USGS Home
Contact USGS
Search USGS

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

Geologic units in Orange county, Vermont

[Additional scientific data in this geographic area]

Perry Mountain Formation, undivided (Lower? - Middle? Silurian) at surface, covers < 0.1 % of this area

Perry Mountain Formation, undivided - Sharply interbedded quartzites, light-gray nongraphitic metapelite, and "fast-graded" meta-turbidites. Coticule layers common.

Lithology: quartzite; meta-argillite; metasedimentary rock

Undifferentiated Granitic Rocks (Ordovician) at surface, covers 0.4 % of this area

Undifferentiated granitic rocks.

Lithology: granite

Partridge Formation, undivided (Middle - Upper Ordovician) at surface, covers < 0.1 % of this area

Partridge Formation, undivided - Black, rusty-weathering sulfidic-graphitic slate or schist and sparse to abundant metagraywacke. Lies stratigraphically between upper and lower parts of the Ammonoosuc Volcanics.

Lithology: slate; schist; metasedimentary rock

Missisquoi Formation, Cram Hill Member (Ordovician) at surface, covers 0.4 % of this area

Missisquoi Formation, Cram Hill Member - Pale greenish-gray to black phyllite grades locally into gray to black slate; felsic to mafic volcanic rocks.

Lithology: phyllite; slate; felsic metavolcanic rock; mafic metavolcanic rock

Missisquoi Formation, Harlow Bridge Quartzite Member (Ordovician) at surface, covers < 0.1 % of this area

Missisquoi Formation, Harlow Bridge Quartzite Member - Buff to pale-green quartzite with interbeds of quartz-sericite-chlorite phyllite.

Lithology: quartzite; phyllite

Orfordville Formation, Post Pond Volcanics (Ordovician) at surface, covers 0.9 % of this area

Orfordville Formation, Post Pond Volcanics - Greenstone, green chloritic schist interbedded with schistose felsite, quartz-feldspar-sericite schist; fine-grained chloritic, biotitic gneiss, all west of Ammonoosuc fault; mainly amphibolite east of the Ammonoosuc fault.

Lithology: greenstone; greenschist; mica schist; biotite gneiss; amphibolite

Missisquoi Formation, Moretown Member (Ordovician) at surface, covers 1 % 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

Greenvale Cove Formation (Lower Silurian? ) at surface, covers < 0.1 % of this area

Greenvale Cove Formation - Grayish-violet interlaminated metashale, feldspathic metasandstone, and calc-silicate rock of the Piermont allochthon in western New Hampshire.

Lithology: meta-argillite; metasedimentary rock; calc-silicate rock

Rangeley Formation, undivided (Lower Silurian (Llandoverian)) at surface, covers < 0.1 % of this area

Rangeley Formation, undivided.

Lithology: metasedimentary rock; calc-silicate rock; meta-argillite; quartzite; pelitic schist; granofels; felsic metavolcanic rock

Ammonoosuc Volcanics, Bimodal volcanic rocks (Middle - Upper Ordovician) at surface, covers 0.1 % of this area

Ammonoosuc Volcanics, Bimodal volcanic rocks - Locally includes unmapped Oals.

Lithology: bimodal suite

Littleton Formation, undivided (Lower Devonian; Siegenian) at surface, covers < 0.1 % of this area

Littleton Formation undivided - Gray metapelite and metawacke and subordinate metavolcanic rocks; generally, but not everywhere, conformable with underlying Fitch or Madrid Formations. Fossiliferous in western New Hampshire.

Lithology: metasedimentary rock; metavolcanic rock

Bethlehem Granodiorite (Early Devonian) at surface, covers < 0.1 % of this area

Bethlehem Granodiorite (Bethlehem Gneiss of Billings, 1955) - Gray, strongly foliated biotite-muscovite granodiorite and associated tonalite and granite.

Lithology: granodiorite; tonalite; granite

Ammonoosuc Volcanics, Metabasalt (Middle - Upper Ordovician) at surface, covers < 0.1 % of this area

Ammonoosuc Volcanics, Metabasalt.

Lithology: meta-basalt

Gile Mountain Formation, Meetinghouse Slate Member (Devonian) at surface, covers 1 % of this area

Gile Mountain Formation, Meetinghouse Slate Member - Chiefly gray slate or phyllite characterized by beds of gray schistose quartzite 1/8 inch to 3 inches thick. Gile Mountain Formation and its Meetinghouse Slate Member were previously considered to be Early Devonian based on Emsian plant fossils from Compton Formation of QUE (Hueber and others, 1990; Hatch, 1991). Age assignment here changed to Early Devonian(?) because recent mapping indicates that Gile Mountain and Compton are not coextensive across VT-QUE border as formerly believed by Doll and others (1961, State map) and St. Julien and Slivitsky (1987). Instead, the formations are separated by Ironbound Mountain Formation. Ironbound Mountain Formation is conformably overlain by Compton, but it is not yet known whether Ironbound Mountain is overlain or underlain by Gile Mountain; this is shown by queried Ironbound Mountain-Gile Mountain contact in area of Averill 7.5-min quad, VT. Correlation of Gile Mountain and Compton is justified only if Gile Mountain in this area conclusively is shown to be underlain by Ironbound Mountain; otherwise, Gile Mountain (with possible exception of its Meetinghouse Slate Member) would be coeval with Silurian Frontenac Formation. Hatch (1988) proposed that Meetinghouse represents upper part of Gile Mountain on basis of graded bedding seen south of map area. This relationship is not proven, however, because Gile Mountain-Meetinghouse contact is difficult to define and graded beds are not always easily interpreted. On this map, Meetinghouse is tentatively shown to occur below main body of Gile Mountain on basis of remarkable similarity between it and Ironbound Mountain Formation. This relationship easily explains highly pelitic character of the Meetinghouse with upward-coarsening character of Lower Devonian sequences elsewhere in map area. Meetinghouse Slate Member includes volcanic facies (Moench and others, 1995).

Lithology: slate; phyllite; quartzite

Ottauquechee Formation (Cambrian) at surface, covers < 0.1 % 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 0.6 % of this area

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

Lithology: greenstone; amphibolite

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

Northfield Formation (Devonian - Silurian) at surface, covers 0.3 % of this area

Northfield Formation - Dark gray to black quartz-sericite slate or phyllite with fairly widely-spaced interbeds a few inches thick of siltstone and silty crystalline limestone like that of the Waits River Formation; calcareous slate north of Lamoille River; phyllite passes into gray quartz-sericite schist containing abundant porphyroblasts of biotite and garnet in southern Vermont.

Lithology: slate; phyllite; mica schist; siltstone; limestone

Waits River Formation (Devonian) at surface, covers 53 % of this area

Waits River Formation - Gray quartzose and micaceous crystalline limestone weathered to distinctive brown earthy crust; interbedded and intergradational with gray quartz-muscovite phyllite or schist. Where more metamorphosed the limestones contain actinolite, hornblende, zoisite, diopside, wollastonite, and garnet, and the phyllite and schist, biotite, garnet, and locally andalusite, kyanite or sillimanite.

Lithology: limestone; phyllite; mica schist

Waits River formation, Standing Pond Volcanic Member (Devonian) at surface, covers 0.5 % of this area

Waits River formation, Standing Pond Volcanic Member - Amphibolite, garnet amphibolite, coarse garnet schist with fasciculitic hornblende, and hornblende maculite; contains pillow lavas near St. Johnsbury and passes eastward into actinolitic greenstone and greenstone south of Windsor.

Lithology: amphibolite; schist; greenstone

Orfordville Formation, Sunday Mountain Volcanics (Ordovician) at surface, covers 0.2 % of this area

Orfordville Formation, Sunday Mountain Volcanics - Greenstone, chloritic schist, felsite, and quartz-feldspar-sericite schist.

Lithology: greenstone; greenschist; mica schist

Littleton Formation, Volcanic lentils (Lower Devonian) at surface, covers < 0.1 % of this area

Littleton Formation, Volcanic lentils - Both mafic and felsic

Lithology: mafic metavolcanic rock; felsic metavolcanic rock

Shaw Mountain Formation (Silurian) at surface, covers < 0.1 % of this area

Shaw Mountain Formation - Quartzite, quartz conglomerate, cummingtonite schist, amphibolite, and quartz-sericite schist with porphyroblasts of biotite and garnet.

Lithology: quartzite; conglomerate; schist; amphibolite; mica schist

Orfordville Formation (Ordovician) at surface, covers 1 % of this area

Orfordville Formation - Carbonaceous phyllite; minor quartzite.

Lithology: phyllite; quartzite

Undifferentiated Granitic Gneiss (Devonian) at surface, covers 2 % of this area

Undifferentiated Granitic Gneiss - Small dikes and sills do not show.

Lithology: granitic gneiss

Perry Mountain Formation, Sedimentary and subordinate distal felsic and mafic volcanic facies in Piermont allochthon (Lower?- Middle? Silurian) at surface, covers < 0.1 % of this area

Perry Mountain Formation, Sedimentary and subordinate distal felsic and mafic volcanic facies in Piermont allochthon.

Lithology: metasedimentary rock; felsic metavolcanic rock; mafic metavolcanic rock

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

Missisquoi Formation, Barnard Volcanic Member - Fine- to medium-grained biotite gneiss, hornblende gneiss, and amphibolite.

Lithology: biotite gneiss; mafic gneiss; amphibolite

Albee Formation (Ordovician) at surface, covers 5 % of this area

Albee Formation - Massive, gray, white-weathered quartzite and feldspathic quartzite interbedded with greenish-gray slate, phyllite, feldspthic phyllite and quartzose argillaceous phyllite. Micaceous quartzite, quartz-mica schist, mica schist and hornfels contining porphyroblasts of biotite, garnet, staurolite and sillimanite in the vicinity of granitic plutons. Soda-rhyolite tuff occurs locally. Micaceous quartzite characterized by thin, schistose "pinstripe" partings is common in many areas.

Lithology: quartzite; slate; phyllite; mica schist; hornfels; tuff

Gile Mountain Formation (Devonian) at surface, covers 30 % of this area

Gile Mountain Formation - Gray quartz-muscovite phyllite or schist, interbedded and intergradational with gray micaceous quartzite (graywacke northeast of Nulhegan River), calcareous mica schist, and, locally, quartzose and micaceous crystalline limestone like that of the Waits River formation. The phyllite and schist commonly contain porphyroblasts of biotite, garnet, or staurolite, and locally kyanite, andalusite, or sillimanite. Used as Early Devonian Gile Mountain Formation. Generally consists of gray to tan metawacke and schist or phyllite, gradational into its Meetinghouse Slate Member, but much more thickly bedded and less pelitic. Contains minor metavolcanic lentils. Unnamed metavolcanic member is possibly equivalent to Putney Volcanics of southeastern VT. Separately mapped interbedded gray slate or phyllite and brown-weathering calcite-ankerite metasiltstone, and minor marble and quartzite, resembles Waits River Formation of VT. Meetinghouse Slate Member consists of gray to black phyllite and silty metasandstone turbidite. Report includes geologic map, cross sections, correlation chart, and four 1:500,000-scale derivative maps (Lyons and others, 1997).

Lithology: phyllite; mica schist; quartzite; limestone; graywacke

Pink equigranular biotite granite (Late Devonian) at surface, covers < 0.1 % of this area

Pink equigranular biotite granite - Found in Woodsville and Whitefield quadrangles and in small intrusive units in northern and southeastern New Hampshire.

Lithology: granite

Stowe Formation (Cambrian-Ordovician) at surface, covers 2 % 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