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Geologic units containing quartzite

Earth material > Metamorphic rock > Metasedimentary rock
Quartzite
A granoblastic metamorphic rock consisting mainly of quartz and formed by recrystallization of sandstone or chert by either regional or thermal metamorphism.
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Alabama
Attalla Chert Conglomerate Member of the Chickamauga Limestone (Ordovician)
Attalla Chert Conglomerate Member of the Chickamauga Limestone - conglomerate of pebbles, cobbles, and boulders of chert and rare dolomite and quartzite in a sand-sized chert and quartz matrix; thin beds of gray-green or dusky-red shale common at base.
Attalla Chert Conglomerate Member of the Chickamauga Limestone (Ordovician)
Attalla Chert Conglomerate Member of the Chickamauga Limestone - conglomerate of pebbles, cobbles, and boulders of chert and rare dolomite and quartzite in a sand-sized chert and quartz matrix; thin beds of gray-green or dusky-red shale common at base.
Chickamauga Limestone (Ordovician)
Chickamauga Limestone - Medium to dark-gray thick to thin-bedded partly argillaceous, locally fossiliferous limestone. Restricted to the western part of the Valley and Ridge province and Murphrees Valley and Wills Valley anticlines. Locally includes a thin interval of Attalla Chert Conglomerate Member at base. Attalla Chert Conglomerate - conglomerate of pebbles, cobbles, and boulders of chert and rare dolomite and quartzite in a sand-sized matrix; thin beds of gray-green or dusky-red shale common at base.
Chickamauga Limestone (Ordovician)
Chickamauga Limestone - Medium to dark-gray thick to thin-bedded partly argillaceous, locally fossiliferous limestone. Restricted to the western part of the Valley and Ridge province and Murphrees Valley and Wills Valley anticlines. Locally includes a thin interval of Attalla Chert Conglomerate Member at base. Attalla Chert Conglomerate - conglomerate of pebbles, cobbles, and boulders of chert and rare dolomite and quartzite in a sand-sized matrix; thin beds of gray-green or dusky-red shale common at base.
Dadeville Complex; Waresville Schist (Precambrian to Paleozoic)
Waresville Schist - banded amphibolite interlayered with chlorite schist, chlorite amphibolite, chlorite-actinolite schist, chlorite +/- magnetite quartzite, and actinolite quartzite; may include small ultramafic pods.
Dadeville Complex; Waverly Gneiss (Precambrian to Paleozoic)
Waverly Gneiss - feldspathic biotite-hornblende gneiss with thin layers of amphibolite, calc-silicate rock, garnet quartzite, and muscovite schist; locally rich in manganese.
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.
Hatchet Creek Group; Hanover Schist (Precambrian to Paleozoic)
Hanover Schist - coarse to fine-grained feldspathic biotite-sericite-quartz-muscovite schist, commonly containing staurolite, garnet, and locally sillimanite in northeastern outcrop areas includes zones of aluminous graphite schist, hornblende quartzite, garnet quartzite, and rare amphibolite. Schist commonly retrograded to sericite-garnet-quartz schist. Numerous granitic pegmatites.
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.
Higgins Ferry Group; Garnet quartzite (garnetite) and garnitiferous altered mafic rock (Precambrian to Paleozoic)
Higgins Ferry Group; Garnet quartzite (garnetite) and garnitiferous altered mafic rock.
Higgins Ferry Group; Roscoelite-graphite-quartz schist and graphitic quartzite (Precambrian to Paleozoic)
Higgins Ferry Group; Roscoelite-graphite-quartz schist and graphitic quartzite
Jacksons Gap Group; Jacksons Gap Group undifferentiated in part (Precambrian to Paleozoic)
Jacksons Gap Group undivided - principally graphitic sericite (muscovite)-quartz schist; includes sericite-quartz phyllonite; sericite phyllonite, blastomylonite, porphyroclastic blastomylonite schist, and mylonite quartzite occur principally along margins in south and form most of unit northeast of Jacksons Gap, Tallapoosa County.
Jacksons Gap Group; Tallassee Metaquartzite (Precambrian to Paleozoic)
Jacksons Gap Group; Tallassee Metaquartzite - medium to fine-grained, massive to thin-bedded quartzite and metaconglomerate and thin beds of graphitic quartz schist, locally contains small garnets.
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; Kalona Quartzite Member of Wash Creek Slate (Precambrian?-Cambrian?)
Kalona Quartzite Member of Wash Creek Slate - light-brown to light-gray coarse-grained, feldspathic quartzite and metaconglomerate in lower part of Wash Creek Slate.
Kahatchee Mountain Group; Sawyer Limestone Member of Brewer Phyllite (Precambrian?-Cambrian?)
Sawyer Limestone Member of Brewer Phyllite - light to medium-gray argillaceous, silty to siliceous calcite and dolomite marble interbedded with phyllite and quartzite, locally cherty.
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.
Mylonitic and Cataclastic Rocks in the Brevard, Towaliga, and Goat Rock Fault Zones (Precambrian to Paleozoic)
Mylonitic and Cataclastic Rocks in the Brevard, Towaliga, and Goat Rock Fault Zones - blastomylonite, mylonite gneiss, locally includes mylonite schist and mylonite quartzite in Towaliga fault zone.
Opelika Complex; Loachapoka Schist (Precambrian to Paleozoic)
Loachapoka Schist - muscovite-quartz schist; locally contains biotite-garnet-muscovite schist, many layers conatin sillimanite (northeast of Mount Jefferson, Lee County); kyanite (west of Mount Jefferson); locally muscovite-rich schist and quartzite common.
Pine Mountain Group; Hollis Quartzite (Precambrian to Paleozoic)
Hollis Quartzite - quartzite containing minor mica, feldspar, and pyrite; locally arkosic; commonly sheared.
Pine Mountain Group; Manchester Schist (Precambrian to Paleozoic)
Manchester Schist - interlayered muscovite-quartz schist and quartzite, locally contains garnet, sillimanite and graphite; commonly intensely shared.
Poe Bridge Mountain Group; Garnet quartzite (garnetite) and garnitiferous altered mafic rock (Precambrian to Paleozoic)
Poe Bridge Mountain Group; Garnet quartzite (garnetite) and garnitiferous altered mafic rock. Rocks in the area of Turkey Heaven Mountain in Cleburne and Randolph Counties that are here assigned to the Poe Bridge Mountain Group also have been interpreted as part of the Wedowee Group.
Poe Bridge Mountain Group; Roscoelite-graphite quartz schist and graphitic quartzite (Precambrian to Paleozoic)
Poe Bridge Mountain Group; Roscoelite-graphite quartz schist and graphitic quartzite. Rocks in the area of Turkey Heaven Mountain in Cleburne and Randolph Counties that are here assigned to the Poe Bridge Mountain Group also have been interpreted as part of the Wedowee Group.
Talladega Group; Cheaha Quartzite Member of Lay Dam Formation (Silurian?-Devonian)
Cheaha Quartzite Member of Lay Dam Formation - white to light-gray medium to coarse-grained arkosic quartzite and metaconglomerate.
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.
Talladega Group; Miller Mill Quartzite Member of the Lay Dam Formation (Silurian?-Devonian)
Miller Mill Quartzite Member of the Lay Dam Formation - white to medium-gray medium to coarse-grained arkosic quartzite and metaconglomerate.
Tuscaloosa Group undifferentiated (Cretaceous)
Tuscaloosa Group undifferentiated - Light-gray to moderate-reddish-orange clayey, gravelly fine to very coarse sand; massive mottled sandy clay; local wood and leaf beds; and thin beds of indurated sandstone. Gravel consists mainly of quartz and quartzite and range in size from very fine pebbles to large cobbles. Mapped eats of the Tallapoosa River.
Wedowee Group; Hackneyville Schist (Precambrian to Paleozoic)
Hackneyville Schist - medium to coarse-grained quartz-plagioclase +/- almandine +/- kyanite +/- biotite-muscovite schist, graphite-muscovite-quartz schist, and quartzite containing biotite. Large porphyroblasts of muscovite, andalusite and/or chiastrolite common. Rocks in the areas between Goodwater in Coosa County and Millerville in Clay County that are here assigned to the Hackneyville Schist also have been interpreted as part of the Higgins Ferry Group.
Wedowee Group; Wedowee Group undifferentiated (Precambrian to Paleozoic)
Wedowee Group undifferentiated - Wedowee Group undifferentiated includes the Cragford Phyllite and Cutnose Gneiss. Cragford Phyllite -- interbedded fine-grained graphite-chlorite-sericite schist and phyllite, garnet-sericite schist and phyllite, graphite-quartz-sericite phyllite, locally feldspathic biotite gneiss, calc-silicate rock, and quartzite. Cutnose Gneiss -- cyclically interbedded fine-grained quartz-biotite feldspathic gneiss, graphite-chlorite-sericite schist, locally thin interbeds of graphite-quartz-sericite phyllite, and quartzite. Rocks in the area northeast of Clanton in Chilton and Coosa Counties that are here assigned to the Wedowee Group also have been interpreted as part of the Higgins Ferry Group.
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)
Early Proterozoic metavolcanic rocks (Early Proterozoic)
Weakly to strongly metamorphosed volcanic rocks. Protoliths include basalt, andesite, dacite, and rhyolite deposited as lava or tuff, related sedimentary rock, and shallow intrusive rock. These rocks, widely exposed in several belts in central Arizona, include metavolcanic rocks in the Yavapai and Tonto Basin supergroups. (1650 to 1800 Ma)
Early Proterozoic quartzite (Early Proterozoic)
Brown to maroon, resistant quartzite and minor conglomerate of the Mazatzal Group, exposed primarily in the Payson area. (1650? -1700 Ma)
Glen Canyon Group (Early Jurassic)
Conspicuous red, cross-bedded Wingate Sandstone and the conspicuously cross-bedded, eolian, red to buff Navajo Sandstone form prominent cliffs in northern Arizona. These two sandstone units are separated by variably colored siltstone, silty sandstone, and sandstone of the Kayenta and Moenave Formations. (180-210 Ma)
Jurassic and Triassic sedimentary and volcanic rocks (Triassic and Jurassic)
Undivided massive quartz-feldspar porphyry of the Jurassic Planet Volcanics, quartz-rich metasandstone of the Jurassic Vampire Formation, and quartzite, phyllite, and fine grained, variably calcareous metasiltstone of the Triassic Buckskin Formation; exposed primarily in the Buckskin and Rawhide Mountains of western Arizona. This unit also includes sandstone and conglomerate beneath Jurassic volcanic rocks in the central Dome Rock Mountains. (160-240 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)
Jurassic volcanic rocks (Jurassic)
Massive quartz-feldspar porphyry, generally interpreted as thick, welded rhyolitic tuffs, with locally abundant lava, and sandstone and conglomerate derived from volcanic rocks. Rare eolian quartzite units are interbedded in southern Arizona. Includes Ali Molina Formation, Mount Wrightson Formation, part of the Canelo Hills Volcanics, Cobre Ridge tuff, Black Rock volcanics, Planet Volcanics, and equivalent rocks. (160-200 Ma)
Middle Proterozoic sedimentary rocks (Middle Proterozoic)
Red-brown shale and sandstone, buff to orange quartzite, limestone, basalt, black shale, and sparse conglomerate. This unit includes the Grand Canyon Supergroup, Apache Group, and Troy Quartzite. These rocks were deposited in shallow marine, coastal nonmarine, and fluvial settings. (700-1300)
Mississippian, Devonian, and Cambrian sedimentary rocks (Cambrian, Devonian, and Mississippian)
Brown to dark gray sandstone grades upward into green and gray shale, overlain by light to medium gray or tan limestone and dolostone. This unit includes the Tapeats Sandstone, Bright Angel Shale, Muav Limestone, Temple Butte Formation and Redwall Limestone in northern Arizona, and the Bolsa Quartzite, Abrigo Formation, Martin Formation, and Escabrosa Limestone in southern Arizona. These rocks record intermittent sea-level rise and inundation in early Paleozoic time. (330-540 Ma)
Moenkopi Formation (Early and Middle(?) Triassic)
Dark red sandstone and mudstone; includes gypsum beds in northwestern Arizona; deposited on a low-relief coastal plain. (230-245 Ma)
Orocopia Schist (Late Cretaceous to Early Tertiary)
Mostly gray, fine-grained quartz-feldspar-mica schist, with sparse metabasalt and metachert. The unit is exposed in tectonic windows in the southwestern corner of Arizona. It is interpreted as metamorphosed marine sandstone that was tectonically emplaced beneath southwestern Arizona during early Tertiary subduction of Pacific Ocean sea floor. (65-165 Ma)
Paleozoic sedimentary rocks (Paleozoic)
Undivided Paleozoic limestone, dolostone, quartzite, shale, and related sedimentary rocks. (248-544 Ma)
Permian sedimentary rocks (Permian)
Gray to tan, cherty limestone of Kaibab and Toroweap Formations, and underlying white to tan, fine-grained Coconino Sandstone. Limestone was deposited in a shallow sea, and sandstone was deposited in near-shore dunes and beach settings. (270-280 Ma)
Permian to Pennsylvanian sedimentary rocks (Pennsylvanian to Permian)
Interbedded sandstone, shale, and limestone usually characterized by ledgy outcrops. Orange to reddish sandstone forms cliffs near Sedona. This unit includes Supai Group and Hermit Shale in northern Arizona and Naco Group in southern Arizona. It was deposited in coastal-plain to shallow-marine settings during time of variable and changing sea level. Rocks of this map unit in southern Arizona may be in part equivalent to Permian rocks of map unit P in central and northern Arizona. (280-310 Ma)
San Rafael Group (Middle to Late Jurassic)
Commonly cross-bedded, ledge-forming sandstone and slope-forming siltstone. Rock typically has a striped red and white aspect. The Carmel Formation and Entrada Sandstone are prominent members of this group. (Late to Middle Jurassic, about 160-180 Ma)
California
Cambrian marine rocks (Late Proterozoic to Middle Devonian)
Sandstone, shale, limestone, dolomite, chert, quartzite, and phyllite; includes some rocks that are possibly Precambrian
Carboniferous marine rocks, unit 1 (Western Mojave Desert) (Late Proterozoic to Pennsylvanian)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Carboniferous marine rocks, unit 5 (Northwestern Sierra Nevada) (Paleozoic or Mesozoic)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Devonian marine rocks, unit 1 (Death Valley) (Middle to Late Devonian)
Limestone and dolomite, sandstone and shale; in part tuffaceous
Jurassic marine rocks, unit 4 (Peninsular Ranges and Western Transverse Ranges) (Paleozoic(?) to Late Jurassic)
Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks
Jurassic marine rocks, unit 5 (Northern Sierra Nevada and Eastern Klamath Mountains) (Devonian to Late Jurassic)
Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks
Paleozoic marine rocks, undivided, unit 1 (Mojave Desert and Death Valley area) (Late Proterozoic to Jurassic)
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 2 (Northern Mojave Desert and Southeastern Sierra Nevada) (Cambrian to Jurassic)
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 3 (Eastern Sierra Nevada) (Late Proterozoic(?) to Mesozoic(?))
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 4 (Western Sierra Nevada) (Ordovician to Triassic)
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic marine rocks, undivided, unit 9 (Western Klamath Mountains) (Devonian to Jurassic)
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Permian marine sedimentary rocks, unit 2 (Northwestern Sierra Nevada) (Paleozoic or Mesozoic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
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
pre-Cenozoic metasedimentary and metavolcanic rocks undivided (Early Proterozoic to Cretaceous)
Undivided pre-Cenozoic metasedimentary and metavolcanic rocks of great variety. Mostly slate, quartzite, hornfels, chert, phyllite, mylonite, schist, gneiss, and minor marble.
Schist of various types and ages, unit 1 (Peninsular Ranges) (Triassic(?))
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian
Schist of various types and ages, unit 2 (Southern and West-central California) (Late Cretaceous to Eocene)
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Schist of various types and ages, unit 6 (Santa Cruz Mountains) (Paleozoic or Mesozoic)
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Schist of various types and ages, unit 9 (Cargo Muchacho Mountains) (Jurassic(?))
Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.
Silurian and/or Ordovician marine rocks, unit 1 (Death Valley) (Ordovician to Early Devonian)
Sandstone, shale, conglomerate, chert, slate, quartzite, hornfels, marble, dolomite, phyllite; some greenstone
Silurian and/or Ordovician marine rocks, unit 2 (Bishop) (Late Cambrian(?) to Early Permian(?))
Sandstone, shale, conglomerate, chert, slate, quartzite, hornfels, marble, dolomite, phyllite; some greenstone
Silurian and/or Ordovician marine rocks, unit 3 (Eastern Klamath Mountains) (Ordovician to Early Devonian)
Sandstone, shale, conglomerate, chert, slate, quartzite, hornfels, marble, dolomite, phyllite; some greenstone
Triassic marine rocks, unit 1 (Death Valley area and Mojave Desert) (Early to Middle Triassic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Triassic marine rocks, unit 7 (Mono Lake) (Paleozoic or Mesozoic)
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Colorado
Biotitic gneiss, schist, and migmatite (Proterozoic | Paleoproterozoic)
Locally contains minor hornblende gneiss, calc-silicate rock, quartzite, and marble. Derived principally from sedimentary rocks
Leadville, Gilman, Dyer, Parting, and Sawatch Fms in west-central and south-central. Leadville Limestone, Ouray Limestone, Elbert Fm, and Ignacio Quartzite in far southwest (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous)
Elbert Fm: shale and sandstone.
Leadville Limestone, Gilman Sandstone, Dyer Dolomite, and Parting Fm (Phanerozoic | Paleozoic | Ordovician Silurian(?) Devonian)
Parting Fm: quartzite and shale.
Leadville Limestone, Williams Canyon Limestone , Manitou Limestone, and Sawatch Quartzite (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous)
Manitou Limestone and Sawatch Quartzite in Southern Front Range and Wet Mountains. One or more Ordovician Fms (Fremont Limestone, Harding Sandstone, and Manitou Dolomite), Dotsero Fm, Peerless Fm, and Sawatch Quartzite in west-ce (Phanerozoic | Paleozoic | Cambrian Ordovician)
Dotsero Fm: Dolomite, in White River plateau only. Peerless Fm: sandstone and dolomite.
Parting, Fremont, and Harding Fms (Phanerozoic | Paleozoic | Ordovician Silurian(?) Devonian)
Quartzite, conglomerate, and interlayered mica schist (Proterozoic | Paleoproterozoic)
Quartzite, conglomerate, and interlayered mica schist
Red Creek Quartzite (Archean)
Metaquartzite, amphibolite, and mica schist. Present only in small area at Utah border in Uinta Mountains
Sawatch Quartzite (Phanerozoic | Paleozoic | Cambrian)
Locally includes Peerless Fm
Uinta Mountain Group (Proterozoic | Mesoproterozoic)
Quartzite, conglomerate, and shale
Uncompahgre Fm (Proterozoic | Paleoproterozoic Mesoproterozoic)
Quartzite, slate, and phyllite
Williams Canyon Limestone, Manitou Limestone, and Sawatch Quartzite (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian)
Connecticut
Basal member [of The Straits Schist] (Silurian)
Basal member [of The Straits Schist] ( = Russell Mountain Formation of Massachusetts) - Distinguished by presence of layers of amphibolite, marble, calc-silicate rock, and quartzite within more uniform schist like that on either side. Minor, unevenly distributed mineralization in W, Bi, Cu, Ni, and other metals.
Basal member of upper slice of Canaan Mountain Schist (Cambrian?)
Basal member of upper slice of Canaan Mountain Schist - Gray, generally rusty- or tan-weathering gneiss, composed of quartz, plagioclase, microcline, biotite, and muscovite, interlayered with feldspathic quartzite.
Cheshire Quartzite (Lower Cambrian)
Cheshire Quartzite - Mainly pure, white, glassy, tough quartzite.
Clough Quartzite (Silurian)
Clough Quartzite - White, medium-grained, glassy to granular, well-layered quartzite and muscovitic quartzite, locally with garnet; conglomeratic (commonly with tourmaline) in lower part.
Dalton Formation (Lower Cambrian and perhaps partly older)
Dalton Formation (including Poughquag and Lowerre Formation) - Gray, tan-weathering, medium-grained, generally well layered gneiss or feldspathic quartzite, composed of quartz, microcline, plagioclase, muscovite, biotite, and generally tourmaline; some schistose micaceous layers have sillimanite; commonly as quartz-sillimanite nodules rimmed with muscovite. Layers of purer quartzite in many areas, especially near the top or where the formation is thin.
Littleton Formation (Devonian)
Littleton Formation - Gray to silvery, generally non-rusty, medium-grained, massive to well-layered alternating schist and micaceous quartzite, composed of quartz, muscovite, biotite, garnet, and oligoclase, also staurolite, graphite, and ilmenite, and in certain areas kyanite or sillimanite in schist.
Littleton Formation (uncertain) (Devonian)
Littleton Formation (uncertain)- Gray to silvery, generally non-rusty, medium-grained, massive to well-layered alternating schist and micaceous quartzite, composed of quartz, muscovite, biotite, garnet, and oligoclase, also staurolite, graphite, and ilmenite, and in certain areas kyanite or sillimanite in schist.
Mamacoke Formation (Proterozoic Z?)
Mamacoke Formation - Interlayered (but layers locally indistinct) light- to dark-gray, medium-grained gneiss, composed of plagioclase, quartz, and biotite; sillimanite, garnet, hornblende, or microcline in certain layers; in upper part locally contains quartz-sillimanite nodules or thin layers of quartzite, amphibolite, or calc-silicate rock.
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.
Plainfield Formation (Proterozoic Z?)
Plainfield Formation - Interlayered light-gray, thin-bedded quartzite, in places with feldspar, mica, graphite, or pyrite, light- to medium-gray gneiss composed of quartz, oligoclase, and biotite (rarely microcline), medium- to dark-gray schist composed of quartz, oligoclase, biotite, sillimanite, and garnet, dark-gray or green gneiss composed of plagioclase, quartz, biotite, and hornblende (commonly with diopside), amphibolite, diopsite-bearing quartzite, and calc-silicate rock. In places contains quartz-sillimanite nodules.
Plainfield Formation plus Potter Hill Granite Gneiss plus Narragansett Pier Granite (Proterozoic Z? and Permian)
Plainfield Formation plus Potter Hill Granite Gneiss plus Narragansett Pier Granite - Plainfield Formation - Interlayered light-gray, thin-bedded quartzite, in places with feldspar, mica, graphite, or pyrite, light- to medium-gray gneiss composed of quartz, oligoclase, and biotite (rarely microcline), medium- to dark-gray schist composed of quartz, oligoclase, biotite, sillimanite, and garnet, dark-gray or green gneiss composed of plagioclase, quartz, biotite, and hornblende (commonly with diopside), amphibolite, diopsite-bearing quartzite, and calc-silicate rock. In places contains quartz-sillimanite nodules. Potter Hill Granite Gneiss - Light-pink to gray, tan-weathering, fine- to medium-grained, rarely porphyritic, well-foliated (not lineated) granitic gneiss, composed of microcline, quartz, oligoclase (or albite), biotite, and magnetite, minor muscovite, and local garnet. Narragansett Pier Granite - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.
Plainfield Formation plus Stony Creek Granite Gneiss plus Narragansett Pier Granite (Proterozoic Z? and Permian)
Plainfield Formation - Interlayered light-gray, thin-bedded quartzite, in places with feldspar, mica, graphite, or pyrite, light- to medium-gray gneiss composed of quartz, oligoclase, and biotite (rarely microcline), medium- to dark-gray schist composed of quartz, oligoclase, biotite, sillimanite, and garnet, dark-grey or green gneiss composed of plagioclase, quartz, biotite, and hornblende (commonly with diopside), amphibolite, diopside-bearing quartzite, and calc-silicate rock. In places contains quartz-sillimanite nodules. Stony Creek Granite Gneiss - Red to pink, unevenly medium to very coarse grained, variably foliated granite or granite gneiss, composed of oligoclase, K-feldspar, and quartz with minor biotite and magnetite, sporatic garnet (in foliated varieties), and local muscovite. Commonly contains granite and pegmatite of Narragansett Pier type (and probably age). In much of area both granites occur as innumerable veins penetrating other units or as larger bodies full of inclusions of those units, which can be mapped through the bodies of granite. Narragansett Pier Granite (Permian) - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.
Quartzite unit [in Plainfield Formation] (Proterozoic Z?)
Quartzite unit [in Plainfield Formation] - Light-gray, glassy, generally thin bedded quartzite, also feldspathic and micaceous quartzite containing quartz-sillimanite nodules.
Quartzite unit [in Plainfield Formation] plus Stony Creek Granite Gneiss plus Narragansett Pier Granite (Proterozoic Z? and Permian)
Quartzite unit [in Plainfield Formation] plus Stony Creek Granite Gneiss plus Narragansett Pier Granite - Quartzite unit [in Plainfield Formation] - light-gray, glassy, generally thin bedded quartzite, also feldspathic and micaceous quartzite containing quartz-sillimanite nodules. Stony Creek Granite Gneiss - Red to pink, unevenly medium to very coarse grained, variably foliated granite or granite gneiss, composed of oligoclase, K-feldspar, and quartz with minor biotite and magnetite, sporatic garnet (in foliated varieties), and local muscovite. Commonly contains granite and pegmatite of Narragansett Pier type (and probably age). In much of area both granites occur as innumerable veins penetrating other units or as larger bodies full of inclusions of those units, which can be mapped through the bodies of granite. Narragansett Pier Granite (Permian) - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.
Quartzite unit [in Scotland Schist] (Devonian or Silurian or both)
Quartzite unit [in Scotland Schist] - Quartzite, generally micaceous, interlayered with mica schist.
Rusty mica schist and gneiss (Proterozoic Y; may contain some older rocks)
Rusty mica schist and gneiss (equivalent in part to Washington Gneiss of Massachusetts) - Dark-gray, rusty-weathering, well-foliated and well- to poorly layered schist and gneiss composed of quartz, plagioclase, biotite, muscovite, sillimanite, and locally garnet; some layers of feldspathic quartzite and garnetiferous amphibolite.
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.
Unit b [of Stockbridge Marble] (Upper and Middle? Cambrian)
Unit b [of Stockbridge Marble] - White, pink, cream, and light-gray, generally well bedded dolomitic marble interlayered with phyllite and schist and with siltstone, sandstone, or quartzite, commonly dolomitic.
Georgia
Amphibolite/ Epidote Quartzite/ Granite Gneiss (Precambrian-Paleozoic)
Amphibolite/ Epidote Quartzite/ Granite Gneiss
Epidote Quartzite/ Amphibolite/ Sericite Schist/ Biotite Granite Gneiss (Precambrian-Paleozoic)
Epidote Quartzite/ Amphibolite/ Sericite Schist/ Biotite Granite Gneiss
Metagraywacke/ Mica Schist-Quartzite/ Amphibolite (Precambrian-Paleozoic)
Metagraywacke/ Mica Schist-Quartzite/ Amphibolite
Mica Schist/ Quartzite/ Gneiss/ Amphibolite (Precambrian-Paleozoic)
Mica Schist/ Quartzite/ Gneiss/ Amphibolite
Phyllite and Quartzite (Precambrian-Paleozoic)
Phyllite and Quartzite
Phyllite/ Quartzite/ Calc-silicate gneiss (Precambrian-Paleozoic)
Phyllite/ Quartzite/ Calc-silicate gneiss
Quartzite (Precambrian-Paleozoic)
Quartzite
Quartzite/ Biotite Granite Gneiss (Precambrian-Paleozoic)
Quartzite/ Biotite Granite Gneiss
Quartzite/ Metagraywacke (Precambrian-Paleozoic)
Quartzite/ Metagraywacke
Quartzite/ Mica Schist (Precambrian-Paleozoic)
Quartzite/ Mica Schist
Quartzite/ Mica Schist/ Amphibolite (Precambrian-Paleozoic)
Quartzite/ Mica Schist/ Amphibolite
Quartzite/ Phyllite (Precambrian-Paleozoic)
Quartzite/ Phyllite
Sericite Schist/ Micaceous Quartzite/ Sericite Phyllite (Precambrian-Paleozoic)
Sericite Schist/ Micaceous Quartzite/ Sericite Phyllite
Slate/ Quartzite/ Conglomerate (Precambrian-Paleozoic)
Slate/ Quartzite/ Conglomerate
Iowa
Sioux Quartzite (Proterozoic | Mesoproterozoic)
Pink-colored fine grains of quartz sand cemented to non-porous quartzite of silica; contains some red slate; Rb-Sr dates > 1200 M.Y.
Idaho
Argillite, quartzite, and calc-silicate rock; Middle Proterozoic Yellowjacket Formation; southern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, dark-colored, feldspathic quartzite with minor limestone beds of southern Idaho.
Argillite, siltite, and quartzite; Middle Proterozoic Ravalli Group; northern Belt Province (Middle Proterozoic)
Intermediate Precambrian sediments, multicolored siltite and argillite overlying quartzite and siltite of northern Idaho.
Argillite, siltite, quartzite, carbonate; Middle Proterozoic Belt metasedimentary rocks (subunits are Y1s, Y2s, Y3s, and Y4s); southern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, northern and southern Idaho; northern Idaho subdivisions are (Y4n, Y3n, Y2n, Y1n) and southern Idaho subdivisions are (Y4s, Y3s, Y2s, Y1s).
Argillite, siltstone, quartzite, and dolostone; Middle Proterozoic Missoula Group; northern Belt province (Middle Middle Proterozoic)
Intermediate Precambrian sediments, light-colored siltite overlying multicolored fine-grained detrital beds of northern Idaho.
Black argillite, quartzite, siltite, marble, chert, and syngenetic silver-lead-zinc deposits; Devonian euxinic marine-basin deposits; central Idaho (Devonian)
Devonian thrusted, deep-water siliceous argillite and quartzite of central Idaho.
Garnet-mica schist, gneiss, and quartzite; Proterozoic high-grade metasedimentary rocks; trans-Idaho metamorphic province (Late to Early Proterozoic)
Precambrian high-grade metamorphic rock; metasediment; Kyanite-sillimanite-garnet-mica schist and gneiss; minor quartzite
Garnet-sillimanite-biotite gneiss, quartzite, and amphibolite; Middle Proterozoic Lemhi Group; southern Belt trans-Idaho metamorphic provinces (Middle Proterozoic)
Precambrian high-grade metamorphic rock; metasediment; kyanite-sillimanite-garnet-mica coarse-grained schist and gneiss; minor quartzite
Garnet-sillimanite-biotite schist; Middle Proterozoic Prichard Formation, northern Belt province (Early Middle Proterozoic)
Precambrian high-grade metamorphic rock; metasediment; kyanite-sillimanite-garnet-mica coarse-grained schist and gneiss; minor quartzite
Metamorphosed granitoid plutonic rocks and metasedimentary rocks, undivided; Cretaceous orthogneiss in Middle Proterozoic metasedimentary host rocks; west-central Idaho (Cretaceous to Middle Proterozoic)
Highly metamorphosed rock of central Idaho; age and origin of rock questionable.
Metasedimentary and meta-igneous rocks; Triassic to Mississippian greenschist-facies dismembered ophiolite, western Idaho, Blue Mountains island-arc complex (Triassic to Mississippian)
Jurassic marine wacke, volcanic, or carbonate metasediments of western Idaho.
Metasedimentary and metavolcanic rocks; Permian greenschist-facies rocks; western Idaho, Blue Mountains island-arc complex (Late Permian)
Upper Permian submarine volcanic complex in the Snake Canyon 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
Mica schist, marble, quartzite, and amphibolite; Early Middle to Early Proterozoic metasedimentary rocks; southern Belt province (Early Middle Proterozoic to Early Proterozoic)
Older Precambrian high-grade metamorphic complex of eastern Idaho.
Mica schist, quartzite, and calc-silcicate rock; Proterozoic high-grade metasedimentary rocks; trans-Idaho metamorphic province (Proterozoic)
Precambrian high-grade metamorphic rock; metasediment; kyanite-sillimanite calc-silicate schist and gneiss, scapolite common
Mica schist, quartzite, gneiss, and amphibolite; Late to Early Proterozoic high-grade metasedimentary rocks (subunits are ZXmhs, ZXmhq, and ZXmhc); trans-Idaho metamorphic province (Proterozoic)
Precambrian high-grade metamorphic rock; metasediment
Mica schist, quartzite, migmatite, amphibolite; Middle to Early Proterozoic metamorphic rocks; northern Belt province, Spokane dome of Priest River metamorphic core complex (Middle Proterozoic to Early Proterozoic)
Precambrian, high-grade metamorphic rock; metasediment; kyanite-silimanite garnet-mica coarse-grained schist and gneiss; minor quartzite
Migmatitic paragneiss, quartzite, orthogneiss, and amphibolite; Early Proterozoic to Late Archean metamorphic rocks; northern Belt province; Settlement antiform in Priest River metamorphic core complex (Early Proterozoic to Late Archean)
Precambrian, high-grade metamorphic rock; metasediment; kyanite-sillimanite garnet-mica coarse-grained schist and gneiss; minor quartzite
Quartzite and biotite schist in fault contact; Middle Proterozoic metasedimentary rocks; southern Belt province (Middle Proterozoic)
Intermediate Precambrian age metasediments; dominantly quartzite with minor micaceous layers and mica schists of northern Idaho
Quartzite and marble; Middle Proterozoic Hoodoo Quartzite; southern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, light-colored, massive quartzite of southern Idaho.
Quartzite and muscovite schist; Middle Protrerozoic metasedimentary rocks of the Ravalli Group; northern Belt province (Middle Proterozoic)
Intermediate Precambrian age metasediments; dominantly quartzite with minor micaceous layers and mica schists of northern Idaho.
Quartzite, argillite, carbonate, meta-conglomerate, siltite, intermediate volcanic rock; Late Proterozoic rifted continental margin; southeastern Idaho (Late Proterozoic)
Younger Precambrian detrital units of central and southeastern Idaho; subdivisions are (Z2s and Z1s).
Quartzite, marble, Calc-silicate rock, schist, and meta-conglomerate; Ordovician to Middle Proterozoic metasedimentary rocks; central Idaho, Pioneer Mountains metamorphic core complex (Ordovician to Middle Proterozoic)
Ordovician to Middle Proterozoic metasedimentary rocks, undivided
Quartzite, meta-conglomerate, dolostone, argillite; Middle Proterozoic Swauger quartzite; southern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, red-tinted quartzite with minor conglomeratic and dolomitic lenses of southern Idaho
Quartzite, mica schist, and calc-silicate rock; Proterozoic high-grade metasedimentary rocks; trans-Idaho metamorphic province (Proterozoic)
Precambrian, high-grade metamorphic rock; metasediments; kyanite-sillimanite schist, and micaceous quartzite
Quartzite, mica schist, and marble; Cambrian and Late Proterozoic metasedimentary rocks; south-central Idaho, Albion-Range metamorphic core complex (Cambrian to Late Proterozoic)
Schist, quartzite and other metasediments of probable Lower Ordovician to Cambrian age.
Quartzite, siltite, argillite, and mica schist; Middle Proterozoic Lemhi Group; southern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, feldspathic quartzite and siltstone of southern Idaho.
Quartzite, siltstone, conglomerate, and metavolcanic rocks; Late and Middle Proterozoic, undivided; Atlanta batholith roof pendants (Late and Middle Proterozoic, undivided)
Precambrian, high-grade metamorphic rock
Schist, phyllite, quartzite, and calc-silicate rock; Middle Proterozoic metasedimentary rocks of Wallace Formation; northern Belt province (Middle Proterozoic)
Intermediate Precambrian age metasediments; generally low-to-medium grade; carbonate bearing argillite and siltite of northern Idaho.
Schist, quartzite, marble, skarn, and mafic gneiss; Jurassic to Mississippian amphibolite-facies rocks; southwestern Idaho, western accreted island-arc complex (Jurassic to Mississippian)
Metamorphic complex of probable Paleozoic units of southwestern Idaho.
Siltite, argillite, and quartzite; Middle Proterozoic Prichard Formation; northern Belt province (Middle Proterozoic)
Intermediate Precambrian sediments, gray interlaminated siltite and argillite with minor quartzite of northern Idaho.
Siltite, argillite, dolostone, and quartzite; Middle Proterozoic Wallace Formation; northern Belt province (Early Middle Proterozoic)
Intermediate Precambrian sediments, dark-colored calcareous and dolomitic argillite and siltite of northern Idaho.
Massachusetts
Ammonoosuc Volcanics (Middle Ordovician)
Ammonoosuc Volcanics - Basal quartzite and conglomerate.
Ammonoosuc Volcanics (Middle Ordovician)
Ammonoosuc Volcanics - Amphibolite, felsic gneiss, garnet-amphibole quartzite, and marble too thin to show separately at map scale. Gedrite, anthophyllite, cummingtonite locally abundant in amphibolite layers.
Blackstone Group (Proterozoic Z)
Blackstone Group - Quinnville Quartzite.
Blackstone Group (Proterozoic Z)
Blackstone Group - Undivided - Quartzite, schist, phyllite, marble, and metavolcanic rocks.
Boylston Schist (Silurian or Ordovician)
Boylston Schist - Carbonaceous phyllite and schist, locally sulfidic; quartzite; calc-silicate beds.
Cambridge Argillite (Proterozoic Z to earliest Paleozoic)
Cambridge Argillite - Gray argillite and minor quartzite; rare sandstone and conglomerate. Contains acritarchs. Cambridge Argillite of Boston Bay Group contains sandy horizons which are in some places quartzite. Most prominent are Milton quartzite unit of Billings (1976), and Tufts Quartzite Member (described by Billings, 1929, and LaForge, 1932) in northern part of basin. Red sandstone and sandy argillite in Chelsea, Revere, and Milton-Quincy areas intertongue with green argillite (Kaye, 1980). Red beds lie above cleaner quartzites such as Tufts and Milton units. Core analysis by D.A. Ashenden (Metropolitan District Commission, 1980, written commun.) indicates that Cambridge and Braintree Argillites are identical. Age of Boston Bay rocks has been controversial and was once thought to be Cambrian to Pennsylvanian (the latter based on lithologic similarity to rocks of Narragansett basin and now discredited plant fossils). Age of Cambridge and of Boston Bay Group as a whole is Proterozoic Z and possibly Early Cambrian based on presence of acritarchs in Cambridge. Acritarchs are diagnostic species that ranges in age from Proterozoic Z to Early Cambrian, but is most abundant in Proterozoic Z time (Lenk and others, 1982; [also see Goldsmith and others, 1982]). Age is also supported by the following: 1) plant fossils so numerous in strata of Narragansett basin are absent in the Boston Bay Group strata, 2) Late Ordovician and Early Silurian Quincy Granite contains argillite inclusions that are on strike with Cambridge Argillite, and 3) Boston Bay Group stratigraphy is primarily marine, not similar to terrestrial stratigraphy of Narragansett basin (Goldsmith, 1991).
Cheshire Quartzite (Lower Cambrian)
Cheshire Quartzite - White, massive vitreous quartzite.
Clough Quartzite (Upper Silurian)
Clough Quartzite - Quartz-pebble conglomerate, quartzite, and minor mica schist and calc-silicate rocks. Fossils at Bernardston are similar to those at Croyden Mountain, New Hampshire which indicate late Llandoverian age. Parts of the Littleton and Partridge Formations, and Clough Quartzite in MA are here reassigned to the Rangeley Formation [here geographically extended to MA]. The four mapped areas of Clough Quartzite in the Amherst area west of the Connecticut Valley border fault are now interpreted as conglomerate lenses in the Rangeley. Clough is considered the key stratigraphic unit in Bronson Hill anticlinorium because 1) it is dominated by distinctive, readily recognizable rock types, 2) where present, it is base of Silurian-Devonian sequence, resting with detectable unconformity on older rocks, and 3) it contains late Llandoverian fossils at several localities in western NH and adjacent VT, and at Bernardston, MA. Consists mostly of quartz-pebble conglomerate in which pebbles are typically deformed; other lithologies are quartz grit or white to pink, well-bedded quartzite. Locally contains some mica schist beds. On the MA State bedrock geologic map (Zen and others, 1983), thickness is locally exaggerated because at many localities, the unit was only a few meters or less thick and could not be shown at a scale of 1:250,000. Maximum thickness is 200 m on west limb of Northfield syncline. Unconformably overlies Fourmile Gneiss in Pelham dome and in Kempfield anticline, or Ammonoosuc Volcanics over most gneiss domes. Partridge Formation occurs along Clough-Ammonoosuc contact as lenses in many areas (Hatch and others, 1988).
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 - 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 - Tan weathering, muscovite-microcline quartzite and feldspathic quartzite rich in black tourmaline, locally includes thin beds of other rock types listed below.
Dalton Formation (Lower Cambrian and Proterozoic Z)
Dalton Formation - Orangish-gray, gray, and light-greenish-gray muscovite-quartz schist and interlayered feldspathic quartzite and quartz conglomerate; minor beds of rusty albitic schist.
Dalton Formation (Lower Cambrian and Proterozoic Z)
Dalton Formation - White to yellowish-gray weathering, flaggy quartzite interbedded in feldspathic quartzite.
Dry Hill Gneiss (Proterozoic Z)
Dry Hill Gneiss - Pink microcline-biotite and microcline-hornblende gneiss containing pink microcline megacrysts and minor quartzite.
Dry Hill Gneiss (Proterozoic Z)
Dry Hill Gneiss - Pelham Quartzite Member. White to buff quartzite and feldspathic quartzite commonly with biotite and/or actinolite.
Dry Hill Gneiss (Proterozoic Z)
Dry Hill Gneiss - Biotite-tourmaline schist and quartzite.
Everett Formation (Lower Cambrian and Proterozoic Z)
Everett Formation - Olive-gray to green, blue-quartz pebble metagraywacke and quartzite.
Fourmile Gneiss (Ordovician, Cambrian, or Proterozoic Z)
Fourmile Gneiss - Muscovite quartzite.
Gile Mountain Formation (Lower Devonian)
Gile Mountain Formation - Like Dgm but having a higher percentage of quartzite.
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.
Goshen Formation (Lower Devonian)
Goshen Formation - Similar to Dg but having scattered beds of calcareous granofels.
Goshen Formation (Lower Devonian)
Goshen Formation - Well-bedded micaceous quartzite or quartz schist grading upward into light- to dark-gray, carbonaceous aluminous schist in beds 5 to 15 cm thick.
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 - 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.
Gray, well-layered biotite-plagioclase-quartz gneiss (Proterozoic Y)
Gray, well-layered biotite-plagioclase-quartz gneiss - Containing beds of amphibolite, aluminous schist, quartzite, and calc-silicate gneiss.
Green Lodge Formation of Rhodes and Graves (Upper Cambrian?)
Green Lodge Formation of Rhodes and Graves - Quartzite and slate; contains fossils of questionable Late Cambrian age.
Greylock Schist (Lower Cambrian and Proterozoic Z)
Greylock Schist - Soft, lustrous green phyllite with minor beds of green quartzite and well laminated gray dolomitic phyllite; resembles Hoosac (CAZhg) and Nassau (CAZnp).
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).
Hawley Formation (Middle Ordovician)
Hawley Formation - Black, fine-grained, splintery, rusty-weathering schist and thin dark quartzite; interlayered amphibolite commonly has plagioclase 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).
Hoosac Formation (Lower Cambrian and Proterozoic Z)
Hoosac Formation - Green to gray-green chlorite-sericite-quartz phyllite; interbeds of chloritoid- or albite-rich schist and minor quartzite, locally rich in garnet and kyanite.
Hoosac Formation (Lower Cambrian and Proterozoic Z)
Hoosac Formation - Undifferentiated Hoosac Formation.
Hoppin Formation (Middle and Lower Cambrian)
Hoppin Formation - Quartzite, argillite, and minor limestone; contains Middle Cambrian fauna.
Kittery Formation (Silurian or Ordovician)
Kittery Formation - Quartzite, partly calcareous; phyllite, schist.
Mount Mineral Formation (Proterozoic Z)
Mount Mineral Formation (Probably correlates with Poplar Mountain Gneiss but is more aluminous) - Aluminous schist, amphibolite, and quartzite, undifferentiated; locally rich in garnet and kyanite, and with relict sillimanite and orthoclase from pre-Middle Ordovician metamorphism.
Nassau Formation (Lower Cambrian and Proterozoic Z)
Nassau Formation - Gray to dark-greenish-gray, siliceous phyllite with abundant beds of quartzite, olive-gray metasiltstone and subgraywacke (includes Bomoseen Graywacke Member and Zion Hill quartzite Member).
Paxton Formation (Silurian)
Paxton Formation - Rusty-weathering sulfidic quartzite 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).
Paxton Formation (Silurian)
Paxton Formation - Sulfidic magnesian biotite and magnesian cordierite schist and sillimanite quartzite. 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).
Plainfield Formation (Proterozoic Z)
Plainfield Formation - Quartzite, pelitic schist, minor calc-silicate rock and amphibolite. Plainfield Formation extend into MA in Webster-Oxford area from eastern CT and western RI along west flank of Rhode Island batholith, along same strike as elongate lenses of Westboro Formation (as shown on State bedrock map of Zen and others, 1983). Lithology of Plainfield in New London area of southeastern CT (Goldsmith, 1966, 1976) and in eastern CT (Harwood and Goldsmith, 1971), and its structural and stratigraphic position indicate Plainfield and Westboro are equivalent. Plainfield is truncated along CT-RI border by Lake Char fault; however, in New London area, Plainfield is overlain by suite of largely mafic metavolcanic rocks (Waterford Group of Goldsmith, 1980), a relationship similar to that of the Westboro Formation and overlying metavolcanic rocks. Base of Plainfield is unknown, but gneiss and schist in center of Lyme dome may lie below it. Probably equivalent to quartzite and schist of Blackstone Group on basis of similar lithology and structural relations with Rhode Island batholith rocks (Goldsmith, 1991).
Poplar Mountain Gneiss (Proterozoic Z)
Poplar Mountain Gneiss (Probably correlates with Mount Mineral Formation but is more feldspathic) - Dark biotite gneiss containing white microcline megacrysts and beds of quartzite.
Poplar Mountain Gneiss (Proterozoic Z)
Poplar Mountain Gneiss (Probably correlates with Mount Mineral Formation but is more feldspathic) - Basal quartzite, where thick enough to map; commonly feldspathic, containing biotite and actinolite or muscovite.
Rowe Schist (Lower Ordovician and Cambrian)
Rowe Schist - Gray to black, fine-grained , slightly rusty, moderately carbonaceous schist; minor fine- to medium-grained dark-gray to white quartzite. Minor lenses of rock identical to OCAr.
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).
Stockbridge Formation (Lower Cambrian)
Stockbridge Formation - Beige, tan, and dark-gray weathering quartzose dolomite marble containing interbeds of black, green and maroon phyllite and punky weathering blue quartz pebble quartzite.
Stockbridge Formation (Lower Ordovician)
Stockbridge Formation - Tan-beige weathering quartzose calcite and dolomite marble; minor cross-laminated quartzite.
Tadmuck Brook Schist (Silurian?, Ordovician, or Proterozoic Z)
Tadmuck Brook Schist - Andalusite phyllite and sillimanite schist, partly sulfidic; local quartzite in upper part.
Tower Hill Quartzite (Silurian)
Tower Hill Quartzite - Quartzite and phyllite.
Undifferentiated Poplar Mountain and Dry Hill Gneisses (Proterozoic Z)
Undifferentiated Poplar Mountain and Dry Hill Gneisses .
Vaughn Hills Quartzite (Silurian or Ordovician)
Vaughn Hills Quartzite - Quartzite, phyllite, conglomerate, and chlorite schist.
Walloomsac Formation (Middle Ordovician)
Walloomsac Formation - Tan to dark-blue-gray laminated quartzite and calcareous quartzite previously mapped as Bellowspipe Quartzite.
Westboro Formation (Proterozoic Z)
Westboro Formation - Quartzite, schist, calc-silicate quartzite, and amphibolite. Consists of quartzite and argillite in Saugus and Lynnfield areas. Westboro Formation consists primarily of orthoquartzite and subordinate mica schist, calc-silicate rock, amphibolite, and quartzitic biotite gneiss and schist. Westboro as portrayed by Nelson (1974), Bell and Alvord (1976), and Hepburn and DiNitto (1978) are correlative [with varying certainty]. West and south of Boston, disconnected masses of quartzite and associated rocks are shown on State bedrock map by Zen and others (1983) as Westboro although not continuous with belts mapped by Nelson (1974) or Hepburn and DiNitto (1978). Includes isolated quartzite masses mapped by Castle (1964) in Reading area. On State bedrock map, arbitrarily includes thin quartzite mapped as Burlington Formation by Bell and Alvord (1976) because the units are similar and to reduce number of small units on State map. Rocks mapped as Rice Gneiss by Nelson (1974) were included in unnamed metamorphosed mafic and felsic volcanic unit on State bedrock map, but author now feels it should be either a part of Westboro, or a separate unit below it. Westboro in Framingham area and to the northeast is overlain by unnamed assemblage of metamorphosed mafic and felsic volcanic rocks. South of town of Westborough, Westboro is truncated by Bloody Bluff-Lake Char fault system. Intruded by Proterozoic Z batholithic rocks. Equivalent to Plainfield Formation of eastern CT because it lies in same strike belt, and is probably equivalent to Quinnville Quartzite and unnamed mica schist and phyllite of Blackstone Group. Contact between Westboro and Blackstone is arbitrary on State bedrock map on basis of proximity of isolated exposures of the two units to their respective type areas. No area of continuous exposure exists between Westboro and Blackstone (Goldsmith, 1991).
Maryland
Cardiff Metaconglomerate (Late Precambrian (?))
Cardiff Metaconglomerate - Silvery-gray, well foliated, micaceous quartz-pebble metaconglomerate and quartzite; apparent maximum thickness 700 feet.
Chilhowee Group; Antietam Formation (Cambrian)
Antietam Formation - White to dark gray and brown, thick-bedded, fine- to coarse-grained quartzite with thin argillaceous partings; first occurrence of Lower Cambrian fossils; cleavage generally obscures bedding; increasingly metamorphosed and phyllitic toward east; estimated thickness 300 to 800 feet.
Chilhowee Group; Weverton Formation (Late Precambrian - Cambrian)
Weverton Formation - Interbedded white to dark gray, thin-bedded, micaceous, ferruginous, and sericitic quartzites, phyllites, and white, thick-bedded, ledge-making quartzites; some gray to brown ferruginous quartz conglomerate and purple-banded phyllite; thickness approximately 100 feet in south, increases to 425 feet in north.
Clinton Group, including Rochester Shale (Silurian)
Clinton Group, including Rochester Shale - Gray, thin-bedded calcareous shale and dark gray, thin- to medium-bed7 ded lenticular limestone; thickness 25 to 40 feet; Keefer Sandstone - White to yellowish-gray, thick-bedded protoquartzite and orthoquartzite; calcareous to west; thickness 10 feet in west, increases to 35 feet in east; and Rose Hill Formation - Olive-gray to drab, thin-bedded shale; some purple shale and gray, thin-bedded sandstone; including Cresaptown Iron Sandstone Member - Purple, hematite-cemented, quartzose sandstone; thickness 5 to 30 feet; occurs in lower half of formation; total thickness 300 feet in east, increases to 570 feet in west.
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.
Marburg Schist (Late Precambrian (?))
Marburg Schist - Bluish-gray to silvery-green, fine-grained, muscovite-chlorite-albite-quartz schist; intensely cleaved and closely folded; contains interbedded quartzites.
Peach Bottom Slate (Ordovician (?))
Peach Bottom Slate - Hard, bluish-black graphitic slate; thin beds of fine-grained black quartzite near base; apparent maximum thickness 1,000 feet.
Setters Formation (Late Precambrian (?))
Setters Formation - Upper member: Feldspathic mica schist and mica gneiss; total thickness 200 to 500 feet. Middle member: Impure quartzite interstratified with thin beds of mica schist; total thickness 200 to 500 feet. And Lower member: Medium-grained, feldspathic mica schist; locally granitized; total thickness 200 to 500 feet.
Sugarloaf Mountain Quartzite (Late Precambrian (?))
Sugarloaf Mountain Quartzite - Massive white quartzite interbedded with softer sericitic quartzite, slate, and phyllite.
Swift Run Formation (Late Precambrian)
Swift Run Formation - Sericitic quartzite and phyllite; blue and green tuffaceous slate with sericitic blebs; some white marble with interbedded phyllite.
Urbana Formation (Late Precambrian (?))
Urbana Formation - Dark gray to green sericite-chlorite phyllite, metasiltstone, and quartzite; thin lenses of impure marble and calcareous phyllite occur locally.
Wissahickon Formation; Metaconglomerate (Late Precambrian (?))
Wissahickon Formation; Metaconglomerate - Silvery-gray, well foliated, micaceous quartz-pebble metaconglomerate and quartzite; thickness about 1,200 feet at Deer Creek, Harford County.
Wissahickon Formation (Undivided) (Late Precambrian (?))
Wissahickon Formation (Undivided) - Muscovite-chlorite-albite schist, muscovite-chlorite schist, chloritoid schist, and quartzite; intensely folded and cleaved.
Wissahickon Formation; Upper Pelitic Schist (Late Precambrian (?))
Wissahickon Formation; Upper Pelitic Schist - (Formerly mapped as albite facies of Wissahickon Formation.) Albite-chlorite-muscovite-quartz schist with sporadic thin beds of laminated micaceous quartzite; coarsens from west to east; primary sedimentary structures include normal bedding, graded bedding, and soft-sediment deformational structures; apparent thickness 14,000 feet or more.
Maine
Cambrian Hurricane Mountain Formation, black and gray metaquartzite (Cambrian)
Cambrian Hurricane Mountain Formation, black and gray metaquartzite
Devonian Carrabassett Formation quartzite member (Devonian)
Devonian Carrabassett Formation quartzite member
Devonian Seboomook Formation unnamed quartzite (Devonian)
Devonian Seboomook Formation unnamed quartzite
Devonian - Silurian Madrid Formation (Devonian - Silurian)
Devonian - Silurian Madrid Formation
Devonian Tarratine Formation (Devonian)
Devonian Tarratine Formation
Devonian Tarratine Formation Misery Quartzite (Devonian)
Devonian Tarratine Formation Misery Quartzite
Devonian Tomhegan Formation (Devonian)
Devonian Tomhegan Formation
Ordovician - Cambrian Aziscohos Formation (Ordovician - Cambrian)
Ordovician - Cambrian Aziscohos Formation
Ordovician - Cambrian Dead River formation (Ordovician - Cambrian)
Ordovician - Cambrian Dead River formation
Ordovician - Cambrian Dead River formation lower member (Ordovician - Cambrian)
Ordovician - Cambrian Dead River formation lower member
Ordovician - Cambrian Dead River formation upper member (Ordovician - Cambrian)
Ordovician - Cambrian Dead River formation upper member
Ordovician - Cambrian Megunticook Formation (Ordovician - Cambrian)
Ordovician - Cambrian Megunticook Formation
Ordovician Chandler Ridge Formation (Ordovician)
Ordovician Chandler Ridge Formation
Ordovician - Precambrian Z Cape Elizabeth Formation (Ordovician - Precambrian Z)
Ordovician - Precambrian Z Cape Elizabeth Formation
Ordovician - Precambrian Z Cape Elizabeth Formation quartzite member (Ordovician - Precambrian Z)
Ordovician - Precambrian Z Cape Elizabeth Formation quartzite member
Ordovician - Precambrian Z Cushing Formation quartzite (Ordovician - Precambrian Z)
Ordovician - Precambrian Z Cushing Formation quartzite
Silurian - Ordovician Lobster Lake Formation (Silurian - Ordovician)
Silurian - Ordovician Lobster Lake Formation
Silurian - Ordovician Vassalboro formation (Silurian - Ordovician)
Silurian - Ordovician Vassalboro formation
Silurian Perry Mountain formation (Silurian)
Silurian Perry Mountain formation
Silurian - Precambrian Z Berwick Formation (Silurian - Precambrian Z)
Silurian - Precambrian Z Berwick Formation
Silurian - Precambrian Z Eliot Formation (Silurian - Precambrian Z)
Silurian - Precambrian Z Eliot Formation
Whiskey Quartzite (Devonian)
Whiskey Quartzite
Michigan
Chocolay Group, undivided (Early Proterozoic)
Chocolay Group, undivided - In Dickinson County, Mich., includes Randville Dolomite, Sturgeon Quartzite, and Fern Creek Formation. In Marquette range, between Marquette Bay and Champion, includes Wewe Slate, Kona Dolomite, Mesnard Quartzite, and Enchantment Lake Formation
Menominee Group; Composite unit of Siamo Slate and Ajibik Quartzite (Early Proterozoic)
Menominee Group; Composite unit of Siamo Slate and Ajibik Quartzite - Siamo Slate is laminated green siltstone and argillite. Ajibik Quartzite is white, buff, and pink orthoquartzite and less abundant sericite quartzite.
Menominee Group, undivided (Early Proterozoic)
Menominee Group, undivided - Includes Negaunee Iron-formation, Siamo Slate, and Ajibik Quartzite in areas where units are too thin to map individually.
Minnesota
Sioux Quartzite (Early Proterozoic)
Sioux Quartzite - Red quartzite of fluvial to possibly marginally marine origin. Includes quartz-pebble conglomerate, claystone (catlinite, also called pipestone), a basal (rhyolite) pebble conglomerate in Pipestone County, and a basal (granite, quartz, chert, iron-formation) conglomerate in Nicollet County on the Minnesota River
Mississippi
Catahoula formation (Miocene)
Catahoula formation - Irregularly bedded gray sand and sandstone; mottled red and gray, green, and chocolate-colored clay; some quartzite, and some gravel; the Paynes Hammock sand, sandy limestone cross-bedded fine green sand, and thin-bedded sand and clay, is mapped with the underlying Chickasawhay limestone in eastern MS.
Kosciusko formation (Eocene)
Kosciusko formation - (Claiborne group), irregularly bedded sand, clay, and some quartzite.
Montana
Altyn limestone (Proterozoic | Mesoproterozoic)
Altyn limestone: dominantly dolomite and magnesian limestone that weathers to a distinctive yellowish brown; some feldspathic quartzite and conglomerate. Correlation with the Ravalli group is provisional.
Appekunny argillite (Proterozoic | Mesoproterozoic)
Appekunny argillite: gray quartzitic argillite and quartizite.
Empire shale (Proterozoic | Mesoproterozoic)
Empire shale: green dense, laminated shale with some red beds. Distinguished only in general vicinity of Helena.
Greyson shale (Proterozoic | Mesoproterozoic)
Greyson shale: dark-gray to dark-brown argillaceous and sandy rock; weathers brown or red; grades into the Spokane above and the Newland below. Distinguished only in the general vicinity of Helena.
Grinnell argillite (Proterozoic | Mesoproterozoic)
Grinnell argillite: reddish-purple and green argillite, quartzitic argillite, and some quartzite; generally contains some feldspar and carbonates.
Helena limestone (Proterozoic | Mesoproterozoic)
Helena limestone: gray, unevenly laminated limestone, argillaceous and dolomitic; weathers light brown or yellow. Segregation structures and stromatolites are common. Distinguished only in general vicinity of Helena.
Missoula group (Proterozoic | Mesoproterozoic)
Missoula group: chiefly red, maroon, or purple argillite; sandy or quartzitic argillite, and generally impure quartzite and limestone. The larger limestone masses are similar to the Siyeh limestone of the Piegan group. The Missoula group includes numerous named formations, most of which cannot be traced with confidence far from their type localities. Among these are the Marsh shale in the Helena region, the Striped Peak and Libby formations in northwestern Montana, five near Missoula, and others in and south of Glacier National Park.
Missoula group (Proterozoic | Mesoproterozoic)
Missoula group: chiefly red, maroon, or purple argillite; sandy or quartzitic argillite, and generally impure quartzite and limestone. The larger limestone masses are similar to the Siyeh limestone of the Piegan group. The Missoula group includes numerous named formations, most of which cannot be traced with confidence far from their type localities. Among these are the Marsh shale in the Helena region, the Striped Peak and Libby formations in northwestern Montana, five near Missoula, and others in and south of Glacier National Park.
Neihart quartzite (Proterozoic | Mesoproterozoic)
Neihart quartzite: reddish coarse-grained sandstone or quartzite with interbedded dark-green sandstone and shale; rocks near Philipsburg that were formerly doubtfully correlated with the Neihart are here mapped with the Prichard. Near Neihart the formation rests on gneiss of pre-Belt age. Age relations between the Neihart and the Prichard are unknown.
Newland limestone (Proterozoic | Mesoproterozoic)
Newland limestone: dark bluish-gray argillaceous, dolomitic limestone with some argillite, locally schistose; segregation structures not conspicuous. In central and western Montana the Newland and Wallace formations have been treated as essentially synonymous terms by some authors.
North Boulder group (Proterozoic | Mesoproterozoic)
North Boulder group: greenish-gray coarse conglomerate at base, with arkose, conglomerate, and sandy and silty strata above. Locally includes strata resembling the Greyson and Spokane shales, thought to rest directly on the pre-Belt complex of metamorphic rocks. Some areas shown as Spokane shale, and possibly other units may include rocks of the North Boulder group. Distinguished from the vicinity of North Boulder River eastward along and north of Jefferson River and in the Bridger Range.
Piegan group (Proterozoic | Mesoproterozoic)
Piegan group: most of the Piegan group is subdivided into formations that are in part equivalent to each other. Where correlations are relatively doubtful the group designation is retained. Carbonate-bearing rocks predominate in the group, but the proportions and character of the impurities in these rocks and the relations to non-carbonate-bearing rocks vary from place to place.
Piegan group (Proterozoic | Mesoproterozoic)
Piegan group: most of the Piegan group is subdivided into formations that are in part equivalent to each other. Where correlations are relatively doubtful the group designation is retained. Carbonate-bearing rocks predominate in the group, but the proportions and character of the impurities in these rocks and the relations to non-carbonate-bearing rocks vary from place to place.
Prichard formation (Proterozoic | Mesoproterozoic)
Prichard formation: dark-gray, generally argillaceous rocks, locally sandy or quartzitic; locally metamorphosed to schist.
Ravalli group (Proterozoic | Mesoproterozoic)
Ravalli group: a diverse assemblage with numerous subdivisions, only a few of which have been recognized over large enough areas to be distinguished here. Near Idaho the rocks are light colored and siliceous, ranging from pure white quartzite to siliceous shale, mostly in subdued tones of gray, green, purple, and red. Near Missoula the rocks are dark-gray quartzite and quartzitic argillite. In and near Glacier National Park the Grinnell, Appekunny, and Altyn formations are distinguished.
Ravalli group (Proterozoic | Mesoproterozoic)
Ravalli group: a diverse assemblage with numerous subdivisions, only a few of which have been recognized over large enough areas to be distinguished here. Near Idaho the rocks are light colored and siliceous, ranging from pure white quartzite to siliceous shale, mostly in subdued tones of gray, green, purple, and red. Near Missoula the rocks are dark-gray quartzite and quartzitic argillite. In and near Glacier National Park the Grinnell, Appekunny, and Altyn formations are distinguished.
Siyeh limestone (Proterozoic | Mesoproterozoic)
Siyeh limestone: crystalline limestone of varying impurity; mostly thick bedded or massive, but with thin wavy banding on fresh fractures within the beds; dusky blue or greenish where fresh, weathering orange and brownish; "molar tooth", similar structures, and stromatolites are common.
Spokane shale (Proterozoic | Mesoproterozoic)
Spokane shale: red or red-purple shale with numerous green beds locally and some quartzite; grades into the Empire above and the Greyson below and in some areas as mapped probably includes all or part of Empire and Greyson shales. The name has been used over a wide area in Montana, but in a strict sense can be used safely only in the general vicinity of Helena.
Wallace formation (Proterozoic | Mesoproterozoic)
Wallace formation: A heterogeneous unit that includes dark-gray argillite, arenaceous and argillaceous limestone, in part dolomitic, and gray limy quartzite, with shale and sandstone in large areas. The argillaceous and sandy or quartzitic rocks are commonly slightly calcareous. The dominantly carbonate-rich rocks contain "molar tooth" or segregation structures. Commonly characterized by thin laminae. Locally red rocks near the top may represent a transition into the Missoula group.
North Carolina
Battleground Formation (Late Proterozoic)
Battleground Formation - quartz-sericite schist with metavolcanic rock, quartz-pebble metaconglomerate, kyanite-sillimanite quartzite, and garnet-quartz rock.
Blacksburg Formation (Cambrian/Late Proterozoic)
Blacksburg Formation - sericite schist, locally with graphite, phyllite with sericite quartzite, banded marble, amphibolite, and minor calc-silicate rock.
Blowing Rock Gneiss (Middle Proterozoic)
Blowing Rock Gneiss (1000 my) - unconformity; abundant white potassic feldspar megacrysts in finely banded biotite schist, locally calcareous; interlayered with quartz-feldspar schist, calcareous biotite schist, phyllite, black slate, calcareous quartzite, sulfidic greenstone, and siliceous tuff.
Brasstown Formation (Late Proterozoic)
Brasstown Formation - cross-biotite schist; includes micaceous quartzite in lower part.
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.
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.
Mica Schist (Cambrian/Late Proterozoic)
Mica Schist - Garnet, staurolite, kyanite, or sillimanite occur locally; lenses and layers of quartz schist, micaceous quartzite, calc-silicate rock, biotite gneiss, amphibolite, and phyllite.
Mica Schist (Cambrian/Late Proterozoic)
Mica Schist - contains garnet, staurolite, kyanite, or sillimanite; includes lenses and layers of quartz schist, micaceous quartzite, biotite gneiss, amphibolite, and phyllite.
Mineral Bluff Formation (Late Proterozoic)
Mineral Bluff Formation - quartz-chlorite-sericite schist and phyllite with thin quartzite layers and minor interbedded graphitic schist, garnet-mica schist, staurolite schist, cross-biotite schist, and dark slate.
Murphy Marble, Andrews Formation, and Nottely Quartzite, undivided (Late Proterozoic)
Murphy Marble, Andrews Formation, and Nottely Quartzite, undivided - Murphy Marble: calcareous to dolomitic; Andrews Formation: calcareous cross-biotite schist; Nottely Quartzite: meta-orthoquartzite with slate.
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, Snowbird Group; Longarm Quartzite (Late Proterozoic)
Longarm Quartzite - cross-bedded, feldspathic, locally conglomeratic; includes dark slate and metasiltstone.
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.
Phyllite and Schist (Cambrian/Late Proterozoic)
Phyllite and Schist - minor biotite, pyrite, and sillimanite; includes minor quartzite.
Quartzite (Cambrian/Late Proterozoic)
Quartzite - interlayered with quartz-muscovite schist, contains muscovite, andalusite, kyanite, or sillimanite.
Quartzite (Cambrian/Late Proterozoic)
Quartzite - massive to well foliated; contains andalusite, kyanite, or sillimanite, chloritoid, and pyrite.
Quartzite and Quartz-Muscovite Schist (Cambrian/Late Proterozoic)
Quartzite and Quartz-Muscovite Schist - garnet, andalusite, kyanite, or sillimanite occur locally.
New Hampshire
Clough Quartzite (Lower Silurian (upper Llandoverian))
Clough Quartzite - Orthoquartzite, quartz metaconglomerate, muscovite schist, minor polymictic metaconglomerate. Disconformable below Fitch Formation and unconformable on Ordovician formations. Equivalent, in part, to member C of Rangeley Formation of Maine. Fossiliferous.
Dead River Formation, undivided (Upper Cambrian? - Lower Ordovician?)
Dead River Formation, undivided - Thinly laminated, "pin-striped" gray, green, or tan metapelite and quartzite.
Fitch and Clough Formations, undivided (Silurian)
Fitch and Clough Formations, undivided.
Fitch Formation (Upper Silurian; Pridolian and Ludlovian) (Upper Silurian - (Pridolian and Ludlovian))
Fitch Formation - Metamorphosed limestone, calcareous sandstone, siltstone, and dark pelitic schist; lower contact is disconformable on the Clough Quartzite. Fossiliferous.
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.
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, Metaconglomerate and quartzite (Lower Devonian)
Littleton Formation, Metaconglomerate and quartzite - Locally fossiliferous in Whitefield quadrangle.
Member C (uppermost) of the Rangeley Formation in Maine and northeastern and southwestern New Hampshire (Lower Silurian (Llandoverian))
Member C (uppermost) of the Rangeley Formation in Maine and northeastern and southwestern New Hampshire - Quartz-pebble conglomerate overlain by rusty metapelite and feldspathic quartzite.
Merrimack Group, Eliot Formation (Ordovician? - Silurian?)
Merrimack Group, Eliot Formation - Gray to green phyllite, calcareous quartzite, quartz-mica schist, and well-bedded calc-silicate.
Perry Mountain and Rangeley Formations, undivided (Silurian)
Perry Mountain and Rangeley Formations, undivided.
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.
Rangeley Formation, undivided (Lower Silurian (Llandoverian))
Rangeley Formation, undivided.
Rye Complex (Ordovician? - Late Proterozoic?)
Rye Complex - Light-colored to gray schists and gneisses, quartzites, and amphibolites. Variably migmatized and mylonized. Contact with Kittery Formation on west is the Portsmouth Fault.
New Jersey
Chestnut Hill Formation (Late Proterozoic)
Chestnut Hill Formation (Drake, 1984) - Interbedded arkose, ferruginous quartzite, quartzite conglomerate, metarhyolite, and metasaprolite. Confined to a few small areas north and east of Phillipsburg, on the western side of Bowling Green Mountain, northwest of High Bridge, and a few areas too small to show at this map scale.
Franklin Marble (Middle Proterozoic)
Franklin Marble - White- to light-gray-weathering, white, grayish-white, or, less commonly pinkish-orange, coarse- to locally fine-crystalline calcite marble with accessory amounts of graphite, phlogopite, chondrodite, clinopyroxene, and serpentine. Contains pods and layers of clinopyroxene-garnet skarn, hornblende skarn, and clinopyroxene-rich rock. Thin layers of metaquartzite occur locally. Intruded by the Mount Eve Granite in the Pochuck Mountain area. Franklin Marble is host to the Franklin and Sterling Hill zinc ore bodies; exploited for talc and asbestiform minerals near Easton, Pennsylvania. Subdivided into an upper marble, "Wildcat marble," and a lower marble, "Franklin marble," by New Jersey Zinc Co. geologists (Hague and others, 1956).
Green Pond Conglomerate (Lower (?) and Middle Silurian)
Green Pond Conglomerate (Rogers, 1836) - Medium- to coarse-grained quartz-pebble conglomerate, quartzitic arkose and orthoquartzite, and thin- to thick-bedded reddish-brown siltstone. Grades downward into gray, very dark-red, or grayish-purple, medium- to coarse-grained, thin- to very thick bedded pebble to cobble conglomerate containing clasts of red shale, siltstone, and chert; yellowish-gray sandstone and chert; dark-gray shale and chert; and white-gray and pink milky quartz. Quartz cobbles are as long as 10 cm (4 in.), and rare red shale clasts as much as 46 cm (18 in.) across. Milky quartz pebbles average 2.5 cm (1 in.) in length. Red arkosic quartz-pebble conglomerate and quartzite are more abundant than gray and grayish-green quartzite. Unconformably overlies Martinsburg Formation, Allentown Dolomite, Leithsville Formation, or Proterozoic rocks. About 305 m (1000 ft) thick.
Hardyston Quartzite (Lower Cambrian)
Hardyston Quartzite (Lower Cambrian) (Wolff and Brooks, 1898) - Light- to medium-gray and bluish-gray conglomeratic sandstone. Varies from pebble conglomerate, to fine-grained, well-cemented quartzite, to arkosic or dolomitic sandstone. Conglomerate contains subangular to subrounded white quartz pebbles up to 2.5 cm (1 in.). Lower contact unconformable. About 0 to 9 m (1-30 ft) thick.
Hardyston Quartzite (Lower Cambrian)
Hardyston Quartzite (Wolff and Brooks, 1898) - Medium- to light-gray, fine- to coarse-grained, medium- to thick-bedded quartzite, arkosic sandstone and dolomitic sandstone. Basal pebble to cobble conglomerate typically contains clasts of local basement affinities. Contains fragments of the trilobite Olenellus thompsoni of Early Cambrian age. Thickness approximately 0.5 to 62 m (1.6-200 ft).
Jutland Klippe Sequence Unit B (Middle Ordovician)
Jutland Klippe Sequence Unit B of Perissoratis and others (1979) - Heterogeneous sequence of interbedded red, green, tan and gray shale; interlaminated dolomite and shale; interbedded fine-grained graywacke siltstone and beds or lenses of sandstone; light-gray to pale-pinkish-gray quartzite; and interbedded fine-grained, thin-bedded limestone and red and green shale. Limestone locally resembles an intraformational conglomerate because it is disrupted, boudinaged, and surrounded by shale beds. Lower contact gradational and within interbedded sequence of thin- to medium-bedded sandstone, siltstone, and limestone. Perissoratis and others (1979) placed this contact at boundary between graptolite faunas Isograptus caduceus and Paraglossograptus etheridgei of Berry (1968). The youngest graptolites occur within Climacograptus bicornis zone of Berry (1968). Some shale beds contain conodonts (Ethington and others, 1958; Karklins and Repetski, 1989) and brachiopod fragments. Carbonate and pelitic rocks locally contain conodonts of Prioniodus triangularis to Pygodus anserinus faunas of North Atlantic Realm. Thickness varies due to structural complexity, but may be about 460 to 550 m (1,500-1,800 ft).
Quartzite (Middle Proterozoic)
Quartzite - Light-gray, medium-grained, massive- to well-layered, vitreous, partly feldspathic quartzite having sparse flakes of graphite. Associated with potassium-feldspar gneiss (Yk), biotite-quartz-feldspar gneiss (Yb), pyroxene gneiss (Yp), Franklin Marble (Yf), and pyroxene-epidote gneiss (Ype).
Skunnemunk Conglomerate (Middle Devonian)
Skunnemunk Conglomerate (Darton, 1894) - Grayish-purple to grayish-red, thin- to very thick bedded, locally cross-bedded, polymictic conglomerate and sandstone containing clasts of white vein quartz, red and green quartzite and sandstone, red and gray chert, and red shale; interbedded with medium-gray, thin-bedded sandstone and greenish-gray and grayish-red, mud-cracked shale. Conglomerate and sandstone matrix is primarily hematite and microcrystalline quartz. Conglomerate cobbles range to 16.5 cm (6.5 in) long, and average cobble size increases in upper part of unit. Lower contact conformable and gradational as defined by Kummel and Weller (1902). About 915 m (3,000 ft) thick.
Nevada
Chert, shale, argillite, siltstone, quartzite, and greenstone (Cambrian to Devonian)
CHERT, SHALE, ARGILLITE, SILTSTONE, QUARTZITE, AND GREENSTONE-Undivided siliceous assemblage. Mostly Ordovician
Dolomite (Late Ordovician to Late Silurian)
DOLOMITE-Includes uppermost part of Ordovician System (Ely Springs Dolomite and equivalent rocks) and all of Silurian System.
Dolomite and limestone (Middle Cambrian to Devonian)
DOLOMITE AND LIMESTONE (Lower Paleozoic)
Dolomite, limestone, and minor amounts of sandstone and quartzite (Devonian)
DOLOMITE, LIMESTONE, AND MINOR AMOUNTS OF SANDSTONE AND QUARTZITE-Includes units such as Sevy and Simonson Dolomites, Guilmette and Nevada Formations, and Devils Gate Limestone.
Igneous and metamorphic complex (Paleozoic sedimentary rocks with Mesozoic intrusive rocks)
IGNEOUS AND METAMORPHIC COMPLEX-Pegmatitic granite and other granitic rocks complexly intermixed with metasedimentary rocks. Considered to be Mesozoic igneous complex intruding lower Paleozoic and possibly Precambrian Z sedimentary rocks. Grades into units shown on map as lower Paleozoic. Ruby Mountains and East Humboldt Range, Elko County
Limestone, dolomite, and shale (Mississippian to Permian)
LIMESTONE, DOLOMITE, AND SHALE (Upper Paleozoic)-Includes Van Duzer Limestone of Decker (1962)
Limestone, dolomite, shale, and quartzite (Ordovician)
LIMESTONE, DOLOMITE, SHALE, AND QUARTZITE-Includes units such as Pogonip Group, Eureka Quartzite, and Ely Springs Dolomite. Where Ely Springs Dolomite or equivalent rocks are included in SOc unit, this unit includes only the Pogonip Group and Eureka Quartzite or their equivalents.
Phyllitc siltstone, quartzite, and lesser amounts of limestone and dolomite (Late Proterozoic to Early Cambrian)
PHYLLITIC SILTSTONE, QUARTZITE, AND LESSER AMOUNTS OF LIMESTONE AND DOLOMITE-Includes Reed Dolomite; Deep Spring, Campito, Poleta, Harkless, and Saline Valley Formations; and Mule Spring Limestone
Quartzite and minor amounts of conglomerate, phyllitic siltstone, limestone, and dolomite (Late Proterozoic to Early Cambrian)
QUARTZITE AND MINOR AMOUNTS OF CONGLOMERATE, PHYLLITIC SILTSTONE, LIMESTONE, AND DOLOMITE-Includes Prospect Mountain Quartzite, Osgood Mountain Quartzite, and Gold Hill Formation in northern Nevada, and Stirling Quartzite, Wood Canyon Formation, and Zabriskie Quartzite in southern Nevada.
Quartzite, phyllitic siltstone, conglomerate, limestone, and dolomite (Late Proterozoic)
QUARTZITE, PHYLLITIC SILTSTONE, CONGLOMERATE, LIMESTONE, AND DOLOMITE-Includes McCoy Creek Group (excluding Stella Lake Quartzite) in east-central Nevada and Johnnie Formation in southern Nevada.
Sandstone and quartzite (Cambrian)
SANDSTONE AND QUARTZITE-Includes Tapeats Sandstone and related rocks. Rests on Precambrian metamorphic rocks.
Scott Canyon Formation (Early Cambrian to Middle Cambrian)
SCOTT CANYON FORMATION (Lower or Middle Cambrian)-Chert, shale, greenstone, and sparse limestone and quartzite. Southeast Humboldt County and northwest Lander County.
Shale and thin-bedded or laminated limestone; also thinly interbedded limestone and chert (Middle Cambrian to Late Cambrian)
SHALE AND THIN-BEDDED OR LAMINATED LIMESTONE; ALSO THINLY INTERBEDDED LIMESTONE AND CHERT-Includes units such as Preble and Emigrant Formations
Shale, chert, and limestone (Ordovician)
SHALE, CHERT, AND LIMESTONE-Includes Aura Formation of Decker (1962) in northwest Elko County and Perkins Canyon Formation of Kay and Crawford (1964) in northern Nye County
Shale, chert, and minor amounts of quartzite, greenstone, and limestone (Ordovician)
SHALE, CHERT, AND MINOR AMOUNTS OF QUARTZITE, GREENSTONE, AND LIMESTONE-Includes units such as Vinini Formation of north-central Nevada, Palmetto Formation in southern and central parts of Esmeralda County, and Comus Formation in Humboldt County. Locally includes rocks of Silurian and Devonian age.
Shale, siltstone, sandstone, chert-pebble conglomerate, and limestone (Devonian to Mississippian)
SHALE, SILTSTONE, SANDSTONE, CHERT-PEBBLE CONGLOMERATE, AND LIMESTONE-Includes units such as Pilot Shale, Joana Limestone, Chainman Shale, and Diamond Peak Formation in northern and eastern Nevada and Narrow Canyon Limestone, Mercury Limestone, and Eleana Formation in southern Nevada
Siliceous and volcanic rocks (Ordovician to Devonian)
SILICEOUS AND VOLCANIC ROCKS-Chert, shale, quartzite, greenstone, and minor amounts of limestone. Includes units such as Valmy Formation of north-central Nevada and some rocks mapped as Palmetto Formation in northern part of Esmeralda County and adjacent parts of Mineral and Nye Counties. Locally includes rocks of Silurian and Devonian age.
Siliceous and volcanic rocks (Mississippian)
SILICEOUS AND VOLCANIC ROCKS-In Humboldt County, consists of altered pillow lavas, coarse volcanic breccias, clastic limestone, and minor amounts of sandstone, shale, siliceous shale, and chert of the Goughs Canyon Formation (Lower and Upper Mississippian). In the East Range, Pershing County, consists of quartzite, conglomerate, slate, limestone, chert, and greenstone of the Inskip Formation (Mississippian?).
Siltstone, sandstone, limestone, and dolomite (commonly silty or sandy) and gypsum (Early Permian)
SILTSTONE, SANDSTONE, LIMESTONE, AND DOLOMITE (COMMONLY SILTY OR SANDY), AND GYPSUM (Lower Permian)-Includes units such as Rib Hill Sandstone and Pequop Formation of Steele (1959) in Elko County, Rib Hill Sandstone and Arcturus Formation in White Pine County, Queantoweap Sandstone of NcNair (1951), Hermit Shale, and Coconino Sandstone in Clark and southern Lincoln Counties.
New York
Austerlitz Phyllite (Cambrian?)
Austerlitz Phyllite - minor quartzite
Beekmantown Group (in part) (Cambrian)
Beekmantown Group (in part) - In Champlain Valley: Whitehall Formation-dolostone, limestone (with Cryptozoon reefs); Ticonderoga Formation-dolostone (locally cherty), sandstone. In Vermont: Clarendon Springs Dolostone; Danby Formation-sandstone, quartzite, dolostone.
Biotite-quartz-plagioclase gneiss (Middle Proterozoic)
Biotite-quartz-plagioclase gneiss - commonly very low in biotite content, with interbedded feldspathic and biotitic quartzite and amphibolite; sillimanite and garnet common, graphite sporadic.
Biotite-quartz-plagioclase paragneiss (Middle Proterozoic)
Biotite-quartz-plagioclase paragneiss - commonly very low in biotite content, with interbedded feldspathic and biotitic quartzite and amphibolite; sillimanite and garnet common, graphite sporadic.
Bloomsburg Formation (Upper Silurian)
Bloomsburg Formation - shale, sandstone; Guymard Quartzite; Otisville Shale; Shawangunk Conglomerate-sandstone, conglomerate.
Cheshire Quartzite (Cambrian)
Cheshire Quartzite - In Vermont.
Cheshire Quartzite (Cambrian)
Cheshire Quartzite
Cheshire Quartzite (Cambrian)
Cheshire Quartzite
Cheshire Quartzite and Dalton Formation (Cambrian)
Cheshire Quartzite and Dalton Formation
Dolomitic and calcitic marbles interlayered with significant amounts of calcsilicate rock (Middle Proterozoic)
Dolomitic and calcitic marbles interlayered with significant amounts of calcsilicate rock - metasedimentary amphibolite, pyroxene granulite, and various gneisses; includes interlayered diopsidic and tremolitic marble and quartzite, and talc-tremolite rock (mined in Balmat-Edwards belt, northwest Adirondacks).
Elizaville Formation (Cambrian - Ordovician)
Elizaville Formation - shale, argillite, quartzite.
Elizaville Formation (Cambrian - Ordovician)
Elizaville Formation - shale, argillite, quartzite.
Fordham Gneiss (C and D member) (Precambrian - Middle Proterozoic )
Fordham Gneiss (C and D member) - fc: biotite-hornblende-quartz-plagioclase gneiss, quartz-feldspar lenses, amphibolite, biotite and/or hornblende-quartz-feldspar gneiss; fd: sillimanite-garnet schistose gneiss, quartzite.
Fordham Gneiss, undivided (Precambrian - Middle Proterozoic )
Fordham Gneiss, undivided - fe: garnet-biotite-quartz-plagioclase gneiss, and amphibolite; fd: sillimanite-garnet schistose gneiss, quartzite; fc: biotite- hornblende-quartz-plagioclase gneiss, quartz-feldspar lenses, amphibolite, biotite and/or hornblende-quartz-feldspar gneiss; fb: amphibolite, biotite and/or hornblende-garnet-quartz-plagioclase gneiss; fa: garnet-biotite-quartz-plagioclase gneiss, amphibolite, biotite-hornblende-quartz-plagioclase gneiss, quartz-feldspar granulite.
Garnet-bearing gneiss and interlayered quartzite (Middle Proterozoic)
Garnet-bearing gneiss and interlayered quartzite - contains varying amounts of biotite, garnet, sillimanite; minor marble, amphibolite, rusty paragneiss.
Garnet-biotite-quartz-feldspar gneiss (Middle Proterozoic)
Garnet-biotite-quartz-feldspar gneiss - quartzite, quartz-feldspar gneiss, calcsilicate rock.
Inwood Marble (Early Cambrian - Lower Ordovician)
Inwood Marble - dolomite marble, calc-schist, granulite, and quartzite, overlain by calcite marble; grades into underlying patchy Lowerre Quartzite of Early Cambrian age.
Mettawee Slate (Cambrian ?)
Mettawee Slate - north of 43 degrees includes Castleton (North Brittain) Conglomerate. Mudd Pond Quartzite, Zion Hill Quartzite, and Bomoseen Graywacke Members.
Mettawee Slate (Cambrian?)
Mettawee Slate (Bull in Vermont) - includes Castleton (North Brittain) Conglomerate. Mudd Pond Quartzite, Zion Hill Quartzite, and Bomoseen Graywacke Members.
Nassau Formation (Cambrian ?)
Nassau Formation - shale, quartzite.
Nassau Formation (Cambrian ?)
Nassau Formation - south of 43 degrees; slate, shale, thin quartzite, includes Stuyvesant Conglomerate, Diamond Rock Quartzite, Curtis Mountain Quartzite, and Bomoseen Graywacke Members.
Poughquag Quartzite (Cambrian)
Poughquag Quartzite - (includes local Dalton Formation at base)-locally conglomeratic.
Quartzite, quartz-biotite schist and graphitic schist (Middle Proterozoic)
Quartzite, quartz-biotite schist and graphitic schist - in part feldspathic, micaceous, garnetiferous, sillimanitic.
Quartzite, quartz schist and graphitic schist (Middle Proterozoic)
Quartzite, quartz schist and graphitic schist - in part feldspathic, micaceous, garnetiferous, sillimanitic.
Quassaic Quartzite (Upper Ordovician)
Quassaic Quartzite - quartzite, sandstone, conglomerate.
Undifferentiated Middle Ordovician thru Lower Cambrian allochthonous rocks (Cambrian - Ordovician)
Undifferentiated Middle Ordovician thru Lower Cambrian allochthonous rocks - principally pelite; lesser quartzite, limestone, conglomerate, graywacke.
Winooski Dolostone, Monkton Quartzite, and Dunham (Rutland) Dolostone (Cambrian)
Winooski Dolostone, Monkton Quartzite, and Dunham (Rutland) Dolostone - in Vermont.
Winooski Dolostone, Monkton Quartzite, and Dunham (Rutland) Dolostone (Cambrian)
Winooski Dolostone, Monkton Quartzite, and Dunham (Rutland) Dolostone
Oregon
Amphibolite of Briggs Creek (Mesozoic or Paleozoic) (Paleozoic or Mesozoic)
Informally called the "Briggs Creek amphibolite" by Garcia (1976) and by Coleman and others (1976). Consists of amphibolite, micaceous quartzite, quartz schist, and recrystallized manganiferous chert. Includes structurally complex amphibole schist and quartz-rich hornblende gneiss of unknown age exposed at and near Chetco Peak west of Cave Junction (Smith and others, 1982)
May Creek Schist (Paleozoic) (Paleozoic(?) to Jurassic)
Layered amphibolite, schist, gneiss, and quartzite. Protolith considered to be of Paleozoic age
Pennsylvania
Antietam and Harpers Formations, undivided (Cambrian)
Antietam and Harpers Formations, undivided - Includes, in descending order, the Antietam (CAa) and Harpers (CAh) Formations. Antietam Formation - gray, buff-weathering quartzite. Harpers Formation - Dark-greenish-gray phyllite and schist containing thin quartzite layers; includes Montalto Member (CAhm) - gray quartztite
Antietam Formation (Cambrian)
Antietam Formation - Gray, buff-weathering quartzite and quartz schist.
Antietam Formation (Cambrian)
Antietam Formation - Gray, buff-weathering quartzite.
Chickies Formation (Cambrian)
Chickies Formation - Light-gray, hard, massive, Scolithus-bearing quartzite and quartz schist; thin, interbedded dark slate at top; conglomerate (Hellam Member) at base.
Hardyston Formation (Cambrian)
Hardyston Formation - Typically light-gray, fine- to medium-grained quartzite, and feldspathic sandstone; color ranges from nearly white to dark gray; massive bedded; Scolithus present in upper part; quartz-pebble conglomerate occurs at base.
Harpers Formation (Cambrian)
Harpers Formation - Dark-greenish-gray phyllite and schist containing thin quartzite layers; includes Montalto Member (CAhm).
Harpers Formation (Cambrian)
Harpers Formation - Dark-greenish-gray phyllite and schist containing thin quartzite layers.
Lower (Middle?) Cambrian rocks, undivided (Cambrian)
Lower (Middle?) Cambrian rocks, undivided - Lower Cambrian of Berks County includes tectonic slices of many of the following rock units: Zooks Corner (CAzc), Ledger (CAl), Kinzers (CAk), Vintage (CAv), Antietam (CAa, CAah), and Harpers (CAh, CAah) Formations.
Montalto Member of Harpers Formation (Cambrian)
Montalto Member of Harpers Formation - Gray quartzite.
New Oxford conglomerate (Triassic)
New Oxford conglomerate - Quartz or quartzite pebbles, cobbles, and rare boulders set in a red, sandy, ferruginous matrix; some silica cement; some feldspar clasts.
Peters Creek Schist (Probably lower Paleozoic)
Peters Creek Schist - Chlorite-sericite schist containing interbedded quartzite.
Quartz fanglomerate (Triassic)
Quartz fanglomerate - Well-rounded quartzite pebbles, cobbles, and rare boulders set in a reddish-brown, sandy matrix.
Setters Quartzite (Probably lower Paleozoic)
Setters Quartzite - Includes white feldspathic quartzite, gray mica gneiss, and mica schist.
Tuscarora Formation (Silurian)
Tuscarora Formation - Light- to medium-gray quartzite and quartzitic sandstone and minor interbedded shale and siltstone, locally conglomeratic in lower part; includes (to the northwest) interbedded red and non-red sandstone (Castanea Member) at top; east of Harrisburg, equivalent to Minsi and Weiders Members of Shawangunk Formation.
Weverton and Loudoun Formations, undivided (Cambrian)
Weverton and Loudoun Formations, undivided - In descending order: Weverton--gray to purplish-gray quartzite and quartzose conglomerate containing rounded pebbles. Loudoun--sericitic slate and purplish-gray, crumbly, poorly sorted, arkosic sandstone and conglomerate.
Rhode Island
Blackstone Group - epidote and biotite schist (Late Proterozoic? or older?)
Blackstone Group - epidote and biotite schist - Green to gray, fine-grained, massive to thinly-bedded mica schist, quartzite, and marble. Schist consists of quartz plus chlorite, muscovite, and/or biotite. Includes rock mapped formerly as Sneech Pond Schist, Mussey Brook Schist, and marble.
Blackstone Group - quartzite (Late Proterozoic? or older?)
Blackstone Group - quartzite - Gray, medium-grained, massive to thinly bedded quartzite; commonly tectonically interleaved with other units of the Blackstone Group. Interpreted as olistostromal deposits. Includes rock mapped formerly as Quinnville Quartzite.
Harmony Group - Absalona Formation (Late Proterozoic? or older?)
Harmony Group - Absalona Formation - Gray, medium- to coarse-grained biotite granite gneiss characterized by alkali feldspar porphyroblasts. Consists of biotite, hornblende, quartz, microcline, microperthite, albite, epidote, garnet, and chlorite. Subordinate amounts of quartz-biotite schist, amphibolite, and quartzite occur as layers and isolated bodies.
mica schist (Late Proterozoic? or older?)
mica schist - Gray to green, fine-grained, thinly bedded schist consisting of muscovite, biotite, chlorite, and quartz. Locally contains think beds of quartzite, marble, and amphibolite. Includes rock mapped formerly as mica schist of Bristol, chlorite-biotite schist of Tiverton, and mica-chlorite schist of Sakonnet.
Plainfield Formation (Late Proterozoic? or older?)
Plainfield Formation - Pale-tan to gray, fine-grained quartzite, and pale- to medium-gray quartz-mica schist. Quartzite is massive to layered (bedded?). Includes Plainfield Formation and some rock mapped formerly as Blackstone Series.
Waterford Group - Mamacoke Formation (Late Proterozoic? or older?)
Waterford Group - Mamacoke Formation - Light- to dark gray, medium-grained amphibolitic gneiss composed of plagioclase, microcline, quartz, biotite, hornblende, and garnet; locally contains quartz-sillimanite nodules, and thin layers of quartzite and calc-silicate rock.
South Carolina
Battleground Formation, Metasedimentary rocks, undivided (Neoproterozoic)
Battleground Formation, Metasedimentary rocks, undivided: quartz-sericite schist/phyllite and interlayered quartzite, quartz-pebble conglomerate, high-alumina quartzite, and manganiferous schist
Blacksburg Formation (Neoproterozoic)
Blacksburg Formation: metamorphosed sedimentary sequence of interlayered sericite schist and phyllite, sericite quartzite, marble, amphibolite and calc-silicate rock
Little River Sequence, metasedimentary rocks (Cambrian or Neoproterozoic)
Little River Sequence, metasedimentary rocks: white-mica schist and phyllite, metatuff, quartz-muscovite schist, and minor quartzite
South Dakota
Metagraywacke (Proterozoic | Paleoproterozoic)
Light- to dark-gray, silceous mica schist and impure quartzite. Differentiated where possible into three primary tongues or lenses. (Xgw1, Xgw2, and Xgw3) Thickness from 1,000 ft to over 5,000 ft (305-1,524 m).
Metagraywacke (Archean(?) Proterozoic | Paleoproterozoic)
Gray, siliceous mica schist and impure quartzite. Thickness undetermined.
Metagraywacke Unit 1 (Proterozoic | Paleoproterozoic)
Lower Xgw- Light- to dark-gray, silceous mica schist and impure quartzite.
Metagraywacke Unit 2 (Proterozoic | Paleoproterozoic)
Middle Xgw- Light- to dark-gray, silceous mica schist and impure quartzite.
Metagraywacke Unit 3 (Proterozoic | Paleoproterozoic)
Upper Xgw- Light- to dark-gray, silceous mica schist and impure quartzite.
Metamorphosed Conglomerate (Proterozoic | Paleoproterozoic)
Gray to grayish-brown, conglomeratic biotite phyllite, siliceous biotite phyllite, mica schist, quartzite, and iron-formation. Thickness up to 2,000 ft (610 m).
Metaquartzite (Proterozoic | Paleoproterozoic)
Light-tan quartzite, siliceous schist, and minor chert. Thickness 800-5,000 ft (244-1,524 m).
Sioux Quartzite (Proterozoic | Paleoproterozoic)
Pink, reddish to tan, siliceous, fine to coarse-grained, iron-stained orthoquartzite with minor conglomerate and mudstone layers. Estimated thickness greater than 1,000 ft (305 m).
Tennessee
Chilhowee Group; Hesse Sandstone (Cambrian)
Chilhowee Group; Hesse Sandstone - White, vitreous quartzite, medium- to coarse-grained, occurs in massive ledges; Helenmode Member at top is gray to greenish sandstone and shale. Thickness about 600 feet.
Chilhowee Group, including Erwin Formation, Hesse Sandstone, Murray Shale, Nebo Sandstone, Nichols Shale, Cochran Conglomerate, Hampton Formation, and Unicoi Formation (Cambrian)
Chilhowee Group - Conformable sequence of dominantly clastic sediments. Thickness 3,000 to 7,500 feet; including Erwin Formation - White, vitreous quartzite, massive, with interbeds of dark-green silty and sandy shale, minor siltstone, and very fine-grained sandstone. Thickness 1,000 to 1,500 feet; Hesse Sandstone - White, vitreous quartzite, medium- to coarse-grained, occurs in massive ledges; Helenmode Member at top is gray to greenish sandstone and shale. Thickness about 600 feet; Murray Shale - Shale, silty, sandy, dull-green to brown, micaceous. Thickness about 500 feet; Nebo Sandstone - Medium-bedded, fine-grained, white, vitreous quartzite, in part feldspathic. Thickness 250 feet; Nichols Shale - Olive-gray to green, silty and sandy, micaceous shale and siltstone; local lenses of fine-grained feldspathic quartzite. Thickness about 700 feet; Cochran Conglomerate - Quartz-pebble conglomerate, gray pebbly arkose, siltstone and shale; irregular bedding, scour features, crossbedding common; maroon micaceous arkose and shale near middle and base. Thickness about 1,200 feet; Hampton Formation - Dark greenish-gray, silty and sandy, micaceous shale; numerous layers of medium-grained, feldspathic, thinly bedded sandstone. Thickness 500 to 2,000 feet; Unicoi Formation - Sequence of gray feldspathic sandstone, arkose, conglomerate, graywacke, siltstone and shale; greenish amygdaloidal basalt flows near middle and base. Thickness 2,000 to 5,000 feet.
Chilhowee Group; Nebo Sandstone (Cambrian)
Chilhowee Group; Nebo Sandstone - Medium-bedded, fine-grained, white vitreous quartzite, in part feldspathic. Thickness 250 feet.
Erwin Formation (Cambrian)
Erwin Formation - White, vitreous quartzite, massive, with interbeds of dark-green silty and sandy shale, minor siltstone, and very fine-grained sandstone. Thickness 1,000 to 1,500 feet.
Hesse Sandstone (Cambrian)
Hesse Sandstone - White, vitreous quartzite, medium- to coarse-grained, occurs in massive ledges; Helenmode Member at top is gray to greenish sandstone and shale. Thickness about 600 feet.
Nebo Sandstone (Cambrian)
Nebo Sandstone - Medium-bedded, fine-grained, white, vitreous quartzite, in part feldspathic. Thickness 250 feet.
Nichols Shale (Cambrian)
Chilhowee Group; Nichols Shale - Olive-gray to green, silty and sandy, micaceous shale and siltstone; local lenses of fine-grained feldspathic quartzite. Thickness about 700 feet.
Nichols Shale (Cambrian)
Nichols Shale - Olive-gray to green, silty and sandy, micaceous shale and siltstone; local lenses of fine-grained feldspathic quartzite. Thickness about 700 feet.
Ocoee Supergroup, including Walden Creek Group, (including Sandsuck Formation, Wilhite Formation, Shields Formation, Licklog Formation), Cades Sandstone, and Rich Butt Sandstone (Precambrian)
Ocoee Supergroup - Terrigenous clastic sedimentary rocks, for the most part poorly sorted and coarse. The groups are subdivided into formations only in the region of the Great Smoky Mountains. Thickness as much as 50,000 feet. Includes Walden Creek Group - The formations, other than the Sandsuck, have been mapped only in the region of the Great Smoky Mountains. Thickness about 8,000 feet; Sandsuck Formation - Olive-green and gray, argillaceous, micaceous shale with coarse feldspathic sandstone and quartz- pebble conglomerate. Thickness about 2,000 feet; Wilhite Formation - Gray to green siltstone and slate with interbeds of pebble conglomerate, sandstone, and quartzite. Thickness about 4,000 feet; Shields Formation - Massive conglomerate, sandstone, argillaceous slate; conglomerate (pebbles of various rock types) characteristic. Thickness about 1,500 feet; Licklog Formation - Feldspathic sandstone, greenish phyllite, and bluish-gray slate. Thickness about 1,500 feet; and the 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; and Rich Butt Sandstone - Gray, massive beds of feldspathic, fine- to medium-grained sandstone, with interbeds of dark slate and arkosic conglomerate; exact stratigraphic position unknown. Thickness about 1,500 feet.
Snowbird Group, including Pigeon Siltstone, Roaring Fork Sandstone, Metcalf Phyllite, Longarm Quartzite, and Wading Branch Formation (Precambrian)
Snowbird Group - The formations at right are applicable chiefly in the area of the Great Smoky Mountains. Thickness 13,000 to about 20,000 feet. Includes Pigeon Siltstone - Laminated, greenish quartzose and feldspathic siltstone; minor fine-grained gray sandstone. Thickness as much as 10,000 feet; Roaring Fork Sandstone - Interbedded massive feldspathic sandstone, greenish siltstone, and greenish phyllite. Maximum thickness 7,000 feet; Metcalf Phyllite - Lustrous, pale-green and silvery sericitic and chloritic phyllite; siltstone interbeds abundant. Thickness uncertain; at least 5,000 feet; Longarm Quartzite - Feldspathic quartzite and arkose, conspicuously light-colored, current bedded and crossbedded. Thickness about 5,000 feet; Wading Branch Formation - Medium- to dark-gray sandy slate to coarse, pebbly feldspathic sandstone and graywacke; basal part is quartz-sericite phyllite; graded bedding common. Thickness about 1,500 feet.
Walden Creek Group, including Sandsuck Formation, Wilhite Formation, Shields Formation, and Licklog Formation (Precambrian)
The formations, other than the Sandsuck, have been mapped only in the region of the Great Smoky Mountains. Thickness about 8,000 feet. Includes Sandsuck Formation - Olive-green and gray, argillaceous, micaceous shale with coarse feldspathic sandstone and quartz- pebble conglomerate. Thickness about 2,000 feet; Wilhite Formation - Gray to green siltstone and slate with interbeds of pebble conglomerate, sandstone, and quartzite. Thickness about 4,000 feet; Shields Formation - Massive conglomerate, sandstone, argillaceous slate; conglomerate (pebbles of various rock types) characteristic. Thickness about 1,500 feet; Licklog Formation - Feldspathic sandstone, greenish phyllite, and bluish-gray slate. Thickness about 1,500 feet.
Walden Creek Group, including Sandsuck Formation, Wilhite Formation, Shields Formation, and Licklog Formation (Cambrian)
Walden Creek Group - The formations, other than the Sandsuck, are applicable mainly in the region of the Great Smoky Mountains. Thickness about 8,000 feet, Includes Sandsuck Formation - Olive-green and gray, argillaceous, micaceous shale with coarse feldspathic sandstone and quartz- pebble conglomerate. Thickness about 2,000 feet; Wilhite Formation - Gray to green siltstone and slate with interbeds of pebble conglomerate, sandstone, and quartzite. Thickness about 4,000 feet; Shields Formation - Massive conglomerate, sandstone, argillaceous slate; conglomerate (pebbles of various rock types) characteristic. Thickness about 1,500 feet.; Licklog Formation - Feldspathic sandstone, greenish phyllite, and bluish-gray slate. Thickness about 1,500 feet.
Texas
Carrizo Mountain Group showing metasedimentary rocks (preCambrian-Proterozoic)
Carrizo Mountain Group showing metasedimentary rocks
Llanoria Quartzite (preCambrian-Proterozoic [Grenville])
Llanoria Quartzite
Packsaddle Schist (preCambrian-Proterozoic [Llano])
Packsaddle Schist
Tarantula Gravel (Phanerozoic | Cenozoic | Tertiary | Miocene)
Tarantula Gravel
Utah
Cambrian quartzite in northwestern Utah (Cambrian?)
Older Precambrian metamorphic rocks in Logan-Huntsville Allochthon (Proterozoic X)
Older Precambrian metamorphic rocks in Uinta Mountains-Uinta Basin region (Proterozoic W)
Younger Precambrian metamorphic rocks in northwestern Utah (Proterozoic X)
Virginia
Alligator Back Formation (Proterozoic Z-Cambrian)
Alligator Back Formation - Garnet-mica schist, garnet amphibolite, hornblende granite gneiss
Alligator Back Formation - Feldspathic metagraywacke (Proterozoic Z-Cambrian)
Alligator Back Formation - Meta-argillite is feldspathic metagraywacke; graphitic mica schist, and quartzite.
Arvonia Formation - Bremo quartzite. Quartzite (Ordovician)
Arvonia Formation - Bremo quartzite. Quartzite
Arvonia Formation - Kyanite quartzite and schist. (Ordovician)
Arvonia Formation - Kyanite quartzite and schist.
Ashe Formation (Proterozoic Z)
Ashe Formation - Biotite gneiss and garnetiferous amphibolite.
Catoctin Formation - Metasedimentary rocks (Proterozoic Z-Cambrian)
Catoctin Formation - Metasedimentary rocks
Chilhowee Group (Cambrian)
Chilhowee Group - Appalachian Plateaus and Valley and Ridge: Quartzite, conglomerate, feldspathic sandstone, phyllite, and minor ferruginous sandstone and volcanic rocks. Blue Ridge Anticlinorium: Conglomerate, quartzite, metasiltstone, and phyllite.
Erwin and Hampton Formations (Cambrian)
Erwin and Hampton Formations - Sandstone, quartzite, and shale.
Fork Mountain Formation (Proterozoic Z-Cambrian)
Fork Mountain Formation - Quartzose mica schist, garnet-biotite gneiss, calc-silicate quartzite, and melange.
Interlayered Mafic and Felsic Metavolcanic Rocks - Ferruginous quartzite (Cambrian)
Interlayered Mafic and Felsic Metavolcanic Rocks - Ferruginous quartzite
Lower Devonian, Silurian and Upper Ordovician Formations Undivided (Ordovician-Devonian)
Lower Devonian, Silurian and Upper Ordovician Formations Undivided - Some landslides with intact stratigraphic units in Giles County. Includes: Skrt, Sm, Oun, Ous, Ou, Om. (Shrc, Okpl?)
Lynchburg Group; Charlottesville Formation (Proterozoic Z)
Lynchburg Group; Charlottesville Formation - Graphitic metasiltstone, feldspathic metasandstone, and quartzite.
Lynchburg Group; Graphitic phyllite and metasiltstone (Proterozoic Z)
Lynchburg Group - Graphitic phyllite and metasiltstone
Lynchburg Group; Quartzite (Proterozoic Z)
Lynchburg Group - Quartzite
Massanutten Sandstone (Silurian)
Massanutten Sandstone - Quartzarenite with lenses of conglomerate.
Metasedimentary Rocks Undivided (Cambrian-Ordovician)
Metasedimentary rocks
Micaceous Quartzite (Cambrian)
Micaceous quartzite
Quantico Formation - Micaceous quartzite (Ordovician)
Quantico Formation - Micaceous quartzite
Quartzite and Quartz-Sericite Tectonite (Proterozoic Y)
Quartzite and quartz-sericite tectonite
Silurian and Upper Ordovician Formations Undivided (Ordovician-Silurian)
Silurian and Upper Ordovician Formations Undivided - Includes: Skrt, Sm, Oun, Ous, Ou, Om. (Shrc and Okpl?)
Swift Run Formation (Proterozoic Z)
Swift Run Formation - Phyllite, metasandstone, and metaconglomerate.
Ta River Metamorphic Suite (Cambrian)
Ta River Metamorphic Suite - Amphibolite gneiss
Unicoi Formation (Cambrian)
Unicoi Formation - Sandstone and quartzite with phyllite, tuffaceous phyllite, conglomerate, and minor basalt.
Vermont
Albee Formation (Ordovician)
Albee Formation - Massive, gray, white-weathered quartzite and feldspathic quartzite interbedded with greenish-gray slate, phyllite, feldspthic phyllite and quartzose argillaceous phyllite. Micaceous quartzite, quartz-mica schist, mica schist and hornfels contining porphyroblasts of biotite, garnet, staurolite and sillimanite in the vicinity of granitic plutons. Soda-rhyolite tuff occurs locally. Micaceous quartzite characterized by thin, schistose "pinstripe" partings is common in many areas.
Bascom Formation, and undifferentiated Luke Hill, Naylor Ledge and Hastings Creek Limestones (Ordovician)
Bascom Formation, and undifferentiated Luke Hill, Naylor Ledge and Hastings Creek Limestones - Interbedded dolomite, limestone or marble, calcareous sandstone, quartzite and limestone breccia; irregular dolomitic layers, thin sandy laminae, and slaty or phyllitic partings characterize limestone and marble of lower, middle, and upper parts of the Bascom, respectively; south of West Rutland it includes some of the Chipman formation. The combined Luke Hill, Naylor Ledge, and Hastings Creek, east of Philipsburg thrust, are stratigraphically equivalent to the Bascom.
Brezee Formation (Cambrian)
Brezee Formation - Dark gray to black phyllite with beds of blue-gray marble, dark gray dolomite, sandy dolomite, and dolomitic sandstone, in upper part; beds of massive quartzite as much as 20 ft thick occur locally and in places contain pebbles of blue quartz. Phyllites are locally highly albitic.
Cheshire Quartzite (Cambrian)
Cheshire Quartzite - Very massive, white to faintly pink or buff vitreous quartzite near the top in west-central and southwestern VT; predominantly a less massive appearing mottled gray, somewhat phyllitic quartzite; dolomitic sandstone and conglomerate near the base of the formation in west-central VT apparently grades southward into the Dalton Formation. Mapping in Bristol Notch and along the Green Mountain front indicate that the Cheshire Quartzite appears to be at least 2500 ft thick, which is about 2.5 times the original estimated thickness to the north and south. Near the base, the Cheshire is a massive argillaceous feldspathic meta-sandstone, containing recrystallized quartz and K-feldspar in a muscovite and biotite matrix. These lithologies grade upward through medium to thick-bedded schistose feldspathic meta-sandstones to clean, massive 'quartzites' of the Green Mountain front. Rocks currently mapped as the eastern-most Cheshire Quartzite probably belong to the Pinnacle Formation and are in fault contact with the Cheshire (Condon, 1993).
Clough Formation (Silurian)
Clough Formation - Quartzite, quartz-conglomerate, and mica schist; lenses of fossiliferous calcareous quartzite in upper part. (Southeastern Vermont).
Clough Formation (Silurian)
Clough Formation - Boulders, cobbles, pebbles and angular fragments of quartzite, micaceous quartzite, and gray mica schist in matrix of dark gray quartz-mica schist or quartzite; schist commonly contains porphyroblasts of biotite, less commonly garnet. (Northeastern Vermont).
Dalton Formation (Cambrian)
Dalton Formation - Schistose quartzite containing pebbles of feldspar and blue quartz; impure dolomite containing pebbles of quartz and feldspar occurs locally; conglomerate common near base. Occurs in southwestern Vertmont.
Danby and Potsdam Formations (Cambrian)
Danby and Potsdam Formations - The Danby is comprised of interbedded quartzite and dolomite; white quartzite beds, more than a foot thick, separated by 10 to 12 feet of dolomite in eastern areas, increase westward to continuous sections of white to pink weathered, massively bedded Potsdam quartzite, west of Orwell thrust.
Forestdale Marble (Cambrian)
Forestdale Marble - Buff to rusty-weathered white, buff, and pink and white mottled dolomite containing local interbeds of dolomitic sandstone, gray-green phyllitic quartzite, and crossbedded sandy dolomite.
Gile Mountain Formation (Devonian)
Gile Mountain Formation - Gray quartz-muscovite phyllite or schist, interbedded and intergradational with gray micaceous quartzite (graywacke northeast of Nulhegan River), calcareous mica schist, and, locally, quartzose and micaceous crystalline limestone like that of the Waits River formation. The phyllite and schist commonly contain porphyroblasts of biotite, garnet, or staurolite, and locally kyanite, andalusite, or sillimanite. Used as Early Devonian Gile Mountain Formation. Generally consists of gray to tan metawacke and schist or phyllite, gradational into its Meetinghouse Slate Member, but much more thickly bedded and less pelitic. Contains minor metavolcanic lentils. Unnamed metavolcanic member is possibly equivalent to Putney Volcanics of southeastern VT. Separately mapped interbedded gray slate or phyllite and brown-weathering calcite-ankerite metasiltstone, and minor marble and quartzite, resembles Waits River Formation of VT. Meetinghouse Slate Member consists of gray to black phyllite and silty metasandstone turbidite. Report includes geologic map, cross sections, correlation chart, and four 1:500,000-scale derivative maps (Lyons and others, 1997).
Gile Mountain Formation, Meetinghouse Slate Member (Devonian)
Gile Mountain Formation, Meetinghouse Slate Member - Chiefly gray slate or phyllite characterized by beds of gray schistose quartzite 1/8 inch to 3 inches thick. Gile Mountain Formation and its Meetinghouse Slate Member were previously considered to be Early Devonian based on Emsian plant fossils from Compton Formation of QUE (Hueber and others, 1990; Hatch, 1991). Age assignment here changed to Early Devonian(?) because recent mapping indicates that Gile Mountain and Compton are not coextensive across VT-QUE border as formerly believed by Doll and others (1961, State map) and St. Julien and Slivitsky (1987). Instead, the formations are separated by Ironbound Mountain Formation. Ironbound Mountain Formation is conformably overlain by Compton, but it is not yet known whether Ironbound Mountain is overlain or underlain by Gile Mountain; this is shown by queried Ironbound Mountain-Gile Mountain contact in area of Averill 7.5-min quad, VT. Correlation of Gile Mountain and Compton is justified only if Gile Mountain in this area conclusively is shown to be underlain by Ironbound Mountain; otherwise, Gile Mountain (with possible exception of its Meetinghouse Slate Member) would be coeval with Silurian Frontenac Formation. Hatch (1988) proposed that Meetinghouse represents upper part of Gile Mountain on basis of graded bedding seen south of map area. This relationship is not proven, however, because Gile Mountain-Meetinghouse contact is difficult to define and graded beds are not always easily interpreted. On this map, Meetinghouse is tentatively shown to occur below main body of Gile Mountain on basis of remarkable similarity between it and Ironbound Mountain Formation. This relationship easily explains highly pelitic character of the Meetinghouse with upward-coarsening character of Lower Devonian sequences elsewhere in map area. Meetinghouse Slate Member includes volcanic facies (Moench and others, 1995).
gneiss, quartzite, calc-silicate granulite (Precambrian)
Gneiss, quartzite, calc-silicate granulite.
Hatch Hill and West Castleton Formations, Undifferentiated (Cambrian)
Hatch Hill and West Castleton Formations, Undifferentiated - The Hatch Hill, a relatively thin formation that succeeds the West Castleton, is characterized by rusty and spongy weathered gray calcareous quartzite traversed by numerous white-quartz viens. The West Castleton is a gray to black, siliceous, carbonaceous, and pyritiferous slate containing paper-thin white sandy laminae. Black slates are common to both formations. A blue-gray weathered black limestone is near the base of the West Castleton in a few places.
Hazens Notch Formation (Cambrian)
Hazens Notch Formation - Interbedded carbonaceous and noncarbonaceous quartz-sericite-albite-chlorite schist; grades to quartzite and gneiss. (Northern and Central Vermont). According to author, the name Hazens Notch is a big problem in VT stratigraphic nomenclature. In northern VT, it consists of carbonaceous and non-carbonaceous schist associated with ultramafics, mafic schists, and blueschists, while in the Camels Hump quad, it is considered to be strictly a carbonaceous albitic schist with associated mafic schist. The use of the name Hazens Notch is not recommended for the white albitic schist of the Fayston-Buels Gore area. Those rocks are here assigned to the newly named Fayston Formation (Walsh, 1992).
Hoosac Formation, Plymouth Member (Cambrian)
Hoosac Formation, Plymouth Member - Quartzite, schistose quartzite, dolomitic quartzite; carbonaceous phyllite; buff to dark gray dolomite with partings locally of carbonaceous phyllite; quartz-sericite-chlorite-albite schist; carbonaceous albite schist. (Southern and Central Vermont). Revised the Plymouth Member of the Hoosac Formation of Doll and others (1961) to the Plymouth Formation. Consists of a series of feldspathic and dolomitic quartzites, dolostones and black phyllites that overlie probable Middle Proterozoic gneisses. The Plymouth Formation can be divided into several informal members. The lower contact of the formation is below a sequence of dolomitic quartzites or thin bedded quartzite. Dark laminated silty phyllites laterally replace the more feldspathic quartzites and dark-gray schistose quartzites, massive vitreous quartzites, and dolomitic quartzites pass upward to the east into well bedded cream-weathered light-gray dolostone breccia; these lithologies make up the dolostone member of the Plymouth Formation. The upper member of the Plymouth Formation is a black graphitic and siliceous phyllite that contains 1 to 3 cm thick layers of dark-gray ferruginous quartzite, dolomitic quartzite, and ribbony beds of dolostone. The upper contact of the Plymouth Formation is placed at the first occurrence of light-silvery-green magnetite-muscovite-quartz knotted phyllites of the Pinney Hollow Formation (Ratcliffe, 1994).
Littleton Formation (Devonian)
Littleton Formation - Gray slate and phyllite containing interbeds of gray schistose quartzite 1/4 inch to 6 inches thick. West of Guildhall are lustrous, light to dark gray biotite-garnet phyllite and schist, some slate, and subordinate quartzite and impure quartzite. South of Bellows Falls gray phyllite passes eastward into gray mica schist containing porphyroblasts of biotite, garnet, and staurolite.
Missisquoi Formation (Ordovician)
Missisquoi Formation - Rusty weathering carbonaceous mica schist, quartzite and micaceous quartzite.
Missisquoi Formation, Harlow Bridge Quartzite Member (Ordovician)
Missisquoi Formation, Harlow Bridge Quartzite Member - Buff to pale-green quartzite with interbeds of quartz-sericite-chlorite phyllite.
Missisquoi Formation, Moretown Member (Ordovician)
Missisquoi Formation, Moretown Member - Quartzite and quartz-plagioclase granulite, in layers 1/8 to several inches thick, separated by "pinstripe" partings that contain muscovite, chlorite, epidote, biotite, and locally garnet; also greenish quartz-sericite-chlorite phyllite and schist, and minor carbonaceous phyllite. Schist and phyllite commonly contain biotite and garnet porphyroblasts in southern Vermont.
Missisquoi Formation, Whetstone Hill Member (Ordovician)
Missisquoi Formation, Whetstone Hill Member - Carbonaceous black to light gray phyllite and schist containing porphyroblasts of biotite and garnet; beds of gray micaceous quartzite, fine-grained biotite gneiss and amphibolite.
Monkton Quartzite (Cambrian)
Monkton Quartzite - Distinctively red quartzite interbedded with lesser buff and white quartzite and relatively thick sections of dolomite like that of the Winooski; the quartzites thin to the east, and they become gray and phyllitic to the east and south.
Mount Hamilton Formation (Ordovician)
Mount Hamilton Formation - White weatherd black, gray, green, purple, and red hard slates, some interbedded with thin cherty appearing quartzites and ribbon limestones a few vinches apart; smooth, soft, red slate; beds of ankeritic quartzite a few inches to several feet thick, locally containg layers of edgewise conglomerate; and a polymict limestone conglomerate. Lithic features vary laterally and are in many places indistinguishable from those of the underlying Hatch Hill and West Castleton Formations.
Mount Holly Complex (Precambrian)
Mount Holly Complex - Mainly fine- to medium-grained biotitic gneiss, locally muscovitic, and in western areas chloritic; massive and granitoid in some localities, fine-grained or schistose and compositionally layered in others; also abundant amphibolite and hornblende gneiss, and minor beds of mica schist, quartzite, and calc-silicate granulite; includes numerous small bodies of pegmatite and gneissoid granitic rock. Includes a suite of metatonalites, metatrondhjemite, and possible metadacite with chemical characteristics of a calc-alkaline volcanic-plutonic suite. Mappable units are College Hill Granite Gneiss and 10 unnamed subdivisions including several varieties of gneiss as well as schist, amphibolite, and quartzite. U-Pb zircon upper intercept ages of 1.35 to 1.30 Ga have been determined and interpreted as age of crystallization (Ratcliffe and others, unpub. data). Cores of abraded zircon obtained from College Hill Granite Gneiss of Mount Holly Complex have a U-Pb upper intercept age of 1245 +/-14 Ma, interpreted as crystallization age for that granite (Aleinikoff and others, 1990). Dust collected by abrasion of zircons, thought to represent migmatitic overgrowth, has a Pb-Pb age of approx 1100 Ma. These data suggest that College Hill Granite Gneiss was intruded at 1245 Ma and migmatized at 1100 Ma. On north and south slopes of College Hill, College Hill Granite Gneiss grades outward into migmatitic biotite granite gneiss of Mount Holly Complex. College Hill is discordant to contacts and folds in paragneiss units of Mount Holly Complex. Dacitic metavolcanics are found within Washington Gneiss of Berkshire massif of MA (Ratcliffe and Zartman, 1968). They are interbedded with thick succession of rusty-weathering, quartz-pebble gneisses, calc-silicate rocks and garnet-sillimanite schist similar to, but much thicker than, the rusty-weathering gneiss and schist unit of Mount Holly Complex exposed in Green Mountains of VT. It is possible that the metadacitic and metatrondhjemitic suite of VT constitutes a lateral, south-to-north facies of the Washington Gneiss of MA (Ratcliffe, in press).
Mount Holly Complex, quartzite and schist (Precambrian)
Mount Holly Complex, quartzite and schist - Quartzite, locally in massive beds as much as 30 ft thick, micaceous quartzite, and quartz-mica schist that commonly contains garnet or pseudomorphs (largely chlorite) after garnet; schists are locally rusty weathered and contain conspicuous flakes of graphite; also includes amphibolite and minor hornblende gneiss, biotite gneiss, and pegmatite.
Orfordville Formation (Ordovician)
Orfordville Formation - Carbonaceous phyllite; minor quartzite.
Ottauquechee Formation (Cambrian)
Ottauquechee Formation - Black carbonaceous phyllite or schist containing interbeds of massive quartzite commonly criss-crossed by veins of white quartz; quartzite is dark gray and carbonaceous, light gray, or white; also includes light green quartz-sericite-chlorite phyllite or schist and sercitic quartzite; beds of phyllitic graywacke and feldspar granule conglomerate are north of Lamoille River. Schist contains abundant porphyroblasts of garnet and biotite from Ludlow south. The Ottauquechee contains two major units: A black phyllite and the Thatcher Brook Member. The black phyllite contains a previously unreported sub-unit of gray carbonate schist. The Thatcher Brook Member (named in an abstract by Armstrong and others, 1988) is a carbonaceous albitic schist with greenstones and ultramafics. These rocks have previously been included in the Ottauquechee but have never been differentiated from the black phyllite. Member is in fault contact with the silvery green schist of the Pinney Hollow Formation to the west. Age is Cambrian (Ratcliff, in press).
Parker Slate (Cambrian)
Parker Slate - Gray to black micaceous shale and slate, includes dolomite, sandstone, and quartzite lenses; chiefly on west limb of St. Albans synclinorium.
Pinney Hollow Formation (Cambrian)
Pinney Hollow Formation - Pale green quartz-sericite (muscovite-paragonite)-chlorite phyllite and schist with abundant magnetite, chloritoid phyllite and schist, quartz-sericite-albite-chlorite schist, and rare beds of carbonaceous and schistose quartzite; garnet porphyroblasts common south of Ottauquechee River. (Southern and Central Vermont).
Pinney Hollow Formation, Ottauquechee, and Stowe Formations, Undifferentiated (Ordovician)
Pinney Hollow Formation, Ottauquechee, and Stowe Formations, Undifferentiated - Includes quartz-muscovite-garnet-chlorite-biotite schist, rusty carbonaceous schist, amphibolite, and schistose quartzite. Schist locally contains porphyroblasts of staurolite and kyanite. On flanks of Chester and Athens domes.
Shaw Mountain Formation (Silurian)
Shaw Mountain Formation - Quartzite, quartz conglomerate, cummingtonite schist, amphibolite, and quartz-sericite schist with porphyroblasts of biotite and garnet.
Shaw Mountain Formation (Silurian)
Shaw Mountain Formation - Chiefly tan to brown weathered quartzose limestone and calcareous quartzite characterized by specks of limonite after ankerite; locally underlain by quartz conglomerate and overlain by blue fossiliferous crystalline limestone; greenstone and quartz-sericite schist.
St. Catherine Formation (Cambrian)
St. Catherine Formation - Purple, gray-green, and variegated slate and phyllite containing minor interbeds of white to green quartzite; locally albitic. Purple and green chloritoid-bearing slate and phyllite is within dashed line in northern Taconic Range, but not separated farther south.
St. Catherine Formation, Zion Hill Quartzite Member (Cambrian)
St. Catherine Formation, Zion Hill Quartzite Member - White weathered green, vitreous chloritic quartzite and graywacke spotted with limonite.
Tyson Formation (Cambrian)
Tyson Formation - Feldspathic quartz-mica schist containing biotite, chlorite, and carbonate; many beds contain pebbles of quartz and feldspar; cobble or boulder conglomerate commonly at base; thin beds of quartzite, carbonaceous phyllite, and schistose dolomite in upper part, overlain at top by massive buff dolomite as much as 30 ft thick. (Southern and Central Vermont). The Tyson Formation contains grits and conglomerates at its base that unconformably overlie basement. The conglomerates and grits are as much as 150 m thick and contain lenses of dolomitic quartzite and feldspathic grit. Unit also contains black carbonaceous phyllite and interbedded dolostone as much as 100 m thick, followed by beige to tan weathering beds of dolostone that increase in abundance toward the top of the unit and pass into punky weathering dolomitic and feldspathic quartzite at the top. From a point near the southwest corner of the Andover quad, the rocks of the Tyson Formation are laterally replaced by albitic schists and granofels of the Hoosac Formation to the south. Therefore, Tyson laterally replaces the Hoosac from south to north along the eastern margin of the Green Mountain massif. The Tyson Formation is of Late Proterozoic(?) and Early Cambrian age (Ratcliffe, 1994).
Underhill Formation, Battell Member (Cambrian)
Underhill Formation, Battell Member - Carbonaceous sericite-quartz-albite-chlorite schist and schistose quartzite, also carbonaceous and noncarbonaceous limestone; quartz-sericite-chlorite-albite schist. (Northern and Central Vermont). The Battell is raised to Formation rank by T.R. Armstrong (in press) [not in bibliography] to describe graphitic schists with carbonates that depositionally overlie the Monastery Formation in the Granville-Hancock area of central VT. The name Battell Formation is tentatively assigned in this report to a distinct group of graphitic rocks with limited occurrence in the study area. The basal portion of the Battell is assigned by Armstrong to the White River Member (new name) and following that nomenclature, the White River is the only part of the Battell seen in the Fayston-Buels Gore area. The White River appears to be in fault contact with the Underhill Formation along the eastern boundary of the Underhill in Buels Gore. The member also appears to be in depositional contact with the Monastery Formation at all observed locations and occurs as small bodies within the schists of the Monastery (Walsh, 1992).
Underhill Formation, Jay Peak Member (Cambrian)
Underhill Formation, Jay Peak Member - Pale, silver-green, quartz-sericite-chlorite-albite schist, locally quartzitic. (Northern and Central Vermont).
Waits River Formation, Crow Hill Member (Devonian)
Waits River Formation, Crow Hill Member - Tough gray quartzite near St. Johnsbury is distinctive; similar rock (not shown on map) occurs at several other places.
Washington
Cambrian quartzite (Cambrian)
Gritstone with conglomerate in lower part and gray, white, and buff platy quartzite in upper part grading upward into phyllite; northern Pend Oreille County. Light-gray, platy, medium- to thick-bedded quartzite in upper part and darker impure quartzite with some interbedded argillite or phyllite in lower part; north-central Stevens County. White, gray, and reddish, medium- to thick-bedded quartzite in lower part and thin interbeds of quartzite and argillite in upper part, with very low Lower Cambrian fossils (Nevadia, Hyolthellus, and three genera of brachipods) near base of upper part; Addy district of central Stevens County. Thick argillite and thin quartzite units form an uppermost zone in southwestern Stevens County. Conspicuous phyllite units near base in north-central Lincoln County.
Carboniferous-Permian sedimentary and volcanic rocks (Devonian to Permian; some Jurassic)
Sedimentary and volcanic rocks, undivided. Cherty and slaty argillite, siltstone, graywacke, chert, greenstone, tuff, andesite, and spilitic volcanics.
Carboniferous-Permian sedimentary and volcanic rocks (Devonian to Permian, minor Mesozoic)
Predominantly sedimentary rocks. Graywacke, argillite, and slate; includes minor marble, siltstone, arkose, conglomerate, ribbon cherts, and volcanic rocks. Some Devonian rocks may be included in northwestern Washington.
Lower Paleozoic rocks, undivided (Paleozoic; likely Ordovician)
Predominantly gneiss and schist in northern Ferry County. Quartzite, partly interbedded with dolomitic and calcitic marble, lime-silicate gneiss, and amphibolite; including in places forsterite marblean diopside marble, quartz-biotite-sillimanite schist and sillimanite-orthoclase gneiss in northeastern Ferry County. Quartzite with overlying limestone in southeastern Stevens County. Some upper Paleozoic and Precambrian rocks may be included.
Ordovician rocks (Middle Ordovician)
Mainly black to gray slate or slaty argillite, argillite, black to dark-gray siltstone in north-central Stevens County and grayish olive-green silty argillite in west-central Stevens County. Many occurrences of Early and Middle Ordovician graptolites; also rare conodonts.
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 conglomerate (Late-Proterozoic)
Gray-brown, coarse, poorly sorted pebbles and cobbles of limestone, dolomite, reddish-brown quartzite, black slate or phyllite, and rarely granitic rocks in a gray sandy phyllite matrix; northeastern Pend Oreille County and southwestern Stevens County. Rocks become finer grained and more schistose and the unit becomes thicker toward the southwest, where there is included an isolated subunit which may be a tillite, consisting of cobbles, boulders, and blocks of argillite and carbonate rocks in a fine silty matrix.
Precambrian (?) phyllite (Cambrian-Precambrian boundary)
Mostly phyllite with interbedded carbonate rocks, quartzite, and gritstone; some tufflike beds and conglomerate at the base. Rocks confined to northeastern Pend Oreille County and central Stevens County.
Precambrian rocks, undivided (Proterozoic)
Predominantly phyllite with some schist, limestone, dolomite, quartzite, and volcanic rocks; northeastern Pend Oreille County. Mainly quartzite sandstone in upper part, dark-gray argillite with sandstone and limestone in middle part, and sandstone with argillite in lower part; southeastern Pend Oreille County. Banded slate with quartzite and dolomite; southwestern Stevens County. Quartzite, siliceous argillite, and argilliceous quartzite grading into argillite and quartz-mica schists form south ot north; southeastern Stevens County. Quartzite, argillite, quartz-feldspar gneiss, and other metamorphic rocks in northeastern Whitman and southeastern Spokane Counties are partly if not all extenstions of the Belt strata.
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 volcanic rocks, undivided (Probably mostly Jurassic)
Andesite and basalt flows, and greenstone; includes minor interbedded limestone, arkose, quartzite, and chert beds.
Pre-Upper Jurassic gneiss (Mostly Cretaceous)
Biotite, quartz diorite, trondhjemite, and hornblende gneisses, many of which are migmatitic; includes small granitic bodies locally. Small areas of mica schist, marble, amphibolite, and lime-silicate rocks in Entiat Mountains area of Chelan County.
Pre-Upper Jurassic metamorphic rocks of the low-grade zone (Jurassic)
Greenschist, phyllite, and slate; includes some limestone, quartzose phyllite, schistose metaconglomerate, breccia, and basic igneous rocks. Includes schist locally.
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.
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
Barron Quartzite (Early Proterozoic)
Barron Quartzite - Pink to maroon to light-gray, medium-grained, moderately sorted quartzite. Red argillite (pipestone) interbedded locally. At least 213 m thick
Chocolay Group, undivided (Early Proterozoic)
Chocolay Group, undivided - In Dickinson County, Mich., includes Randville Dolomite, Sturgeon Quartzite, and Fern Creek Formation. In Marquette range, between Marquette Bay and Champion, includes Wewe Slate, Kona Dolomite, Mesnard Quartzite, and Enchantment Lake Formation
Ironwood Iron-formation of Menominee Group and Palms Formation of Chocolay Group (Early Proterozoic)
Ironwood Iron-formation of Menominee Group and Palms Formation of Chocolay Group - Mapped where units are too thin to show separately on map (Gogebic Range). Palms Formation includes Bad River Dolomite and Sunday Quartzite of Chocolay Group
Quartzite (Early Proterozoic)
Quartzite - Maroon but locally white, gray, and red quartzite (quartz arenite) with a basal quartzose conglomerate. At Flambeau Ridge (Chippewa County) consists of conglomerate. Distinguished from other quartzite units in being strongly deformed and metamorphosed. Includes Flambeau, Rib Mountain, McCaslin, and Thunder Mountain Quartzites of local usage
Volcanic rocks, undivided (Early Proterozoic)
Volcanic rocks, undivided - Mafic to felsic flows, pyroclastic rocks, impure quartzite, and conglomerate in Eau Claire River, Eau Claire and northern Clark Counties. Rhyolite has zircon ages of 1,858 +/- 5 Ma. Possibly correlative with Milladore Volcanic Complex.
West Virginia
Antietam Formation (Cambrian)
Antietam Formation (Chilhowee Group) - gray to white quartzite, sandstone and quartz-schist; thick-bedded, and resistant; contains Scolithus.
Conococheague Formation (Cambrian)
Conococheague Formation - predominantly algal and mechanically deposited limestone, with interbeds of aphanitic limestone and dolomite. Contains siliceous and dolomitic laminations. Resistant sandy Big Spring Station Member near the base.
Harpers Formation (Cambrian)
Harpers Formation (Chilhowee Group) - greenish-gray phyllite, with interbeds of fine-grained quartzite.

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