South of 43 degrees; slate, shale, thin quartzite, includes Stuyvesant Conglomerate, Diamond Rock Quartzite, Curtis Mountain Quartzite, and Bomoseen Graywacke Members.
Minor shale.
Canajoharie Shale
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.
Principally pelite; lesser quartzite, limestone, conglomerate, graywacke.
Nassau Formation of Potter (1972) - Rensselaer Graywacke member. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
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).
Austerlitz Phyllite - minor quartzite
Slate, phyllite, schist, metagraywacke.
Underlying bedrock geology unknown.
South of Troy; shale, conglomerate, limestone.
Chaotic mixture of Early Cambrian thru Middle Ordovician pebble to block-size angular to rounded clasts in a pelitic matrix of Middle Ordovician (Barneveld) age. Rims and floors earlier submarine gravity slides of Taconian Orogeny.
South of Troy; shale, siltstone.
Minor mudstone, sandstone.
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.
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.
Shale, slate, cherts.
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).
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.
Graywacke, shale
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-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.
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.
North of Troy; shale, slate, siltstone.
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.
Calcitic and dolomitic marble.
Mohawk Valley: Dolgeville, Denley, Sugar River, Kings Falls, Glens Falls, Rockland, Amsterdam, and Lowville Limestones. Washington County: Glens Falls and Orwell Limestones.
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.
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).
Occuring as slivers caught along thrusts of later allochthones, or carbonate blocks in Taconic Melange. Also mapped as horses along normal faults.
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.
Greenstones and tuffs and/or basalt
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.
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.
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.
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.
Includes basaltic volcanics. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
Shale, argillite, quartzite.
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.
Gray and grayish-green rocks associated with Whipstock breccia on Whipstock Hill but of uncertain correlation. Part of the Taconic Allochthon.
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.
Boudins of whitish-gray-weathering, bluish-gray quartzite. Rocks of the Giddings Brook, Sunset Lake, and Bird Mountain slices. Part of the Taconic Allochthon.
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.
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.
In the Walloomsac Formation; perhaps intrusive. 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.
A black carbonaceous highly graptoliferous phyllite. 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).