Sandstone and conglomerate, rarely forms prominent outcrops; massive conglomerate is typical near base of unit and locally in upper part. These deposits are nonmarine except in southeastern Arizona, where prominent gray marine limestone (Mural Limestone) forms the middle of the Bisbee Group. Sandstones are typically medium-bedded, drab brown, lithic-feldspathic arenites. Includes Bisbee Group (largely Early Cretaceous) and related rocks, Temporal, Bathtub, and Sand Wells formations, rocks of Gu Achi, McCoy Mountains Formation, and Upper Cretaceous Fort Crittenden Formation and equivalent rocks. (80-160 Ma)

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)

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)

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)

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)

Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks

Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks

Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks

Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks

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

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

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

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

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

Undivided pre-Cenozoic metasedimentary and metavolcanic rocks of great variety. Mostly slate, quartzite, hornfels, chert, phyllite, mylonite, schist, gneiss, and minor marble.

Sandstone, shale, conglomerate, chert, slate, quartzite, hornfels, marble, dolomite, phyllite; some greenstone

Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks

Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks

Intermediate Precambrian sediments, northern and southern Idaho; northern Idaho subdivisions are (Y4n, Y3n, Y2n, Y1n) and southern Idaho subdivisions are (Y4s, Y3s, Y2s, Y1s).

Younger Precambrian mafic volcanic flows and conglomerates of northern Idaho.

Upper Permian submarine volcanic complex in the Snake Canyon of western Idaho.

Jurassic mixed marine detrital and volcanic rocks of western Idaho.

Middle and Lower Triassic metabasalt and submarine volcaniclastics of western Idaho

Intermediate Precambrian age metasediments; dominantly quartzite with minor micaceous layers and mica schists of northern Idaho

Younger Precambrian detrital units of central and southeastern Idaho; subdivisions are (Z2s and Z1s).

Intermediate Precambrian sediments, red-tinted quartzite with minor conglomeratic and dolomitic lenses of southern Idaho

Intermediate Precambrian sediments, feldspathic quartzite and siltstone of southern Idaho.

Braintree Argillite and Weymouth Formation - Argillite, some with rare limestone; contains Middle and Early Cambrian faunae respectively.

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).

Hoppin Formation - Quartzite, argillite, and minor limestone; contains Middle Cambrian fauna.

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).

Roxbury Conglomerate - Conglomerate, sandstone, siltstone, argillite, and melaphyre. Consists of Brookline, Dorchester, and Squantum Members. Roxbury Conglomerate forms base of Boston Bay Group. Divided into Brookline, Dorchester, and Squantum Members. Conglomerate in Brookline Member contains clasts of Dedham Granite, quartzite (possibly from Westboro Formation), and volcanic rock from underlying Mattapan Volcanic Complex. Dorchester Member consists of interbedded argillite and sandstone and forms an intermediate unit between Brookline Member and overlying Cambridge Argillite. Uppermost Squantum Member is a distinctive diamictite which appears to pinch out in northern part of basin. Brighton Melaphyre lies within Brookline Member and consists of mafic volcanic rocks (quartz keratophyre, keratophyre, and spilite). Roxbury clearly lies nonconformably on Dedham Granite near Hull, MA; can be traced continuously over Mattapan Volcanic Complex. Age is Proterozoic Z and possibly Early Cambrian (Goldsmith, 1991).

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).

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

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.

Devonian Matagamon Sandstone

Ordovician Pile Mountain Argillite

Baraga Group; Tyler Formation - Light- to dark-gray, feldspathic, fine-grained sandstone, argillaceous siltstone, and argillite. Near base, ferruginous argillite contains beds of cherty sideritic and pyritic iron-formation

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.

Little Falls Formation; Quartz-rich slate, argillite, and schist in the northwestward extent of the unit and coarse-grained megacrystic garnet-staurolite-schist in the southwestward extent - Unit as an uncertain stratigraphic position relative to other Paleoproterozoic stratified units but is apparently younger than the Mille Lacs and North Range Groups.

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

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

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Slate, argillite, and metasiltstone metamorphosed to the lower greenschist facies - Includes lesser amounts of mafic hypabyssal intrusions, and fragmental mafic volcanic rocks

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.

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.

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.

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.

(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.

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

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

(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.

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 - Contains more calc-silicate (15 percent) than does the remainder of the formation (5 percent).

Perry Mountain and Rangeley Formations, undivided.

Rangeley Formation, undivided.

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.

Lockatong Formation - Predominantly cyclic lacustrine sequences of silty, dolomitic or analcime-bearing argillite; laminated mudstone; silty to calcareous, argillaceous very fine grained sandstone and pyritic siltstone; and minor silty limestone, mostly light- to dark-gray, greenishgray, and black. Grayish-red, grayish-purple, and dark-brownish-red sequences (Trlr) occur in some places, especially in upper half. Two types of cycles are recognized: freshwater-lake (detrital) and alkaline-lake (chemical) cycles. Freshwater-lake cycles average 5.2 m (17 ft) thick. They consist of basal, transgressive, fluvial to lake-margin deposits that are argillaceous, very fine grained sandstone to coarse siltstone with indistinct lamination, planar or cross lamination, or are disrupted by convolute bedding, desiccation cracks, root casts, soil-ped casts, and tubes. Medial lake-bottom deposits are laminated siltstones, silty mudstones, or silty limestones that are dark gray to black with calcite laminae and grains and lenses, or streaks of pyrite; fossils are common, including fish scales and articulated fish, conchostracans, plants, spores, and pollen. Upper regressive lake margin, playa lake, and mudflat deposits are light- to dark-gray silty mudstone to argillitic siltstone or very fine grained sandstone, mostly thick bedded to massive, with desiccation cracks, intraformational breccias, faint wavy laminations, burrows, euhedral pyrite grains, and dolomite or calcite specks. Alkaline-lake cycles are similar to freshwater-lake cycles, but are thinner, averaging 3 m (10 ft), have fewer fossils (mainly conchostracans), and commonly have red beds, extensive desiccation features, and abundant analcime and dolomite specks in the upper parts of cycles. Thickness near Byram is about 1,070 m (3,510 ft). The formation thins to the southeast and northeast; thickness near Princeton is less than 700 m (2,297 ft).

Lockatong Formation (Kummel, 1897) - Cyclically-deposited sequences consisting of light- to dark-gray, greenish-gray, and black, dolomitic or analcime-bearing silty argillite, laminated mudstone, silty to calcareous, argillaceous, very-fine-grained pyritic sandstone and siltstone, and minor silty limestone (Trl). Grayish-red, grayish-purple, and dark-brownish-red sequences (Trlr) common in upper half. Two types of cycles are recognized: detrital and chemical. Detrital cycles average 5.2 m (17 ft) thick and consist of basal, argillaceous, very fine grained sandstone to coarse siltstone; medial, dark-gray to black, laminated siltstone, silty mudstone, or silty limestone; and upper, light- to dark-gray, silty to dolomitic or analcime-rich mudstone, argillitic siltstone, or very-fine-grained sandstone. Chemical cycles are similar to detrital cycles, but thinner, averaging 3.2 m (10.5 ft). Cycles in northern Newark basin are thinner and have arkosic sandstone in lower and upper parts. Upper part of formation in northern basin composed mostly of light-gray to light-pinkish-gray or light-brown, coarse- to fine-grained, thick- to massive-bedded arkosic sandstone (Trla). Thermally metamorphosed into hornfels where intruded by diabase (Jd). Interfingers laterally and gradationally with quartz sandstone and conglomerate (Trls) and quartzite conglomerate (Trlcq) near Triassic border fault in southwestern area of map. Maximum thickness of Lockatong Formation about 1,070 m (3,510 ft).

Lockatong Formation red bed - Cyclically-deposited sequences consisting of light- to dark-gray, greenish-gray, and black, dolomitic or analcime-bearing silty argillite, laminated mudstone, silty to calcareous, argillaceous, very-fine-grained pyritic sandstone and siltstone, and minor silty limestone (Trl). Grayish-red, grayish-purple, and dark-brownish-red sequences (Trlr) common in upper half.

Lockatong Formation red bed - Predominantly cyclic lacustrine sequences of silty, dolomitic or analcime-bearing argillite; laminated mudstone; silty to calcareous, argillaceous very fine grained sandstone and pyritic siltstone; and minor silty limestone, mostly light- to dark-gray, greenishgray, and black. Grayish-red, grayish-purple, and dark-brownish-red sequences (Trlr) occur in some places, especially in upper half. Two types of cycles are recognized: freshwater-lake (detrital) and alkaline-lake (chemical) cycles. Freshwater-lake cycles average 5.2 m (17 ft) thick. They consist of basal, transgressive, fluvial to lake-margin deposits that are argillaceous, very fine grained sandstone to coarse siltstone with indistinct lamination, planar or cross lamination, or are disrupted by convolute bedding, desiccation cracks, root casts, soil-ped casts, and tubes. Medial lake-bottom deposits are laminated siltstones, silty mudstones, or silty limestones that are dark gray to black with calcite laminae and grains and lenses, or streaks of pyrite; fossils are common, including fish scales and articulated fish, conchostracans, plants, spores, and pollen. Upper regressive lake margin, playa lake, and mudflat deposits are light- to dark-gray silty mudstone to argillitic siltstone or very fine grained sandstone, mostly thick bedded to massive, with desiccation cracks, intraformational breccias, faint wavy laminations, burrows, euhedral pyrite grains, and dolomite or calcite specks. Alkaline-lake cycles are similar to freshwater-lake cycles, but are thinner, averaging 3 m (10 ft), have fewer fossils (mainly conchostracans), and commonly have red beds, extensive desiccation features, and abundant analcime and dolomite specks in the upper parts of cycles. Thickness near Byram is about 1,070 m (3,510 ft). The formation thins to the southeast and northeast; thickness near Princeton is less than 700 m (2,297 ft).

MASSIVE LIMESTONE-In the San Antonio Mountains, western Nye County

SHALE, SANDSTONE, VOLCANOGENIC CLASTIC ROCKS, ANDESITE, RHYOLITE, AND LOCALLY THICK CARBONATE UNITS-Undivided sequence locally containing recognizable equivalents of the Luning and Dunlap Formations

Cumberland Head Argillite

Elizaville Formation - shale, argillite, quartzite.

Elizaville Formation - shale, argillite, quartzite.

Mount Merino and Indian River Formations - shale, argillite, chert.

Normanskill Formation - shale, argillite, siltstone.

Black, green, and gray argillite, mudstone, and shale; graywacke, sandy limestone, tuff, and some coarse volcaniclastic rocks; chert, sandstone comprised of chert clasts, and chert pebble conglomerate; thin-bedded and massive limestone. Locally contains some interbedded lava flows, mostly spilite or keratophyre. In places metamorphosed. Invertebrate marine fauna indicates unit mostly of Late Triassic (Karnian and Norian) age. Includes the Begg and Brisbois Formations of Dickinson and Vigrass (1965; Vester Formation of Brown and Thayer, 1966) and the Rail Cabin Argillite of Dickinson and Vigrass (1965); Fields Creek Formation and Laycock and Murderers Creek Graywackes of Brown and Thayer (1966); Martin Bridge Formation and lower sedimentary series in and near the Wallowa Mountains (Prostka, 1962; Nolf, 1966); and Doyle Creek and Wild Sheep Creek Formations (Vallier, 1977). Probably partly age correlative with rocks of the Applegate Group (Wells and Peck, 1961) of southwestern Oregon

Structurally complex mixture of basaltic rocks, serpentinite, chert, argillite, conglomerate, silty sandstone, and lenses of marble composing the melange of the Takilma area of Smith and others (1982)

Poorly bedded argillite, chert, phyllite, phyllitic quartzite, calc-phyllite, impure limestone, and marble. In places rocks are strongly foliated. Sparse fossils (Fusilina, corals, and crinoids) indicate that the unit includes rocks of Leonardian, Ochoan, and Late Triassic age (OR084). Includes Elkhorn Ridge Argillite (OR035), Mesozoic and Paleozoic sedimentary rocks of Brown and Thayer (OR008), and the Permian Coyote Butte Formation (OR085). In Baker County includes "sedimentary and volcanic rocks" (MzPza) of Brooks and others (OR039) and metamorphosed sedimentary and minor volcaniclastic rocks containing mineral assemblages indicative of quartz-albite-muscovite-chlorite subfacies and quartz-albite-epidote-biotite subfacies of the greenschist facies. In Jefferson and Wasco Counties north of Prineville, includes "phyllite and sedimentary rocks " of Swanson (OR031). Includes part of the Burnt River Schist (OR035; OR081) and volcaniclastic facies of several metavolcanic units of Permian and Late Triassic age. Not on State map (OR001) in area of La Grande 100K quadrangle, butmapped in OR291 as Elkhorn Ridge Argillite (Triassic Permian, Pennsylvannian, and Devonian?)

Brunswick Formation - Reddish-brown mudstone, siltstone, and shale, containing a few green and brown shale interbeds; red and dark-gray, interbedded argillites near base. Youngest beds in Brunswick may be Jurassic in age.

Heidlersburg Member of Gettysburg Formation - Red, green, and gray shale and argillite, and minor thin beds of gray arkosic sandstone; some quartz conglomerate and limestone conglomerate.

Lockatong Formation - Dark-gray to black, thick-bedded argillite containing a few zones of thin-bedded black shale; locally has thin layers of impure limestone and calcareous shale.

Hoppin Formation - Quartz arenite, argillite, and minor limestone; contains fossils of Lower Cambrian age.

Catoctin Formation - Metasedimentary rocks

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.

Hathaway Formation - Gray to black argillite and bedded radiolarian chert, with included blocks and fragments of chert, limestone, dolomite, sandstone and graywacke.

Mostly massive dolomite, with a basal unit of gray to dark-gray limestone interbedded with limy shale, and an upper unit of fine-grained massive limestone with some marble; Pend Oreille and northern and central Stevens Counties. Three-fold division less evident in Colville area. Dolomite, with minor basal unit of interbedded limestone and phyllite in the Addy-Dunn Mountain area of Stevens County. Marble, dolomite, limestone, and limy slate in Hunters' district. Dolomitic marble in southern Stevens and northern Lincoln Counties. Middle Cambrian fossils near base in Metaline district, and Bathyuriscus-Elrathina fauna in lower unit in Leadpoint district. Phosphatic brachiopods in upper unit in Leadpoint district tentatively assigned to Middle and Upper Cambrian.

Predominantly gray-green, banded phyllite, some sericite schist, abundant thin beds of quartzite, especially in lower part of unit, and limestone in upper part; northern Pend Oreille County. Much the same lithology but more conspicuous subunits of quartzite, limestone, and schist in northeastern Stevens County. Gray phyllite, greenish argillite, andalusite schist, minor inerbedded quartzite and siliceous dolomite, especially in lower part, and much gray limestone in upper part; north-central Stevens County. Limestone bed in lower part of unit contains Lower Cambrian fossils (Archaeocyathus).

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.

Predominantly altered andesite, basalt, and diabase with interbedded chert and argillite; includes some tuff, greenstone, and spilitic volcanic rocks; northern Cascade Mountains. Mostly schistose greenstone, some agglomerate, and rarely lapilli; includes minor beds of limestone with associated argillite and graywacke; northwestern Stevens County.

Sedimentary and volcanic rocks, undivided. Cherty and slaty argillite, siltstone, graywacke, chert, greenstone, tuff, andesite, and spilitic volcanics.

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.

Thin-bedded graywacke, shale, argillite, slate, schist, volcanic breccia, gritstone, conglomerate, and limestone on northeast shore of Orcas Island. Limestone or dolomitic limestone, apparently interbedded with limy argillite and graywacke, forms belt of small separate outcrops between Springdale and Valley in southeastern Stevens County. Late Devonian to Early Pennsylvanian in age.

Predominantly sandstone and shale. Includes some conglomerate in the Cle Elum area in Kittilas County. Contains extensive coal seams near Roslyn and carbonaceous shale and coal beds in White Pass area. Contains tuff beds in northwestern Ferry County.

Predominantly andesite flows and breccia; includes interbedded sedimentary rocks south of Startup in Snohomish and King Counties.

Predominantly andesite flows and flow breccia; includes basalt flows, minor rhyolitic rocks, and some sedimentary rocks.

Dark-gray, massive to poorly bedded gray-wacke of the interior Olympic Peninsula; commonly with interbedded slate, argillite, volcanic rocks, and minor arkosic sandstone. Includes rocks both older and younger than Ev2, some of which may be Paleozoic.

Altered basalt, pillow lavas, and flow breccia of inner volcanic belt of Olympic Peninsula; includes minor interbedded red limy argillite and associated manganese ore.

Andesite, dacite, and minor basalt with slate and graywacke interbeds in the Nooksack River region of Whatcom County.

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.

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.

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.

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.

Meta-quartz diorite, hypersthene diorite, and gneissose and directionless quartz diorite of eastern Skagit County. Quartz diorite and diorite in the San Juan Islands. Includes amphibolite and gneiss locally.

Predominantly sedimentary rocks. Graywacke, argillite, and slate; includes minor marble, siltstone, arkose, conglomerate, ribbon cherts, and volcanic rocks.

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

Predominantly greenstone and spilitic volcanic rocks; includes some slate, argillite, and graywacke.

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

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

Argillite and graywacke between inner and outer volcanic belts in Olympic Peninsula. Sheared carbonaceous argillite, argillite, graywacke, and minor conglomerate lenses and altered lava flows in western Yakima County.

Greenschist, phyllite, and slate; includes some limestone, quartzose phyllite, schistose metaconglomerate, breccia, and basic igneous rocks. Includes schist locally.

Diorite and gabbro in western Snohomish County.

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

Rhyolite flows and some interbedded tuff beds in Cle Elum area, Kittitas County.

Sedimentary and volcanic rocks, undivided. Graywacke, argillite, siltstone, slate, volcanic rocks, phyllite, greenschist, and greenstone.

Predominantly sedimentary rocks. Graywacke, argillite, and siltstone with some slate and phyllite; includes graywacke breccia and ribbon chert with minor local limestone lenses and basalt flows.

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.

Conglomerate, gritstone, graywacke, and carbonaceous argillite of northwestern Whatcom County.

Baraga Group; Tyler Formation - Light- to dark-gray, feldspathic, fine-grained sandstone, argillaceous siltstone, and argillite. Near base, ferruginous argillite contains beds of cherty sideritic and pyritic iron-formation

Felsic volcanic and volcanogenic rocks - Tuff, argillite, graywacke, and minor volcanic rocks of lower greenschist-facies in southern Rusk County. Could be younger in age than adjacent metavolcanic rocks.