained, gray- to rusty-brown-weathering garnet-biotite-muscovite-quartz schist, gray albitic biotite-quartz granofels, well-bedded light-gray to steel-gray biotite, minor epidote-magnetite-actinolite-chlorite feldspathic wacke, and, near base, grayish-green laminated chlorite-muscovite-albite granofels and phyllite. Unit mapped in Hancock and Ripton in part as lateral equivalent of the Tyson Formation to the south and the Underhill Formation to the north. Eastern flank of the Green Mountain massif and eastern domes.
White, light-gray- and green-banded, medium-grained, well-layered epidote-white mica-quartz-albite (±garnet±magnetite) gneiss with plagioclase and polycrystalline quartz porphyroblasts. Green, chloritic layers 2 to 10 cm thick also contain chlorite pseudomorphs after garnet. Gneiss is similar to gneiss at the base of the Belvidere Mountain Structural Complex. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Gray limestones, fossiliferous limestones, and dolostones. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
A heterogeneous unit of interlayered and interfingering metamorphosed volcanic, volcaniclastic, and sedimentary rocks. Compositions range from basalt to sodic rhyolite. Fragmental rocks dominate (tuff to tuff breccia), but include sparse mafic pillow lava and felsic lava. Sedimentary protoliths include dark-gray sulfidic shale, ironstone, siltstone, graywacke, volcanic conglomerate, and rare limestone. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Dark-gray to gray, rusty-weathering, well-laminated tourmaline-biotite-muscovite-quartz phyllite containing thin beds of laminated quartzite. Resembles dark phyllite of the Moosalamoo Formation (CZmp), with which it is in part correlative. Unit interfingers to the north with rocks of the Tyson Formation and to the east with rocks of the Hoosac Formation. Cover rocks of the Southern Green Mountains.
Coarse-grained hornblende-plagioclase (±quartz) dioritic gneiss and gabbroic gneiss mapped in the Londonderry area, where it is interpreted as metagabbro and has a U-Pb zircon SHRIMP age of 1,393±9 Ma, no. 1 (Aleinikoff and others, 2011). South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-pinkish-gray-weathering, biotite-microcline-perthite or porphyritic rapakivi granite and pegmatitic granite; where deformed is a mylonitic augen gneiss. U-Pb zircon upper-intercept age of 965±4 Ma, no. 19 (Karabinos and Aleinikoff, 1990). Cardinal Brook Intrusive Suite (965±4 Ma to 945±7 Ma). Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Tan to light-bluish-gray, brown-weathering, medium- to coarse-grained, equigranular to porphyritic foliated granodiorite composed of quartz, plagioclase, perthite, microcline, biotite, and sericite. Part of the Lake Memphremagog Intrusive Suite (425±3 Ma to 418.5±2 Ma).
Light-gray to whitish-gray-weathering, magnetite-biotite-microcline-quartz-plagioclase metatrondhjemite to granodioritic gneiss; intrudes paragneiss units of the Chester dome. U-Pb zircon SHRIMP age of 1,370±11 Ma, no. 5 (Aleinikoff and others, 2011). South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Outer zone of quartz gabbro and quartz diorite. Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Silvery-green to rusty-tan, fine-grained chlorite-quartz-sericite (±garnet±chloritoid±allanite) schist and phyllite. Resembles green phyllites of the Pinney Hollow Formation (CZph) and Mount Abraham Forma-tion (CZa) and chloritic phyllite (CZtg) of the Tyson Formation. Cover rocks north of the Lincoln Mountain massif.
Heterogeneous unit consisting mainly of dark-gray to medium-light-gray-weathering, white-plagioclase-studded schist, gray slabby quartz-rich muscovite (±garnet) schist, and layers of dark-gray biotitic quartzite and metawacke. Eastern flank of the Green Mountain massif and eastern domes.
Light-gray to cream-weathering, massive to gneissic, hornblende-biotite and muscovite-biotite metatrondhjemite and metatonalite. Forms a thick, sill-like intrusive extending northward from South Newfane, where it intrudes metavolcanics (Ochv) of the Cram Hill Formation. U-Pb zircon SHRIMP age of 502±4 Ma, no. 22 (Aleinikoff and others, 2011). North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-green to medium-green, massive, epidote-ilmenite-sphene-chlorite-hornblende-plagioclase amphibolite, marked by coarse hornblende and abundant phenocrysts of plagioclase. North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Tan to gray phyllitic metawacke composed of rounded to angular grains of quartz, blue quartz, albite, and traces of detrital rock fragments in a fine-grained matrix of quartz, sericite, and chlorite. Feldspathic metawacke is common; quartz grains range in size from 0.5 mm to 0.5 cm. Conglomerate and breccia occur locally at The Knob (northwest of Lake Eden) and just north of the Lowell-Westfield town line. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Massive to poorly layered, highly lineated, light-tannish-gray to grayish-green, medium-grained, granulose, epidote-magnetite-biotite (chlorite)-muscovite-albite-quartz gneiss, veined with magnetite; spots of ankerite and clots of chlorite after original amphibole, pyroxene, or garnet are common. Highly altered rock is perhaps metasomatic and related to 1,170- to 1,120-Ma period of granitic intrusions. Unit shows all gradations from pinkish-gray biotite-quartz-plagioclase gneiss having centimeter-thick veins of garnet-bearing albitic micropegmatite, to nonlayered albitic granulose white gneiss. Occurs in central Green Mountain massif from Plymouth to Shrewsbury, on Robinson Hill, and along the eastern margin of the Green Mountain massif east of Rutland. Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Gray to whitish-gray, coarse-grained biotite-microcline megacrystic granite and monzogranitic gneiss; passes locally into more equigranular granitic gneiss (Y3Ag) and locally into extensive areas of biotite pegmatoid granitic gneiss (Y3Apg), locally muscovite-bearing. Enclaves of metasedimentary units in these granites and associated gneisses are locally albitized and enriched in magnetite; enclaves of highly aluminous altered rocks now contain restites of chloritoid and abundant sericite. U-Pb zircon ages of 1,119±3.3 Ma (no. 15) and 1,121±1.4 Ma (no. 14) determined on samples near Sherburne Center and on Telegraph Hill east of Chittenden Reservoir by Karabinos and Aleinikoff (1990). Chittenden Intrusive Suite (1,149±8 Ma to 1,119±3 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Heterogeneous composite intrusive well-layered unit consisting of biotite and hornblende metatrondhjemite, garnet-hornblende-plagioclase amphibolite, and metadiabase dikes; locally called Ruger Hill facies (Onr) in the Spring Hill syncline (Ratcliffe and Armstrong, 2001). Layering thickness ranges from 5 cm to 1 m. Unit may be in part metavolcanic as well as intrusive. Resembles well-layered undated felsic and mafic volcanics intercalated with metasediments of the Cram Hill Formation (Ochv). North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Lustrous to rusty-weathering biotite-muscovite (±chloritoid) schist and retrograde coarse-garnet schist; probably is the retrograde equivalent of charnockitic garnet-rich feldspathic quartz gneisses of the eastern Adirondacks. Locally contains mappable quartzite, garnet quartzite, calc-silicate gneiss, and marbles, mapped separately. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Heterogeneous unit consists of dark-green hornblende-diopside rock or pale-green diopside rock; hornblende-calcite-diopside knotted rock; and rusty-weathering, beige scapolite-quartz-plagioclase gneiss, tremolite-phlogopite schist, and diopside quartzite. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Predominantly light- to medium-gray and grayish-green phyllite and metasiltstone. The Netop Formation may be in part equivalent in age and facies to parts of the West Castleton and Hatch Hill Formations, but may extend lower and into the Neoproterozoic. Rocks of the Dorset Mountain slice (includes Dorset Mountain proper and Mount Equinox, southward to West Mountain near Bennington). Part of the Taconic Allochthon.
Light-gray to tan, thinly bedded quartzite in beds 2 to 10 cm thick, exposed north of the Chester dome and south of Springfield; contains detrital zircon having Grenvillian provenance. Part of the Connecticut Valley Trough.
Rusty-weathering, gray to grayish-green, chlorite-muscovite-quartz phyllite and minor beds of pebbly-quartz metawacke. Eastern and western flank of the Green Mountain massif.
Mainly yellowish-green, lustrous, biotite-chlorite-muscovite-plagioclase-quartz-garnet schist, distinguished by large garnets and coarse cross-biotite. Typical of rocks within the Stowe Formation elsewhere. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks. Rowe Schist: Mapped in southern Vermont where the uppermost part is continuous with amphibolites, schists, and feldspathic schists of the Rowe Schist of Massachusetts. These upper units are continuous with rocks of the Stowe Formation to the north. Units in the middle and lowermost structural positions (above the Hoosac Formation) are in a similar structural position as rocks of the Ottauquechee and Pinney Hollow Formations, although structural continuity and correlations with the Ottauquechee and Pinney Hollow Formations are uncertain owing to extensive structural duplication by thrust faulting and folding.
Medium-dark-gray to lustrous silvery-gray garnet-biotite-muscovite-plagioclase-quartz schist and feldspathic garnet schist; associated with CZhs member which it laterally replaces. Eastern flank of the Green Mountain massif and eastern domes.
Tan- to dark-gray-weathering, carbonaceous, medium- to coarse-grained chlorite-plagioclase-muscovite-quartz schist and interbedded tan, gray, and bluish-gray quartzite. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Pale-greenish-gray to yellowish-greenish-gray, chlorite-muscovite-quartz phyllite and schist; locally contains beds of pebbly metawacke and magnetite phyllite. Similar to but finer grained than the metawacke and phyllite member of the Pinnacle Formation (CZps). Eastern and western flank of the Green Mountain massif.
Light-gray, coarse-grained, biotite-microcline megacrystic to even-grained granite gneiss closely associated with 1,149- to 1,120-Ma augen gneisses, in the northern part of the Green Mountain massif. Not distinguishable with certainty from older granitoids of the Stratton Mountain Intrusive Suite of the central and southern Green Mountains. Chittenden Intrusive Suite (1,149±8 Ma to 1,119±3 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Gray and grayish-green, biotite-chlorite-muscovite-albite-quartz schist or phyllite and granofels; contains coticule, locally richly garnetiferous. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Light-gray to medium-dark-gray, rusty-weathering, white-plagioclase-spotted biotite-quartz-plagioclase granofels, massive grayish-green chlorite-spotted, magnetite-studded, biotite-plagioclase-quartz granofels and gneiss, and porphyroclastic plagioclase-augen-biotite mylonite gneiss. Unit less well-bedded than granofels of the Hoosac Formation and lacks amphibolites common in the Hoosac flanking the Chester and Athens domes. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes. The term “Cavendish Formation” is restricted to two belts of rocks within the Chester dome; the larger belt occurs at Cavendish and on Hawks Mountain, and a less extensive belt, containing similar rocks, occurs near Star Hill. An Early Mesoproterozoic age is here favored for the Cavendish Formation on the basis of (1) the presence of deformed pegmatite (Y3Cp) and areas of Felchville Gneiss (Y1fg and Y1fga) within the Cavendish and (2) the marked resemblance of members of the Cavendish to aluminous and feldspathic schists, calc-silicate rocks, and quartzites within the Mount Holly Complex. Similarities to rocks of the Hoosac Formation are also striking and cannot be altogether dismissed; however, the Hoosac Formation lacks pegmatite and contains distinctive and well-bedded albitic granofels, mafic volcanics, and coarse pebble-to-cobble conglomerate, all absent from the Cavendish. Zircons from a quartzite lens in dolomite marble at locality 4 have Pb-Pb ages between 1,290 and 934 Ma and suggest some of the marble of the Cavendish may be younger than the Felchville Gneiss (Karabinos and others, 1999). Retrograded muscovite-rich, chlorite-spotted, chloritoid-bearing quartz phyllites and garnet granofels and other rocks of the Wilcox Formation (Y2wxs) closely resemble those of the Cavendish Formation, as do chloritic-muscovitic retrograded Y2rs members of the Mount Holly Complex in the Green Mountain massif. Dolomite marble, talc-tremolite rock, diopside quartzite, calc-silicate gneiss, and lustrous chlorite-spotted, chlorite-muscovite-rich retrograded garnet gneiss and schist in the Mount Holly Complex contain abundant pegmatite (Y3Cp) on Blue Ridge Mountain in Chittenden and are identical but lower-grade correlatives of the Cavendish Formation. The coarse garnet-staurolite- and kyanite-bearing Gassetts Schist Member is interpreted to be an Acadian remetamorphosed product of the retrograde aluminous rocks now seen throughout the Mount Holly Complex of the Green Mountain massif and in the Pine Hill area.
Light-gray, medium- to fine-grained garnet-biotite-microcline-perthite granodiorite, magnetite-studded white aplite, and kyanite-tourmaline pegmatite. Contains 0.5-cm clots of muscovite possibly after beryl. Intrudes quartzite, lustrous schists (Y1rs), and calc-silicate rocks on Ludlow Mountain. U-Pb zircon SHRIMP age of 1,309±6 Ma, no. 9 (Aleinikoff and others, 2011). South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Dark-gray to black, poorly layered, porphyritic and nonporphyritic ilmenite-epidote-chlorite-plagioclase-hornblende amphibolite. North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-gray to pink, medium- to very coarse grained, massive, miarolitic garnet-muscovite peraluminous leucogranite. Biotitic granodioritic western zone. Rb/Sr whole-rock age of 376±9 Ma (Ayuso and Arth, 1992). Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Dark-gray to silvery-gray, tourmaline-muscovite-biotite-quartz schist and feldspathic schist and quartzite. Occurs on eastern flank of the southern Green Mountain massif; similar in appearance to CZhs of the Hoosac Formation exposed to the east. Unit interfingers to the north with rocks of the Tyson Formation and to the east with rocks of the Hoosac Formation. Cover rocks of the Southern Green Mountains.
Light-buff-tan- weathering, massive to thick-bedded, fine-grained dark-gray dolostone; has “beeswax-scored” surfaces; contains thin layers of fossiliferous bluish-gray limestone (largely equivalent to the Bridport Member of the Chipman Formation, north of Orwell). Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Occurs at different stratigraphic levels. Includes dark-gray and white layered metadacite and meta-andesite, gray- to tan-weathering blue-quartz phenocrystic metadacitic agglomerate, and grayish-green fragmental metadacitic and meta-andesite breccia. Similar to the volcanic agglomerate (Omwhv) within the Whetstone Hill Member of the Moretown Formation. A similar felsic layer interlayered within the Cram Hill Formation has a U-Pb zircon SHRIMP age of 483±3 Ma, no. 25 (Aleinikoff and others, 2011). Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Dark- to light-gray, massively bedded fossiliferous limestone and calcareous sandstone. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts). Also part of the Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Light-greenish-gray, feldspathic chlorite-actinolite greenstone and bedded andesitic to basaltic tuff and amphibolite, associated with ironstone, coticule, and minor pods of dolostone. Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-gray to medium-dark-gray, porphyritic biotite-microcline-perthite granodioritic gneiss and pegmatite. Strongly deformed, lineated, and saturated with less deformed later pegmatite; grades outward into a migmatitic border exhibiting decreasing concentration of microcline megacrysts. Forms a single large intrusive mass on College Hill in Jamaica and west of Stratton Mountain; truncates structure in older gneisses. U-Pb zircon TIMS age of 1,244±8 Ma, no. 11 (Ratcliffe and others, 1991; Aleinikoff and others, 2011). Stratton Mountain Intrusive Suite (Middle Mesoproterozoic) (1,244±8 Ma to 1,221±4 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Abundant, foliated to weakly foliated, metatholeiitic mafic dikes; some sheeted. Shown as overprint. Part of the Lake Memphremagog Intrusive Suite (425±3 Ma to 418.5±2 Ma).
Dark-gray or green, dull-gray- and rusty-weathering, slabby, well-foliated, quartz-rich muscovite-biotite-plagioclase-quartz schist, garnet schist, and splintery chlorite-chloritoid-muscovite-plagioclase (±garnet)-quartz schist, with minor feldspathic biotite gneiss. Unit noncarbonaceous and atypical of the Ottauquechee Formation except for minor layers of carbonaceous schist (CZrc). Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks. Rowe Schist: Mapped in southern Vermont where the uppermost part is continuous with amphibolites, schists, and feldspathic schists of the Rowe Schist of Massachusetts. These upper units are continuous with rocks of the Stowe Formation to the north. Units in the middle and lowermost structural positions (above the Hoosac Formation) are in a similar structural position as rocks of the Ottauquechee and Pinney Hollow Formations, although structural continuity and correlations with the Ottauquechee and Pinney Hollow Formations are uncertain owing to extensive structural duplication by thrust faulting and folding.
Dark-gray, carbonaceous garnet-pyrite-sericite-chlorite-quartz phyllite with clasts of siltstone, phyllite, quartzite, and dark-gray slate breccia interbedded with Coburn Hill Metabasalt Member (Ochcv). Unit correlative with the St. Daniel Group of Québec. Part of the Cram Hill Formation of the Newport Center area. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Dark-green, pitted-weathering, foliated mafic schist to massive greenstone containing varying amounts of chlorite, albite, carbonate, epidote, amphibole, and sphene; and amphibolite containing varying amounts of hornblende, actinolite, albite, chlorite, epidote, biotite, magnetite, and sphene. Cover rocks north of the Lincoln Mountain massif.
Thinly laminated but massive-appearing, gray- and brownish-gray- to tan-weathering flaggy biotite-muscovite feldspathic quartzite and phyllitic quartzite. Resembles feldspathic quartzite of the Dalton Formation (CZdfq) and similar quartzite of the Moosalamoo Formation (CZmf) above the Forestdale Formation. Eastern flank of the Green Mountain massif and eastern domes.
Light-tan to gray-weathering, massive to thin-bedded, flaggy, tourmaline-muscovite-feldspar quartzite and interbedded phyllitic quartzite. Unit interfingers to the north with rocks of the Tyson Formation and to the east with rocks of the Hoosac Formation. Cover rocks of the Southern Green Mountains.
Greenish-gray to pink hornblende-biotite quartz syenite. Monadnock Mountain pluton: Composite stock of quartz syenite, syenite granite, and essexite. K-Ar age of 175±4 Ma (Foland and Faul, 1977). Part of the White Mountain Igneous Suite.
Granodioritic to quartz dioritic gneissic border phase of Oobg, perhaps in part metasomatic. Part of the Bronson Hill arch intrusive rocks.
Dark-grayish-green, fine-grained quartz-hornblende-plagioclase amphibolite, locally garnetiferous, and medium-grained hornblende-plagioclase amphibolite. Occurs with belts of calc-silicate rocks and as lenses within biotite-quartz-plagioclase paragneiss. Unit probably includes both meta-igneous and metasedimentary rocks intercalated throughout the Early and Middle Mesoproterozoic-age rocks of the Mount Holly Complex. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Dark-gray, sooty-weathering, splintery sulfidic to non-sulfidic quartz phyllite and pebbly and gritty biotite metawacke. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Silvery-green to grayish-green, garnet (large)- plagioclase-biotite (chlorite)-quartz-muscovite schist. Comparable to garnet schist member of the Rowe Schist in southern Vermont and around the Chester and Athens domes (CZrgs). Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Commonly tan- to yellowish-tan-weathering, coarse- to fine-grained quartz-pebble to -cobble, quartz conglomerate and schistose quartz conglomerate. Locally dark-gray biotite-muscovite-blue-quartz-pebble wacke to conglomerate. Occurs at or near base of unit. Unit interfingers to the north with rocks of the Tyson Formation and to the east with rocks of the Hoosac Formation. Cover rocks of the Southern Green Mountains.
Black to gray, graphitic, quartzose phyllite and schist, with tan-weathering layers and pods of gray dolostone and black quartzite. Cover rocks of the Saint Albans area.
Rusty-weathering, non-graphitic, sulfidic chlorite-muscovite-quartz schist. Cover rocks north of the Lincoln Mountain massif.
Light- to medium-gray, fine-grained micaceous metasandstones that grade upward into subordinate dark-gray slate or phyllite; some rocks are calcareous. Graded sets range in thickness from a few centimeters to about a meter; typically they are 10 to 30 cm thick. Contact with Di gradational. Part of the Connecticut Valley Trough.
Interbedded graded bioclastic limestone, bluish-gray calcareous shale, and laminated shale. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Light-gray to tan, rusty-weathering, laminated sandy muscovite-plagioclase-quartz schist and tan quartzite. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Gray and light-gray-weathering, medium- to coarse-grained biotite-plagioclase-sericite-quartz schist and gneiss, commonly flecked with large cross-biotite. Locally contains coarse garnet. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks. Rowe Schist: Mapped in southern Vermont where the uppermost part is continuous with amphibolites, schists, and feldspathic schists of the Rowe Schist of Massachusetts. These upper units are continuous with rocks of the Stowe Formation to the north. Units in the middle and lowermost structural positions (above the Hoosac Formation) are in a similar structural position as rocks of the Ottauquechee and Pinney Hollow Formations, although structural continuity and correlations with the Ottauquechee and Pinney Hollow Formations are uncertain owing to extensive structural duplication by thrust faulting and folding.
Light-gray to tan and rusty-weathering, fine-grained, well-foliated mylonitic albite-chlorite-muscovite-quartz (±dolomite)-laminated schist. Cover rocks north of the Lincoln Mountain massif.
Light-gray to tan, rusty-weathering, fine- grained quartz-sericite-chlorite-albite phyllite, quartzite, and flinty sulfidic granofels; thin layers of felsite, conglomerate, and breccia occur in the vicinity of Coburn Hill. Paper schist fabric occurs locally on the west side of Coburn Hill. Part of the Cram Hill Formation of the Newport Center area. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Greenish-gray, light-bluish-gray, or medium-bluish-gray metarhyolite tuff, lapilli tuff, tuff breccia, and lava. Generally porphyritic with 5 to 20 percent plagioclase and, in some places, quartz phenocrysts. Generally strongly foliated with waxy sheen on foliation surfaces. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Syenite-porphyrite to sericite-perthite-hornblende-biotite syenite; contains minor fayalite, augite, and quartz; occurs as a partial ring dike in the Little Ascutney stock. Part of the White Mountain Igneous Suite; Ascutney Mountain igneous complex - Consists of two plutons, a partial ring dike, and screens of volcanic rocks. K-Ar ages of 122 to 120 Ma (Foland and Faul, 1977).
Pale-green to light-greenish-gray, chlorite-magnetite-white-albite-spotted-quartz granofels and schist. Eastern flank of the Green Mountain massif and eastern domes.
Medium-dark- to dark-gray slate interlayered with light-gray, fine-grained micaceous quartzite; in southeastern Vermont near the Vernon dome Dl is equated with DSwb and may be older than in the Bradford area. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Dark- to light-gray fossiliferous limestone. Part of the Chazy Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts). Also part of the Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Light-gray to grayish-green, chlorite-biotite-muscovite-plagioclase-quartz schist and fragmental quartz-plagioclase granofels or metatuff. In Springfield, contains a dated metafelsite layer interpreted as a dike cutting the Standing Pond Volcanics, that yielded a U-Pb zircon TIMS age of 423±4 Ma, no. 32 (Aleinikoff and Karabinos, 1990; Hueber and others, 1990). Part of the Connecticut Valley Trough.
Dark-green hornblende-rich biotite-plagioclase (±garnet) amphibolite, epidote-hornblende-plagioclase-quartz amphibolite, and light-grayish-green, rusty-weathering, carbonate-pitted ankerite-magnetite-albite-epidote (plagioclase) feldspathic greenstone and interbedded feldspathic quartzite (CZsg). Locally a mafic basaltic metawacke and interbedded amphibolite. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Calcite-biotite-sphene-albite-actinolite-epidote-chlorite greenstone with dark-green porphyroblasts of actinolitic hornblende. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Gray to silvery-green, sericite-chlorite-quartz phyllite with thin beds of rusty-weathering, pearly-white, fine-grained granofels. Interlayered with Ochuc and Ochsb at the contacts. Mapped locally in the Albany area. Part of the Cram Hill Formation of the Newport Center area. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Medium-light-bluish-gray, medium-bluish-gray, medium-dark-gray, to medium-dark-greenish-gray metasiltstone and phyllite, and medium-gray feldspathic metawacke. Purple tinge common; coticule and magnetite locally abundant. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Light-bluish-gray mottled dolomitic limestone. Chipman Formation (mapped south of Wings Point). Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Medium-gray- to light-gray-weathering, biotite (±hornblende) tonalite gneiss exposed on Torment Hill in Weston; probably correlative with the Baileys Mills tonalitic gneiss or the Felchville trondhjemite facies (Y1fg) of the Chester dome, but undated. South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Thin-bedded to massive dolostone, sandy dolostone, and light-gray limestone; vertical burrows in basal beds; upper beds fossiliferous with black chert. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
A fine-grained facies consisting of white-weathering, muscovite-biotite-microcline-plagioclase aplitic granite locally forms a border facies or thin internal dikes. U-Pb zircon upper-intercept age of 962±1 Ma, no. 20 (revised from Karabinos and Aleinikoff, 1990). Cardinal Brook Intrusive Suite (965±4 Ma to 945±7 Ma). Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Dark-green plagioclase-hornblende (±quartz) amphibolite and rusty-pale-green, punky-weathering ankeritic-chloritic greenstone. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Mafic schist and amphibolite unit. Dark-bluish-gray, fine- to medium-grained, massive to foliated blueschist composed of amphibole (glaucophane, barroisite, and actinolite), epidote, garnet, chlorite with minor magnetite, pyrite, and apatite. Quartz and garnet coticule occur locally. Eclogite occurs locally, delimited by green, medium-grained layers and pods of garnet, omphacite, glaucophane, epidote, quartz, albite, and white mica. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Quartz-pebble and phyllitic-fragment conglomerate, and tan to gray phyllite. Occurs as lenses, locally unconformable with the underlying Stowe Formation at Umbrella Hill; occurs at different stratigraphic levels in the Cram Hill Formation north of Albany. Interbedded with Coburn Hill Metabasalt Member (Ochcv) and phyllite-chip conglomerate and slate conglomerate member (Ochsb) north of Albany. Part of the Cram Hill Formation of the Newport Center area. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-gray to pinkish-gray, biotite-muscovite (±garnet±tourmaline±magnetite) granite pegmatite as crosscutting pods and larger bodies. Albitic garnet-muscovite pegmatite common in metapelitic rocks of the Mount Holly Complex, and especially prominent in the northern and east-central parts of the Green Mountain massif. Assignment of individual pegmatites to Y3C is highly interpretive based on crosscutting of gneissosity and weakly deformed character. Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Gray quartzite and feldspathic quartzite, in part volcaniclastic and locally interbedded with amphibolite. Part of the Connecticut Valley Trough.
Buff-weathering, tan to green, fine-grained massive to thinly bedded quartzite intercalated with green phyllite and schist. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Rusty-brown to silvery-gray, coarse-grained, garnet (large)-muscovite-biotite-hornblende schist and hornblende-fascicule schist. Part of the Connecticut Valley Trough.
Rusty-grayish-brown- to brown-weathering, knubbly coarse-grained magnetite-garnet-hornblende and pyroxene-bearing charnockitic gneiss and garnet-hornblende granite gneiss. Has large polycrystalline aggregates of plagioclase as much as 1.5 cm long, recrystallized from pre-Ottawan phenocrysts (?) of plagioclase. Contains mappable and folded screens of marble, calc-silicate rock (Y2cs), mafic diopside-hypersthene gneiss, and interbedded sillimanite-garnet quartzite (Y2qz). Interpreted as largely intrusive but may contain some charnockitic gneiss of uncertain origin. Rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
Gray, homogeneous, fine- to medium-grained muscovite-biotite granodiorite. U-Pb zircon Sensitive High Resolution Ion Microprobe (SHRIMP) age of 368±4 Ma, no. 47 (Aleinikoff and others, 2011). Part of other plutons of the New Hampshire Plutonic Suite.
Light-tan to whitish-gray, massive vitreous quartzite in beds several meters thick, interlayered with rusty-grayish-brown garnet-muscovitic quartzite and aluminous sericite-muscovite-tourmaline retrograde phyllite. Occurs as a thick unit on Ludlow Mountain, in Okemo State Forest. U-Pb ages of detrital zircons range from 1,359±32 Ma to 1,261±62 Ma, no. 10 (Aleinikoff and others, 2011), and suggest derivation from trondhjemitic gneiss of the South Londonderry Igneous Suite. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-gray, medium-grained, medium- to thick-bedded dolostone, locally cherty. Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Massive to well-bedded chlorite-biotite (±albite)-quartz-pebble, -cobble, and -boulder conglomerate, feldspathic conglomeratic metawacke, and locally a dolomite-cemented feldspathic quartz-pebble conglomerate. Occurs at base and in lower part of the Tyson Formation. Eastern and western flank of the Green Mountain massif.
Pinkish-gray to medium-dark-gray, biotite-magnetite-microcline-plagioclase augen gneiss. U-Pb zircon SHRIMP age of 1,149±8 Ma, no. 13 (Aleinikoff and others, 2011). Unit is associated with minor exposures of metadiorite to tonalitic gneisses; crosscuts a gneissosity in country rocks and may extend northward along eastern limb of Lincoln Mountain massif as unit Y3Ama. Chittenden Intrusive Suite (1,149±8 Ma to 1,119±3 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Thinly bedded carbonate-albite-epidote greenstone and massive magnetite-albite-amphibole-biotite-epidote amphibolite; light- to dark-green, fine- to medium-grained epidote-chlorite albite-amphibole schist; dark-green, coarse-grained, weakly foliated epidote-biotite-albite-amphibole amphibolite. Cover rocks north of the Lincoln Mountain massif.
Bluish-gray, fine-grained metawacke and metasiltstone, perhaps equivalent to the Bomoseen Graywacke Member of the Bull Formation. Rocks of the Dorset Mountain slice (includes Dorset Mountain proper and Mount Equinox, southward to West Mountain near Bennington). Part of the Taconic Allochthon.
Shown locally from Whitehall, N.Y., to Orwell, Vt. Laterally equivalent to Providence Island Dolostone. Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Medium- to coarse-grained augite-hornblende-biotite gabbro infiltrated by hornblende and biotite diorite. Part of the White Mountain Igneous Suite; Little Ascutney stock: A composite gabbro-diorite stock having two (eastern and western) intrusive centers defined by weakly developed igneous foliation. Gabbro is intruded by abundant, poorly defined areas of diorite. Includes two areas of syenite (Kas).
Phyllite and metawacke. Shown east of Rutland. Eastern and western flank of the Green Mountain massif.
Light-greenish-gray to whitish-gray-weathering, massive vitreous quartzite; locally contains quartz-pebble conglomerate and wacke near the base. Unit commonly 5 to 10 m thick but is as much as 65 m thick; occurs as many lenticular quartzites within the Mettawee slate facies in the Bull Formation, not restricted to one horizon. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Greenish-gray to dark-gray, pyritic, locally calcareous phyllite and light-gray, locally pyritic and calcareous, fine- to medium-grained, feldspar-rich metasandstone; some beds punky weathering. Graded grit and conglomerate beds (having cobble-size clasts of quartz and felsite) toward base. Interpreted as transitional between Connecticut Valley and Bronson Hill sequences and correlative with Frontenac Formation. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Dark-gray to black, locally carbonaceous, rusty-brown-weathering biotite-rich quartz schist and dark biotite-albite schist. Eastern and western flank of the Green Mountain massif.
Largely massive, gray-, beige-, and pinkish-gray-weathering dolostone, beds of pebbly quartz dolostone, and pink- to orange-tan-weathering dolostone as lenses in phyllite. Contains beds of bluish-gray and whitish-gray vitreous quartzite. Similar to dolostone of the Forestdale Formation (CZfd). Eastern and western flank of the Green Mountain massif.
Tan-weathering, gray, well-bedded and crossbedded laminated quartzite and dolostone; sandy beds weather to a woody-grained surface texture. Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Pale-tannish-gray- to purplish-gray-weathering, phyllitic metadacitic volcanic breccia, agglomerate, and grayish-green fragmental meta-andesitic breccia; may occur at several levels. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-gray, yellowish-gray- to buff- weathering quartzose dolostone, pebbly dolomitic quartzite, and interbedded quartzite. Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Dark-medium-gray biotite-plagioclase-quartz granofels and grayish-green chlorite-plagioclase-quartz granofels; contains thin layers of ankerite-epidote greenstone, ankerite-spotted feldspathic granofels, and coticule. Locally hornblende rich at higher metamorphic grade. Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Local lenses of white to pale-gray quartzite, quartz-albite granofels, quartz-granule chlorite (±biotite) metawacke. Cover rocks north of the Lincoln Mountain massif.
Rusty-weathering and pitted, dark-green greenstone with laminae and splotches of calcareous material; locally interbedded with calcareous metagraywacke. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Metamorphosed gray siltstone, quartzite, volcanogenic chert, and ironstone, all typically containing coticule and magnetite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Chalky-white to light-gray-weathering, medium- to coarse-grained aplite. Dated sample with U-Pb zircon SHRIMP age of 1,367±16 Ma, no. 3 (Ratcliffe and others, 1991; Aleinikoff and others, 2011) from crest of Bromley Mountain; U-Pb zircon age of 1,348±3 Ma, no. 6 (Ratcliffe and others, 1991). South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Greenish-gray, pink-tinged, weakly foliated, coarse-grained to porphyritic biotite granite of the Fairlee pluton. U-Pb zircon age of 410±5 Ma, no. 42 (Moench and Aleinikoff, 2003). Part of the Bronson Hill arch intrusive rocks.
Rusty-gray- to yellowish-brown-weathering, lustrous, non-carbonaceous, well-foliated chlorite-quartz-muscovite (±plagioclase) schist. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks. Rowe Schist: Mapped in southern Vermont where the uppermost part is continuous with amphibolites, schists, and feldspathic schists of the Rowe Schist of Massachusetts. These upper units are continuous with rocks of the Stowe Formation to the north. Units in the middle and lowermost structural positions (above the Hoosac Formation) are in a similar structural position as rocks of the Ottauquechee and Pinney Hollow Formations, although structural continuity and correlations with the Ottauquechee and Pinney Hollow Formations are uncertain owing to extensive structural duplication by thrust faulting and folding.
Buff to cream-colored massive dolomite and dolomitic sandstone, containing prominent zone of massive and specular hematite near top at Sheldon. Cover rocks north of the Lincoln Mountain massif.
Grayish-green, chlorite-biotite-plagioclase-quartz granofels and schist containing abundant fine layers of pinkish-gray small-garnet quartzite and coticule. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Pale-reddish-brown to light-gray-weathering, medium- and fine-grained, massive to thickly bedded, olive-green to gray micaceous quartz-feldspar graywacke and siltstone, locally containing coarse detrital muscovite, biotite, and autoclastic slate chips. Resembles finer grained parts of the Rensselaer Graywacke Member of the Nassau Formation (of Potter, 1972), and the Bird Mountain Grit (of Dale, 1900). Unit interfingers with and grades laterally into the Mettawee slate facies. In the Mt. Anthony area is shown as CZnb (Bomoseen Member of the Nassau Formation of Potter, 1972). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Gray to medium-dark-gray, biotite-rich metatonalite gneiss, having irregular screens, and xenoliths of more mafic hornblende-biotite tonalite or diorite gneiss. U-Pb zircon SHRIMP age of 1,321±9 Ma, no. 7 (Ratcliffe and others, 1991; Aleinikoff and others, 2011). South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Massive beds of white to buff dolostone. Cover rocks of the Saint Albans area.
Dark-gray to coaly-black, fine-grained plagioclase-muscovite-quartz schist and metawacke, shown southeast of Springfield; in part correlative with staurolite-grade rocks mapped as Littleton Formation (Dl) flanking the Vernon dome (shown as DSwb/Dl). Part of the Connecticut Valley Trough.
Gray, thin-bedded to massive sandstone and fossiliferous limestone. Part of the Chazy Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts). Also part of the Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Dolomite, and dolomite breccia composed of angular clasts of dolostone, sandstone, and chert in a buff to gray quartzose dolostone. Cover rocks of the Saint Albans area.
Beds of quartzose limestone. Part of the Connecticut Valley Trough.
Dark-gray to black, sulfidic biotite-plagioclase-quartz schist, commonly interbedded with or adjacent to amphibolite and greenstone member (CZpha); locally is a silvery-gray sulfidic biotite phyllite. Cover rocks of Green Mountain anticlinorium.
Green, fine-grained schist composed of chlorite, actinolite, albite, and epidote with biotite, calcite, sericite, quartz, sphene, pyrite, and magnetite; includes homogeneous schistose greenstone, albitic greenstone, and massive banded greenstone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Metamorphosed diorite, trondhjemite, and diabase, consisting of massive to foliated, light-gray to grayish-green, chalky-weathering diorite with xenoliths of green phyllite and trondhjemite; and massive, tan-weathering, medium- to coarse-grained trondhjemite with xenoliths of diabase. Numerous crosscutting quartz-feldspar veinlets show in relief on the weathering surface. Unit intrudes Cram Hill Formation. U-Pb zircon SHRIMP age of 425±3 Ma, no. 39 (Aleinikoff and others, 2011). Part of the Lake Memphremagog Intrusive Suite (425±3 Ma to 418.5±2 Ma).
Olive-drab-weathering, dark-green, fine-grained greenstone with remnant plagioclase feldspar phenocrysts up to 1.5 cm in diameter. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Dark-gray, fine-grained carbonaceous biotite-muscovite-quartz (±garnet) phyllite and schist. Occurs west of Montpelier. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Tan to whitish-gray vitreous quartzite and minor blue-quartz-pebble quartzite. Unit interfingers to the north with rocks of the Tyson Formation and to the east with rocks of the Hoosac Formation. Cover rocks of the Southern Green Mountains.
Interbedded dark-gray and grayish-green chlorite-muscovite-quartz-knotted albitic phyllite, containing pods of bluish-gray dolostone. (Correlation with West Bridgewater Formation uncertain.) Mapped only in the area west of Granville. Cover rocks north of the Lincoln Mountain massif.
Dark-gray, sooty- and rusty-weathering, sulfidic biotite-muscovite-plagioclase-quartz schist and granofels; is a lateral variant of Omwh. Contains layers of rusty-weathering amphibolite and dark-gray quartzite. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Undated light-gray biotite granite gneiss containing abundant rose-colored zircon also is confined to the Pine Hill slice. Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-gray to white, very fine grained microcline-plagioclase-quartz (±magnetite) aplitic gneiss; contains sparing amounts of biotite, and secondary muscovite. Unit interpreted to be border facies of Y2lgg. Y2ap is similar aplitic gneiss, but is not in contact with either Y2lgg or Y2phg. Exposed on Ludlow Mountain. South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Dark-gray to greenish-gray and whitish-gray, massive chlorite-quartz wacke, pebble conglomerate, and purplish-gray hematitic lithic wacke. Unit is rich in fragmental plagioclase, phosphatic nodules, fragments of gray quartzite, and purple and green slate chips. Interpreted as a coarse-grained variant of part of the Zion Hill Quartzite Member, well exposed in and around Bird Mountain. Unit resembles in stratigraphic position and lithology the Rensselaer Graywacke Member of the Nassau Formation (of Potter, 1972) in the Bennington area (CZnr). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
White to yellowish-gray quartz-pebble conglomerate and conglomeratic quartzite, having clasts of milky-white quartz as much as 2.5 cm in diameter in a white to tan quartzite matrix, in beds 0.5 to 1 m thick; and yellowish-gray to light-gray phyllitic quartzite, quartz-pebble to -granule phyllite, and steel-gray to tan vitreous quartzite in beds as much as 5 m thick. Part of the Connecticut Valley Trough.
Weakly foliated, light-gray to whitish-gray, garnet-biotite-muscovite granite, minor pegmatite, and aplite dikes (Dg). Rb/Sr muscovite age of 383±7 Ma (Naylor, 1971) and a U-Pb zircon upper- intercept age of 364±4 Ma, no. 48 (Aleinikoff and others, 2011). Devonian granitic rocks of southern Vermont. Part of the New Hampshire Plutonic Suite.
Light-grayish-brown- to tan-weathering biotite-muscovite feldspathic quartzite and muscovitic quartz schist. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
A highly heterogeneous unit, distinguished from Y?cms by its generally rusty-weathering, nonlustrous appearance and by the abundance of large albite crystals, conspicuous large plates of muscovite and biotite, and abundant clinozoisite. Locally contains fresh garnet as inclusions in albite, or abundant totally retrograded chlorite-sericite clots after original highly poikiloblastic garnet. Near the contacts with Y1fga, abundant sills of granitic gneiss, plagioclase-tourmaline veins and highly albitic, very coarse grained schist occur. Unit is interbedded near its base with either garnet-muscovite-quartz-plagioclase quartzite (Y2q) or a fine-grained, black hornblende-garnet amphibolite (Y2a) or calc-silicate rock (Y2cs), all of the Mount Holly Complex and containing pegmatite (Y3Cp). Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes. Unit is part of the Problematic rocks at Devils Den in Weston and Danby areas: Near Devils Den and Moses Pond includes albitic biotite-muscovite schist, chloritoid-chlorite-muscovite (±garnet) schist, dolomite marble and minor quartzite which resemble rocks of the Tyson Formation, and retrograde varieties of the paragneisses of the Mount Holly Complex. Because these rocks are structurally compatible with Grenvillian or older folds in the Mount Holly Complex and are transitional into rocks of the Mount Holly Complex, a Mesoproterozoic age is favored. Nevertheless the resemblance to rocks of the Tyson Formation is striking.
Metamorphosed sedimentary breccia interlayered with dark-gray slate and micaceous siltstone. Clasts include light-colored, fine-grained metasandstone and metasiltstone of the Albee Formation, dark-gray or greenish-gray slate, and coticule-bearing metasiltstone and chert as well as sparse quartz pebbles. Matrix consists of fine-grained metasandstone, metasiltstone, or dark-gray or greenish-gray slate. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Contains basal limestone, locally referred to as the Whipple Marble Member. Unit mapped along east side of the Taconic allochthon south to Bennington. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Conglomerate with dolostone and sandstone clasts in a calcareous sandy matrix. Cover rocks of the Saint Albans area.
Highly variable unit. Includes white, coarse-grained calcite marble; beige to gray, medium- to coarse-grained phlogopite-tremolite-dolomite-quartz-(±talc) marble; greenish actinolite-dolomite-calcite marble; phlogopite-diopside-scapolite-calcite-dolomite marble; and minor quartzite, diopside quartzite, and schistose bluish-gray marble. Contains pods, stringers, and larger masses of granite pegmatite and interlayered aplitic gneiss. Marble and calc-silicate rocks are identical to units (Y2cs) within the biotite-quartz-plagioclase paragneiss member (Y1,2bg) of the Mount Holly Complex of the Green Mountain massif and eastern domes. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes. The term “Cavendish Formation” is restricted to two belts of rocks within the Chester dome; the larger belt occurs at Cavendish and on Hawks Mountain, and a less extensive belt, containing similar rocks, occurs near Star Hill. An Early Mesoproterozoic age is here favored for the Cavendish Formation on the basis of (1) the presence of deformed pegmatite (Y3Cp) and areas of Felchville Gneiss (Y1fg and Y1fga) within the Cavendish and (2) the marked resemblance of members of the Cavendish to aluminous and feldspathic schists, calc-silicate rocks, and quartzites within the Mount Holly Complex. Similarities to rocks of the Hoosac Formation are also striking and cannot be altogether dismissed; however, the Hoosac Formation lacks pegmatite and contains distinctive and well-bedded albitic granofels, mafic volcanics, and coarse pebble-to-cobble conglomerate, all absent from the Cavendish. Zircons from a quartzite lens in dolomite marble at locality 4 have Pb-Pb ages between 1,290 and 934 Ma and suggest some of the marble of the Cavendish may be younger than the Felchville Gneiss (Karabinos and others, 1999). Retrograded muscovite-rich, chlorite-spotted, chloritoid-bearing quartz phyllites and garnet granofels and other rocks of the Wilcox Formation (Y2wxs) closely resemble those of the Cavendish Formation, as do chloritic-muscovitic retrograded Y2rs members of the Mount Holly Complex in the Green Mountain massif. Dolomite marble, talc-tremolite rock, diopside quartzite, calc-silicate gneiss, and lustrous chlorite-spotted, chlorite-muscovite-rich retrograded garnet gneiss and schist in the Mount Holly Complex contain abundant pegmatite (Y3Cp) on Blue Ridge Mountain in Chittenden and are identical but lower-grade correlatives of the Cavendish Formation. The coarse garnet-staurolite- and kyanite-bearing Gassetts Schist Member is interpreted to be an Acadian remetamorphosed product of the retrograde aluminous rocks now seen throughout the Mount Holly Complex of the Green Mountain massif and in the Pine Hill area.
Unit Y2rs locally includes steel-gray-weathering, garnet (small)-quartz-biotite gneiss and quartzite (Y2bgt). Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Gray to dark-gray, biotite-albite-quartz granofels and flaser-bedded tan to gray feldspathic quartzite; the latter resembles similar rocks of the Dalton Formation (CZdfq), whereas the former resembles albitic rocks of the Hoosac Formation (CZhab). Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Light- to medium-gray, medium-grained, biotite-quartz-plagioclase-microcline gneiss; contains microcline augen as much as 4 cm in length. Chittenden Intrusive Suite (1,149±8 Ma to 1,119±3 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-gray, well-foliated subporphyritic biotite (±hornblende)-quartz diorite and trondhjemite gneiss; forms sills in overlying Ammonoosuc Volcanics. Part of the Bronson Hill arch intrusive rocks.
Green, carbonate-albite-epidote-chlorite greenstone. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Equigranular granitic gneiss. Enclaves of metasedimentary units in these granites and associated gneisses are locally albitized and enriched in magnetite; enclaves of highly aluminous altered rocks now contain restites of chloritoid and abundant sericite. U-Pb zircon ages of 1,119±3.3 Ma (no. 15) and 1,121±1.4 Ma (no. 14) determined on samples near Sherburne Center and on Telegraph Hill east of Chittenden Reservoir by Karabinos and Aleinikoff (1990). Chittenden Intrusive Suite (1,149±8 Ma to 1,119±3 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-gray to white, garnet-muscovite-biotite granodiorite at Gassetts quarry, having a U-Pb zircon SHRIMP age of 392±6 Ma, no. 46 (Aleinikoff and others, 2011), from rims on Proterozoic-age cores (J.N. Aleinikoff, USGS, written commun., 2002); and whitish-gray muscovite-rich quartz monzonite and granodiorite, granite pegmatite, and aplite which occur as crosscutting nonfoliated dikes within the core of the domes and as folded and well-foliated dikes on the east and west flanks of the domes; also granite dikes and small stocks of very light gray to white, muscovite-rich, locally garnet-bearing, fine- to medium-grained biotite-muscovite quartz monzonite and granodiorite, locally orbicular, that intrude cover rocks east of the Green Mountain massif from Jamaica to Northfield, including the Liberty Hill locality and the granodiorite stock east of Plymouth. The latter contains inherited zircon with rims having an imprecise SHRIMP age of about 380 to 390 Ma (Aleinikoff and others, 2011); a similar dike south of Plymouth has a U-Pb zircon SHRIMP age of 365±5 Ma, no. 49 (Aleinikoff and others, 2011). These closely resemble undated white granodiorites of the Bethel area and dikes in the Chester and Athens domes; also resemble small dikes of granite, trondhjemite, and quartz monzonite largely west of the Connecti-cut Valley trough. Devonian granitic rocks of southern Vermont. Part of the New Hampshire Plutonic Suite.
White to pinkish-gray, medium-grained plagioclase-microcline-perthite aplitic to pegmatitic granite forms dikes in country rocks and irregular border facies. U-Pb zircon upper-intercept age of 965±4 Ma, no. 19 (Karabinos and Aleinikoff, 1990). Cardinal Brook Intrusive Suite (965±4 Ma to 945±7 Ma). Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Limestone and sandstone clasts in a limestone matrix, interbedded with sandstone. Cover rocks of the Saint Albans area.
Dark-bluish-gray to black, fine-grained vitreous quartzite. Beds are as thick as 30 m or are thin and interbedded with black phyllite. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Deep-maroon and bluish-green-weathering, well-bedded and variegated slate; contains minor centimeter-thick, white-weathering, red and bluish-black cherty layers characteristic of the Mount Merino Formation. Contains graptolites of the C. bicornis Biozone (Berry, 1961). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Light-gray to whitish-gray, fine-grained sericite-quartz-phenocrystic phyllitic metatuff and whitish pyritiferous soda-rhyolite metatuff. Abundant screens and layers occur within mafic rocks of the North River Igneous Suite and at scattered localities north of the Braintree intrusive complex and in the Coburn Hill area. Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Cream-colored, light-gray- to whitish-gray-weathering, coarse-grained chlorite-biotite-muscovite-quartz-plagioclase (±garnet ±hornblende) metatrondhjemite and metatonalite; southern lens near Massachusetts State line is coextensive with trondhjemite in the Hawley Formation. North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Dense, compact hornfels consisting of recognizable but altered schists of the country rock. Shown only around main Ascutney Mountain stock in structural continuity with rocks outside the contact aureole. Locally aluminous rocks of the Waits River Formation contain andalusite, sillimanite, cordierite, pleonaste, and corundum; calcareous pelites contain diopside, quartz-wollastonite, plagioclase, grossular garnet, and scapolite. Part of the White Mountain Igneous Suite; Ascutney Mountain stock; Ascutney Mountain igneous complex - Consists of two plutons, a partial ring dike, and screens of volcanic rocks. K-Ar ages of 122 to 120 Ma (Foland and Faul, 1977).
Hornblende amphibolite and hornblende-plagioclase-quartz granofels; interpreted as metabasaltic and volcaniclastic rocks. Part of the Connecticut Valley Trough.
Dark-gray to black, sooty- to rusty-weathering, splintery-fractured pyritic slate and phyllite and interbedded bluish-gray dolomitic quartzite. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Banded limestone and calcareous slate with local lenses of conglomerate composed of limestone, sandstone, and dolostone clasts in a sandy limestone matrix. Cover rocks of the Saint Albans area.
Gray and greenish-gray, magnetite-chlorite-(biotite)-muscovite-albite-quartz granofels and schist. Similar to gray or green albitic granofels of the Hoosac Formation (CZhab and CZhgab). Eastern and western flank of the Green Mountain massif.
Predominantly chalky-white-weathering, massive biotite tonalite gneiss. Passes laterally into white, fine-grained trondhjemitic aplite near contacts with larger screens of paragneiss. U-Pb zircon Thermal Ionization Mass Spectrometry (TIMS) age of 1329±37 Ma (McLelland and Chiarenzelli, 1990) obtained from exposure 1.5 km west of Austin Hill on the west side of South Bay, west of Whitehall, N.Y. Contains lenses and screens of rusty sulfidic garnet-biotite-feldspar-quartz schist, dark-gray garnet-feldspar quartzite, and calc-silicate gneiss on south end of Austin Hill. Unit interpreted as intrusive into some paragneiss units that are here older than 1328±32 Ma (McLelland and Chiarenzelli, 1990). Rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
Light-gray to grayish-green, laminated, gritty feldspathic chlorite-muscovite-plagioclase-quartz schist. Cover rocks of Green Mountain anticlinorium.
Quartzite and quartz-cobble metaconglomerate. Locally contains quartz-cobble conglomerate with abundant dark-gray phyllite matrix that resembles phyllite of the Littleton Formation. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Poorly sorted, matrix-supported quartz- and gneiss-cobble to boulder conglomerate, locally containing quartzite boulders as large as 3 m in diameter, in a matrix of gray-weathering magnetite-calcite-chlorite-muscovite-biotite-feldspar schist. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Heterogeneous composite intrusive well-layered unit consisting of biotite and hornblende metatrondhjemite, garnet-hornblende-plagioclase amphibolite, and metadiabase dikes; locally called Ruger Hill facies (Onr) in the Spring Hill syncline (Ratcliffe and Armstrong, 2001). Layering thickness ranges from 5 cm to 1 m. Unit may be in part metavolcanic as well as intrusive. Resembles well-layered undated felsic and mafic volcanics intercalated with metasediments of the Cram Hill Formation (Ochv). North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-grayish-brown- to tan-weathering, medium-dark-gray, fine-grained garnet (small)-biotite-muscovite phyllite and schist. Similar to phyllite facies (Omwh) in the Whetstone Hill Member of the Moretown Formation. Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Greenish-gray to light-brownish-gray, medium-grained, weakly foliated metamorphosed tonalite. Primary minerals include quartz, plagioclase, biotite, magnetite, pyrite, and apatite; secondary minerals include chlorite, epidote, sericite, and calcite. Granophyric intergrowths of quartz and plagioclase. U-Pb zircon age of 469±1.5 Ma, no. 27 (Moench and Aleinikoff, 2003). Part of the Highlandcroft Plutonic Suite: Epizonal to mesozonal, foliated and metamorphosed (greenschist facies) plutons exposed northwest of the Ammonoosuc fault. Compositions range from granite to diorite to lesser amounts of gabbro. Part of the Bronson Hill arch intrusive rocks.
On Skitchewaug Mountain, lower conglomerate and granofels. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Dark-gray, rusty-weathering carbonaceous to graphitic schist associated with quartzite and calc-silicate rock near Killington. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Largely carbonate-epidote-albite-chlorite (±actinolite) greenstones. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Feldspathic biotite phyllitic metawacke interlayered with lenses of quartz, feldspar, and gneiss-pebble to -cobble conglomerate. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Brown to white-weathering, green, massive, moderately to fully serpentinized dunite and peridotite and schistose serpentinite; rusty-weathering, medium-grained talc-carbonate rock and quartz-carbonate (magnesite) rock. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Pale-greenish-gray, finely laminated, magnetite-chlorite-biotite feldspathic metasiltstone and pale-greenish-yellow-weathering muscovite-chlorite-quartz phyllite. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-gray to white, fine-grained aplitic granite gneiss as border of Y2gg or as thin dikes or sills in paragneiss units. Stratton Mountain Intrusive Suite (Middle Mesoproterozoic) (1,244±8 Ma to 1,221±4 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Near base contains bluish-gray, granular, smooth-weathering fossiliferous limestone. Unit mapped west of the Taconic allochthon, and northwest of the Sudbury slice. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Light-gray- to beige-weathering massive dolostone and bluish-gray-weathering mottled dolostone breccia and conglomerate, passing upward into more thinly bedded bluish-gray and buff dolostone breccia; dark-gray phyllitic dolostone and limestone in upper part. Correlative in part with boulder and conglomerate beds of the Dunham Dolostone near Rutland and with similar beds in the upper part of the Forestdale Formation. Eastern flank of the Green Mountain massif and eastern domes.
Dark-gray- to sooty-black-weathering siliceous ironstone, magnetite quartzite, garnet quartzite, rusty-weathering amphibolite, coticule, and pods of orangey-gray to pinkish-gray-weathering dolostone. Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Nonfoliated to foliated pegmatitic metatonalite to metagabbro. Part of the Lake Memphremagog Intrusive Suite (425±3 Ma to 418.5±2 Ma).
Light-gray, tan, and dark-gray, well- bedded pebbly quartzite, crossbedded vitreous quartzite, and local conglomerate. Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Rim zone of granodiorite of unit Ddbg. Rb/Sr whole-rock isochron age of 370±17 Ma (Ayuso and Arth, 1992). Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
White-weathering, medium- to dark-gray, foliated and laminated, aphanitic to very fine grained granofels to schist or metatuff, welded tuff, and lithic tuff commonly with a few percent millimeter-size quartz and microcline phenocrysts. U-Pb zircon age of 407.5±3.9 Ma, no. 44 (Rankin and Tucker, 2000). Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Light-gray-, yellowish-gray- to dark-dull-gray-weathering, biotite or muscovite quartzite, feldspathic quartzite, and pebbly muscovitic quartzite, commonly occuring as basal member or as layers in schist member (CZhs). Eastern flank of the Green Mountain massif and eastern domes.
Medium- to coarse-grained biotite-microperthite-orthoclase-albite granite. Part of the White Mountain Igneous Suite; Ascutney Mountain igneous complex - Consists of two plutons, a partial ring dike, and screens of volcanic rocks. K-Ar ages of 122 to 120 Ma (Foland and Faul, 1977).
Light-bluish-gray and white, coarse- and medium-grained calcite-diopside marble and calcite-diopside-talc marble in beds or pods less than 5 m thick, interbedded with or passing laterally into other calc-silicate rock. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Largely a tectonic breccia formed in situ; contains abundant pseudo-pebbles. Part of the Taconic Allochthon. Wildflysch-like conglomerates within the Hortonville, Ira, and Walloomsac Formations occur as local areas of black slate rich in inclusions of quartzite, greenish-gray slate, wacke, and punky-weathering bluish-gray limestone, interpreted as sedimentary breccias, deposited in front of the advancing Taconic allochthon (Upper Ordovician) (Zen, 1961; Potter, 1972; Fisher, 1985). Exposed near the western and northern margin of the allochthon and in the Bennington area at the type Whipstock. Here and at many localities the Forbes Hill and Whipstock breccias are tectonic breccias formed in situ by disruption of thin to thick beds, laminae, and carbonate-quartz-sulfide veins rather than clastic sedimentary rocks. The cleavage and related folding commonly is a late strain-slip cleavage characterized by a strong down-plunge lineation parallel to reclined hingelines of minor folds of foliation and compositional layering. Units are retained although interpretation as sedimentary wildflysch deposits is in part questionable.
Rusty-tan to gray, thinly layered phyllite, tourmaline-biotite-muscovite-quartz phyllite, and quartzite mapped along western flank of the Green Mountain massif in the South Wallingford area. Unit interfingers to the north with rocks of the Tyson Formation and to the east with rocks of the Hoosac Formation. Cover rocks of the Southern Green Mountains.
Light-gray to whitish-gray, coarse-grained muscovite-biotite-quartz-plagioclase metatrondhjemite on the east flank of the Chester dome; similar to Onb, Onnt, and Ontw. North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Inner zone of granite. Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Bluish-black, rusty-weathering, fine-grained albite-sericite-chlorite-quartz schist with pyrite. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-gray quartz-feldspar conglomerate and quartzite. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Dark-gray, medium- to coarse-grained, massive, quartz-biotite-hornblende (±pyroxene) gabbro and diorite. Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
With xenocrysts of calcic andesine and, locally, xenoliths of anorthosite; with increasing percentage of anorthosite component, passes gradationally into anorthositic rocks.
Highly schistose, biotite-muscovite (±chlorite) feldspathic mylonite and mylonitic gneiss mapped near Brandon Gap; in the Pine Hill slice near South Wallingford is mapped as Yur. Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Clasts of limestone, dolostone, sandstone, and chert within beds of black shale and chert. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Magnetite-rich areas of the Albee Formation (OCal) - Shown as an overprint. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Light-gray muscovite-quartz schist and quartz conglomerate and dark-gray carbonaceous, polymict schistose quartz conglomerate, associated with DSwb, DSwb/Dl, DSws, and DSwv southeast of Springfield. Part of the Connecticut Valley Trough.
Dark-grayish-brown-weathering, coarse-grained garnet-biotite-plagioclase-quartz schist. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks. Rowe Schist: Mapped in southern Vermont where the uppermost part is continuous with amphibolites, schists, and feldspathic schists of the Rowe Schist of Massachusetts. These upper units are continuous with rocks of the Stowe Formation to the north. Units in the middle and lowermost structural positions (above the Hoosac Formation) are in a similar structural position as rocks of the Ottauquechee and Pinney Hollow Formations, although structural continuity and correlations with the Ottauquechee and Pinney Hollow Formations are uncertain owing to extensive structural duplication by thrust faulting and folding.
Chloritoid-rich rocks appear gritty owing to distributed porphyroblasts of chloritoid. Unit is locally albitic and contains minor beds of quartzite. Cover rocks of Green Mountain anticlinorium.
Yellowish-gray to light-gray, medium- to coarse-grained magnetite-biotite-mesoperthite granodiorite and granite having a U-Pb zircon SHRIMP age of 421±7 Ma, no. 38 (Aleinikoff and others, 2011). Has mutually intrusive contacts with associated metadiorites. Unmapped dike of Sbg in the layered, mixed felsic and mafic rocks (Onbm) of the North River Igneous Suite at Bridgewater has a U-Pb zircon age of 418±1 Ma, no. 37 (Aleinikoff and Karabinos, 1990). Part of the Lake Memphremagog Intrusive Suite (425±3 Ma to 418.5±2 Ma).
Medium-gray-weathering, porphyritic dikes and sills of fine- to medium-grained hornblende-biotite diorite and quartz diorite, and coarse-grained quartz monzodiorite. Has a U-Pb zircon TIMs age of 419±0.39 Ma, no. 36 (Black and others, 2004). Narrow zone of garnet-biotite-plagioclase-cordierite hornfels in the Moretown Formation postdates dominant foliation (Taconian) in host rocks. Part of the Lake Memphremagog Intrusive Suite (425±3 Ma to 418.5±2 Ma).
Light-gray to yellowish-gray, coarse-grained dolomite-phlogopite-scapolite marble; pyritiferous varieties weather salmon pink to beige. Unit occurs on West Mountain in Chittenden, in Sherburne Center, Weston, and in the Pine Hill slice; is commonly associated with tremolite-talc marble and tremolite-talc schist. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Coarse-grained facies of the Baileys Mills tonalitic gneiss exposed on the northeast flank of the Chester dome. South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Biotite-hornblende (±pyroxene) gabbro and diorite at Robinson Hill in Shrewsbury; exhibits fine-grained chill contact that crosscuts paragneiss units. Unit also in Lincoln Mountain massif and at Brandon Gap; similar rock mapped in the Adirondacks. Chittenden Intrusive Suite (1,149±8 Ma to 1,119±3 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Locally contains light-bluish-gray to whitish-gray calcite marble within dolostone and beneath the calcitic marbles of the overlying Shelburne Marble. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Dark-gray to light-gray, vitreous magnetite quartzite, and coticule. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Greenish-gray laminated albite-metasiltstone. The Netop Formation may be in part equivalent in age and facies to parts of the West Castleton and Hatch Hill Formations, but may extend lower and into the Neoproterozoic. Rocks of the Dorset Mountain slice (includes Dorset Mountain proper and Mount Equinox, southward to West Mountain near Bennington). Part of the Taconic Allochthon.
Light-silvery-green to grayish-green, lustrous muscovite-chlorite-quartz (±garnet±chloritoid±ilmenite) schist and biotite-albite-muscovite-quartz schist. Unit is highly variable both in texture and in composition (from ultrafine-grained phyllonitic schist to medium-grained muscovite-garnet schist). Albitic varieties tend to contain more biotite and less muscovite. Rock is highly retrograded and contains abundant chlorite derived from the breakdown of garnet that contained large anhedral quartz and grains of coarse muscovite and biotite. Robust grains of rutile are abundant. Chloritoid commonly occurs in the fine-grained sericitic matrix but locally is found within large subhedral garnets. The contact with adjacent Y?mfs is gradational and determined by a higher abundance of biotite (commonly chloritized) and albite in Y?mfs near Y?cms. The contact with Y2rs of the Mount Holly Complex is gradational. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes. Unit is part of the Problematic rocks at Devils Den in Weston and Danby areas: Near Devils Den and Moses Pond includes albitic biotite-muscovite schist, chloritoid-chlorite-muscovite (±garnet) schist, dolomite marble and minor quartzite which resemble rocks of the Tyson Formation, and retrograde varieties of the paragneisses of the Mount Holly Complex. Because these rocks are structurally compatible with Grenvillian or older folds in the Mount Holly Complex and are transitional into rocks of the Mount Holly Complex, a Mesoproterozoic age is favored. Nevertheless the resemblance to rocks of the Tyson Formation is striking.
Hornblende-spotted “dioritic” amphibolite. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Metamorphosed limestone, calcareous sandstone, siltstone, and pelite. Some limestone conglomerate and polymict conglomerate with calcareous matrix. Locally equivalent to Madrid and Smalls Falls Formations in Chesterfield, N.H., area. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Potsdam Sandstone (Covey Hill in Quebec)
Medium-grayish-green, medium-grained hornblende-biotite tonalite gneiss, with minor amphibolite. U-Pb zircon TIMS age of 486±3 Ma, no. 24 (Aleinikoff and others, 2011), from 4 km northwest of Brockways Mills, near Bartonsville. North River Igneous Suite (502±4 Ma to 471.4±3.7 Ma): collection of metatonalite, metatrondhjemite, and metabasalt occurring as intrusive dikes, sills, and small stocks, and possibly meta-andesite and metadacitic tuffs. Correlative with extrusive dacitic metavolcanic and meta-andesitic rocks of the Moretown and Cram Hill Formations. Coextensive in part with igneous rocks of the Hawley Formation of Massachusetts. Part of the Volcanic-arc intrusive and volcanic rocks of the North River Igneous Suite of the Rowe-Hawley zone. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Extensive areas of biotite pegmatoid granitic gneiss, locally muscovite-bearing. Enclaves of metasedimentary units in these granites and associated gneisses are locally albitized and enriched in magnetite; enclaves of highly aluminous altered rocks now contain restites of chloritoid and abundant sericite. U-Pb zircon ages of 1,119±3.3 Ma (no. 15) and 1,121±1.4 Ma (no. 14) determined on samples near Sherburne Center and on Telegraph Hill east of Chittenden Reservoir by Karabinos and Aleinikoff (1990). Chittenden Intrusive Suite (1,149±8 Ma to 1,119±3 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-pale-yellowish-green to gray quartzite gneiss containing abundant epidote and locally magnetite, and frosted round grains of quartz associated with diopside-bearing quartzite. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-gray-, cream- or pinkish-gray-weathering, medium- to fine-grained phlogopite-quartz-dolomite marble. Occurs as thin beds in gray albitic granofels member (CZhab); locally contains beds of vitreous to bluish-gray laminated quartzite. Eastern flank of the Green Mountain massif and eastern domes.
Basal limestone member. Tectonically shredded, silty varieties near and on Whipstock Hill constitute the Whipstock Breccia Member of Potter (1972) (Oww). Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Nepheline and sodalite syenite, hornblende syenite. Part of the White Mountain Igneous Suite; Cuttingsville stock - Composite stock and intrusive breccia dikes consisting of augite and hastingsite syenite, nepheline and sodalite syenite, essexite, and monzodiorite. Associated dikes of monchiquite, camptonite, boston-ite, and spessartite. Average of five K-Ar ages 101 Ma; ages range between 103±4 and 99±2 Ma (Armstrong and Stump, 1971).
Light-gray to pink, medium- to very coarse grained, massive, miarolitic garnet-muscovite peraluminous leucogranite. Inner hydrothermally altered zone. Rb/Sr whole-rock age of 376±9 Ma (Ayuso and Arth, 1992). Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.
Undifferentiated Hoosac Formation.
Grayish-brown- to pale-green-weathering, well-laminated, magnetite-studded chloritic metasiltstone; near base contains magnetite-cemented quartz-pebble conglomerate and bedded magnetite quartzite. Directly overlies dolostones of the Forestdale Formation. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Gray or greenish-gray, albite- and magnetite-studded granulose biotite-quartz-plagioclase gneiss, containing chloritized biotite and garnet. Occurs as altered varieties of Y1,2bg near 1,150-Ma intrusive augen gneisses of the Chittenden Intrusive Suite (Y3Ama); in the Lincoln Mountain massif a dark-gray biotite-microcline-chlorite-spotted gneiss contains magnetite grains as much as 1 cm in diameter. Part of the altered rocks adjacent to the Chittenden Intrusive Suite. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Gray to medium-dark-gray, rusty-weathering, carbonaceous albite-chlorite-quartz-muscovite schist, containing porphyroblasts of black albite. Unit resembles gray albitic granofels and schist of the Hoosac Formation (CZhab). Cover rocks north of the Lincoln Mountain massif.
Heterogeneous, thin (<10 m thick) unit of interbedded quartzite, amphibolite, felsic granofels, and phyllite, occurring at the base of the Waits River Formation on the north end of the Chester dome. Interpreted as recycled volcaniclastic rocks derived from the underlying volcanic and intrusive rocks in the Cram Hill Formation. Part of the Connecticut Valley Trough.
Silvery-gray, “pinstriped,” coarse- to medium-grained, blue-quartz-pebble chlorite-biotite-plagioclase-quartz metawacke; locally conglomeratic and rich in epidote. Cover rocks of Green Mountain anticlinorium.
Dark-gray- to rusty-grayish-brown-weathering, sulfidic muscovite-biotite-magnetite gneiss or schist marked by abundant small garnets, biotite, and fine laminae of quartz and plagioclase. Contains thin belts of amphibolite and calc-silicate gneiss. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-green, fine- to medium-grained, massive carbonate-biotite-quartz-sphene-chlorite-actinolite-epidote greenstone with deformed pillows; interfingers with the Umbrella Hill Conglomerate Member (Ochuc) and with phyllite-chip conglomerate (Ochsb). Part of the Cram Hill Formation of the Newport Center area. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Gray to very light gray, vitreous and nonvitreous, massive to thin-bedded quartzite, magnetite and biotite quartzite, and feldspathic quartz-ite, locally interbedded with dolostone. Similar to quartzite in the Forestdale Formation (CZfq). Eastern and western flank of the Green Mountain massif.
Tan to rusty-brown or gray, thinly layered garnet-biotite quartzite and schistose quartzite associated with aluminous schists and calc-silicate rocks or interbedded within biotite-quartz-plagioclase paragneiss. Unit probably occurs at various stratigraphic levels; may be Early Mesoproterozoic in part (Y1q). Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
White, light-gray- and green-banded, fine- to medium-grained, well-layered epidote-white mica-quartz-albite (±garnet±magnetite) gneiss; contains plagioclase and polycrystalline quartz porphyroblasts. The 0.5- to 2-cm-thick layers are defined by variations in the amount of quartz, albite, white mica, and chlorite. Gneiss is similar to gneiss at the base of the Tillotson Peak Structural Complex. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Tan, yellowish-gray-weathering garnet-muscovite quartzite and feldspathic retrograde-garnet quartz gneiss. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Cream-colored to light-bluish-gray, brown-weathering, talc-carbonate schist and talc-cabonate-rich rocks. Part of Ultramafic rocks: occur as tectonic slivers and olistoliths in blocks within the Hazens Notch, Ottauquechee, Stowe, Rowe, and Moretown Formations. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Bluish-gray, fine- to medium-grained albite-horn-blende-epidote-actinolite (±garnet) amphibolite and quartz-bearing amphibolite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Dull-gray, pitted, and bluish-gray dolomitic quartz wacke and quartzite distinguished by small pebbles and grains of dark-blue to black quartz, dacitic rock fragments, and abundant plagioclase. Beds resembling the Eagle Bridge Quartzite may occur at several stratigraphic positions within the black slate and gray phyllite of the West Castleton and Hatch Hill(?) Formations, undifferentiated (Cwcu), and near the base of the Poultney Formation, and probably are not all correlative. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Dark-gray to sooty-black carbonaceous phyllite, interbedded dolostone boulder conglomerate to breccia, and blue- and gray-mottled sulfidic dolostone. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Buff- to gray-weathering vitreous quartzite as much as 6 m thick, containing deeply weathered ovoidal areas of carbonate-cemented quartzite. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Dark-gray to steel-bluish-gray vitreous quartzite in beds as much as 10 m thick but commonly less than 1 m thick. Resembles quartzites of the Ottauquechee Formation (Cobq). Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Dark-green, pitted-weathering, foliated carbonate-albite-chlorite (±magnetite±epidote) greenstone or amphibolite. Cover rocks north of the Lincoln Mountain massif.
Pods, lenses, or zones of thinly bedded limestone (ls), dolostone (d), and limestone conglomerate in the Mettawee slate facies in the Bull Formation, West Castleton Formation, and Hatch Hill Formation. These rocks locally contain Lower Cambrian fossils, but may range in age from Neoproterozoic to Late Cambrian. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Dark-gray, coarse-grained amphibolite and layered amphibolite composed of barroisite, epidote, garnet, actinolite, albite, chlorite, sphene, sericite, biotite, and calcite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Light-gray, fine- grained, and dark-gray, fossiliferous, and platy bluish-gray limestone. Contains upper Ibexian to lower Whiterockian conodonts at the type locality near Sciota School House, in the Benson quadrangle (J.E. Repetski, USGS, written commun., 2004). Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Hornblende-biotite-microperthite granite, gradational into quartz syenite. Monadnock Mountain pluton: Composite stock of quartz syenite, syenite granite, and essexite. K-Ar age of 175±4 Ma (Foland and Faul, 1977). Part of the White Mountain Igneous Suite.
Medium- to coarse-grained, equigranular to porphyritic, muscovite-biotite-microcline-plagioclase metaquartz monzonite; contains garnet, sillimanite-andalusite and cordierite; intrudes rocks of the Rangeley Formation in New Hampshire. U-Pb zircon age of 407±5 Ma, no. 43 (Kohn and others, 1992) at Bellows Falls. Part of the Bronson Hill arch intrusive rocks.
Grayish-tan to light-gray vitreous quartzite and white feldspathic gritty quartzite. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Light-gray, massive, coarse-grained biotite-white albite-quartz granofels like CZhab but containing boulders of pegmatite and of granitic gneiss, and disarticulated beds of albitic granofels as pseudoconglomerate. Eastern flank of the Green Mountain massif and eastern domes.
Light-grayish-tan-weathering, biotite-muscovite-quartz conglomerate and pebbly muscovite quartzite, and dark-medium-gray blue-quartz biotite quartzite and schist. Eastern flank of the Green Mountain massif and eastern domes.
Quartz syenite. Part of the White Mountain Igneous Suite; Cuttingsville stock - Composite stock and intrusive breccia dikes consisting of augite and hastingsite syenite, nepheline and sodalite syenite, essexite, and monzodiorite. Associated dikes of monchiquite, camptonite, boston-ite, and spessartite. Average of five K-Ar ages 101 Ma; ages range between 103±4 and 99±2 Ma (Armstrong and Stump, 1971).
Salt-and-pepper-colored, medium- to coarse-grained quartz-albite-biotite gneiss. Cover rocks north of the Lincoln Mountain massif.
White to gray biotite-oligoclase-microcline Rapakivi granite gneiss containing blue quartz. Intrudes Yb, Ybu.
Gray and grayish-green rocks associated with Whipstock breccia on Whipstock Hill but of uncertain correlation. Part of the Taconic Allochthon.
Within unit Y2phg: aplitic and hornblende-rich reaction zones where in contact with calc-silicate rocks. Crosscuts all paragneiss units; is a thoroughly gneissic rock. Correlated with the Ludlow Mountain granodiorite gneiss. South Londonderry Igneous Suite (Middle and Early Mesoproterozoic) (1,393±9 Ma to 1,309±6 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Dark-green, massive, diopside-hornblende rock, lenses of bluish-gray to gray, medium- to coarse-grained calcite marble and calcite-diopside marble and dolomitic talc-phlogopite-tremolite schist. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Pink to gray, nonfoliated, porphyritic to coarse-grained biotite granite; phenocrysts of potassium feldspar are as large as 2 by 3 cm. U-Pb zircon age of 364±5 Ma, no. 50 (Moench and Aleinikoff, 2003). Part of the Bronson Hill arch intrusive rocks.
Tan- to gray-weathering, quartz-pebble and -cobble conglomerate, feldspathic quartzite and associated slabby, rusty-weathering amphibolite and coticule. Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Lustrous, silvery-green to bluish-gray, fine- to medium-grained, white mica-chloritoid-quartz-chlorite schist and phyllite, locally with minor garnet and magnetite porphyroblasts (CZap). Distinctive chlorite streaks and 1-cm rusty needles of altered kyanite are common. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Light-gray, powdery-weathering, and red, green, and dark-gray, thinly bedded siliceous argillite and mudstone distinguished from the Indian River Slate by abundance of cherty siliceous layers. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Light-greenish-gray to pinkish-gray, well-foliated and well-layered quartz-rich gneiss and more mafic biotite-hornblende-pyroxene-quartz-plagioclase gneiss irregularly distributed within unit. Unit may be in part older than the tonalitic gneiss (Y2bt). Paragneiss. Rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
On Skitchewaug Mountain, upper quartzite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Gray, purplish-gray, and light-gray dacitic to andesitic metavolcanic and metavolcaniclastic rocks, similar to Omwhv. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
White quartzite and tan to light-gray, medium-grained muscovite quartzite locally rich in magnetite. Resembles quartzite of the Tyson Formation (CZtq). Cover rocks north of the Lincoln Mountain massif.
Light-tan to gray, vitreous and non-vitreous quartzite and feldspathic quartzite and quartz conglomerate. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Containing layers of dark-gray biotite-muscovite-quartz phyllite near top. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Very light-bluish-gray to white, medium-grained, muscovite-biotite quartz monzonite, locally orbicular; commercially known as “Bethel white” and similar to the predominantly lighter-colored granitic rocks of southern Vermont. Part of other plutons of the New Hampshire Plutonic Suite.
Unit CZngs locally contains beds of grayish-green vitreous quartzite and quartz-pebble conglomerate, and thin beds of chloritic wacke, all shown as CZngq (unit is in part equivalent to rocks of the Mettawee slate facies and Zion Hill Quartzite Member of the Bull Formation). Rocks of the Dorset Mountain slice (includes Dorset Mountain proper and Mount Equinox, southward to West Mountain near Bennington). Part of the Taconic Allochthon.
Dark-gray quartz-pebble metawacke and gray quartzite and conglomerate at base of the Northfield Formation, south of Springfield. Part of the Connecticut Valley Trough.
Hornblende amphibolite and hornblende-plagioclase-quartz granofels; interpreted as metabasalt and mafic volcaniclastic rock. Part of the Connecticut Valley Trough.
Limestone and sandstone clasts in a quartz sand matrix. Cover rocks of the Saint Albans area.
Sandy dolostone containing limestone clasts, interfingered with sandy dolostone containing dolostone clasts. Cover rocks of the Saint Albans area.
Thin- to thick-bedded calcareous coarse-grained sandstone. Cover rocks of the Saint Albans area.
Pyroxene-biotite-hornblende andesine gabbroic rock grading into quartz syenite. Monadnock Mountain pluton: Composite stock of quartz syenite, syenite granite, and essexite. K-Ar age of 175±4 Ma (Foland and Faul, 1977). Part of the White Mountain Igneous Suite.
Medium- to coarse-grained, foliated, actinolite-chlorite-calcite-epidote retrograded metadiabasic dikes; commonly have relict diabasic texture. Cardinal Brook Intrusive Suite (965±4 Ma to 945±7 Ma). Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Local lenses of garnet schist within the Underhill Formation. Cover rocks north of the Lincoln Mountain massif.
White to pale-green, laminated to massive epidote-calcite-muscovite-quartz-albite metarhyolitic gneiss or schist; is a volcanic or volcaniclastic rock. U-Pb zircon age of 571±5 Ma, no. 21 (Walsh and Aleinikoff, 1999). Contains purplish-gray feldspathic quartzite. Cover rocks of Green Mountain anticlinorium.
Medium-dark-gray to dark-gray, rusty-weathering garnet-biotite-muscovite-quartz-plagioclase schist and granofels; has coarse spangles of muscovite and locally is kyanite rich. Mapped in core of Spring Hill syncline. Part of the metasedimentary host rocks of the North River Igneous Suite. Cram Hill Formation: western part of the Cram Hill Formation is in part correlative with Whetstone Hill Member of the Moretown Formation. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Dark-gray- to sooty-gray-weathering, sulfidic, graphitic biotite-muscovite-plagioclase-quartz schist, containing thin beds of dark-bluish-gray vitreous quartzite. Restricted to minor occurrence in CZrch, along the base of the major amphibolite above CZrch, and within amphibolite at a structurally high position within the Rowe Schist near the Massachusetts State line. Closely resembles rocks typical of the Ottauquechee Formation but at a different structural or stratigraphic level. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks. Rowe Schist: Mapped in southern Vermont where the uppermost part is continuous with amphibolites, schists, and feldspathic schists of the Rowe Schist of Massachusetts. These upper units are continuous with rocks of the Stowe Formation to the north. Units in the middle and lowermost structural positions (above the Hoosac Formation) are in a similar structural position as rocks of the Ottauquechee and Pinney Hollow Formations, although structural continuity and correlations with the Ottauquechee and Pinney Hollow Formations are uncertain owing to extensive structural duplication by thrust faulting and folding.
Dark-gray to black, fine-grained, magnetite-garnet-hornblende-biotite-diopside-plagioclase gneiss, commonly containing beds of dark-gray vitreous magnetite-garnet quartzite, 2 to 5 cm thick, tremolite-pyroxene gneiss, and biotite-rich, rusty-weathering garnet-quartz schist and gray sulfidic sillimanite quartzite. Occurs as screens within tonalitic gneiss and the Pharaoh Mountain Gneiss and is interpreted as paragneisses older than the tonalitic gneiss (Y2bt). Paragneiss. Rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
Lenticular masses of coarse-grained quartzose volcaniclastic grit and cobble metaconglomerate commonly with abundant dark-gray metapelitic matrix (diamictite) interlayered with metasandstone, metapelite, and porphyritic metarhyolite. Grit contains subangular clasts of plagioclase and potassic feldspar as large as 2.5 cm across and larger clasts of dark-gray slate. Conglomerate contains rounded clasts of metarhyolite, fine-grained granitoid, and rare marble, and angular clasts of dark-gray slate. Part of the Connecticut Valley Trough.
Pods, lenses, or zones of thinly bedded limestone (ls), dolostone (d), and limestone conglomerate in the Mettawee slate facies in the Bull Formation, West Castleton Formation, and Hatch Hill Formation. These rocks locally contain Lower Cambrian fossils, but may range in age from Neoproterozoic to Late Cambrian. Includes named units shown locally as the North Brittain Conglomerate member of the West Castleton Formation (Cwcnb), the Bebe Limestone Member of the West Castleton Formation (Cwcbb), and the Castleton Conglomerate (of Shumaker and Thompson, 1967) (Cco). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Interlayered, commonly rusty-weathering quartz-feldspar micaceous granofels and dark-gray mica schist containing porphyroblasts of garnet, staurolite, and kyanite. Calc-silicate lenses common in the granofels; granule and pebble metaconglomerate locally are present. Part of Piermont and other allochthons.
Portion of unit CZbms locally containing light-gray, medium- to thick-bedded quartzite and dolomitic quartzite. Rocks of the Dorset Mountain slice (includes Dorset Mountain proper and Mount Equinox, southward to West Mountain near Bennington). Part of the Taconic Allochthon.
Quartz-sericite phyllite and schist. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Interbedded medium- to dark-gray, moderately rusty weathering, highly contorted, unbedded schist and punky-weathering calcareous granofels or quartzose marble, and pods and stringers of vein quartz.
Well-bedded micaceous quartzite or quartz schist grading upward into light- to dark-gray, carbonaceous aluminous schist in beds 5 to 15 cm thick.
(Shown only in New York State). Medium- to dark-gray and mottled, medium- to thick-bedded dolomitic limestone and buff-weathering dolostone. Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Garnetiferous hornblende schist and minor hornblende amphibolite. Part of the Connecticut Valley Trough.
Pods, lenses, or zones of thinly bedded limestone (ls), dolostone (d), and limestone conglomerate in the Mettawee slate facies in the Bull Formation, West Castleton Formation, and Hatch Hill Formation. These rocks locally contain Lower Cambrian fossils, but may range in age from Neoproterozoic to Late Cambrian. Includes named units shown locally as the North Brittain Conglomerate member of the West Castleton Formation (Cwcnb), the Bebe Limestone Member of the West Castleton Formation (Cwcbb), and the Castleton Conglomerate (of Shumaker and Thompson, 1967) (Cco). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Dark-gray, graphitic quartz phyllite and schist containing minor lenses of limestone.
Thin-bedded muscovite-biotite-garnet-staurolite-kyanite schist and micaceous quartz-feldspar granofels; some calc-silicate lenses and layers. Part of Piermont and other allochthons.
Locally sillimanitic; commonly garnetiferous in and adjacent to Adirondack Highlands.
Silvery-green albite-chlorite-quartz-muscovite (±garnet) schist characterized by coarse muscovite porphyroblasts. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Lustrous, dark-gray to silvery-gray tourmaline-muscovite-biotite-quartz schist and steel-gray muscovitic quartzite. Eastern flank of the Green Mountain massif and eastern domes.
Dark-gray phyllite containing bluish-gray dolostone and tan-weathering to locally mappable gray-weathering dolomitic quartzite. The Netop Formation may be in part equivalent in age and facies to parts of the West Castleton and Hatch Hill Formations, but may extend lower and into the Neoproterozoic. Rocks of the Dorset Mountain slice (includes Dorset Mountain proper and Mount Equinox, southward to West Mountain near Bennington). Part of the Taconic Allochthon.
Gray- to bluish-gray polymict limestone metaconglomerate containing pebbles to cobbles of limestone, pelite, granite, and intermediate to felsic volcanic rocks; also locally occurs in the Northfield Formation. Part of the Connecticut Valley Trough.
Rusty, gray, quartz-albite-mica (-chlorite) schist and gneiss. Locally conglomeratic.
Conglomerate with dolostone and sandstone clasts in a shaly matrix. Cover rocks of the Saint Albans area.
Rusty-weathering sulfidic schist and minor amphibolite older than part of the South Londonderry Igneous Suite. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Pinkish-gray garnet-biotite-albite pegmatite and granitic augen gneiss, distinguished by abundant rose-colored zircon; U-Pb zircon SHRIMP age of 1,037±6 Ma, no. 16 (Aleinikoff and others, 2011). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Frontenac Formation, Graded-bedded metagraywacke and subordinate gray phyllite.
Essexite (alkali gabbro). Part of the White Mountain Igneous Suite; Cuttingsville stock - Composite stock and intrusive breccia dikes consisting of augite and hastingsite syenite, nepheline and sodalite syenite, essexite, and monzodiorite. Associated dikes of monchiquite, camptonite, boston-ite, and spessartite. Average of five K-Ar ages 101 Ma; ages range between 103±4 and 99±2 Ma (Armstrong and Stump, 1971).
Within unit Sr; rusty sulfidic schist occurs in Fall Mountain nappe near Bellows Falls. Part of Piermont and other allochthons.
Light-gray to tannish-white, well-bedded and vitreous steel-gray quartzite interbedded with orangey-tan- and beige-weathering dolostone and thin beds of fossiliferous limestone. Named for occurrences near Root Pond in the Benson quadrangle, but herein extended to include thin lenses of quartzite that occur interbedded at several positions in the Fort Cassin Formation. Interbedded limestones contain upper Ibexian conodonts southwest of Root Pond (J.E. Repetski, USGS, written commun., 2004). Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Layers of gray limestone. Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Heterogeneous unit consisting of ankeritic greenstone, ankeritic or dolomitic muscovite quartzite, bluish-gray calcareous quartzite, and pods of brecciated dolostone. Exposed at Plymouth Five Corners. Rocks of the Rowe-Hawley Zone. Allochthonous cover sequence east of the Green Mountains: rift and drift stage metasedimentary and metavolcanic rocks and tectonic inclusions of ultramafic rocks.
Lustrous muscovite-chlorite-chloritoid or muscovite-chlorite-biotite-clinozoisite retrograde schistose quartzite and large-garnet schist. Resembles a retrograde variety of the Hague Gneiss (of Alling, 1918) (Y2hgn) near Whitehall, N.Y. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Greenish-gray, light-bluish-gray, or medium-bluish-gray metarhyolite tuff, lapilli tuff, tuff breccia, and lava. Generally porphyritic with 5 to 20 percent plagioclase and, in some places, quartz phenocrysts and minor amphibolite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Medium-dark-gray to light-gray diopside-phlogopite-scapolite-calcite marble, phlogopite-tremolite-talc schist, and dark-gray diopside-hornblende (actinolite)-plagioclase calc-silicate gneiss. Paragneiss. Rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
Trachytic to rhyolitic tuffs, and breccias containing fragments of volcanic rocks having trachytic flow structure and layering. Interpreted as volcanic rocks of the edifice. Part of the White Mountain Igneous Suite; Ascutney Mountain igneous complex - Consists of two plutons, a partial ring dike, and screens of volcanic rocks. K-Ar ages of 122 to 120 Ma (Foland and Faul, 1977).
Lens of light-gray- weathering fossiliferous limestone. Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Commonly sulfidic and rusty weathering. Indistinguishable from the Scarritt Member, but crops out in small areas. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Pinkish-gray to light-gray, unfoliated, magnetite-biotite (±tourmaline) granite pegmatite, <1 m to 10 m thick. Crosscuts Ottawan foliation and locally fills narrow, northeast-trending, steeply dipping normal ductile shear zones. Intrusive rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
Silvery-gray, medium-grained schist composed of white mica, quartz, chlorite (±garnet±albite±glaucophane±chloritoid); local centimeter-thick lenses of coticule. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Buff to gray, medium- to coarse-grained, poorly bedded mica-rich schist showing dark-green chlorite clots. Some pinstriped granofels.
Conglomerate consisting of round clasts of orange dolostone in a black arenaceous matrix. Cover rocks of the Saint Albans area.
Hornblende granite occurring as small intrusive masses in Kas. Part of the White Mountain Igneous Suite; Ascutney Mountain igneous complex - Consists of two plutons, a partial ring dike, and screens of volcanic rocks. K-Ar ages of 122 to 120 Ma (Foland and Faul, 1977).
Porphyritic, light-gray, hypabyssal biotite granite and tonalite in sill-like bodies - Contains phenocrysts of euhedral and embayed quartz, euhedral micro-cline with Carlsbad twinning (in granite), plagioclase, and euhedral biotite (±muscovite). Part of other plutons of the New Hampshire Plutonic Suite.
Coarse-grained dark-green diopside (±hornblende±zoisite)-calc-silicate rocks; white talc-tremolite (±dolomite)-calc-silicate schist; and minor quartzite, diopside quartzite, and schistose bluish-gray marble. Contains pods, stringers, and larger masses of granite pegmatite and interlayered aplitic gneiss. Marble and calc-silicate rocks are identical to units (Y2cs) within the biotite-quartz-plagioclase paragneiss member (Y1,2bg) of the Mount Holly Complex of the Green Mountain massif and eastern domes. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes. The term “Cavendish Formation” is restricted to two belts of rocks within the Chester dome; the larger belt occurs at Cavendish and on Hawks Mountain, and a less extensive belt, containing similar rocks, occurs near Star Hill. An Early Mesoproterozoic age is here favored for the Cavendish Formation on the basis of (1) the presence of deformed pegmatite (Y3Cp) and areas of Felchville Gneiss (Y1fg and Y1fga) within the Cavendish and (2) the marked resemblance of members of the Cavendish to aluminous and feldspathic schists, calc-silicate rocks, and quartzites within the Mount Holly Complex. Similarities to rocks of the Hoosac Formation are also striking and cannot be altogether dismissed; however, the Hoosac Formation lacks pegmatite and contains distinctive and well-bedded albitic granofels, mafic volcanics, and coarse pebble-to-cobble conglomerate, all absent from the Cavendish. Zircons from a quartzite lens in dolomite marble at locality 4 have Pb-Pb ages between 1,290 and 934 Ma and suggest some of the marble of the Cavendish may be younger than the Felchville Gneiss (Karabinos and others, 1999). Retrograded muscovite-rich, chlorite-spotted, chloritoid-bearing quartz phyllites and garnet granofels and other rocks of the Wilcox Formation (Y2wxs) closely resemble those of the Cavendish Formation, as do chloritic-muscovitic retrograded Y2rs members of the Mount Holly Complex in the Green Mountain massif. Dolomite marble, talc-tremolite rock, diopside quartzite, calc-silicate gneiss, and lustrous chlorite-spotted, chlorite-muscovite-rich retrograded garnet gneiss and schist in the Mount Holly Complex contain abundant pegmatite (Y3Cp) on Blue Ridge Mountain in Chittenden and are identical but lower-grade correlatives of the Cavendish Formation. The coarse garnet-staurolite- and kyanite-bearing Gassetts Schist Member is interpreted to be an Acadian remetamorphosed product of the retrograde aluminous rocks now seen throughout the Mount Holly Complex of the Green Mountain massif and in the Pine Hill area.
Lenticular masses of metamorphosed quartzose volcaniclastic grit and conglomerate, commonly having abundant dark-gray pelitic matrix interlayered with sandstone, pelite, and porphyritic rhyolite (Dgmr). Conglomerate contains rounded clasts of rhyolite, fine-grained granitoid, and angular clasts of dark-gray slate. Correlative with Halls Stream Grit Member of the Ironbound Mountain Formation (of Myers, 1964) to the north. Part of the Connecticut Valley Trough.
Beds of gritty feldspathic quartzite. Unit mapped in Hancock and Ripton in part as lateral equivalent of the Tyson Formation to the south and the Underhill Formation to the north. Eastern flank of the Green Mountain massif and eastern domes.
Silvery-blue, medium-grained tectonic mélange composed of muscovite schist with minor amounts of chlorite, epidote, albite, and tourmaline; contains fragments and discontinuous lenses of greenstone, coarse-grained amphibolite, and talc phyllite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Boudins of whitish-gray-weathering, bluish-gray quartzite. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Beige, tan, and dark-gray weathering quartzose dolomite marble containing interbeds of black, green and maroon phyllite and punky weathering blue quartz pebble quartzite.
Gray, medium-grained, nonfoliated biotite-muscovite tonalite. Part of other plutons of the New Hampshire Plutonic Suite.
Amphibolite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
A boulder and cobble dolostone conglomerate. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
White to light-powdery-blue-gray dolostone with disseminated grains of quartz and prominent sprays of tremolite in higher-grade areas.
Light-tan to gray, thinly bedded and crossbedded, calcareous and dolomitic siltstone and quartzite in beds similar to the quartzite of the Root Pond Quartzite Member (Ofcrp). Part of the Beekmantown Group. Rocks of the Laurentian Margin. Part of the Adirondack lowlands and Lake Champlain lowlands (west of the Orwell and Champlain thrusts).
Andesite breccia containing xenoliths of Mesoproterozoic gneiss and autoclasts of felsic alkalic and fine-grained mafic rocks. Part of the White Mountain Igneous Suite; Cuttingsville stock - Composite stock and intrusive breccia dikes consisting of augite and hastingsite syenite, nepheline and sodalite syenite, essexite, and monzodiorite. Associated dikes of monchiquite, camptonite, bostonite, and spessartite. Average of five K-Ar ages 101 Ma; ages range between 103±4 and 99±2 Ma (Armstrong and Stump, 1971).
Nassau Formation of Potter (1972) - Rensselaer Graywacke member. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Bright-green and white, fine- to medium-grained, variably foliated calcite-quartz-albite-mariposite-actinolite-tremolite-epidote-zoisite granofels to gneiss. Associated with greenstone and ultramafic rocks in Roxbury. Part of the metasedimentary host rocks of the North River Igneous Suite. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Tan weathering, muscovite-microcline quartzite and feldspathic quartzite rich in black tourmaline, locally includes thin beds of other rock types listed below.
Massive to finely laminated steel-gray calcitic dolomite marble containing a prominent zone of white quartz nodules near top.
Unit is indistinguishable from beds in the Austin Glen Graywacke (after Potter, 1972) (Oag) interpreted as synorogenic autochthonous rocks. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Dark-gray to greenish-gray, very fine grained, ocellar basaltic to medium-grained augite-plagioclase diabasic dikes, occurring as a subvertical northeast-trending discontinuous zone in the center of Bald Mountain. Intrusive rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
Containing beds of amphibolite, aluminous schist, quartzite, and calc-silicate gneiss.
Metagabbro, olivine metagabbro, derived amphibolite.
Interbedded thick feldspathic wackes, tan and green slates, and minor calcareous lenses.
Light-tan to yellowish-gray, massive to well-layered magnetite-garnet quartzite and magnetite-biotite-garnet quartzite in beds as much as 10 m thick. Occurs in two layers, one within or attached to the Hague Gneiss and one within biotite-quartz-plagioclase gneiss (Y2bpg) beneath the Hague Gneiss. The latter is rich in microcline and passes through interbedding into a quartzose facies of Y2bpg. Paragneiss. Rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
Lustrous, soft green, yellowish-green and purple laminated chloritoid-chlorite phyllite (Mettawee Member).
Very light gray, fine-grained porphyritic metafelsite schist or granofels near Maidstone Lake. Groundmass recrystallized to an aggregate of quartz, microcline, plagioclase, biotite, muscovite, and apatite; grain size about 0.05 mm. Relict phenocrysts of embayed quartz, microcline (some in granophyric intergrowths with quartz), and saussuritized plagioclase. U-Pb zircon age of 407.0±3.3 Ma, no. 45 (Rankin and Tucker, 2009). Part of the Connecticut Valley Trough.
White, massive vitreous quartzite.
Gray, slightly rusty, poorly bedded phyllite and schist containing 20 cm to 2 m beds of light-gray, fine-grained quartzite, local punky-brown weathering calcareous granofels or quartzose marble, and pods and stringers of vein quartz.
Black slate of Climacograptus bicornis Biozone on and west of Whipstock Hill, otherwise typical of slates of the Walloomsac Formation shown as Ow. Part of the Taconic Allochthon.
Beige to pinkish-gray-weathering, pyrite-bearing, medium- and fine-grained phlogopite-chlorite-dolomite marble exposed in cliffs east of the road at Devils Den. Grades into chlorite-biotite (±actinolite)-carbonate schist at structural base and has sharp contact with structurally overlying quartzite (Y?q). Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes. Unit is part of the Problematic rocks at Devils Den in Weston and Danby areas: Near Devils Den and Moses Pond includes albitic biotite-muscovite schist, chloritoid-chlorite-muscovite (±garnet) schist, dolomite marble and minor quartzite which resemble rocks of the Tyson Formation, and retrograde varieties of the paragneisses of the Mount Holly Complex. Because these rocks are structurally compatible with Grenvillian or older folds in the Mount Holly Complex and are transitional into rocks of the Mount Holly Complex, a Mesoproterozoic age is favored. Nevertheless the resemblance to rocks of the Tyson Formation is striking.
Green to gray-green chlorite-sericite-quartz phyllite; interbeds of chloritoid- or albite-rich schist and minor quartzite, locally rich in garnet and kyanite.
Organic silt, sand and gravel and slumped and dismembered lignite occurring as elongate disrupted deposits in underlying kaolin, residual hematite, and ochre deposits near Brandon. Lignite was let down into kaolin perhaps by karst collapse along a concealed west-dipping normal fault between the Dunham Dolostone on the west and the Cheshire Quartzite on the east. Deposit largely concealed but known from historic underground workings for kaolin, hematite ochre, and lignite.
Biotite metadiorite in unit Dgq northeast of St. Johnsbury - Medium-light-bluish-gray, fine-grained, foliated and lineated. Part of other plutons of the New Hampshire Plutonic Suite.
Lustrous, yellowish-grayish-green, ilmenite-staurolite (±kyanite)-garnet (large)-plagioclase-biotite-muscovite-quartz schist and warty-textured, dark-gray, biotite-rich garnet (large)-plagioclase-quartz schist. Passes locally into greenish, chlorite-spotted, magnetite-garnet (small)- plagioclase granofels in which large chlorite clots appear to replace earlier large garnet crystals. Unit closely resembles retrograded chlorite-spotted, biotite-garnet-plagioclase-quartz granofels and garnet-quartz-feldspar schist or gneiss of the Wilcox Formation of the Mount Holly Complex (Y2wsx). Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes. The term “Cavendish Formation” is restricted to two belts of rocks within the Chester dome; the larger belt occurs at Cavendish and on Hawks Mountain, and a less extensive belt, containing similar rocks, occurs near Star Hill. An Early Mesoproterozoic age is here favored for the Cavendish Formation on the basis of (1) the presence of deformed pegmatite (Y3Cp) and areas of Felchville Gneiss (Y1fg and Y1fga) within the Cavendish and (2) the marked resemblance of members of the Cavendish to aluminous and feldspathic schists, calc-silicate rocks, and quartzites within the Mount Holly Complex. Similarities to rocks of the Hoosac Formation are also striking and cannot be altogether dismissed; however, the Hoosac Formation lacks pegmatite and contains distinctive and well-bedded albitic granofels, mafic volcanics, and coarse pebble-to-cobble conglomerate, all absent from the Cavendish. Zircons from a quartzite lens in dolomite marble at locality 4 have Pb-Pb ages between 1,290 and 934 Ma and suggest some of the marble of the Cavendish may be younger than the Felchville Gneiss (Karabinos and others, 1999). Retrograded muscovite-rich, chlorite-spotted, chloritoid-bearing quartz phyllites and garnet granofels and other rocks of the Wilcox Formation (Y2wxs) closely resemble those of the Cavendish Formation, as do chloritic-muscovitic retrograded Y2rs members of the Mount Holly Complex in the Green Mountain massif. Dolomite marble, talc-tremolite rock, diopside quartzite, calc-silicate gneiss, and lustrous chlorite-spotted, chlorite-muscovite-rich retrograded garnet gneiss and schist in the Mount Holly Complex contain abundant pegmatite (Y3Cp) on Blue Ridge Mountain in Chittenden and are identical but lower-grade correlatives of the Cavendish Formation. The coarse garnet-staurolite- and kyanite-bearing Gassetts Schist Member is interpreted to be an Acadian remetamorphosed product of the retrograde aluminous rocks now seen throughout the Mount Holly Complex of the Green Mountain massif and in the Pine Hill area.
Interbedded amphibolite, greenstone, feldspathic schist and granofels. Coarse plagioclase in some amphibolite near top; local coarse hornblende blades or sprays. Sparse coticule (Emerson, 1917, p. 43). As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).
Heterogeneous unit consists of coarse- to medium-grained clastic wacke, beige-weathering dolostone, and quartz-rich dolostone. Cover rocks of the Lincoln Mountain massif and northwestern flank of the Green Mountain massif.
Interbedded gray phyllite, in places containing feldspathic clasts, and feldspathic metasandstone, variably graded.
Black slate containing angular to irregular chips of greenish-gray to yellowish-gray slate, quartz wacke, and limestone; interpreted by Zen (1961) as sedimentary wildflysch. Part of the Taconic Allochthon. Wildflysch-like conglomerates within the Hortonville, Ira, and Walloomsac Formations occur as local areas of black slate rich in inclusions of quartzite, greenish-gray slate, wacke, and punky-weathering bluish-gray limestone, interpreted as sedimentary breccias, deposited in front of the advancing Taconic allochthon (Upper Ordovician) (Zen, 1961; Potter, 1972; Fisher, 1985). Exposed near the western and northern margin of the allochthon and in the Bennington area at the type Whipstock. Here and at many localities the Forbes Hill and Whipstock breccias are tectonic breccias formed in situ by disruption of thin to thick beds, laminae, and carbonate-quartz-sulfide veins rather than clastic sedimentary rocks. The cleavage and related folding commonly is a late strain-slip cleavage characterized by a strong down-plunge lineation parallel to reclined hingelines of minor folds of foliation and compositional layering. Units are retained although interpretation as sedimentary wildflysch deposits is in part questionable.
Black, fine-grained, splintery, rusty-weathering schist and thin dark quartzite; interlayered amphibolite commonly has plagioclase megacrysts. As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).
Medium-greenish-gray to dark-greenish-gray, medium-grained, foliated metamorphosed granite, granodiorite, and tonalite containing quartz, microcline, saussuritized plagioclase, hornblende, biotite (chlorite alteration), and secondary calcite and sericite. Nonconformably overlain by the Clough Quartzite and Fitch Formation. U-Pb zircon age of 450±5 Ma, no. 28 (Lyons and others, 1986). Part of the Highlandcroft Plutonic Suite: Epizonal to mesozonal, foliated and metamorphosed (greenschist facies) plutons exposed northwest of the Ammonoosuc fault. Compositions range from granite to diorite to lesser amounts of gabbro. Part of the Bronson Hill arch intrusive rocks.
Includes volcanic debris flow, laminated tuff, and strongly foliated felsite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Thickly bedded feldspathic volcaniclastic grit and interbedded gray slate. Equivalent to Grenier Ponds Member of the Ironbound Mountain Formation in western Maine.
Beige-weathering to whitish-gray, fine-grained dolomite marble. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
A small, 0.5-km-long, northwest-trending stock consisting of a coarse-grained alkali syenite core, a fine-grained quartz syenite border, and associated trachyte dikes (Kfd). K-Ar biotite age of 114±2 Ma (Armstrong and Stump, 1971). Part of the White Mountain Igneous Suite.
A polymict limestone conglomerate. Unit mapped along east side of the Taconic allochthon south to Bennington. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Screens, dikes, or sills of more mafic gneiss within unti Y2bt. Passes laterally into white, fine-grained trondhjemitic aplite near contacts with larger screens of paragneiss. U-Pb zircon Thermal Ionization Mass Spectrometry (TIMS) age of 1329±37 Ma (McLelland and Chiarenzelli, 1990) obtained from exposure 1.5 km west of Austin Hill on the west side of South Bay, west of Whitehall, N.Y. Contains lenses and screens of rusty sulfidic garnet-biotite-feldspar-quartz schist, dark-gray garnet-feldspar quartzite, and calc-silicate gneiss on south end of Austin Hill. Unit interpreted as intrusive into some paragneiss units that are here older than 1328±32 Ma (McLelland and Chiarenzelli, 1990). Rocks of the Adirondacks in Vermont and in the Whitehall, N.Y., area.
Nubble garnet schist, pinstriped granofels, and fine-grained amphibolite in equal parts.
Garnetiferous hornblende schist and minor hornblende amphibolite. Part of the Connecticut Valley Trough.
Pods, lenses, or zones of thinly bedded limestone (ls), dolostone (d), and limestone conglomerate in the Mettawee slate facies in the Bull Formation, West Castleton Formation, and Hatch Hill Formation. These rocks locally contain Lower Cambrian fossils, but may range in age from Neoproterozoic to Late Cambrian. Includes named units shown locally as the North Brittain Conglomerate member of the West Castleton Formation (Cwcnb), the Bebe Limestone Member of the West Castleton Formation (Cwcbb), and the Castleton Conglomerate (of Shumaker and Thompson, 1967) (Cco). Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Light-greenish-gray to buff, fine-grained, pinstriped granofels and schist.
Fine- to medium-grained, well-layered and foliated amphibolite; epidote-rich layers locally abundant. Includes its typical Chester Amphibolite Member at Chester, Massachusetts.
Buff, sandy, massive dolostone as lens in CZdph. Unit interfingers to the north with rocks of the Tyson Formation and to the east with rocks of the Hoosac Formation. Cover rocks of the Southern Green Mountains.
Black to gray aluminous mica schist, quartzose schist, and aluminous phyllite.
Brown-weathering, dark-green serpentinite. Part of Ultramafic rocks: occur as tectonic slivers and olistoliths in blocks within the Hazens Notch, Ottauquechee, Stowe, Rowe, and Moretown Formations. Rocks of the Early to Late Taconic Accreted Terrane of the Rowe-Hawley Zone. Eastern allochthonous sequence, oceanic and accretionary realm, ultramafic inclusions, volcanic-arc intrusives, and volcanic rocks.
Fine-grained syenitic dike similar to spherulitic dikes found within the plutons and in the adjacent country rocks. One paisanite dike occurs well outside the Ascutney Mountain stocks in the saddle between the Chester and Athens domes. Part of the White Mountain Igneous Suite; Little Ascutney stock: A composite gabbro-diorite stock having two (eastern and western) intrusive centers defined by weakly developed igneous foliation. Gabbro is intruded by abundant, poorly defined areas of diorite. Includes two areas of syenite (Kas).
Orangish-gray, gray, and light-greenish-gray muscovite-quartz schist and interlayered feldspathic quartzite and quartz conglomerate; minor beds of rusty albitic schist.
White to blue-gray and white layered calcite marble.
Tan to orangish-tan quartz and gneiss cobble and pebble conglomerate, rusty feldspathic schist, and lustrous greenish-gray muscovite quartz schist.
Greenish chlorite-albite-magnetite-sericite-quartz schist and granofels.
Ironstone, magnetite-rich rock and coticule. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Amphibolite or hornblende schist locally containing conspicuous hornblende or garnet megacrysts. Rocks mapped as Conway Schist by Emerson (1898, 1917) and subsequently subdivided by Segerstrom (1956) and Willard (1956) were mapped across the MA-VT State line as Waits River and Gile Mountain Formations by Doll and others (1961) on Centennial Geologic Map of Vermont. Although controversy still exists over relative ages, detailed reconnaissance mapping by authors and S.F. Clark, Jr., L.M. Hall, and J.W. Pferd shows that Waits River and Gile Mountain Formations are readily distinguished in the field. For these reasons, and to maintain continuity across the State line, authors chose to follow VT nomenclature on here and on MA State bedrock geologic map (Zen and others, 1983). Primary difference between Waits River and Gile Mountain is presence in Gile Mountain of beds of noncalcareous, commonly micaceous quartzite. Both formations contain conspicuous beds of punky brown-weathering impure marble or calcareous granulite, mostly in Waits River and less abundant in Gile Mountain. Predominant lithology of both formations is typically contorted gray, graphitic, locally very sulfidic, moderately aluminous mica schist containing quartz veins. Gradational but definitely significant boundary can be mapped between both formations. Amphibolite in both formations may correlate with Standing Pond Volcanics occurring at or near Waits River-Gile Mountain contact in VT. Report goes into great detail regarding informal subdivision of each formation. Rocks previously mapped as Waits River Formation northeast of Shelburne Falls dome by Hatch and Hartshorn (1968) are here reassigned to an unnamed member of Goshen Formation because the rocks are indistinguishable from the Goshen. Goshen-Waits River contact is defined as the line along which, going eastward, the schist changes from aluminous, planar-bedded, and virtually quartz-free (Goshen), to alumina-poor, contorted, and rich in quartz veins (Waits River) (Hatch and others, 1988).
White, coarse-grained graphite dolomite-calcite marble at Sherman Reservoir at the State line.
Associated trachyte dikes of Kbh. Rb/Sr whole-rock isochron on trachyte dikes of 125±5 Ma (McHone and Corneille, 1980). Part of the White Mountain Igneous Suite.
In Champlain Valley: Whitehall Formation-dolostone, limestone (with Cryptozoon reefs); Ticonderoga Formation-dolostone (locally cherty), sandstone. In Vermont: Clarendon Springs Dolostone; Danby Formation-sandstone, quartzite, dolostone.
Pods, lenses, or zones of thinly bedded limestone (ls), dolostone (d), and limestone conglomerate in the Mettawee slate facies in the Bull Formation, West Castleton Formation, and Hatch Hill Formation. These rocks locally contain Lower Cambrian fossils, but may range in age from Neoproterozoic to Late Cambrian. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Light-gray to pinkish-gray, magnetite-muscovite-plagioclase quartzite at Devils Den. Grades into structurally overlying biotite-muscovite feldspathic schist and garnet-bearing feldspathic gneiss that contains pegmatite. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes. Unit is part of the Problematic rocks at Devils Den in Weston and Danby areas: Near Devils Den and Moses Pond includes albitic biotite-muscovite schist, chloritoid-chlorite-muscovite (±garnet) schist, dolomite marble and minor quartzite which resemble rocks of the Tyson Formation, and retrograde varieties of the paragneisses of the Mount Holly Complex. Because these rocks are structurally compatible with Grenvillian or older folds in the Mount Holly Complex and are transitional into rocks of the Mount Holly Complex, a Mesoproterozoic age is favored. Nevertheless the resemblance to rocks of the Tyson Formation is striking.
Locally a polymict limestone and dolostone-clast conglomerate. Unit mapped west of the Taconic allochthon, and northwest of the Sudbury slice. Vermont Valley sequence and Middlebury synclinorium (above the Orwell and Champlain thrusts).
Pale-buff, light-green or white, medium-grained plagioclase gneiss. As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).
Thin lens of metadiamictite with abundant dark-gray, pyritic, and calcareous metapelite matrix at the base of the Meetinghouse Slate Member (Dgm), south of Bradford. Part of the Connecticut Valley Trough.
Mylonitic chlorite-biotite-microcline-quartz gneiss, occurring as a sliver in the Shelburne Marble, South Wallingford. Part of the aluminous schists and gneisses of the Washington Gneiss and Wilcox Formation and related rocks. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
Light-green to light-bluish-gray schist having thin granular quartz lenses and lamellae. Kyanite and staurolite typical at higher grades.
In part feldspathic, micaceous, garnetiferous, sillimanitic.
Dg containing beds of punky-weathering calcareous granofels more than 15 cm thick near the contact with the Waits River Formation.