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Geologic units containing metasedimentary rock

Alabama

Emuckfaw Group; Emuckfaw Group undifferentiated in part (Precambrian to Paleozoic)

Emuckfaw Group undifferentiated in part - interbedded muscovite +/- garnet-biotite schist, metagraywacke, calc-silicate rock, and quartzite; rare thin amphibolite. Includes thin layers of aluminous graphitic schist. Locally sheared to mylonite schist.

Emuckfaw Group; Glenloch Schist (Precambrian to Paleozoic)

Glenloch Schist - graphite-garnet-muscovite schist with interlayered metagraywacke.

Heflin Phyllite (Cambrian?)

Heflin Phyllite - grayish-green, medium-gray, and medium-bluish-gray calcareous sandy metasiltstone interbedded with minor greenish-gray fine to coarse-grained metasandstone and rare thin lenses of calcite and dolomite marble; an interval of greenish-gray to dark-gray phyllitic quartzite or quartz-pebble metaconglomerate is locally present near the base. The Heflin underlies the Lay Dam Formation and overlies the rocks tentatively identified as the Chilhowee Group undifferentiated.

Kahatchee Mountain Group; Brewer Phyllite (Precambrian?-Cambrian?)

Brewer Phyllite - dusky-red micaceous slate and phyllite, locally containing interbedded micaceous arkosic quartzite and metasiltstone; locally at the base is interbedded calcite and dolomite marble.

Kahatchee Mountain Group; Stumps Creek Formation (Precambrian?-Cambrian?)

Stumps Creek Formation - grayish-green micaceous metasiltstone and minor phyllite; grayish-green fine to medium-grained pyritic metasandstone in middle to upper part.

Kahatchee Mountain Group; Wash Creek Slate (Precambrian?-Cambrian?)

Wash Creek Slate - grayish-green to black micaceous, partly carbonaceous to graphitic slate and metasiltstone containing interbedded light-gray to light-brown fine to coarse-grained metasandstone.

Kahatchee Mountain Group; Waxahatchee Slate (Precambrian?-Cambrian?)

Waxahatchee Slate - dark-gray to grayish-green thin-bedded, micaceous metasiltstone, slate, and fine-grained quartzite.

Metaclastic rocks of unknown affinity (Precambrian to Paleozoic)

Metaclastic rocks of unknown affinity - in the area south of Talladega, Talladega County, the unit includes greenish-gray chlorite-sericite phyllite; in small area south of Childersburg the unit consists of greenish-gray chlorite-sericite phyllite and slate locally containing interbeds of metagraywacke; and in the area east of Columbiana, Shelby County, the unit includes dark-greenish-gray slate and metasiltstone containing interbedded coarse-grained to conglomerate quartzite.

Moffits Mill Schist (Precambrian to Paleozoic)

Moffits Mill Schist - interlayered biotite-epidote-muscovite-quartz schist, metagraywacke, and quartzite.

Sylacauga Marble Group; Fayetteville Phyllite (Cambrian?-Ordovician?)

Fayetteville Phyllite - dusky-red and medium-gray phyllite and slate interlayered with light-brown to light-gray feldspathic metasiltstone, fine-grained metasandstone and dolomite marble.

Sylacauga Marble Group; Gooch Branch Chert (Cambrian?-Ordovician?)

Gooch Branch Chert - light-gray to light-brown dolomite marble associated with abundant light-gray to white massive to moderately foliated metachert.

Talladega Group; Jemison Chert and Chulafinnee Schist undifferentiated (Silurian?-Devonian)

Jemison Chert and Chulafinnee Schist undifferentiated - grayish-white to yellowish-orange massive, thick-bedded, fine-grained, locally argillaceous, locally fossiliferous metachert and light to dark-greenish-gray fine to medium-grained fissile quartz-sericite-chlorite phyllite and schist which locally includes thin chlorite phyllite and quartzose phyllite beds.

Talladega Group; Lay Dam Formation (Silurian?-Devonian)

Lay Dam Formation (Talladega Group) - interbedded dark-green phyllite, medium-gray to light-brown and black metasiltstone, dark-green feldspathic metagraywacke, and light-gray and dark-gray medium to coarse-grained arkosic quartzite and metaconglomerate; graphitic phyllite common in upper part. In Cleburne and Calhoun Counties, rocks mapped as the Lay Dam include the Abel Gap Formation of Bearce (1973) and consist of interbedded greenish-gray metasiltstone and quartzite, black phyllitic metasiltstone, medium-gray to greenish-gray arkosic quartzite, and dark-gray pyritic quartzite. In Clay Chounty the upper part of the Lay Dam includes black graphitic sericite phyllite and slate reportedly containing plant fossils (Erin Slate Member).

Talladega Group; Lay Dam Formation, unnamed diamictite facies (Silurian?-Devonian)

Talladega Group; Lay Dam Formation, unnamed diamictite facies - Unnamed diamictite facies of Lay Day Formation in Coosa and Chilton Counties consists of cobbles and boulders of carbonate, pelitic rocks, quartzite, chert, felsic plutonic rocks, and gneiss in a metagraywacke matrix.

Arizona

Early Proterozoic metamorphic rocks (Early Proterozoic)

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

California

Franciscan Complex, unit 2 (Southern California) (late Early to early Late Cretaceous)

Franciscan complex: Cretaceous and Jurassic sandstone with smaller amounts of shale, chert, limestone, and conglomerate. Includes Franciscan melange, except where separated--see KJfm.

Franciscan schist (Early Cretaceous)

Blueschist and semi-schist of Franciscan complex

Paleozoic marine rocks, undivided, unit 5 (Northeastern Sierra Nevada) (Ordovician to Jurassic)

Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite

pre-Cenozoic granitic and metamorphic rocks undivided (Early Proterozoic to Late Cretaceous)

Granitic and metamorphic rocks, mostly gneiss and other metamorphic rocks injected by granitic rocks. Mesozoic to Precambrian.

Connecticut

Lower part [of Maltby Lakes Metavolcanics] (Middle? Ordovician)

Lower part [of Maltby Lakes Metavolcanics] - Gray-green to green, fine-grained, generally well foliated greenschist, greenstone, and schist or phyllite, composed of albite and chlorite, plus quartz and sericite or epidote and actinolite. Mixed metavolcanics and metasedimentary rocks.

Wepawaug Schist (Devonian or Silurian or both)

Wepawaug Schist - Medium- to dark-gray, medium- to fine-grained, well-layered schist or phyllite and metasiltstone, composed of quartz, muscovite or sericite, plagioclase, biotite, and in appropriate metamorphic zones chlorite, garnet, staurolite, and kyanite. Schist or phyllite generally graphic.

Georgia

Amphibolitic Schist/ Amphibolite-Metagraywacke/ Mica Schist (Precambrian-Paleozoic)

Amphibolitic Schist/ Amphibolite-Metagraywacke/ Mica Schist

Meta-argillite/ Phyllite (Precambrian-Paleozoic)

Meta-argillite/ Phyllite

Meta-argillite/ Sericite phyllite/ Metavolcanics (Precambrian-Paleozoic)

Meta-argillite/ Sericite phyllite/ Metavolcanics

Metagraywacke/ Mica Schist (Precambrian-Paleozoic)

Metagraywacke/ Mica Schist

Metagraywacke/ Mica Schist/ Calc-silicate Gneiss (Precambrian-Paleozoic)

Metagraywacke/ Mica Schist/ Calc-silicate Gneiss

Metagraywacke/ Mica Schist-Quartzite/ Amphibolite (Precambrian-Paleozoic)

Metagraywacke/ Mica Schist-Quartzite/ Amphibolite

Metagraywacke undifferentiated (Precambrian-Paleozoic)

Metagraywacke undifferentiated

Mica Schist/ Metasiltstone (Precambrian-Paleozoic)

Mica Schist/ Metasiltstone

Quartzite/ Metagraywacke (Precambrian-Paleozoic)

Quartzite/ Metagraywacke

Undifferentiated pelitic rocks (Precambrian-Paleozoic)

Undifferentiated pelitic rocks, includes mica schists, metasiltstones, metaconglomerates, and metagraywackes

Idaho

Granitoid intrusions, metasedimentary rocks, and migmatite, undivided; Cretaceous intrusions and Proterozoic host rocks, undivided; northern and central Idaho (Cretaceous to Early Proterozoic)

Mixed, highly altered and migmatitic rocks; derived from imbrication and dynamic events

Metavolcanic and metasedimentary rocks; Jurassic greenschist-facies metamorphic rocks; western Idaho, Blue Mountains island-arc complex (Jurassic)

Jurassic mixed marine detrital and volcanic rocks of western Idaho.

Metavolcanic and metasedimentary rocks; Middle to Lower Triassic greenschist-facies metamorphic rocks; western Idaho, Blue Mountains island-arc complex (Middle and Early Triassic)

Middle and Lower Triassic metabasalt and submarine volcaniclastics of western Idaho

Quartz diorite, metasedimentary rock, metavolcanic rock, and migmatite; Cretaceous to Jurassic plutons in Triassic to Permian metamorphic host rocks, undivided; western Idaho (Cretaceous to Permian)

Mixed, highly altered and migmatitic rocks; derived from imbrication and dynamic events

Massachusetts

Berwick Formation (Silurian)

Berwick Formation - Thin- to thick-bedded metamorphosed calcareous sandstone, siltstone, and minor muscovite schist. In New Hampshire: Used as Berwick Formation of Merrimack Group. Consists of purple biotite-feldspar granofels or schist. Contains interbeds of calcsilicate granofels and minor metapelites. Includes Gove Member, mapped separately. Stratigraphic sequence with respect to Eliot Formation is uncertain. Age of all formations in Merrimack Group changed to Ordovician(?) to Silurian(?) based on isotopic age determinations of approx 440 and 420 Ma from detrital zircons from Berwick by J.N. Aleinikoff (oral commun., 1994) (Lyons and others, 1997).

Coal Mine Brook Formation (Middle Pennsylvanian)

Coal Mine Brook Formation - Fossiliferous, carbonaceous slate and garnet phyllite with a lens of meta-anthracite; conglomerate and arkose.

Everett Formation (Lower Cambrian and Proterozoic Z)

Everett Formation - Olive-gray to green, blue-quartz pebble metagraywacke and quartzite.

Greylock Schist (Lower Cambrian and Proterozoic Z)

Greylock Schist - Light-green to gray, white albite-spotted phyllite and interbedded blue-quartz metagraywacke, salmon-pink dolostone, and blue-quartz conglomerate. Minor interbeds of black and white albite-spotted phyllite resembles Hoosac (CAZhga).

Nassau Formation (Lower Cambrian and Proterozoic Z)

Nassau Formation - Rensselaer Graywacke Member - Greenish-gray, plagioclase-rich, blue quartz pebble metagraywacke and minor gneiss-cobble conglomerate.

Oakdale Formation (Silurian)

Oakdale Formation - Metamorphosed thin-bedded, pelitic and calcareous siltstone and muscovite schist, probably low-grade equivalent of Paxton Formation. The Oakdale Formation is here revised to include strata previously mapped in CT and adjacent MA as the Hebron Formation and the Scotland Schist. The Scotland Member (Pease, 1980) is renamed the Scotland Schist Member of the Oakdale. The Oakdale is a homogeneous, calcareous metasiltstone at the base of a thick stratigraphic sequence in a geosyncline terrane and extends from NH to the Honey Hill fault in eastern CT. In central eastern CT it underlies the Hebron Formation; in northeast CT and adjacent MA it underlies conformably the Dudley Formation of the Paxton Group; in central MA it underlies the Paxton Group undivided. The lower part of the Oakdale is cut out along the Clinton-Newbury fault zone. Thickness in type area is about 1500 m. Correlative with the Gove Member of the Berwick Formation in NH and the Gonic Formation in ME. Age is Late Proterozoic(?) based on intrusion of 440 Ma Hedgehog Hill gneiss in the upper part of the Brimfield Group at the top of the stratigraphic sequence, and an age of 1188 Ma for detrital zircons from the Paxton in north-central MA (Pease, 1989).

Worcester Formation (Lower Devonian and Silurian)

Worcester Formation - Carbonaceous slate and phyllite and minor metagraywacke.

Maryland

Ijamsville Formation (Late Precambrian (?))

Ijamsville Formation - Blue, green, or purple phyllite and phyllitic slate, with interbedded metasiltstone and metagraywacke; flattened pumiceous blebs occur locally.

Ijamsville Formation and Marburg Schist (Late Precambrian (?))

Ijamsville Formation - Blue, green, or purple phyllite and phyllitic slate, with interbedded metasiltstone and metagraywacke; flattened pumiceous blebs occur locally; and Marburg Schist - Bluish-gray to silvery-green, fine-grained, muscovite-chlorite-albite-quartz schist; intensely cleaved and closely folded; contains interbedded quartzites.

Wissahickon Formation; Metagraywacke (Late Precambrian (?))

Wissahickon Formation; Metagraywacke - (Formerly mapped as Peters Creek Formation.) Rhythmically interbedded chlorite-muscovite meta-graywacke and fine-grained chlorite-muscovite schist; graded bedding locally preserved; thickness probably 2,000 to 3,000 feet.

Maine

Cambrian Jim Pond Formation (Cambrian)

Cambrian Jim Pond Formation

Devonian Carrabassett Formation (Devonian)

Devonian Carrabassett Formation

Devonian Littleton Formation (Devonian)

Devonian Littleton Formation

Devonian Seboomook Formation Day Mountain member (Devonian)

Devonian Seboomook Formation Day Mountain member

Devonian Seboomook Formation Mount Blue member (Devonian)

Devonian Seboomook Formation Mount Blue member

Devonian Seboomook Formation Temple Stream member (Silurian-Devonian)

Devonian Seboomook Formation Temple Stream member

Ordovician Ammonoosuc Volcanics (Ordovician)

Ordovician Ammonoosuc Volcanics

Ordovician - Precambrian Z metasedimentary and metavolcanic rocks of the Passagassawakeag block (Ordovician - Precambrian Z)

Ordovician - Precambrian Z metasedimentary and metavolcanic rocks of the Passagassawakeag block

Ordovician - Precambrian Z Scarboro and Diamond Island formations (Ordovician - Precambrian Z)

Ordovician - Precambrian Z Scarboro and Diamond Island formations

Precambrian Z Rye Formation (Precambrian)

Precambrian Z Rye Formation

Silurian Greenvale Cove Formation (Silurian)

Silurian Greenvale Cove Formation

Silurian - Precambrian Z Kittery Formation (Silurian - Precambrian Z)

Silurian - Precambrian Z Kittery Formation

Silurian Sangerville Formation (Silurian)

Silurian Sangerville Formation

Silurian Sangerville Formation Anasagunticook member (Silurian)

Silurian Sangerville Formation Anasagunticook member

Silurian Sangerville Formation Anasagunticook member sulfidic pelite (Silurian)

Silurian Sangerville Formation Anasagunticook member sulfidic pelite

Silurian The Forks Formation (Silurian)

Silurian The Forks Formation

Silurian Waterville Formation limestone member (Silurian)

Silurian Waterville Formation limestone member

Michigan

Baraga Group; Michigamme Formation, undivided (Early Proterozoic)

Baraga Group; Michigamme Formation, undivided - Thick and stratigraphically varied formation of sedimentary and less abundant volcanic rocks. Metamorphosed graywacke is predominant rock of Michigamme Formation. Calcareous concretions common. Metamorphosed from cholorite to sillimanite grade (Cannon, 1986). Mapped undivided in poorly exposed areas

Baraga Group; Volcanic-sedimentary unit (Early Proterozoic)

Baraga Group; Volcanic-sedimentary unit - Interlayered fine- to medium-grained metasedimentary rocks and metavolcanic rocks in poorly exposed areas in southern Baraga County, Mich.

Dickinson Group, undivided (Late Archean) (Late Archean)

Dickinson Group, undivided (Late Archean) - Metavolcanic and metasedimentary rocks in Dickinson County, Mich. From youngest to oldest, consists of Six-Mile Lake Amphibolite, Solberg Schist, and East Branch Arkose.

Menominee and Chocolay Groups, undivided (Early Proterozoic)

Menominee and Chocolay Groups, undivided - Mapped where units are too thin to show separately on map

Metagraywacke (Late Archean) (Late Archean)

Metagraywacke (Late Archean) - Gray, fine-grained, thin- to thick-bedded, commonly graded graywacke and slate in Marenisco, Mich. area

Minnesota

Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower greenschist facies (Early Proterozoic)

Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower greenschist facies - Includes fragmental volcanic rocks, mafic hypabyssal intrusions, graywacke, graphitic argillite and oxide iron-formation

Metasedimentary rocks, undivided (Late Archean)

Metasedimentary rocks, undivided - Graywacke, slate, local units of conglomerate, arenite, graphitic slate, fine-grained felsic volcanogenic, and volcaniclastic rocks, lean oxide iron-formation and its metamorphic equivalents. Includes the Knife Lake Group and the Lake Vermilion Formation in northeastern Minnesota.

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower amphibolite facies (Early Proterozoic)

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower amphibolite facies - Includes fragmental volcanic rocks, mafic hypabyssal intrusions, graphitic argillite, and oxide iron-formation

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metagraywacke, metasiltstone, and a variety of schistose rocks metamorphosed to the amphibolite facies (Early Proterozoic)

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metagraywacke, metasiltstone, and a variety of schistose rocks metamorphosed to the amphibolite facies

Montana

Border zone of Idaho batholith and associated masses (Proterozoic Phanerozoic | Mesozoic Cenozoic | Cretaceous-Late Tertiary)

Border zone of Idaho batholith and associated masses: granitic gneiss and sedimentary rocks, mainly of Belt age, impregnated with granitic material. Because of lack of information they are not distinguished aournd some of the smaller granitic masses that have such border zones.

North Carolina

Alligator Back Formation; Amphibolite (Late Proterozoic)

Amphibolite - equigranular, massive to well foliated, interlayered, rarely discordant, metamorphosed intrusive and extrusive mafic rock; may include metasedimentary rock.

Amphibolite (Middle Proterozoic)

Amphibolite - unconformity; equigranular, massive to well foliated, interlayered, rarely discordant, metamorphosed intrusive to extrusive mafic rock; may include metasedimentary rock.

Amphibolite (Middle Proterozoic)

Amphibolite - unconformity; equigranular, massive to well foliated, interlayered, rarely discordant, metamorphosed intrusive to extrusive mafic rock; may include metasedimentary rock.

Ashe Metamorphic Suite and Tallulah Falls Formation; Amphibolite (Late Proterozoic)

Amphibolite - equigranular, massive to well foliated, interlayered, rarely discordant, metamorphosed intrusive to extrusive mafic rock; may include metasedimentary rock.

Ashe Metamorphic Suite and Tallulah Falls Formation; Metagraywacke (Late Proterozoic)

Metagraywacke - foliated to massive, locally conglomeratic; interlayered and gradational with mica schist, muscovite-biotite gneiss, and rare graphitic schist.

Banded Gneiss (Cambrian/Late Proterozoic)

Banded Gneiss - interlayered with calc-silicate rock, metaconglomerate, amphibolite, sillimanite-mica schist, and granitic rock.

Battleground Formation (Late Proterozoic)

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

Chilhowee Group, Grandfather Mountain Formation; Felsic metavolcanic rocks and metasedimentary rocks (Late Proterozoic)

Felsic metavolcanic rocks and metasedimentary rocks (820my) - tentatively correlated with Grandfather Mountain Formation.

Chilhowee Group, Grandfather Mountain Formation; Greenstone (Late Proterozoic)

Greenstone - schistose to massive, amygdaloidal; interlayered with metasedimentary rocks. Includes Montezuma Member (metabasalt) in upper part.

Chilhowee Group, Grandfather Mountain Formation; Meta-arkose (Late Proterozoic)

Meta-arkose - sericitic, conglomeratic, locally cross-bedded; interlayered metasiltstone and slate.

Chilhowee Group, Grandfather Mountain Formation; Metagraywacke (Late Proterozoic)

Metagraywacke - cross-bedding and graded bedding common, locally conglomeratic; interlayered with metasiltstone and phyllite.

Chilhowee Group, Grandfather Mountain Formation; Metasiltstone (Late Proterozoic)

Metasiltstone - locally contains thin bedded iron-bearing dolomitic marble; interlayered with phyllite, metagraywacke, and meta-arkose.

Chilhowee Group; Lower Chilhowee (Cambrian)

Lower Chilhowee - feldspathic quartzite, white to yellowish gray. Minor silty slate, feldspathic metasiltstone, and metaconglomerate in lower part.

Chilhowee Group; Upper Chilhowee (Cambrian)

Upper Chilhowee - vitreous quartzite, white to light gray; interbedded sandy metasiltstone and slate.

Cid Formation; Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)

(southwest of Asheboro); Felsic Metavolcanic Rock - metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate metavolcanic rock, meta-argillite, and metamudstone.

Cid Formation; Mafic Metavolcanic Rock (Cambrian/Late Proterozoic)

(Southwest of Asheboro); Mafic Metavolcanic Rock - metamorphosed basaltic flows and tuffs, dark green to black; interbedded with felsic and intermediate metavolcanic rock and metamudstone.

Cid Formation; Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)

(Southwest of Asheboro); Metamudstone and Meta-Argillite - thin to thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone, metaconglomerate, and metavolcanic rock.

Coweeta Group (Late Proterozoic)

Coweeta Group - quartz dioritic gneiss, feldspar-quartz-biotite gneiss, metasandstone and quartzite, alumino-silicate schist, garnetiferous biotite gneiss, and minor amphibolite. Quartz dioritic gneiss predominant.

Coweeta Group; Amphibolite (Middle/Late Proterozoic)

Amphibolite - equigranular, massive to well foliated, interlayered, rarely discordant, metamorphosed intrusive to extrusive mafic rock; may include metasedimentary rock.

Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)

Felsic Metavolcanic Rock - metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate metavolcanic rock, meta-argillite, and metamudstone.

Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)

Felsic Metavolcanic Rock - metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate metavolcanic rock, meta-argillite, and metamudstone.

Floyd Church Formation; Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)

(Southwest of Asheboro); Metamudstone and Meta-Argillite - thin to thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone, metaconglomerate, and metavolcanic rock.

Mafic Metavolcanic Rock (Cambrian/Late Proterozoic)

Mafic Metavolcanic Rock - metamorphosed basaltic flows and tuffs, dark green to black; interbedded with felsic and intermediate metavolcanic rock and metamudstone.

Mafic Metavolcanic Rock (Cambrian/Late Proterozoic)

Mafic Metavolcanic Rock - metamorphosed basaltic flows and tuffs, dark green to black; interbedded with felsic and intermediate metavolcanic rock and metamudstone.

Metagraywacke (Cambrian/Late Proterozoic)

Metagraywacke - contains quartz and microcline porphyroblasts.

Metagraywacke, Amphibolite, and Kyanite Schist (Cambrian/Late Proterozoic)

Metagraywacke, Amphibolite, and Kyanite Schist - metagraywacke (biotite gneiss) interlayered and gradational with amphibolite and kyanite schist; minor ultramafic and granitic rock.

Metagraywacke and Muscovite-Biotite Schist (Cambrian/Late Proterozoic)

Metagraywacke and Muscovite-Biotite Schist - metagraywacke (biotite gneiss) interlayered and gradational with muscovite-biotite schist; minor marble and granitic rock.

Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)

Metamudstone and Meta-Argillite - bedding plane and axial-planar cleavage common; interbedded with metasandstone, meta-conglomerate, and metavolcanic rock.

Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)

Metamudstone and Meta-Argillite - thin to thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone, metaconglomerate, and metavolcanic rock.

Metavolcanic-Epiclastic Rock (Cambrian/Late Proterozoic)

Metavolcanic-Epiclastic Rock - metamorphosed argillite, mudstone, volcanic sandstone, conglomerate, and volcanic rock.

Metavolcanic-Epiclastic Rock (Cambrian/Late Proterozoic)

Metavolcanic-Epiclastic Rock - metamorphosed argillite, mudstone, volcanic sandstone, and conglomerate, and volcanic rock.

Mount Rogers Formation; Metagraywacke (Late Proterozoic)

Metagraywacke - interlayered with metaconglomerate, laminated metasiltstone, and slate; minor calcareous metasandstone, greenstone, and metarhyolite.

Nantahala Formation and Tusquitee Quartzite, undivided (Late Proterozoic)

Nantahala Formation and Tusquitee Quartzite, undivided - Nantahala Formation: slate and metasiltstone, dark gray, laminated to thin bedded, sulfidic; Tusquitee Quartzite: white to light yellowish gray, numerous, thin slate layers.

Ocoee Supergroup, Great Smokey Group; Anakeesta Formation (Late Proterozoic)

Anakeesta Formation - slate to schist, dark gray, graphitic and sulfidic; includes interbedded argillaceous, feldspathic metagraywacke.

Ocoee Supergroup, Great Smokey Group; Boyd Gap Formation (Late Proterozoic)

Boyd Gap Formation - dark gray, highly-sulfidic slate and metasiltstone interbedded and gradational with metagraywacke. Stratigraphic position uncertain. In Cherokee County includes upper part of Buck Bald Formation.

Ocoee Supergroup, Great Smokey Group; Copperhill Formation (Late Proterozoic)

Copperhill Formation - metagraywacke, massive, graded bedding common; includes dark-gray slate, mica schist, and nodular calc-silicate rock.

Ocoee Supergroup, Great Smokey Group; Dean Formation (Late Proterozoic)

Dean Formation - sericite schist with cross-biotite, staurolite, and garnet porphyroblasts; interbedded metagraywacke and quartz-pebble metaconglomerate.

Ocoee Supergroup, Great Smokey Group; Metasandstone, Metagraywacke, Metasiltstone, and Mica Schist (Late Proterozoic)

Metasandstone, Metagraywacke, Metasiltstone, and Mica Schist - beds and lenses of calc-silicate rock locally abundant; garnet, staurolite, and cross-biotite porphyroblasts common in fine-grained layers. Includes Hughes Gap and Hothouse formations in southern area; Horse Branch Member of Ammons Formation and Grassy Branch Formation in northern area.

Ocoee Supergroup, Great Smokey Group; Slate of Copperhill Formation (Late Proterozoic)

Slate of Copperhill Formation - slate to phyllite, dark gray, graphitic, sulfidic; includes metagraywacke with local graded bedding.

Ocoee Supergroup; Great Smokey Group, undivided (Late Proterozoic)

Great Smokey Group, undivided - thick metasedimentary sequence of massive to graded beds of metagraywacke and metasiltstone with interbedded graphitic and sulfidic slate and schist.

Ocoee Supergroup, Great Smokey Group; Wehutty Formation (Late Proterozoic)

Wehutty Formation - slate to schist, dark gray, graphitic and sulfidic; includes mica schist, metagraywacke, and metaconglomerate.

Ocoee Supergroup, Snowbird Group; Longarm Quartzite (Late Proterozoic)

Longarm Quartzite - cross-bedded, feldspathic, locally conglomeratic; includes dark slate and metasiltstone.

Ocoee Supergroup, Snowbird Group; Pigeon Siltstone (Late Proterozoic)

Pigeon Siltstone - thin bedded to laminated, commonly cross-bedded, metamorphosed; locally includes argillite and calcareous and arkeritic metasiltstone grading to silty metalimestone.

Ocoee Supergroup, Snowbird Group; Roaring Fork Sandstone (Late Proterozoic)

Roaring Fork Sandstone - greenish gray, fine to medium grained, locally cross-bedded, metamorphosed; interbedded metasiltstone and phyllite.

Ocoee Supergroup, Snowbird Group, undivided (Late Proterozoic)

Snowbird Group, undivided - feldspathic metasiltstone, metasandstone, and phyllite. Basal schist contains lenses of quartz-pebble conglomerate.

Ocoee Supergroup, Snowbird Group; Wading Branch Formation (Late Proterozoic)

Wading Branch Formation - sandy slate to coarse-grained pebbly metagraywacke with local graded bedding. Basal quartz-sericite schist or phyllite.

Ocoee Supergroup, Walden Creek Group; Sandsuck Formation (Late Proterozoic)

Sandsuck Formation - slate and metasiltstone, dark green to black. Metaconglomerate lentils in upper part; calcareous metasandstone, sandy metalimestone, and quartzite in lower part.

Ocoee Supergroup; Walden Creek Group, undivided (Late Proterozoic)

Walden Creek Group, undivided - slate to metasiltstone, locally limy beds and pods; interbedded with quartz-pebble metaconglomerate and metasandstone.

Phyllite and Schist (Cambrian/Late Proterozoic)

Phyllite and Schist - minor biotite and pyrite; includes phyllonite, sheared fine-grained metasediment and metavolcanic rock.

Phyllite and Schist (Cambrian/Late Proterozoic)

Phyllite and Schist - locally laminated and pyritic; includes phyllonite, sheared fine-grained metasediment, and metavolcanic rock. In Lilesville granite aureole, includes hornfels.

Phyllite and Schist (Cambrian/Late Proterozoic)

Phyllite and Schist - minor biotite and pyrite; includes phyllonite, sheared fine-grained metasediment and metavolcanic rock.

Rocks of Brevard Fault Zone (Uncertain, possibly Permian or Devonian)

Rocks of Brevard Fault Zone - "fish scale" schist and phyllonite, graphitic; interlayered with feldspathic metasandstone, marble lenses.

Tillery Formation; Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)

(Southwest of Asheboro); Metamudstone and Meta-Argillite - thin to thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone, metaconglomerate, and metavolcanic rock.

Uwharrie Formation; Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)

(at Asheboro and to south); Felsic Metavolcanic Rock - metamorphosed dacitic to rhyolitic flows and tuffs, light gray to greenish gray; interbedded with mafic and intermediate metavolcanic rock, meta-argillite, and metamudstone.

Volcanic Metaconglomerate (Cambrian/Late Proterozoic)

Volcanic Metaconglomerate - includes metagraywacke and metamudstone.

Yadkin Formation (Cambrian/Late Proterozoic)

Yadkin Formation - metamorphosed graywacke, volcanic sandstone, and siltstone; interbedded with mafic and intermediate metavolcanic flows and tuffs.

New Hampshire

Ammonoosuc Volcanics, Metasedimentary rocks (Middle - Upper Ordovician)

Ammonoosuc Volcanics, Metasedimentary rocks - Contains mafic metavolcanic lenses.

Ammonoosuc Volcanics, Metasedimentary rocks (Middle - Upper Ordovician)

Ammonoosuc Volcanics, Metasedimentary rocks.

Ammonoosuc Volcanics, Volcaniclastic metagraywackes (Middle - Upper Ordovician)

Ammonoosuc Volcanics, Volcaniclastic metagraywackes.

Frontenac Formation, Graded-bedded metagraywacke and subordinate gray phyllite (Silurian?)

Frontenac Formation, Graded-bedded metagraywacke and subordinate gray phyllite.

Frontenac Formation, Mixed volcanic and sedimentary facies (Silurian?)

Frontenac Formation, Mixed volcanic and sedimentary facies.

Frontenac Formation, undivided (Silurian?)

Frontenac Formation, undivided - Interbedded thick feldspathic wackes, tan and green slates, and minor calcareous lenses.

Gile Mountain Formation, Interbedded gray slate or phyllite and brown-weathering calcite-ankerite metasiltstone (Lower Devonian)

Interbedded gray slate or phyllite and brown-weathering calcite-ankerite metasiltstone - Contains minor marble and quartzite. Resembles Waits River Formation in Vermont.

Gile Mountain Formation, Meetinghouse Slate Member (Lower Devonian )

Meetinghouse Slate Member - Gray to black phyllite and silty metasandstone turbidite.

Gile Mountain Formation, undivided (Lower Devonian)

Gile Mountain Formation, undivided - Gray to tan metawacke and schist or phyllite; gradational into Meetinghouse Slate Member but more thickly bedded and less pelitic than the member. Includes minor metavolcanic lentils.

Greenvale Cove Formation (Lower Silurian? )

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

Hurricane Mountain Formation (Upper Cambrian?)

Hurricane Mountain Formation - Rusty-weathered, dark siliceous scaly slate or schist of flaser structure, polymictic fragments from a few mm to (in Maine) several hundred meters. A melange consisting of metasedimentary, felsic/mafic metavolcanics, and ultramafic rocks..

Ironbound Mountain Formation, Euxinic metashale member (Lower Devonian)

Ironbound Mountain Formation, Euxinic metashale member.

Ironbound Mountain Formation, undivided (Lower Devonian)

Ironbound Mountain Formation, undivided - Interbedded gray phyllite, in places containing feldspathic clasts, and feldspathic metasandstone, variably graded.

Littleton Formation, Lower unnamed member (Lower Devonian)

Littleton Formation, Lower unnamed member - Thinly or poorly bedded aluminous lower part, somewhat rusty. Rare quartzite lentils. Carrabassett Formation in northwestern Maine is probably correlative.

Littleton Formation, undivided (Lower Devonian; Siegenian)

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.

Littleton Formation, Upper unnamed member (Lower Devonian)

Littleton Formation, Upper unnamed member - Light-gray metaturbidite, lithologically identical to, and probably correlative with, the Seboomook Formation of Maine. Coticule layers common.

Massabesic Gneiss Complex (Late Proterozoic)

Massabesic Gneiss Complex - Migmatite consisting of pink, foliated biotite granite intruding gneissic and granulose metasedimentary and metavolcanic rocks in southeastern New Hampshire.

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

Merrimack Group, Kittery Formation - Tan, graded-bedded, calcareous metasandstone and purple and green phyllite. Grades into the Eliot formation but facing direction is uncertain.

Metavolcanic and metasedimentary rocks of the lower part of Ammonoosuc Volcanics, undivided (Middle Ordovician)

Metavolcanic and metasedimentary rocks of the lower part of Ammonoosuc Volcanics, undivided.

Partridge Formation, undivided (Middle - Upper Ordovician)

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.

Perry Mountain and Rangeley Formations, undivided (Silurian)

Perry Mountain and Rangeley Formations, undivided.

Perry Mountain Formation, Sedimentary and subordinate distal felsic and mafic volcanic facies in Piermont allochthon (Lower?- Middle? Silurian)

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

Perry Mountain Formation, undivided (Lower? - Middle? Silurian)

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

Quimby Formation (Upper Ordovician?)

Quimby Formation - Black graphitic-sulfidic rusty-weathering schist and thickly bedded metagraywacke.

Rangeley Formation, undivided (Lower Silurian (Llandoverian))

Rangeley Formation, undivided.

Upper part of Rangeley Formation (Lower Silurian (Llandoverian))

Upper part of Rangeley Formation - Rusty-weathering, pelitic schist, metasandstone, and local coarse-grained metasandstone lentils; calc-silicate pods common; minor coticule. Probably equivalent to member C of Rangeley Formation of Maine.

New Mexico

metasedimentary rocks (Proterozoic | Paleoproterozoic)

Lower Proterozoic metasedimentary rocks (1650-1700 Ma). Essentially equivalent to Hondo Group; locally includes high-grade quartzite-pelitic schist of unknown age

sedimentary rocks of the Sacramento Mountains (Proterozoic | Mesoproterozoic)

Middle Proterozoic sedimentary rocks of the Sacramento Mountains

New York

Biotite and/or hornblende granite gneiss (Middle Proterozoic)

Biotite and/or hornblende granite gneiss - locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. Overprint signifies inequigranular texture or phacoidal structure. In northwest Adirondacks, grades into Yphg.

Biotite and/or hornblende granite gneiss (Middle Proterozoic)

Biotite and/or hornblende granite gneiss - locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. Overprint signifies inequigranular texture or phacoidal structure. In northwest Adirondacks, grades into Yphg.

Biotite and/or hornblende granite gneiss (Middle Proterozoic)

Biotite and/or hornblende granite gneiss - locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. Overprint signifies inequigranular texture or phacoidal structure. In northwest Adirondacks, grades into Yphg.

Biotite and/or hornblende granite gneiss (Middle Proterozoic)

Biotite and/or hornblende granite gneiss - locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. In northwest Adirondacks, grades into Yphg.

Everett Schist (Cambrian?)

Everett Schist - locally with minor meta-graywacke lenses.

Everett Schist (Cambrian?)

Everett Schist - minor meta-graywacke lenses. Includes Greylock Schist in Massachusetts.

Hybrid rock: anorthositic and metasedimentary rock (Middle Proterozoic)

Hybrid rock: anorthositic and metasedimentary rock - ranges from anorthositic rock with local blocks, shreds or layers of undifferentiated metasediment, to mappable roof pendants and/or xenoliths of metasediment in anorthositic rock.

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss (Middle Proterozoic)

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss.

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss (Middle Proterozoic)

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss.

Interlayered metasedimentary rock and granitic gneiss (Middle Proterozoic)

Interlayered metasedimentary rock and granitic gneiss.

Leucogranitic (alaskitic) gneiss (Middle Proterozoic)

Leucogranitic (alaskitic) gneiss - sodic plagioclase ranges from generally subordinate to locally dominant; locally with biotite, hornblende, pyroxene, garnet, sillimanite, disseminated magnetite; commonly contains metasedimentary layers, amphibolite, migmatite; plagioclase-rich variety is host to magnetite ore bodies in eastern Adirondacks.

Leucogranitic gneiss (Middle Proterozoic)

Leucogranitic gneiss - sodic plagioclase ranges from generally subordinate to locally dominant; locally with biotite, hornblende, pyroxene, garnet, sillimanite, disseminated magnetite; commonly contains metasedimentary layers, amphibolite, migmatite; plagioclase-rich variety is host to magnetite ore bodies in eastern Adirondacks.

Undivided metasedimentary rock and related migmatite (Middle Proterozoic)

Undivided metasedimentary rock and related migmatite.

Undivided metasedimentary rock and related migmatite (Middle Proterozoic)

Undivided metasedimentary rock and related migmatite.

Walloomsac Formation (Middle Ordovician)

Walloomsac Formation - phyllite, schist, metagraywacke.

Walloomsac Formation (Middle Ordovician)

Walloomsac Formation - slate, phyllite, schist, metagraywacke.

Oregon

Melange of Dutchmans Peak (Triassic or Paleozoic) (Paleozoic(?) to Jurassic(?))

Heterogeneous mixture of interlayered metasedimentary and metavolcanic rocks metamorphosed to upper greenschist and (or) almandine-amphibolite facies, and serpentinite, gabbro, and metagabbro (Smith and others, 1982)

Rhode Island

Narragansett Bay Group - Rhode Island Formation (Pennsylvanian)

Narragansett Bay Group - Rhode Island Formation - In northern Rhode Island, consists of gray to black, fine- to coarse-grained quartz arenite, litharenite, shale, and conglomerate, with minor beds of anthracite and meta-anthracite. In southern Rhode Island, consists of meta-sandstone, meta-conglomerate, schist, carbonaceous schist, and graphite. Plant fossils are common.

Narragansett Pier Plutonic Suite - leucocratic granite (Permian)

Narragansett Pier Plutonic Suite - leucocratic granite - White to gray leucocratic granite composed of microcline, oligoclase, and quartz. Up to 10% accessory muscovite and garnet, with lesser apatite, zircon, and monazite. Biotite and opaque minerals notably sparse or absent. Mainly massive, but locally exhibits flow foliation caused by alternating layers of pegmatite, aplite, and medium-grained equigranular granite; pegmatitic and aplitic material of mineralogy similar to the host granite. The granite contains widespread xenolithic inclusions and screens of metasedimentary rock, some of which are PAnbr; bedding and fabric in the screens generally is oriented parallel to that in the host metasedimentary country rock. Unit is a 5 km by 40 km batholith that underlies the southern coast of RI. Intrusion during the latter part of Alleghanian deformation of the Narragansett Basin is indicated by its Permian age, rapid cooling, and field relations. The age of the Narragansett Pier is well constrained by several factors. Brown and others (1978) report a Pennsylvanian fossil contained in an inclusion in the pluton. Radiometric ages of 276 Ma by Kocis and others (1978), 272+/-4 Ma by Hermes and others (1981), and 273+/-2 Ma by Zartman and Hermes (1987) are consistently Early Permian. Structural studies by Mosher (1983) and Reck and Mosther (1988) indicate that intrusion began during the third period of deformation in the Narragansett Basin. Argon release patterns (Dallmeyer, 1982) indicate that the granite and intruded sediments had cooled below argon retention temperatures of hornblende by the Late Permian and of biotite by the Early Triassic. Intruded by the Westerly Granite, which has been radiometrically dated at 276+/-7 Ma. The two granites are probably genetically related based on similarities in age, mineralogy, and geochemistry (Hozik, 1992).

Other metasedimentary rocks - metaclastic rock, undivided (Pennsylvanian? or Late Proterozoic?)

Other metasedimentary rocks - metaclastic rock, undivided - Red to gray to green polymict conglomerate, sandstone, and shale. Variably metamorphosed. Includes rock mapped formerly as Bellingham Conglomerate.

South Carolina

Asbill Pond Formation (Middle Cambrian)

Asbill Pond Formation: metamorphosed siltstones and sandstones having interbedded felsic to mafic metavolcanic rocks

Chauga River Formation and Poor Mountain Formation, undivided (Cambrian or Neoproterozoic)

Chauga River Formation and Poor Mountain Formation, undivided

Cid Formation, Mudstone Member (Ordovician to Late Cambrian)

Cid Formation, Mudstone Member: thin bedded tuffaceous metasiltstone

Metavolcanic and metasedimentary rocks of Bel Air Belt (Ordovician to Neoproterozoic)

Metavolcanic and metasedimentary rocks of Bel Air Belt

Richtex Formation (Ordovician to Middle Cambrian)

Richtex Formation: laminated metamudstone; contains Middle Cambrian or younger sponge spicules

Tuffaceous metasiltstone (Early Paleozoic-Neoproterozoic)

Tuffaceous metasiltstone

South Dakota

Upper Metagraywacke (Proterozoic | Paleoproterozoic)

Light- to dark-gray, quartz-mica-feldspar schist, quartz-mica schist, staurolite and garnet-rich schist, metaconglomerate, calc-silicate gneiss, and cummingtonite-quartz schist. Thickness up to 14,000 ft (4,267 m).

Tennessee

Cades Sandstone (Precambrian)

Cades Sandstone - Gray, well-bedded, fine- to medium-grained feldspathic metasandstone, with interbeds of dark slate and metasiltstone; precise stratigraphic position unknown. Thickness about 1,500 feet.

Texas

Lost Creek Gneiss (preCambrian-Proterozoic)

Lost Creek Gneiss

Utah

Ordovician metasedimentary rocks in northwestern Utah (Ordovician)

Virginia

Aaron Slate (Proterozoic Z)

Aaron Slate - Phyllite and slate.

Annandale Group - Lake Barcroft Metasandstone (Proterozoic Z-Cambrian)

Annandale Group - Lake Barcroft Metasandstone

Candler Formation - Phyllite and schist (Cambrian)

Candler Formation - Phyllite in central Blue Ridge Anticlinorium; Phyllite, metasiltstone and quartz-mica schist in southwest Blue Ridge Anticlinorium

Fauquier Formation - Arkosic metasandstone (Proterozoic Z)

Fauquier Formation - Arkosic metasandstone

Fauquier Formation -Meta-arkose and metasiltstone (Proterozoic Z)

Fauquier Formation - Crossbedded metasandstone

Interlayered Mafic and Felsic Volcanic Rocks (Proterozoic Z)

Interlayered mafic and felsic metavolcanic rocks.

Lunga Reservoir Formation (Cambrian)

Lunga Reservoir Formation - Metadiamictite.

Lynchburg Group - Conglomerate and metagraywacke (Proterozoic Z)

Lynchburg Group - Conglomerate and metagraywacke.

Lynchburg Group; Graphitic phyllite and metasiltstone (Proterozoic Z)

Lynchburg Group - Graphitic phyllite and metasiltstone

Lynchburg Group; Monumental Mills Formation (Proterozoic Z)

Lynchburg Group; Monumental Mills Formation - Metasandstone, laminated metasiltstone, and mudstone.

Mafic Volcanic Rocks (Proterozoic Z)

Mafic volcanic rocks.

Mather Gorge Formation -- Schist (Proterozoic Z-Cambrian)

Mather Gorge Formation - Schist.

Metasandstone and Metasiltstone (Proterozoic Z-Cambrian)

Metasandstone and metasiltstone.

Metasedimentary Rocks Undivided (Cambrian-Ordovician)

Metasedimentary rocks

Micaceous Quartzite (Cambrian)

Micaceous quartzite

Mount Rogers Formation - Greenstone with interbedded sedimentary rocks (Proterozoic Z)

Mount Rogers Formation - Greenstone with sedimentary interbeds.

Purcell Branch Formation (Cambrian)

Purcell Branch Formation - Metadiamictite.

Washington

Lower and Middle Jurassic marine rocks (Devonian-Permian)

Dark-gray, massive to thick-bedded, siliceous argillite, siltstone, and shale; includes minor graywacke and limestone. Confined to northwestern Whatcom County.

Permian rocks (Permian-Triassic)

Conglomerate, graywacke, siltstone, argillite and interbedded fossiliferous limestone, greenstone, and minor angular conglomerate in northwestern Stevens and Ferry Counties. Impure quartzite, sandstone, graywacke, greenstone, ribbon chert, chert breccia, and limestone in Snohomish County and on San Juan Island. Lower Permian limestone on Black Mountain in northwestern Whatcom County. Middle Permian rocks in northeastern Washington.

Precambrian rocks, undivided (Middle to Late Proterozoic)

Magnesite-bearing Stensgar dolomite; southwestern Stevens County.

Pre-Middle Jurassic sedimentary and volcanic rocks (Late Paleozoic deposition? with Cretaceous metamorphism?)

Sedimentary and volcanic rocks, undivided. Graywacke, argillite, slate, greenstone, and spilitic volcanic rocks.

Pre-Tertiary metamorphic rocks, undivided (Probably Permian)

Schist, gneiss, marble, quartzite, amphibolite, greenstone, metaconglomerate, graywacke; includes metasedimentary, volcanic, and intrusive rocks. Some areas, as on San Juan Islands, show little if any metamorphism.

Pre-Tertiary sedimentary and metasedimentary rocks, undivided (Mostly Early Cretaceous to Middle Jurassic, possibly includes minor Eocene rocks)

Graywacke, argillite, phyllite, chert, talc, and graphite schist; some faulted-in blocks of serpentinite and greenstone. Includes minor limestone on San Juan Island.

Pre-Tertiary volcanic rocks, undivided (Probably mostly Jurassic)

Andesite and basalt flows, and greenstone; includes minor interbedded limestone, arkose, quartzite, and chert beds.

Pre-Upper Jurassic metamorphic rocks of the medium and high-grade zone (Early Jurassic-Triassic)

Schist, amphibolite, and minor lime-silicate rocks, marble, quartzite, and metaconglomerate.

Silurian-Devonian rocks (Silurian-Devonian)

Mainly black argillite; some limestone, thin beds of conglomerate, sandstone, quartzite, and dolomite. Rocks confined to northwestern Pend Oreille County and adjacent Stevens County. Silurian age based on Monograptus and corals of several unusual genera; Devonian age based on coral fauna.

Triassic sedimentary rocks, undivided (Triassic with Permian where impossible to differentiate)

Predominantly limestone, marble, and dolomite near Riverside in Okanogan County. Conglomerate, shale, graywacke, gritstone, and limestone on San Juan Island. Siltstone with greenstone locally on Orcas Island. Graywacke conglomerate, cherty greenstone, and limestone in northern Ferry County.

Upper Jurassic-Lower Cretaceous volcanic rocks (Jurassic-Cretaceous on San Juan Islands; possibly Eocene in King County)

Predominantly volcanic rocks, mostly metamorphosed to greenstone and greenschist; includes some sedimentary rocks

Upper Paleozoic rocks, undivided (Ordovician)

Mostly graywacke, interbedded quartzite and phyllite, greenstone and serpentine, and black shale with minor limestone. Some quartz-mica schist in Bald Knob area of Ferry County. Schist, gneiss, and amphibolite in other parts of Ferry County. Some rocks of lower Paleozoic age, possibly Precambrian, and Mesozoic may be included.

Wisconsin

Menominee and Chocolay Groups, undivided (Early Proterozoic)

Menominee and Chocolay Groups, undivided - Mapped where units are too thin to show separately on map

Milladore Volcanic Complex (about 1860 +/- 7 Ma) (Early Proterozoic)

Milladore Volcanic Complex (about 1860 +/- 7 Ma) - Succession of poorly exposed interlayered metavolcanic and metasedimentary rocks. Lithic units described in Sims (1990)

Wyoming

Metasedimentary and metavolcanic rocks (Archean)

METASEDIMENTARY AND METAVOLCANIC ROCKS--Amphibolite, hornblende gneiss, biotite gneiss, quartzite, iron-formation, metaconglomerate, marble, and pelitic schist; locally preserved textures and structures suggest origin to be sedimentary or volcanic. Older than 2,875 Ma in Teton Range; older than 3,200 Ma in Granite Mountains; older than 2,600 Ma in Medicine Bow Mountains and Sierra Madre, where it is the Late Archean Phantom Lake Metamorphic Suite 3.

Metasedimentary and metavolcanic rocks (Proterozoic | Paleoproterozoic )

METASEDIMENTARY AND METAVOLCANIC ROCKS. Sierra Madre--Granite gneiss, felsic gneiss, amphibolite, and metavolcanic rocks. Medicine Bow Mountains--Granite gneiss, felsic gneiss, amphibolite, and hornblende gneiss. Laramie Mountains--Pelitic schist, marble, granite gneiss, layered amphibolite, and felsic gneiss. Black Hills--Pelitic schist; includes minor amounts of granite and amphibolite.

Metasedimentary rocks (Archean)

METASEDIMENTARY ROCKS. Wind River Range--Metagraywacke, pelitic schist, metaconglomerate, graphitic schist, and iron-formation; local meta-andesite. At least 2,800 Ma. Seminoe Mountains (southeast end of Granite Mountains)--Pelitic schist, quartzite, and iron-formation. Casper Mountain (northwest extension of Laramie Mountains)--Felsic gneiss, quartzite, and iron-formation. Laramie Mountains--Pelitic schist, iron-formation, quartzite, marble, metaconglomerate, and metagraywacke.

Metasedimentary rocks: Deep Lake Group (Proterozoic | Paleoproterozoic )

METASEDIMENTARY ROCKS--In Medicine Bow Mountains and Sierra Madre. Deep Lake Group 3--Quartzite, diamictite, pelitic schist, and quartz-pebble conglomerate.

Metasedimentary rocks: Libby Creek Group (Proterozoic | Paleoproterozoic )

METASEDIMENTARY ROCKS--In Medicine Bow Mountains and Sierra Madre. Libby Creek Group 3--Pelitic schist, amphibole schist, quartzite, diamictite, quartz-pebble conglomerate, and marble.