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Geologic units containing granofels

Arizona

Early Proterozoic metamorphic rocks (Early Proterozoic)

Undivided metasedimentary, metavolcanic, and gneissic rocks. (1600-1800 Ma)

Early Proterozoic metasedimentary rocks (Early Proterozoic)

Metasedimentary rocks, mostly derived from sandstone and shale, with minor conglomerate and carbonate rock. Includes quartz-rich, mostly nonvolcanic Pinal Schist in southeastern Arizona and variably volcanic-lithic sedimentary rocks in the Yavapai and Tonto Basin supergroups in central Arizona. (1600-1800 Ma)

Jurassic sedimentary and volcanic rocks (Jurassic)

Sandstone and conglomerate derived from volcanic rocks with associated intermediate-composition lava flows, breccias, and tuffs. In southern Arizona this unit includes rocks of the Artesa sequence, Pitoikam Formation, Mulberry Wash volcanics, Rudolfo Red Beds, Recreation Red Beds, and Gardner Canyon Formation. In western Arizona it includes the Harquar Formation, rocks of Slumgullion, and related(?) unnamed units in the Kofa and Middle Mountains. This unit is characterized by maroon, brown, and purplish-gray volcanic-lithic sandstone and siltstone, with subordinate to abundant conglomerate, quartz-rich sandstone and sparse limestone. (150-170 Ma)

Jurassic to Cambrian metamorphosed sedimentary rocks (Cambrian to Jurassic)

Highly faulted and folded rocks of units Jv, J_, and Pz, deformed and metamorphosed in Jurassic, Cretaceous and Tertiary time. This unit is restricted to west-central Arizona. (160-540 Ma)

Paleozoic sedimentary rocks (Paleozoic)

Undivided Paleozoic limestone, dolostone, quartzite, shale, and related sedimentary rocks. (248-544 Ma)

California

Precambrian rocks, undivided, unit 2 (Mojave Desert and Transverse Ranges) (Early Proterozoic to Miocene)

Conglomerate, shale, sandstone, limestone, dolomite, marble, gneiss, hornfels, and quartzite; may be Paleozoic in part

Connecticut

Basal member [of Taine Mountain Formation] (Lower? Ordovician)

Basal member [of Taine Mountain Formation] around Waterbury dome - Differs from rest of Taine Mountain Formation in being especially well layered and generally less micaceous and schistose.

Black Hill Member [of Quinebaug Formation] (Middle Ordovician or older)

Black Hill Member [of Quinebaug Formation] - Gray, medium- to fine-grained, well-layered schist and granofels, composed of oligoclase, quartz, and biotite, commonly with hornblende or muscovite, and locally with calcite, garnet, or epidote.

Cobble Mountain Formation (Middle Ordovician)

Cobble Mountain Formation - Gray to silver (not rusty), medium- to coarse-grained, generally layered schist and granofels, composed of quartz, oligoclase, muscovite, biotite, and garnet, and locally kyanite and staurolite or sillimanite. Some amphibolite layers.

Erving Formation (Devonian)

Erving Formation - Gray, medium-grained, well-foliated and generally well layered granofels and schist, composed of quartz, plagioclase, and biotite, also muscovite in schist, and accessory garnet and kyanite.

Golden Hill Schist (Lower? Ordovician)

Golden Hill Schist (may be equivalent to part of Trap Falls Formation) - Gray to silvery, medium- to coarse-grained, generally layered schist and granofels, composed of quartz, muscovite, biotite, plagioclase, and garnet.

Golden Hill Schist (Lower? Ordovician)

Golden Hill Schist (may be equivalent to part of Trap Falls Formation) - Gray to silvery, medium- to coarse-grained, generally layered schist and granofels, composed of quartz, muscovite, biotite, plagioclase, and garnet.

Hawley Formation (Middle Ordovician)

Hawley Formation (carbonaceous schist facies) - Gray, rusty-weathering, fine- to medium-grained, generally layered schist and granofels, composed of quartz, oligoclase, and biotite; some muscovite and graphite, rare garnet and kyanite or sillimanite. Layers of quartz-spessartine rock (coticule) common.

Lower member [of Bigelow Brook Formation] (Silurian or Ordovician or both)

Lower member [of Bigelow Brook Formation] - Chiefly gray, medium-grained, well-layered granofels, composed of quartz, oligoclase, and biotite, commonly with garnet and sillimanite, interlayered with thinly fissile sillimanitic, graphitic, pyrrhotite schist.

Middle member [of Bigelow Brook Formation] (Silurian or perhaps Ordovician)

Middle member [of Bigelow Brook Formation] - Greenish-gray, medium-grained calc-silicate rock, composed of plagioclase, quartz, and diopside (locally hornblende and scapolite), interbedded with schist and granofels composed of plagioclase, quartz, biotite, and commonly garnet and sillimanite.

Middletown Formation (Middle Ordovician)

Middletown Formation ( = Ammonoosuc Volcanics of New Hampshire) - Heterogeneously interlayered dark- to light-gray, generally medium grained gneiss and granofels, ranging from quartz-biotite gneiss through felsic amphibole gneiss to amphibolite and characteristically containing anthophyllite or cummingtonite with or without hornblende. Also layers of calc-silicate rock and of biotite gneiss with quartz-sillimanite nodules.

Middletown Formation (Middle Ordovician)

Middletown Formation ( = Ammonoosuc Volcanics of New Hampshire) - Heterogeneously interlayered dark- to light-gray, generally medium grained gneiss and granofels, ranging from quartz-biotite gneiss through felsic amphibole gneiss to amphibolite and characteristically containing anthophyllite or cummingtonite with or without hornblende. Also layers of calc-silicate rock and of biotite gneiss with quartz-sillimanite nodules.

Mount Pisgah Member of Littleton Formation (Devonian)

Mount Pisgah Member of Littleton Formation - Gray, medium-grained, well-layered (locally graded) granofels or micaceous quartzite with some schist, composed of quartz, oligoclase, biotite, garnet, and sillimanite.

Oronoque Schist (Lower? Ordovician)

Oronoque Schist - Gray to silver, medium- to fine-grained, well-layered to laminated schist and granofels, composed of quartz, oligoclase, or albite, muscovite or sericite, biotite, or chlorite, and in western belt local garnet, staurolite, and kyanite. Small lenses of amphibolite or greenstone.

Ratlum Mountain Schist (Lower Ordovician)

Ratlum Mountain Schist - Gray, medium-grained, interlayered schist and granofels, composed of quartz, oligoclase, muscovite (in the schist), biotite, and garnet, also staurolite and kyanite in the schist. Numerous layers and lenses of amphibolite; also some of quartz-spessartine (coticule) and calc-silicate rock.

Ratlum Mountain Schist (Lower? Ordovician)

Ratlum Mountain Schist - Gray, medium-grained, interlayered schist and granofels, composed of quartz, oligoclase, muscovite (in the schist), biotite, and garnet, also staurolite and kyanite in the schist. Numerous layers and lenses of amphibolite; also some of quartz-spessartine (coticule) and calc-silicate rock.

Ratlum Mountain Schist plus Amphibolite unit [in Ratlum Mountain Schist] (Lower Ordovician)

Ratlum Mountain Schist plus Amphibolite unit [in Ratlum Mountain Schist] - Ratlum Mountain Schist - Gray, medium-grained, interlayered schist and granofels, composed of quartz, oligoclase, muscovite (in the schist), biotite, and garnet, also staurolite and kyanite in the schist. Numerous layers and lenses of amphibolite; also some of quartz-spessartine (coticule) and calc-silicate rock. Amphibolite unit [in Ratlum Mountain Schist] (Lower? Ordovician) - Black or mottled, generally massive amphibolite and hornblende gneiss, composed of hornblende and andesine, commonly with minor quartz and magnetite, and locally with garnet, biotite, and epidote.

Rowe Schist (Lower Ordovician or Cambrian or both)

Rowe Schist - Light-gray to silvery, fine- to medium-grained, generally poorly layered schist, composed of quartz, muscovite, biotite, oligoclase, and generally garnet, staurolite, and kyanite or sillimanite. Layers of granofels common; also some layers of amphibolite, quartz-spessartine rock (coticule), and calc-silicate rock.

Schist and granulite member [of Trap Falls Formation] (Middle or Lower Ordovician)

Schist and granulite member [of Trap Falls Formation] - Interlayered gray to silvery, medium- to coarse-grained schist and fine-grained granofels, composed of quartz, sodic plagioclase, biotite, and muscovite; garnet common in schist.

Scotland Schist (Devonian or Silurian or both)

Scotland Schist - Gray to silvery, locally rusty, fine- to medium-grained schist, composed of quartz, muscovite, biotite, staurolite, and oligoclase, locally with kyanite or sillimanite; interlayered, especially below and to the west, with quartz-oligoclase-biotite schist and granofels and locally with quartzite.

Southbridge Formation (Silurian or Ordovician or both)

Southbridge Formation - Dark- to light-gray, locally rusty, fine- to medium-grained interlayered granofels and schist, composed of quartz, plagioclase, and biotite, with muscovite in schist, and amphibole, calc-silicate minerals, K-feldspar in certain layers; also locally mappable units and thinner layers of calc-silicate rock, amphibolite, and sillimanite-garnet and sillimanite-graphite-pyrrhotite schist.

Southbridge Formation (Silurian or Ordovician or both)

Southbridge Formation - Dark- to light-gray, locally rusty, fine- to medium-grained interlayered granofels and schist, composed of quartz, plagioclase, and biotite, with muscovite in schist, and amphibole, calc-silicate minerals, K-feldspar in certain layers; also locally mappable units and thinner layers of calc-silicate rock, amphibolite, and sillimanite-garnet and sillimanite-graphite-pyrrhotite schist.

Southington Mountain Member [of The Straits Schist] (Devonian or Silurian or both)

Southington Mountain Member [of The Straits Schist] - Gray to silvery, non-rusty, medium-grained, well-layered alternating schist and granofels, composed of quartz, oligoclase, muscovite, biotite, and garnet, commonly with staurolite and kyanite (or sillimanite); schist commonly graphitic. Metamorphosed strata named Southington Mountain Schist by Fritts (1963) is traceable into southern Bristol quad., and is here revised as Southington Mountain Member of The Straits Schist. Consists of alternating bands of quartz-feldspar granulite and of graphitic, muscovite-biotite schist. Unit is characterized by distinct, widespread, graded bedding and locally abundant staurolite. Unit may correlate with the Goshen Formation of the Heath quad, MA-VT, of Middle Silurian to Early Devonian age (Simpson, 1990).

Taine Mountain and Collinsville Formations undivided (Middle to Lower? Ordovician)

Taine Mountain and Collinsville Formations undivided - see Ot and Oc.

Taine Mountain Member (Lower? Ordovician)

Taine Mountain Member - Gray, medium-grained, generally fairly well layered to well-laminated ("pin-stripe") gneissic or schistose granofels, composed of quartz, oligoclase, biotite, muscovite, and garnet, and locally staurolite and kyanite or sillimanite. The Taine Mountain Formation of Stanley (1964) is here adopted in the Collinsville and Bristol quads, CT. Includes 3 pinstriped units: the Wildcat, Scranton Mountain, and Whigville Members, also adopted from Stanley (1964). Underlies Bristol Gneiss (revised). Correlates with the Savoy Schist of Emerson (1898), Missisquoi Schist or Group of Richardson (1919, 1924), in MA; and the Moretown Formation of Cady (1956) in MA and VT. Age is Middle Ordovician (Simpson, 1990).

Upper member [of Bigelow Brook Formation] (Silurian and perhaps Ordovician)

Upper member [of Bigelow Brook Formation] - Chiefly gray, rusty-weathering, medium-grained, generally well layered and locally fissile schist, composed of plagioclase, quartz, biotite, garnet, and sillimanite, locally with K-feldspar or cordierite, fissile layers commonly with graphite and pyrrhotite, interlayered with quartzose granofels with less biotite but with calc-silicate minerals.

Upper member [of Middletown Formation] (Middle Ordovician)

Upper member [of Middletown Formation] - Light-gray, generally rusty weathering, well-layered gneiss and granofels, composed of oligoclase, quartz, biotite, and amphibole (cummingtonite, anthophyllite, gedrite, or hornblende, or several of these), also garnet and chlorite. Many layers of amphibolite and biotite gneiss throughout.

Whigville Member [of Taine Mountain Formation] (Lower? Ordovician)

Whigville Member [of Taine Mountain Formation] - Gray, medium-grained, generally fairly well layered to well-laminated ("pin-stripe") gneissic or schistose granofels, composed of quartz. oligoclase, biotite, muscovite, and garnet, and locally staurolite and kyanite or sillimanite. The Taine Mountain Formation of Stanley (1964) is here adopted in the Collinsville and Bristol quads., CT. Includes three pinstriped units, the Wildcat, Scranton Mountain, and Whigville Members of Stanley (1964), also adopted. Whigville Member consists of plagioclase-quartz gneiss marked by distinctive thin layering (pinstriping) of muscovite and biotite. Thickness is 3,000 ft. Overlies the Scranton Mountain Member; underlies the Bristol Gneiss (revised). The Taine Mountain correlates with the Savoy Schist of Emerson (1898), Missisquoi Schist or Group of Richardson (1919, 1924), in MA; and the Moretown Formation of Cady (1956) in MA and VT. Age is Middle Ordovician (Simpson, 1990).

Wildcat Member [of Taine Mountain Formation] (Lower? Ordovician)

Wildcat Member [of Taine Mountain Formation] - Gray, medium-grained, generally fairly well layered to well-laminated ("pin-stripe") gneissic or schistose granofels, composed of quartz, oligoclase, biotite, muscovite, and garnet, and locally staurolite and kyanite or sillimanite. The Taine Mountain Formation of Stanley (1964) is here adopted in the Collinsville and Bristol quads., CT. Includes three pinstriped units, the Wildcat, Scranton Mountain, and Whigville Members of Stanley (1964), also adopted. Wildcat Member is the basal pinstriped gneiss unit of the Taine Mountain, which correlates with the Savoy Schist of Emerson (1898), Missisquoi Schist or Group of Richardson (1919, 1924) in MA; and the Moretown Formation of Cady (1956) in MA and VT. Inferred age is Middle Ordovician (Simpson, 1990).

Massachusetts

Belchertown Complex (Precambrian to Paleozoic)

Belchertown Complex (intrudes De) - Inclusions of granofels (age uncertain).

Calc-silicate granofels and gneiss (Proterozoic Y)

Calc-silicate granofels and gneiss - Including calcitic or dolomitic chondrodite-diopside marble, coarse hornblende-plagioclase-diopside and diopside rock, locally containing beds of lustrous muscovite-kyanite sillimanite-garnet schist.

Cobble Mountain Formation (Middle Ordovician)

Cobble Mountain Formation - Light-brown, fine- to medium-grained pelitic schist and granofels locally graded in beds less than 15 cm thick. Local amphibolite. Rare calc-silicate rock, feldspar gneiss, coticule and cummingtonite schist.

Cobble Mountain Formation (Middle Ordovician)

Cobble Mountain Formation - Red rusty-weathering schist containing thin beds of white quartz-plagioclase granofels and vitreous quartzite. Local amphibolite and thin anthophyllite amphibolite.

Collinsville Formation (Middle Ordovician or older)

Collinsville Formation - Amphibolite and minor plagioclase gneiss. Magnetite-hornblende granofels near top.

Collinsville Formation (Middle Ordovician or older)

Collinsville Formation - Rusty-weathering, massive granofels containing anthophyllite and tourmaline; some rusty-stained gneiss.

Collinsville Formation (Middle Ordovician or older)

Collinsville Formation - Interlayered amphibolite and white felsic gneiss containing biotite, hornblende, and magnetite. Local calc-silicate beds. Coticule-bearing granofels, muscovite quartzite and amphibolite in upper part.

Dalton Formation (Lower Cambrian and Proterozoic Z)

Dalton Formation - Well-layered orange-tan feldspathic, biotite-spotted, muscovite-microcline-quartz gneiss and granofels.

Erving Formation (Lower Devonian)

Erving Formation - Biotite-plagioclase granofels, minor mica schist and calc-silicate granofels, and layers of epidote amphibolite.

Fitch Formation (Upper Silurian)

Fitch Formation - Calc-silicate granofels, biotite granofels, minor sulfidic schist and marble. Correlated with the fossiliferous Fitch Formation of western New Hampshire. Although the text and figures of this report show the Fitch as Silurian, a footnote [added just before this report went to press] cites a change in age from Silurian to Early Devonian based on conodonts found at the Bernardston, MA, locality, as reported in Elbert and others (1988). In Bronson Hill anticlinorium in MA, Fitch occurs as lenses between Clough Quartzite and Littleton Formation. Most common rock types in MA are gray, massive to weakly bedded, quartz-labradorite-biotite granulite containing a moderate amount of some combination of calc-silicate minerals (calcic amphibole, zoisite or clinozoisite, diopside, sphene, and microcline); commonly interbedded with biotite-free granulite that contains same calc-silicate minerals. One small exposure consists of nearly pure calcite marble. Larger lenses of Fitch consist of varieties of schist, similar to Partridge Formation. Best exposures are in low hills west of village of Orange, northeast of junction of MA Hwys 2A and 78. As shown on MA State bedrock geologic map, Fitch everywhere overlies Clough Quartzite and is never in contact with Partridge. Fossils dating the Fitch as Pridolian (Harris and others, 1983) are all from Littleton, NH, area [however, see mention of footnote, above] (Hatch and others, 1988).

Gile Mountain Formation (Lower Devonian)

Gile Mountain Formation - Gray, slightly rusty, poorly bedded phyllite and schist containing 20 cm to 2 m beds of light-gray, fine-grained quartzite, local punky-brown weathering calcareous granofels or quartzose marble, and pods and stringers of vein quartz.

Gile Mountain Formation (Lower Devonian)

Gile Mountain Formation - Like Dgm but having a higher percentage of quartzite.

Goshen Formation (Lower Devonian)

Goshen Formation - Poorly bedded Dg schist containing beds, 0.5 to 2.5 m thick, of punky-weathering calcareous pale green granofels with calc-silicate granofels rims.

Goshen Formation (Lower Devonian)

Goshen Formation - Light gray-brown micaceous quartzite and quartz-mica-garnet schist in beds as much as 6 m thick. Calc-silicate granofels and rare punky-weathering calcareous granofels.

Goshen Formation (Lower Devonian)

Goshen Formation - Dg containing beds of punky-weathering calcareous granofels more than 15 cm thick near the contact with the Waits River Formation.

Goshen Formation (Lower Devonian)

Goshen Formation - Similar to Dg but having scattered beds of calcareous granofels.

Hawley Formation (Middle Ordovician)

Hawley Formation - White to very-light-green plagioclase granofels containing minor garnet. Plagioclase-hornblende-garnet gneiss containing hornblende blades and garnet megacrysts. As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).

Hawley Formation (Middle Ordovician)

Hawley Formation - Interbedded amphibolite, greenstone, feldspathic schist and granofels. Coarse plagioclase in some amphibolite near top; local coarse hornblende blades or sprays. Sparse coticule (Emerson, 1917, p. 43). As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).

Hawley Formation (Middle Ordovician)

Hawley Formation - Medium-gray plagioclase-hornblende-chlorite schist containing megacrysts of plagioclase and angular fragments of feldspar granofels, epidote-plagioclase granofels, and dark-gray amphibolite. As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).

Hoosac Formation (Lower Cambrian and Proterozoic Z)

Hoosac Formation - Undifferentiated Hoosac Formation.

Hoosac Formation (Lower Cambrian and Proterozoic Z)

Hoosac Formation - Light-gray, albite-biotite granofels and schist, pseudoconglomerate and blue quartz pebble conglomerate.

Hoosac Formation (Lower Cambrian and Proterozoic Z)

Hoosac Formation - Greenish chlorite-albite-magnetite-sericite-quartz schist and granofels.

Intimately interfolded Littleton and Partridge Formations (Lower Devonian and Middle Ordovician)

Intimately interfolded Littleton and Partridge Formations - In areas of poor exposure and incomplete mapping.

Lee Gneiss (Proterozoic Y)

Lee Gneiss - Hornblende-spotted plagioclase-hornblende-quartz gneiss and granofels and well-layered biotite-hornblende-plagioclase-quartz gneiss containing knots of diopside or epidote.

Marlboro Formation (Ordovician, Cambrian, or Proterozoic Z)

Marlboro Formation - Thinly layered amphibolite, biotite schist and gneiss, minor calc-silicate granofels and felsic granofels.

Moretown Formation (Middle Ordovician or older)

Moretown Formation - Buff to gray, medium- to coarse-grained, poorly bedded mica-rich schist showing dark-green chlorite clots. Some pinstriped granofels.

Moretown Formation (Middle Ordovician or older)

Moretown Formation - Nubble garnet schist, pinstriped granofels, and fine-grained amphibolite in equal parts.

Moretown Formation (Middle Ordovician or older)

Moretown Formation - Light gray schist; some granofels. More schistose than Om.

Moretown Formation (Middle Ordovician or older)

Moretown Formation - Light-greenish-gray to buff, fine-grained, pinstriped granofels and schist.

Partridge Formation (Middle Ordovician)

Partridge Formation (includes Brimfield Schist of Emerson, 1917) - Mafic and felsic gneisses of volcanic derivation with calc-silicate granofels.

Paxton Formation (Silurian)

Paxton Formation - Diopside calc-silicate granofels. The Paxton, here of group rank, includes strata formerly mapped in CT as the Hebron Formation and in MA as the Paxton Formation. It conformably overlies the Oakdale Formation and structurally and conformably underlies the Brimfield Group. It is undivided in central MA; in northeast CT and adjacent MA it is divided into the Dudley and Southbridge Formations. Age is Late Proterozoic(?) based on the intrusion of 440 m.y. Hedgehog Hill gneiss into the overlying Brimfield Group and an age of 1188 m.y. for detrital zircons from the Paxton (Pease, 1989).

Paxton Formation (Silurian)

Paxton Formation - Southbridge Member - Thick- to thin-bedded biotite granofels and calc-silicate granofels. The Southbridge Formation here includes strata formerly mapped in CT as the Hebron Formation and in adjacent MA as the Paxton Formation. It is assigned to the Paxton Group. A sillimanite schist member is described in CT; it is conformably overlain by biotite schist and gneiss. Age is Late Proterozoic(?) based on intrusion of 440 m.y. Hedgehog Hill gneiss into overlying Brimfield Group and an age of 1188 m.y. for detrital zircons from the Paxton (Pease, 1989).

Paxton Formation (Silurian)

Paxton Formation - Bigelow Brook Member - Biotite granofels, sulfidic schist, and minor calc-silicate granofels. The Paxton, here of group rank, includes strata formerly mapped in CT as the Hebron Formation and in MA as the Paxton Formation. It conformably overlies the Oakdale Formation and structurally and conformably underlies the Brimfield Group. It is undivided in central MA; in northeast CT and adjacent MA it is divided into the Dudley and Southbridge Formations. Age is Late Proterozoic(?) based on the intrusion of 440 m.y. Hedgehog Hill gneiss into the overlying Brimfield Group and an age of 1188 m.y. for detrital zircons from the Paxton (Pease, 1989).

Paxton Formation (Silurian)

Paxton Formation - Undifferentiated biotite granofels, calc-silicate granofels, and sulfidic schist. The Paxton, here of group rank, includes strata formerly mapped in CT as the Hebron Formation and in MA as the Paxton Formation. It conformably overlies the Oakdale Formation and structurally and conformably underlies the Brimfield Group. It is undivided in central MA; in northeast CT and adjacent MA it is divided into the Dudley and Southbridge Formations. Age is Late Proterozoic(?) based on the intrusion of 440 m.y. Hedgehog Hill gneiss into the overlying Brimfield Group and an age of 1188 m.y. for detrital zircons from the Paxton (Pease, 1989).

Putney Volcanics (Lower Devonian)

Putney Volcanics - Light greenish-gray plagioclase-quartz-muscovite phyllite and granofels.

Russell Mountain Formation (Silurian)

Russell Mountain Formation - Quartzite, calc-silicate granofels, and calc-silicate marble. Correlated with the fossiliferous Shaw Mountain Formation of eastern Vermont. In original definition of Russell Mountain Formation (Hatch and others (1970), calcareous granofels on Woronoco dome was included in unit. Subsequent mapping by Stanley and others (1982) indicates that rocks mapped on Woronoco dome are different from the rest of Russell Mountain Formation and are more logically included in overlying Lower Devonian sequence (mapped as an unnamed member of Goshen Formation in fig. 3). Other than this modification and mapping a few lenses of Russell Mountain Formation just north of Massachusetts Turnpike, original definition of Russell Mountain stands. Thickness does not exceed 35 m, but its correlative in CT, the basal member of The Straits Schist of Rodgers (1982, 1985), is locally at least twice as thick. Has not been shown to correlate with either Clough Quartzite or Fitch Formation to the east. Russell Mountain Formation is highly discontinuous except near Shelburne Falls dome. Locally overlies members A and D of Cobble Mountain Formation; overlain everywhere by Goshen Formation. Silurian age is based on correlation with discontinuous lenses of similar rocks at same stratigraphic position as Shaw Mountain Formation of VT. Recent field trips with J.B. Thompson, Jr. (Harvard University) and others has raised questions as to whether many of those rocks in southern VT are actually Shaw Mountain. Shaw Mountain Formation has been assigned a firm age of late Llandoverian to Gedinnian north of Albany, VT, based on HOWELLELA (Boucot and Thompson, 1963; Konig, 1961) (Hatch and others, 1988).

Waits River Formation (Lower Devonian)

Waits River Formation - Dw containing thick (1 m) beds of calcareous granofels. Mapped only in Colrain quadrangle; included in Dw elsewhere.

Waits River Formation (Lower Devonian)

Waits River Formation - Interbedded medium- to dark-gray, moderately rusty weathering, highly contorted, unbedded schist and punky-weathering calcareous granofels or quartzose marble, and pods and stringers of vein quartz.

Washington Gneiss (Proterozoic Y)

Washington Gneiss - Well-layered, rusty-tan weathering muscovite-biotite plagioclase-microcline-quartz granofels containing layers of rusty sulfidic calc-silicate rocks.

Maine

Ordovician - Precambrian Z Ellsworth formation quartz granofels member (Ordovician - Precambrian Z)

Ordovician - Precambrian Z Ellsworth formation quartz granofels member

Silurian Sangerville Formation (Silurian)

Silurian Sangerville Formation

Silurian Sangerville Formation limestone member (Silurian)

Silurian Sangerville Formation limestone member

Silurian Sangerville Formation Patch Mountain member (Silurian)

Silurian Sangerville Formation Patch Mountain member

North Carolina

Battleground Formation (Late Proterozoic)

Battleground Formation - quartz-sericite schist with metavolcanic rock, quartz-pebble metaconglomerate, kyanite-sillimanite quartzite, and garnet-quartz rock.

New Hampshire

Frontenac Formation, Massive tan- or brown-weathering calcite-ankerite-muscovite granofels and interbedded gray metapelite (Silurian?)

Frontenac Formation, Massive tan- or brown-weathering calcite-ankerite-muscovite granofels and interbedded gray metapelite - Probably partly a facies equivalent to the Waits River Formation in Vermont.

Madrid and Smalls Falls Formations, undivided (Silurian)

Madrid and Smalls Falls Formations, undivided.

Madrid Formation (Upper Silurian? )

Madrid Formation - Massive to weakly foliated, purple biotite-feldspar granofels, layered calc-silicate, and dark pelitic-sulfidic schist containing calc-silicate pods in upper member; an eastern facies equivalent to the upper part of the Fitch Formation. Locally mapped as the Warner Formation of Nielson (1981) in southern New Hampshire.

Massabesic Gneiss Complex (Late Proterozoic)

Massabesic Gneiss Complex - Quartzose-feldspathic gneiss and biotite schists (locally rusty), granofels, and cal-silicate rocks closely intruded by, and grading into, a pink gneissic granite (623 Ma) that produced a migmatite.

Merrimack Group, Berwick Formation (Ordovician? - Silurian?)

Merrimack Group, Berwick Formation - Purple biotite-quartz-feldspar granofels or schist and interbeds of calc-silicate granofels and minor metapelites. Stratigraphic sequence with respect to Eliot Formation uncertain

Merrimack Group, Berwick Formation, Unnamed member (Ordovician? - Silurian?)

Merrimack Group, Berwick Formation, Unnamed member - Contains more calc-silicate (15 percent) than does the remainder of the formation (5 percent).

Perry Mountain and Rangeley Formations, undivided (Silurian)

Perry Mountain and Rangeley Formations, undivided.

Rangeley Formation, Pink to green calc-silicate and purple biotite granofels (Lower Silurian (Llandoverian))

Rangeley Formation, Pink to green calc-silicate and purple biotite granofels - Thinly bedded. Close to transition from lower to upper parts of the Rangeley Formation. Probably equivalent to part of Paxton Formation of Zen and others (1983) in Massachusetts.

Rangeley Formation, undivided (Lower Silurian (Llandoverian))

Rangeley Formation, undivided.

Smalls Falls Formation, undivided (Upper to Middle Silurian (Ludlovian and Wenlockian))

Smalls Falls Formation, undivided -Very rusty weathering, thinly bedded sulfidic-graphitic schist and pyrrhotitic calc-silicate granofels. Eastern facies equivalent to lower part of the Fitch Formation. Locally mapped as Francestown Formation of Nielson (1981) in southern New Hampshire.

New Jersey

Gneiss granofels and Migmatite (Middle Proterozoic)

Gneiss granofels and Migmatite - Gneiss and granofels range in composition from felsic to intermediate to mafic; intermediate compositions predominate. Contains a wide variety of rock types including graphitic schist and marble. Many rocks were injected by a granitoid that has blue quartz and augen of potassic feldspar and are arteritic migmatites. One body of gneiss contains a 1 m by 0.5 m (3 by 2 ft) phacoid of gabbro that is interpreted to be an olistolith. Unit probably represents a sequence of meta-sedimentary and metavolcanic rocks that have been heavily injected and migmatized by felsic magma.

Potassic Feldspar Gneiss (Middle Proterozoic)

Potassic Feldspar Gneiss - Light-gray- to pinkish-buff-weathering, pinkish-white to light-pinkish-gray, fine- to medium-grained, moderately foliated gneiss and lesser amounts of granofels composed of quartz, microcline, microcline microperthite and local accessory amounts of biotite, garnet, sillimanite, and opaque minerals.

Quartz-Oligoclase Gneiss (Middle Proterozoic)

Quartz-Oligoclase Gneiss - White-weathering, light-greenish-gray, medium- to coarse-grained, moderately layered to indistinctly foliated gneiss and lesser amounts of granofels composed of quartz, oligoclase or andesine, and, locally, biotite, hornblende and (or) clinopyroxene. Contains thin amphibolite layers.

Washington

Pre-Tertiary ultrabasic intrusive rocks (Late-Jurassic)

Peridotite and pyroxenite; generally altered partly or completely to serpentine. Includes serpentinite and saxonite on Sumas Mountain, Whatcom County.