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Mineral Resources > Online Spatial Data > Geology > by state > Vermont Geology

Geologic units in Lamoille county, Vermont

Missisquoi Formation (Ordovician) at surface, covers < 0.1 % of this area

Missisquoi Formation - Rusty weathering carbonaceous mica schist, quartzite and micaceous quartzite.

Lithology: mica schist; quartzite

Underhill Formation, carbonaceous quartz-sericite-albite-chlorite schist and phyllite. (Cambrian) at surface, covers 0.5 % of this area

Underhill Formation, carbonaceous quartz-sericite-albite-chlorite schist and phyllite. (Northern and Central Vermont).

Lithology: mica schist; phyllite

Hazens Notch Formation, Greenstone and Amphibolite (Cambrian) at surface, covers 0.1 % of this area

Hazens Notch Formation, Greenstone and Amphibolite - Chiefly albite-actinolite-chlorite-epidote greenstone; locally hornblende-epidote-chlorite-albite amphibolite. (Northern and Central Vermont).

Lithology: greenstone; amphibolite

Stowe Formation, carbonaceous schist and phyllite (Cambrian-Ordovician) at surface, covers 0.5 % of this area

Stowe Formation, carbonaceous schist and phyllite - north of Lamoille River. Occurs in several small areas to the south, not shown on map.

Lithology: schist; phyllite

Stowe Formation (Cambrian-Ordovician) at surface, covers 13 % of this area

Stowe Formation - Quartz-sericite (muscovite-paragonite)-chlorite phyllite and schist; porphyroblasts of albite, garnet, chloritoid, or kyanite common locally; includes phyllitic graywacke north of Lamoille River. Schist contains abundant segregations of granular white quartz. The Stowe Formation in the study are contains two unnamed members: a silvery green schist and a greenstone. The schist is a fine-grained, silvery to dark green quartz-muscovite-albite-chlorite schist. It is in fault contact with the black phyllite of the Ottauquechee Formation. The greenstone is a homogenous, fine-grained, light green actinolite-albite-epidote-calcite-chlorite schist. Large outcrops of the resistant greenstone are common. Age according to map symbols is Proterozoic and Cambrian. Unit is correlated with the Rowe Schist (of Zen, 1983). [Rowe Schist on 1983 MA map is Cambrian and Ordovician. No explanation here for older age.] (Walsh, 1992).

Lithology: phyllite; mica schist; graywacke

Underhill Formation, Foot Brook Member (Cambrian) at surface, covers 3 % of this area

Underhill Formation, Foot Brook Member - Sericite (muscovite-paragonite)-quartz-chlorite-chloritoid schist; minor carbonaceous interbeds. (Northern and Central Vermont).

Lithology: mica schist

Ultramafic Rocks (Ordovician) at surface, covers 0.2 % of this area

Ultramafic Rocks - Dunite, peridotite, and serpentinite

Lithology: dunite; peridotite; serpentinite

Underhill Formation (Cambrian) at surface, covers 15 % of this area

Underhill Formation - Silvery, gray-green, quartz-sericite-albite-chlorite-biotite schist, containing abundant lenticular segregations of granular white quartz; locally quartz-sercite-albite-chlorite phyllite; porphyroblasts of albite, garnet, and magnetite are common and locally very abundant in gneissic facies in axial anticlines of the Green Mountain anticlinorium . (Northern and Central Vermont). In study area consists mainly of greenish quartz-chlorite-sericite phyllites lying stratigraphically between Pinnacle and Cheshire Formations, where author would place rocks of type locality within Underhill facies of Pinnacle Formation, for they are clearly stratigraphically equivalent to rocks of Pinnacle Formation in Enosburg area, being below an excellent horizon marker, the Whitebrook dolomite and slate. However, Underhill facies of the Pinnacle and phyllites of Underhill Formation are practically indistinguishable in the field, and it is unavoidable, wherever dividing White Brook dolomite and slate are absent, to map all rocks of Underhill facies as one unit. In western part of outcrop belt, Underhill rocks are well defined between White Brook Dolomite or coarse Pinnacle graywacke below and Cheshire Formation above. Rocks in this clearly defined area are here recognized as Fairfield Pond Member. As mapped, the Underhill includes Fairfield Pond Member, Bakersfield Greenstone, Peaked Mountain Greenstone, White Brook Member, Jay Peak Member, and West Sutton Slate Member. Eastern facies of Underhill is named Bonsecours facies (Dennis, 1964).

Lithology: mica schist; phyllite

Missisquoi Formation, Moretown Member (Ordovician) at surface, covers 16 % of this area

Missisquoi Formation, Moretown Member - Quartzite and quartz-plagioclase granulite, in layers 1/8 to several inches thick, separated by "pinstripe" partings that contain muscovite, chlorite, epidote, biotite, and locally garnet; also greenish quartz-sericite-chlorite phyllite and schist, and minor carbonaceous phyllite. Schist and phyllite commonly contain biotite and garnet porphyroblasts in southern Vermont.

Lithology: granulite; quartzite; phyllite; schist

Hazens Notch Formation, sericite-quartz-chlorite-albite-magnetite schist (Cambrian) at surface, covers 2 % of this area

Hazens Notch Formation, sericite-quartz-chlorite-albite-magnetite schist - near Hyde Park. (Northern and Central Vermont).

Lithology: mica schist

Pinnacle Formation (Cambrian) at surface, covers 0.3 % of this area

Pinnacle Formation - Schistose graywacke, gray to buff, commonly striped, quartz-albite-sericite-biotite-chlorite rock predominates; quartz-cobble and boulder conglomerate is common, chiefly near base. (Northern and Central Vermont).

Lithology: schist; conglomerate

Missisquoi Formation, Umbrella Hill Member (Ordovician) at surface, covers 0.3 % of this area

Missisquoi Formation, Umbrella Hill Member - Quartz and slate pebble phyllitic conglomerate with interbeds of slate and phyllite - chiefly quartz-sericite-magnetite-chloritoid rocks.

Lithology: conglomerate; slate; phyllite

Underhill Formation, White Brook Member (Cambrian) at surface, covers < 0.1 % of this area

Underhill Formation, White Brook Member - Chiefly brown-weathered whitish, tan and gray sandy dolomite, locally only a hematitic zone; includes carbonaceous crystalline limestone in Cambridge syncline. (Northern and Central Vermont).

Lithology: dolostone (dolomite); limestone

Ultramafic Rocks (Ordovician) at surface, covers < 0.1 % of this area

Ultramafic Rocks - Serpentinite, carbonate rock, talc-carbonate rocks and steatite.

Lithology: serpentinite; intrusive carbonatite

Pinney Hollow Formation, carbonaceous phyllite and schist (Cambrian) at surface, covers 37 % of this area

Pinney Hollow Formation, carbonaceous phyllite and schist. (Southern and Central Vermont).

Lithology: phyllite; schist

Ottauquechee Formation (Cambrian) at surface, covers 6 % of this area

Ottauquechee Formation - Black carbonaceous phyllite or schist containing interbeds of massive quartzite commonly criss-crossed by veins of white quartz; quartzite is dark gray and carbonaceous, light gray, or white; also includes light green quartz-sericite-chlorite phyllite or schist and sercitic quartzite; beds of phyllitic graywacke and feldspar granule conglomerate are north of Lamoille River. Schist contains abundant porphyroblasts of garnet and biotite from Ludlow south. The Ottauquechee contains two major units: A black phyllite and the Thatcher Brook Member. The black phyllite contains a previously unreported sub-unit of gray carbonate schist. The Thatcher Brook Member (named in an abstract by Armstrong and others, 1988) is a carbonaceous albitic schist with greenstones and ultramafics. These rocks have previously been included in the Ottauquechee but have never been differentiated from the black phyllite. Member is in fault contact with the silvery green schist of the Pinney Hollow Formation to the west. Age is Cambrian (Ratcliff, in press).

Lithology: phyllite; schist; quartzite; graywacke; conglomerate

Stowe Formation, greenstone and amphibolite (Cambrian-Ordovician) at surface, covers 5 % of this area

Stowe Formation, greenstone and amphibolite - Epidote-albite-chlorite rocks contain actinolite and hornblende where more metamorphosed.

Lithology: greenstone; amphibolite

Hazens Notch Formation, Belvidere Mountain Amphibolite Member (Cambrian) at surface, covers 0.6 % of this area

Hazens Notch Formation, Belvidere Mountain Amphibolite Member - Coarse- to fine-grained hornblende-epidote-albite rock; grades to epidote-chlorite-actinolite-albite greenstone where less metamorphosed. (Northern and Central Vermont).

Lithology: amphibolite; greenstone

Pinnacle Formation, Tibbit Hill Volcanic Member (Cambrian) at surface, covers < 0.1 % of this area

Pinnacle Formation, Tibbit Hill Volcanic Member - Albite-actinolite-chlorite-epidote greenstone; locally pillowed and vesicular. (Northern and Central Vermont).

Lithology: greenstone

Underhill Formation, Greenstone (Cambrian) at surface, covers < 0.1 % of this area

Underhill Formation, Greenstone - varied composition including albite-chlorite-epidote-calcite and sericite-magnetite-chlorite-clinozoisite rocks. (Northern and Central Vermont).

Lithology: greenstone