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

Geologic units in Franklin county, Vermont

Cutting Dolomite, and Undifferentiated Morgan Corner and Wallace Creek Formations (Ordovician) at surface, covers < 0.1 % of this area

Cutting Dolomite, and Undifferentiated Morgan Corner and Wallace Creek Formations - Typical Cutting is a massive, gray weathered, nondescript dolomite with finely laminated calcareous sandstone at base. The combined Morgan Corner and Wallace Creek Formations, east of Philipsburg thrust, are stratigraphically equivalent to the Cutting. Cutting Formation of Cady (1945) is stratigraphically extended to include Division D, member 1 of Brainerd and Seeley, 1890, (now called Smith Basin Member), and is here renamed Cutting Hill Formation. No new type section is designated. Redefined unit includes Winchell Creek Sandstone Member, East Shoreham Member (named), and Smith Basin Member (Washington and Chisick, 1988).

Lithology: dolostone (dolomite); sandstone

Bascom Formation, and undifferentiated Luke Hill, Naylor Ledge and Hastings Creek Limestones (Ordovician) at surface, covers < 0.1 % of this area

Bascom Formation, and undifferentiated Luke Hill, Naylor Ledge and Hastings Creek Limestones - Interbedded dolomite, limestone or marble, calcareous sandstone, quartzite and limestone breccia; irregular dolomitic layers, thin sandy laminae, and slaty or phyllitic partings characterize limestone and marble of lower, middle, and upper parts of the Bascom, respectively; south of West Rutland it includes some of the Chipman formation. The combined Luke Hill, Naylor Ledge, and Hastings Creek, east of Philipsburg thrust, are stratigraphically equivalent to the Bascom.

Lithology: dolostone (dolomite); limestone; marble; sandstone; quartzite; sedimentary breccia

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

Morses Line Formation - Calcareous and non-calcareous slate; local lenses of thin-bedded limestone, limestone conglomerate, and dolomite; in St. Albans synclinorium.

Lithology: slate; limestone; conglomerate; dolostone (dolomite)

Hortonville, or Cumberland Head, and Glens Falls Formations, Undifferentiated (Ordovician) at surface, covers 0.3 % of this area

Hortonville, or Cumberland Head, and Glens Falls Formations, Undifferentiated - Hortonville or Cumberland Head is combined with Glens Falls where the boundary with the Glens Falls is widely covered by surficial deposits, also where the Cumberland Head thins.

Lithology: slate; phyllite; limestone; shale; conglomerate

Saxe Brook Dolomite (Cambrian) at surface, covers 0.4 % of this area

Saxe Brook Dolomite - Sandy gray dolomite, sandstone containing dolomitic cement, and pure dolomite; on west limb of St. Albans synclinorium.

Lithology: dolostone (dolomite); sandstone

Sweetsburg Formation, St. Albans Slate Member (Cambrian) at surface, covers 0.3 % of this area

Sweetsburg Formation, St. Albans Slate Member - Black, gray-black, or tan micaceous slate.

Lithology: slate

Underhill Formation, Fairfield Pond Member (Cambrian) at surface, covers 8 % of this area

Underhill Formation, Fairfield Pond Member - Greenish quartzitic schist (quartz-sericite-albite-chlorite-biotite); sericite-quartz-chlorite phyllite, locally purple or red, common in lower part. (Northern and Central Vermont).

Lithology: mica schist; phyllite

Underhill Formation, Peaked Mountain Member (Cambrian) at surface, covers 0.1 % of this area

Underhill Formation, Peaked Mountain Member - Greenstone. (Northern and Central Vermont).

Lithology: greenstone

Shelburne, Whitehall, and Strites Pond Formations (Ordovician) at surface, covers 0.3 % of this area

Shelburne, Whitehall, and Strites Pond Formations - The Shelburne is chiefly a white marble or gray limestone characterized by raised reticulate lines of gray dolomite on the weathered surface; includes Sutherland Falls marble, intermediate dolomite and Columbian marble of the marble quarries. Interbedded massive dolomite increases westward and predominates in the Whitehall formation, west of Champlain and Orwell thrusts. The Strites Pond, which is identical to the Shelburne, is east of Philipsburg thrust.

Lithology: marble; limestone; dolostone (dolomite)

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

Rugg Brook Formation (Cambrian) at surface, covers 0.4 % of this area

Rugg Brook Formation - Sandy gray dolomite, dolomite conglomerate, and interbeds of gray-weathered sandstone, in St. Albans and Middlebury synclinoria.

Lithology: dolostone (dolomite); conglomerate; sandstone

Dunham Dolomite (Cambrian) at surface, covers 3 % of this area

Dunham Dolomite - Buff-weathered siliceous dolomite, pink and cream mottled or buff to gray on fresh surface; lower part is massive and upper part is sandy and resembles the Winooski Dolomite.

Lithology: dolostone (dolomite)

Underhill Formation, carbonaceous quartz-sericite-albite-chlorite schist and phyllite. (Cambrian) at surface, covers 0.4 % of this area

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

Lithology: mica schist; phyllite

Sweetsburg Formation, Hungerford Slate Member (Cambrian) at surface, covers 1.0 % of this area

Sweetsburg Formation, Hungerford Slate Member - Black slate.

Lithology: slate

Iberville Formation (Ordovician) at surface, covers 6 % of this area

Iberville Formation - Noncalcareous black shale interbedded with occasional dolomite beds and in the lower part with calcareous shale.

Lithology: black shale; dolostone (dolomite)

Sweetsburg Formation, Rockledge Conglomerate Member (Cambrian) at surface, covers 0.3 % of this area

Sweetsburg Formation, Rockledge Conglomerate Member - Phenoclasts chiefly of biohermal limestone in a matrix of gray limestone containing frosted quartz sand grains.

Lithology: conglomerate; limestone

Underhill Formation, Greenstone (Cambrian) at surface, covers 0.2 % 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

Bridgeman Hill Formation (Cambrian) at surface, covers 0.9 % of this area

Bridgeman Hill Formation - Undifferentiated dolomite, slate, and conglomerate, on east limb of St. Albans synclinorium, about equivalent to Dunham, Parker, Rugg Brook, and Saxe Brook Formations.

Lithology: dolostone (dolomite); slate; conglomerate

Sweetsburg Formation (Cambrian) at surface, covers 1.0 % of this area

Sweetsburg Formation - Black, carbonaceous, well-cleaved slate with characteristic thin (1-5 mm) whitish silty bedding laminae; in St Albans and Hinesburg synclinoria and Cambridge syncline.

Lithology: slate

Parker Slate (Cambrian) at surface, covers 0.9 % of this area

Parker Slate - Gray to black micaceous shale and slate, includes dolomite, sandstone, and quartzite lenses; chiefly on west limb of St. Albans synclinorium.

Lithology: slate; shale; dolostone (dolomite); sandstone; quartzite

Clarendon Springs, Ticonderoga, and Rock River Dolomites; Gorge Formation (Cambrian) at surface, covers 0.6 % of this area

Clarendon Springs, Ticonderoga, and Rock River Dolomite; Gorge Formation - Fairly uniform, massive, smooth weathered gray dolomite characterized by numerous geodes and knots of white quartz; quartz sandstone and irregular masses of chert are near the top. Called the Ticonderoga west of Orwell and Champlain thrusts and the Rock River east of Philipsburg thrust. The Gorge is a partly conglomeratic facies on the west limb of the St. Albans synclinorium..

Lithology: dolostone (dolomite); sandstone; chert; conglomerate

Pinnacle Formation, Tibbit Hill Volcanic Member (Cambrian) at surface, covers 7 % of this area

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

Lithology: greenstone

Middlebury and Chazy Limestone; Undifferentiated Youngman and Carman Formations (Ordovician) at surface, covers 0.2 % of this area

Middlebury and Chazy Limestone, Undifferentiated Youngman and Carman Formations - Dark blue-gray, somewhat nodular and granular limestone with buff dolomite and shaly interbeds a fraction of an inch thick and 2 to 4 inches apart. The Middlebury, which is east of Champlain and Orwell thrusts, and the Youngman, which is east of Highgate Springs thrust, are, due partly to deformation, more slaty in appearance than the Chazy, which is west of the major thrusts. The Carman is a quartz sandstone with shaly partings that underlies the Youngman. The Chazy contains 3 members.

Lithology: limestone; dolostone (dolomite); shale; sandstone

Highgate Formation (Ordovician) at surface, covers 0.7 % of this area

Highgate Formation - Banded blue limestone and calcareous slate; local lenses of limestone conglomerate; on west limb of St. Albans synclinorium.

Lithology: limestone; slate; conglomerate

Cheshire Quartzite (Cambrian) at surface, covers 5 % of this area

Cheshire Quartzite - Very massive, white to faintly pink or buff vitreous quartzite near the top in west-central and southwestern VT; predominantly a less massive appearing mottled gray, somewhat phyllitic quartzite; dolomitic sandstone and conglomerate near the base of the formation in west-central VT apparently grades southward into the Dalton Formation. Mapping in Bristol Notch and along the Green Mountain front indicate that the Cheshire Quartzite appears to be at least 2500 ft thick, which is about 2.5 times the original estimated thickness to the north and south. Near the base, the Cheshire is a massive argillaceous feldspathic meta-sandstone, containing recrystallized quartz and K-feldspar in a muscovite and biotite matrix. These lithologies grade upward through medium to thick-bedded schistose feldspathic meta-sandstones to clean, massive 'quartzites' of the Green Mountain front. Rocks currently mapped as the eastern-most Cheshire Quartzite probably belong to the Pinnacle Formation and are in fault contact with the Cheshire (Condon, 1993).

Lithology: quartzite; sandstone; conglomerate

Hazens Notch Formation, Belvidere Mountain Amphibolite Member (Cambrian) at surface, covers < 0.1 % 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

Ottauquechee Formation (Cambrian) at surface, covers 0.8 % 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

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

Hathaway Formation - Gray to black argillite and bedded radiolarian chert, with included blocks and fragments of chert, limestone, dolomite, sandstone and graywacke.

Lithology: argillite; chert; limestone; dolostone (dolomite); sandstone; graywacke

Pinney Hollow Formation, carbonaceous phyllite and schist (Cambrian) at surface, covers 9 % of this area

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

Lithology: phyllite; schist

Chipman, Bridport, and Beldens Formations, Providence Island Dolomite; Beldens Member (Ordovician) at surface, covers 0.9 % of this area

Chipman, Bridport, and Beldens Formations, Providence Island Dolomite; Beldens Member - Interbedded buff to brown heavily scored dolomite and white to blue-gray marble and limestone; designated Beldens Formation east of Highgate Springs thrust.

Lithology: dolostone (dolomite); marble; 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

Sweetsburg Formation, Skeels Corners Slate and Mill River Conglomerate Members Undifferentiated (Cambrian) at surface, covers 3 % of this area

Sweetsburg Formation, Skeels Corners Slate and Mill River Conglomerate Members Undifferentiated - Black slate; local dolomite, sandstone, dolomite conglomerate, limestone bioherm, limestone, and calcareous shale. The Mill River is a basal limestone conglomerate.

Lithology: slate; dolostone (dolomite); sandstone; conglomerate; limestone; shale

Underhill Formation, White Brook Member (Cambrian) at surface, covers 0.2 % 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

Pinnacle Formation (Cambrian) at surface, covers 22 % 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

Orwell Limestone and Isle la Motte and Lowville Limestones (Ordovician) at surface, covers 0.1 % of this area

Orwell Limestone and Isle la Motte and Lowville Limestones - Smooth ledged, sublithographic and lithographic, dove gray weathered limestone commonly cut by veins of white calcite; beds filled with fossil shell fragments are characteristic. The Lowville is a thin, undifferentieated unit near the base of the Orwell that is characteristically ashen gray and contains abundant Phytopsis tubulosum. The Isle La Motte is about the equivalent of the Orwell in areas west of Champlain thrust, on Isle La Motte and near South Hero, Highgate, Swanton, and St. Albans; it is locally underlain by the Lowville, which is too thin to show on map. The Sawyer Bay is herein defined as a member of the Lowville Formation of the Black River Group. Occurs approximately in the middle of the Lowville throughout the Champlain Valley and represents a significant deepening event. Lower part of the Lowville was deposited in a shallow lagoonal environment, while the Sawyer Bay was deposited in a subtidal normal marine environment. Deposition probably the result of high angle block faulting in the Champlain basin. Member is very dark gray to black micrite to sparite in composition with irregular "lumpy" bedding, wavy lamination, cross-lamination, and ripple marks. Irregularly shaped, scattered chert nodules are concentrated in specific horizons. Contains a few large and small brachiopods, trilobite fragments and some fossil hash. Member is approximately 6 ft thick at Sawyer Point, South Hero Island, northwestern VT; thins to 2 ft at Arnold Bay, and becomes an indistinct rubbly unit at Crown Point, northeastern NY. The Lowville, at Crown Point, also contains the House Creek Member. The House Creek is also present in northwestern NY, southern Ontario, and the Black River Valley, but is not seen at Sawyer Point or Arnold Bay. The Lowville reaches a maximum thickness of 50 ft at Crown Point and a minimum of 24 ft at Sawyer Point. The Lowville overlies the Pamelia Formation and underlies the Chaumont Formation. Age is Middle Ordovician (Blackriveran). (Bechtel and Mehrtens, 1995).

Lithology: limestone

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