Geologic units in Lamoille county, Vermont

Additional scientific data in this geographic area

Ottauquechee Formation - carbonaceous phyllite member (Cambrian) at surface, covers 26 % of this area

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.

Hazens Notch Formation - undivided (Cambrian and Neoproterozoic) at surface, covers 18 % of this area

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.

Moretown Formation - “pinstriped” granofels member (Lower Ordovician to Cambrian?) at surface, covers 15 % of this area

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.

Fayston Formation - albite schist member (Lower Cambrian and Neoproterozoic) at surface, covers 11 % of this area

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.

Stowe Formation - schist and phyllite member (Cambrian and Neoproterozoic?) at surface, covers 8 % of this area

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.

Underhill Formation (Cambrian and Neoproterozoic) at surface, covers 5 % of this area

Silvery-green quartz-muscovite-chlorite schist and phyllite, commonly with albite and magnetite; locally contains dolomite. Cover rocks north of the Lincoln Mountain massif.

Jay Peak Formation - schist member (Cambrian and Neoproterozoic) at surface, covers 3 % of this 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.

Stowe Formation - feldspathic quartzite (Cambrian and Neoproterozoic?) at surface, covers 3 % of this area

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.

Stowe Formation - amphibolite member (Cambrian and Neoproterozoic?) at surface, covers 2 % of this area

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.

Stowe Formation - kyanite schist member (Cambrian and Neoproterozoic?) at surface, covers 2 % of this area

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.

Stowe Formation - metadiabase dikes (Cambrian and Neoproterozoic?) at surface, covers 2 % of this area

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.

Fayston Formation - schist member (Lower Cambrian and Neoproterozoic) at surface, covers 1 % of this area

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.

Ottauquechee Formation - metawacke member (Cambrian) at surface, covers 0.9 % of this area

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.

Pinnacle Formation - undivided (Cambrian and Neoproterozoic) at surface, covers 0.6 % of this area

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.

West Bridgewater Formation (Middle Ordovician) at surface, covers 0.5 % of this area

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.

Belvidere Mountain Structural Complex - mafic schist (Cambrian and Neoproterozoic) at surface, covers 0.5 % of this area

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.

Cram Hill Formation - phyllite member (Middle? and Early Ordovician) at surface, covers 0.3 % of this area

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.

Jay Peak Formation - greenstone member (Cambrian and Neoproterozoic) at surface, covers 0.2 % of this area

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.

Ottauquechee Formation - amphibolite and greenstone member (Cambrian) at surface, covers 0.2 % of this area

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.

Belvidere Mountain Structural Complex - ultramafic rocks (Cambrian and Neoproterozoic) at surface, covers 0.2 % of this area

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.

Cram Hill Formation - Umbrella Hill Conglomerate member (Middle? and Early Ordovician) at surface, covers 0.2 % of this area

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.

Hazens Notch Formation - greenstone and amphibolite member (Cambrian and Neoproterozoic) at surface, covers 0.1 % of this area

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.

Underhill Formation - greenstone and amphibolite member (Cambrian and Neoproterozoic) at surface, covers 0.1 % of this area

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.

Stowe Formation - carbonaceous phyllite member (Cambrian and Neoproterozoic?) at surface, covers 0.1 % of this area

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.

Belvidere Mountain Structural Complex - fine-grained amphibolite (Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

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.

Fayston Formation - greenstone member (Lower Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

Dark-green, pitted-weathering, foliated carbonate-albite-chlorite (±magnetite±epidote) greenstone or amphibolite. Cover rocks north of the Lincoln Mountain massif.

Belvidere Mountain Structural Complex - coarse-grained amphibolite (Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

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.

Belvidere Mountain Structural Complex - albite gneiss (Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

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.

Underhill Formation - quartzite, granofels, and metawacke (Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

Local lenses of white to pale-gray quartzite, quartz-albite granofels, quartz-granule chlorite (±biotite) metawacke. Cover rocks north of the Lincoln Mountain massif.

Talc-carbonate schist (Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

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.

Meta-ultramafic rocks - undifferentiated (Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

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.

Belvidere Mountain Structural Complex - spangly schist (Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

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.

Hazens Notch Formation - schist member (Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

Rusty-weathering, non-graphitic, sulfidic chlorite-muscovite-quartz schist. Cover rocks north of the Lincoln Mountain massif.

Fairfield Pond Formation (Cambrian and Neoproterozoic) at surface, covers < 0.1 % of this area

Light-gray to light-green, quartz-sericite-chlorite (±magnetite±biotite) phyllite and foliated quartzite. Cover rocks north of the Lincoln Mountain massif.

Moretown Formation - carbonaceous schist member (Lower Ordovician to Cambrian?) at surface, covers < 0.1 % of this area

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.