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Geologic units containing meta-argillite

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.

Meta-conglomerate mafic metavolcanic rocks, siltite, argillite, and limestone; Late Proterozoic rifted continental margin; northwestern Idaho (Late Proterozoic)

Younger Precambrian mafic volcanic flows and conglomerates of northern Idaho.

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, diorite, trondhjemite, and migmatite; Cretaceous to Jurassic quartz dioritic plutons in Mesozoic to Permian greenschist-facies rocks; western Idaho, Blue Mountains island-arc complex (Cretaceous to Permian)

Triassic and possibly Permian submarine metavolcanic rocks of west-central Idaho.

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

Jurassic mixed marine detrital and volcanic rocks of western Idaho.

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

Middle and Lower Triassic metabasalt and submarine volcaniclastics of western Idaho

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, 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, 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

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

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).

Maryland

Ijamsville Formation (Late Precambrian (?))

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

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

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

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.

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.

Chamberlain shale (Proterozoic | Mesoproterozoic)

Chamberlain shale: dark-gray siliceous and locally arenaceous shale; shown only in Little Belt Mountain region, where it is regarded as the sole unit that can be correlated with the Ravalli group.

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.

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.

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

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

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

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

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

Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)

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

Felsic Metavolcanic Rock (Cambrian/Late Proterozoic)

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

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

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

Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)

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

Metamudstone and Meta-Argillite (Cambrian/Late Proterozoic)

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

Metavolcanic-Epiclastic Rock (Cambrian/Late Proterozoic)

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

Metavolcanic-Epiclastic Rock (Cambrian/Late Proterozoic)

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

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

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

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

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

New Hampshire

Aziscohos Formation, Lower unnamed member (Upper Cambrian? - Lower Ordovician?)

Aziscohos Formation, Lower unnamed member - Rusty, dark metapelite containing thin coticule laminations, feldspathic metatuff, and vein quartz lenses.

Aziscohos Formation, Upper unnamed member (Upper Cambrian? - Lower Ordovician?)

Aziscohos Formation, Upper unnamed member - Gray metapelite containing sparse siltstone laminations and abundant lenses of vein quartz.

Dead River Formation, Graded-bedded metapelite (Upper Cambrian? - Lower Ordovician?)

Dead River Formation, Graded-bedded metapelite - Found in Percy quadrangle of northern New Hampshire.

Dead River Formation, undivided (Upper Cambrian? - Lower Ordovician?)

Dead River Formation, undivided - Thinly laminated, "pin-striped" gray, green, or tan metapelite and quartzite.

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

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

Greenvale Cove Formation (Lower Silurian? )

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

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

Lower part of Rangeley Formation - Gray, thinly laminated (5-25 mm) metapelite with local lentils of turbidites and thin quartz conglomerates in western New Hampshire. Sparse calc-silicate pods and coticule. Probably equivalent to member B of Rangeley Formation of Maine.

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, Berwick Formation (Ordovician? - Silurian?)

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

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

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

Perry Mountain and Rangeley Formations, undivided (Silurian)

Perry Mountain and Rangeley Formations, undivided.

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 - Migmatite of gray, foliated, sheared or mylonitized two-mica granite and pegmatite, minor hornblende-biotite diorite, intruding metapelites and metavolcanic rocks in southeastern New Hampshire.

Oregon

Sedimentary and volcanic rocks, partly metamorphosed (Triassic and Permian) (Permian to Triassic)

Complexly folded, locally highly foliated and recrystallized undifferentiated sedimentary and volcanic rocks that in places are lithologically similar to Jurassic and Triassic rocks in the Aldrich Mountains of the Blue Mountains province and in other places resemble Elkhorn Ridge Argillite, Clover Creek Greenstone, and Burnt River Schist (Gilluly, 1937). Age probably mostly Late Permian to Late Triassic, but, as shown, may include some Early Jurassic rocks

Virginia

Alligator Back Formation - Feldspathic metagraywacke (Proterozoic Z-Cambrian)

Alligator Back Formation - Meta-argillite is feldspathic metagraywacke; graphitic mica schist, and quartzite.

Annandale Group - Accotink Schist (Proterozoic Z-Cambrian)

Annandale Group - Accotink Schist.

Candler Formation - Metasiltstone (Cambrian)

Candler Formation - Meta-argillite is laminated metasiltstone

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.

Fauquier Formation - Metasiltstone and phyllite (Proterozoic Z)

Fauquier Formation - Meta-argillite is laminated metasiltstone; and phyllite.

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; Metagraywacke (Proterozoic Z)

Lynchburg Group - Metagraywacke

Lynchburg Group; Monumental Mills Formation (Proterozoic Z)

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

Mather Gorge Formation - Metagraywacke (Proterozoic Z-Cambrian)

Mather Gorge Formation - Metargillite is metagraywacke

Metagraywacke (Proterozoic)

Metagraywacke - Meta-argillite is metagraywacke, exotic blocks within melange units

Metagraywacke, Quartzose Schist, and Melange (Proterozoic Z-Cambrian)

Metagraywacke, Quartzose Schist, and Melange - Meta-argillite is metagraywacke; quartzose schist

Metasandstone and Metasiltstone (Proterozoic Z-Cambrian)

Metasandstone and metasiltstone.

Phyllite and Metasiltstone (Proterozoic Z)

Phyllite and metasiltstone.

Popes Head Formation - Old Mill Branch Metasiltstone Member. Meta-argillite is metasiltstone (Cambrian-Ordovician)

Popes Head Formation -Old Mill Branch Metasiltstone Member. Meta-argillite is metasiltstone

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