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Geologic units containing mixed clastic/volcanic

Earth material > Sedimentary rock
Mixed volcanic/clastic rock
An undivided mixture of volcanic rock and clastic sedimentary rock.
This category is also used for mixed clastic/volcanic.
Subtopics:
(none)

Colorado - Idaho - Massachusetts - Minnesota - Montana - New Mexico - Oregon - Texas - Virginia - Wisconsin - Wyoming
Colorado
Animas Fm (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary)
Arkosic sandstone, shale, and conglomerate; contains abundant volcanic materials; Upper Cretaceous volcaniclastic McDermott Member at base
Los Pinos Fm (Phanerozoic | Cenozoic | Tertiary)
Volcaniclastic conglomerate interbedded with basalt flows of Hinsdale Fm (Tbb) on east flank of San Juan Mountains. Grades laterally into Santa Fe Fm of San Luis Valley
Middle Park Fm exclusive of Windy Gap Member (Phanerozoic | Cenozoic | Tertiary)
Arkosic sandstone and conglomerate containing abundant volcanic materials. Arbitrary line between Middle Park and Coalmont Formations is at Continental Divide
Windy Gap Member of Middle Park Fm (Phanerozoic | Mesozoic | Cretaceous)
Andesitic breccia and conglomerate
Idaho
Basalt flows, pyroclastic debris, clastic sediments, and diatomite; Pliocene basaltic volcanics and clastic sediments; Snake River Plain and vicinity (Pliocene)
Pliocene olivine basalt flows and associated tuff and detritus of southern Idaho.
Dacite to rhyolite (or rhodacite) ignimbrites; Eocene rhyodacitic cauldron complex; east-central Idaho, central Challis volcanic field (Eocene)
Eocene mixed silicic and basaltic volcanic ejecta, flows and reworked debris.
Rhyolite ignimbrites, latite and basalt lava flows, late Eocene rhyolitic ignimbrite cauldron complex; east-central Idaho, northern Challis volcanic field (Eocene)
Eocene mixed silicic and basaltic volcanic ejecta, flows and reworked debris.
Massachusetts
Metamorphosed mafic to felsic flow, and volcaniclastic and hypabyssal intrusive rocks (Proterozoic Z)
Metamorphosed mafic to felsic flow, and volcaniclastic and hypabyssal intrusive rocks - Includes some diorite and gabbro north and northwest of Boston.
Minnesota
Animikie Group; Shale, siltstone, feldspathic graywacke, and associated volcaniclastic rocks (Early Proterozoic)
Animikie Group; Shale, siltstone, feldspathic graywacke, and associated volcaniclastic rocks - Includes the Rove Formation in Cook County, the Virginia Formation in St. Louis, Itasca, and Lake Counties, and the Thomson Formation in Carlton County
Montana
Tertiary volcanic rocks (Phanerozoic | Cenozoic | Tertiary)
Tertiary volcanic rocks: Flows and associated pyroclastic deposits, with subordinate amounts of intercalated sedimentary beds and lignite. The volcanic material is mostly latite, quartz latite, and andesite but includes some rhyolite and basalt. The distinction between Tertiary and pre-Tertiary volcanic rocks was not made in some of the reports used in the complilation. Hence in the less well-known areas some pre-Tertiary volcanic rocks may be included.
New Mexico
andesite and basaltic andesite flows and associated volcaniclastic units (Phanerozoic | Cenozoic | Tertiary)
Lower Tertiary, (Lower Oligocene and Eocene) andesite and basaltic andesite flows, and associated volcaniclastic units. Includes Rubio Peak Formation, and andesite of Dry Leggett Canyon
Fence Lake Formation (Phanerozoic | Cenozoic | Tertiary)
Fence Lake Formation; conglomerate and conglomeratic sandstone, coarse fluvial volcanoclastic sediments, minor eolian facies, and pedogenic carbonates of the southern Colorado Plateau region; Miocene
rhyolitic pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary)
Upper Oligocene rhyolitic pyroclastic rocks (ash-flow tuffs); includes Davis Canyon Tuff, South Crosby Peak Formation, La Jencia, Vick's Peak, Lemitar, South Canyon, Bloodgood Canyon, Shelley Peak Tuffs, tuff of Horseshoe Canyon, Park Tuff, Rhyolite Canyon Tuff, Apache Springs Tuff, Diamond Creek, Jordan Canyon, Garcia Camp Tuffs, the Turkey Springs Tuff, the tuff of Little Mineral Creek, the Amalia Tuff, and others. Some contain volcaniclastic and reworked volcaniclastic rocks, and eolian sandstone; (24-29 Ma)
sedimentary and vocaniclastic sedimentary rocks (Phanerozoic | Cenozoic | Tertiary)
Mostly Oligocene and upper Eocene sedimentary and volcaniclastic sedimentary rocks with local andesitic to intermediate volcanics; includes Espinaso, Spears, Bell Top, and Palm Park Formations
silicic pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary)
Lower Oligocene silicic pyroclastic rocks (ash-flow tuffs); includes Hell's Mesa, Kneeling Nun, lower part of Bell Top Formation, Caballo Blanco, Datil Well, Leyba Well, Rock House Canyon, Blue Canyon, Sugarlump and Tadpole Ridge Tuffs, the tuffs of the Organ cauldron, Treasure Mountain Tuff (now known as Chiquito Peak Tuff), Bluff Creek Tuff, Oak Creek Tuff, tuff of Steins Mountain, tuff of Black Bill Canyon, tuff of Farr Ranch, Woodhaul Canyon, Gillespie and Box Canyon Tuffs, Cooney Tuff, and other volcanic and interbedded fluvial and pumiceous units; (31-36.5 Ma)
Upper Santa Fe Group (Phanerozoic | Cenozoic | Tertiary Quaternary)
Upper Santa Fe Group. Includes Camp Rice, Fort Hancock, Palomas, Sierra Ladrones, Ancha, Puye, and Alamosa Formations; middle Pleistocene to uppermost Miocene
upper Tertiary sedimentary units (Phanerozoic | Cenozoic | Tertiary)
Upper Tertiary sedimentary units; includes Bidahochi Formation, the Picuris Formation, and Las Feveras Formation, and locally fanglomerates; Pliocene to upper Miocene
volcanic and some volcaniclastic rocks (Phanerozoic | Cenozoic | Tertiary)
Volcanic and some volcaniclastic rocks, undifferentiated; lower Miocene and Upper Oligocene (younger than 29 Ma)
volcanic rocks, lower Oligocene and Eocene (Phanerozoic | Cenozoic | Tertiary)
Lower Oligocene and Eocene volcanic rocks, undifferentiated; dominantly intermediate composition, with interbedded volcaniclastic rocks; (31-44 Ma)
Oregon
Basalt and andesite (Miocene) (Miocene)
Lava flows and breccia of aphyric and plagioclase porphyritic basalt and aphyric andesite; locally includes flow breccia, peperite, some palagonite tuff and breccia, and minor silicic ash-flow tuff and interbeds of tuffaceous sedimentary rocks. In Basin and Range and Owyhee Upland provinces unit grades upward into more silicic, andesitic, and quartz latitic flows and flow breccia, as well as some interbedded tuffs and ash-flow tuffs; also in this region includes aphyric and highly porphyritic, plagioclase-rich basalt. Interfingers with and grades laterally into units Tit and Tts. Commonly contains montmorillonite clays, zeolites, calcite, and secondary silica minerals as alteration products on fractures and in pore spaces. Age, mostly middle Miocene, but includes some rocks of early Miocene age based on vertebrate fossils from related sedimentary units and on potassium-argon ages that range from about 13 Ma to about 19 Ma; most isotopic ages are about 13 to 16 Ma. Includes Steens Basalt (Steens Mountain Basalt of Fuller, 1931) Owyhee Basalt of Corcoran and others (1962) and Kittleman and others (1967), Hunter Creek Basalt and "unnamed igneous complex" of Kittleman and others (1965, 1967), and flows of Prineville chemical type (Uppuluri, 1974; Swanson and others, 1979), which previously were considered part of the Columbia River Basalt Group (Swanson, 1969a)
Basalt (upper and middle Miocene) (Middle to Late Miocene)
Basalt flows, flow breccia, and basaltic peperite; minor andesite flows; some interbeds of tuff and tuffaceous sedimentary rocks. Basalt is aphyric to moderately porphyritic with phenocrysts of plagioclase and olivine and exhibits both subophitic and diktytaxitic textures. Includes Picture Rock Basalt of Hampton (1964), radiometrically dated by potassium-argon methods as middle(?) and late Miocene in age (see Fiebelkorn and others, 1983), flows of Deer Butte Formation of Kittleman and others (1967), and extensive unnamed flow sequences in the Basin-Range and Owyhee Upland Provinces of southern Lake, Harney, and Malheur Counties that are younger than Steens Basalt, dated at about 15 Ma (Baksi and others, 1967) and the Owyhee Basalt, dated at about 14 Ma (Bottomley and York, 1976; see also Fiebelkorn and others, 1983), and older than 7 or 8 Ma. Partly coeval with the Saddle Mountains Basalt of the Columbia River Basalt Group (Swanson and others, 1979)
John Day Formation of east-central Oregon (lower Miocene, Oligocene, and uppermost Eocene?) (Late Eocene to Early Miocene)
Predominantly tuffaceous facies of Clarno Formation (lower Oligocene? and Eocene) (Eocene to Early Oligocene)
Mapped separately by Swanson (1969a) in the Ochoco and Maury Mountains of the Blue Mountains Province
Sedimentary and volcanic rocks (Upper? Triassic) (Late Triassic)
Undifferentiated marine sedimentary rocks and volcanic rocks, locally slightly to moderately metamorphosed, of Late(?) Triassic age, exposed principally in Hells Canyon of Snake River, locally in tributary canyons of Imnaha River, and in several areas marginal to the Wallowa Mountains
Volcanic and metavolcanic rocks (Upper Triassic) (Late Triassic)
Green to gray spilite and keratophyre flows and flow breccia; and subordinate amounts of coarse volcaniclastic sandstone, tuff, sandstone, siltstone, chert, conglomerate, and limestone. Marine fauna from interlayered sedimentary rocks indicates unit is mostly of Karnian (Late Triassic) age. Includes Late Triassic "andesitic and basaltic rocks" of Nolf and Taubeneck (1963), and the basaltic to rhyolitic metavolcanic rocks and interbedded sedimentary rocks of the Huntington Formation of Brooks (1979). Equivalent, in part, to unit TrPv
Texas
Chisos Formation of Schiebout et al (1987) and the Big Yellow Sandstone Member of their Tornillo Formation, undivided (Phanerozoic | Cenozoic | Tertiary | Eocene Oligocene)
Chisos Formation of Schiebout et al (1987) and the Big Yellow Sandstone Member of their Tornillo Formation, undivided
Virginia
Felsic Volcanic and Volcaniclastic Rocks (Proterozoic Z)
Felsic volcanic and volcaniclastic rocks.
Wisconsin
Porcupine Volcanics (Middle Proterozoic)
Porcupine Volcanics - Generally dark-gray basalt, andesite, and felsite flows and subordinate interflow sedimentary rocks
Rhyolite (Early Proterozoic)
Rhyolite - Ash-flow tuffs and interbedded volcaniclastic sedimentary rocks and cogenetic granite (unit Xga) exposed as inliers in southern Wisconsin. In central Wisconsin pink, flow-banded rhyolite and chert-cemented breccia inferred to be 1760 Ma.
Wyoming
Absaroka Volcanic Supergroup: Hominy Peak Formation (Phanerozoic | Cenozoic | Tertiary | Eocene)
ABSAROKA VOLCANIC SUPERGROUP--HOMINY PEAK FORMATION (AGE ABOUT 49 Ma)--Mafic volcaniclastic conglomerate and tuff; sparse claystone in upper part; gold-bearing quartzite conglomerate at base.
Absaroka Volcanic Supergroup: Sunlight Group--Wapiti Formation (Phanerozoic | Cenozoic | Tertiary | Eocene)
ABSAROKA VOLCANIC SUPERGROUP: SUNLIGHT GROUP--Wapiti Formation: andesitic volcaniclastic rocks.
Absaroka Volcanic Supergroup: Thorofare Creek Group--Wiggins Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (44-47 Ma))
ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP Wiggins Formation (age 44-47 Ma)--Light-gray volcanic conglomerate and white tuff, containing clasts of igneous rocks.
Absaroka Volcanic Supergroup: Thoroughfare Creek Group--Aycross Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma))
ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP (AGE 44 TO 49 Ma) Aycross Formation (age 49 Ma)--Brightly variegated bentonitic claystone and tuffaceous sandstone, grading laterally into greenish-gray sandstone and claystone. In and east of Jackson Hole contains gold-bearing lenticular quartzite conglomerate.
Absaroka Volcanic Supergroup: Thoroughfare Creek Group--Tepee Trail Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma))
ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP (AGE 44 TO 49 Ma) Tepee Trail Formation (age probably about 48 Ma)--Green and olive-drab hard generally well bedded andesitic conglomerate, sandstone, and claystone.
Absaroka Volcanic Supergroup: Thoroughfare Creek Group--Two Ocean and Langford Formations (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma))
ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP (AGE 44 TO 49 Ma) Two Ocean and Langford Formations (age 47-48 Ma)--Dark-colored andesitic volcaniclastic rocks and flows underlain by light-colored andesitic tuffs and flows. In places may include Trout Peak Trachyandesite of Sunlight Group.
Absaroka Volcanic Supergroup: Washburn Group (Phanerozoic | Cenozoic | Tertiary | Eocene)
ABSAROKA VOLCANIC SUPERGROUP--WASHBURN GROUP: includes Sepulcher Formation (andesitic and dacitic volcaniclastic rocks), Lamar River Formation (andesitic lava and volcaniclastic rocks), and Cathedral Cliffs Formation (light-colored andesitic volcaniclastic rocks).
Aspen Shale (Phanerozoic | Mesozoic | Cretaceous-Early)
ASPEN SHALE--Light- to dark-gray siliceous tuffaceous shale and siltstone, thin bentonite beds, and quartzitic sandstone.
Blind Bull Formation (Phanerozoic | Mesozoic | Cretaceous-Late)
BLIND BULL FORMATION--Gray to tan conglomeratic sandstone, siltstone, claystone, coal, and bentonite.
Bridger Formation (Phanerozoic | Cenozoic | Tertiary | Eocene)
BRIDGER FORMATION--Greenish-gray, olive-drab, and white tuffaceous sandstone and claystone; lenticular marlstone and conglomerate.
Bug Formation (Phanerozoic | Cenozoic | Tertiary Quaternary | Pliocene Pleistocene)
BUG FORMATION (PLEISTOCENE OR PLIOCENE)--Lacustrine white marl, claystone, sandstone, conglomerate, and tuff; generally radioactive.
Cloverly, Morrison, and Sundance Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early)
CLOVERLY, MORRISON, AND SUNDANCE (Js) FORMATIONS. CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale.
Cloverly, Morrison, Sundance, and Gypsum Spring Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early)
CLOVERLY, MORRISON, AND SUNDANCE (Js), AND GYPSUM SPRING FORMATIONS. CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale. GYPSUM SPRING FORMATION--Interbedded red shale, dolomite, and gypsum. In north Wyoming wedges out south in T. 39 N.
Colter Formation (Phanerozoic | Cenozoic | Tertiary | Miocene)
COLTER FORMATION--Dull-green and gray tuff, volcanic conglomerate, and sandstone.
Fowkes Formation (Phanerozoic | Cenozoic | Tertiary | Eocene)
FOWKES FORMATION--Light-colored tuffaceous sandstone and siltstone, locally conglomeratic. Locally designated by some as Norwood Tuff.
Frontier Formation and Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late)
FRONTIER FORMATION (Kf) AND MOWRY (Kmr) AND THERMOPOLIS SHALES. FRONTIER FORMATION--Gray sandstone and sandy shale. In Northern Yellowstone area, Yellowish- to medium-gray sandstone; tuffaceous and carbonaceous in lower part. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. THERMOPOLIS SHALE--Black soft fissile shale; Muddy Sandstone Member at top.
Greenhorn Formation and Belle Fourche and Mowry Shale (Phanerozoic | Mesozoic | Cretaceous-Early)
GREENHORN FORMATION AND BELLE FOURCHE AND MOWRY (Kmr) SHALE. GREENHORN FORMATION--Light-colored limestone, marl, and limy sandstone interbedded with gray concretionary shale. BELLE FOURCHE SHALE--Black soft bentonitic concretionary shale. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds.
Greenhorn Formation and Belle Fourche Shale (Phanerozoic | Mesozoic | Cretaceous-Late)
GREENHORN FORMATION AND BELLE FOURCHE SHALE. GREENHORN FORMATION--Light-colored limestone, marl, and limy sandstone interbedded with gray concretionary shale. BELLE FOURCHE SHALE--Black soft bentonitic concretionary shale. CARLILE SHALE--Dark-gray sandy shale; Sage Breaks Member at top; Turner Sandy Member in middle.
Green River Formation: Wilkins Peak Member (Phanerozoic | Cenozoic | Tertiary | Eocene)
GREEN RIVER FORMATION Wilkins Peak Member (age about 49 Ma)--Green, brown, and gray tuffaceous sandstone, shale, and marlstone; contains evaporites in subsurface sections.
Green River Formation: Wilkins Peak Member and Tipton Shale member or Tongue (Phanerozoic | Cenozoic | Tertiary | Eocene)
GREEN RIVER FORMATION Wilkins Peak Member (age about 49 Ma) (green, brown, and gray tuffaceous sandstone, shale, and marlstone; contains evaporites in subsurface sections) and Tipton Shale Member or Tongue (oil shale and marlstone).
Lance Formation, Fox Hills Sandstone, Meeteetse Formation, Bearpaw and Lewis Shales (Phanerozoic | Mesozoic | Cretaceous-Late)
LANCE FORMATION (Kl north), FOX HILLS SANDSTONE (Kfh), MEETEETSE FORMATION (Km), AND BEARPAW AND LEWIS (Kle) SHALES--In the Bighorn Basin consists of Lance, Meeteetse and, in the southeastern part, tongue of Lewis Shale; in the northern part of the Wind River Basin, of Lance, Meeteetse, and Lewis, and, in the southeastern part of the basin, of Lance and Lewis; on the west side of the Powder River Basin north of T. 45 N., of Lance, Fox Hills, and Bearpaw, and, to the south, of Lance, Fox Hills, and Lewis. LANCE FORMATION--Thick-bedded buff sandstone and drab to green shale; thin conglomerate lenses. FOX HILLS SANDSTONE--Light-colored sandstone and gray sandy shale containing marine fossils. MEETEETSE FORMATION (AGE ABOUT 73 Ma)--Chalky-white to gray sandstone, yellow, green, and dark-gray bentonitic claystone, white tuff, and thin coal beds. BEARPAW SHALE--Dark-greenish-gray shale containing thin gray sandstone partings. LEWIS SHALE (AGE ABOUT 68 Ma)--Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.
Landslide Creek Formation (Phanerozoic | Mesozoic | Cretaceous-Late)
LANDSLIDE CREEK FORMATION--Greenish-gray bentonitic tuffaceous sandstone and conglomerate.
Lower Miocene and Upper Oligocene rocks, or Rocks equivalent to Upper and Lower Miocene AND White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene-Late Miocene-Early(?) Miocene-Middle(?) Miocene-Late)
LOWER MIOCENE AND UPPER OLIGOCENE ROCKS--Light-colored soft porous sandstone and underlying white tuffaceous claystone and siltstone. Arikaree Formation in Denver Basin; ROCKS EQUIVALENT TO UPPER AND LOWER MIOCENE ROCKS AND WHITE RIVER FORMATION--Light-colored sandstone, white tuffaceous blocky claystone, and siltstone. Black Hills.
Meeteetse Formation (Phanerozoic | Mesozoic | Cretaceous-Late)
MEETEETSE FORMATION (AGE ABOUT 73 Ma)--Chalky-white to gray sandstone, yellow, green, and dark-gray bentonitic claystone, white tuff, and thin coal beds.
Meeteetse Formation and Lewis Shale (Phanerozoic | Mesozoic | Cretaceous-Late)
MEETEETSE FORMATION AND LEWIS SHALE. MEETEETSE FORMATION (AGE ABOUT 73 Ma) (Km)--Chalky-white to gray sandstone, yellow, green, and dark-gray bentonitic claystone, white tuff, and thin coal beds. LEWIS SHALE (AGE ABOUT 68 Ma) (Kle)--Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.
Mesozoic and Paleozoic rocks (Phanerozoic | Paleozoic Mesozoic | Carboniferous Mississippian-Late Pennsylvanian(?) Permian(?) Triassic(?) Jurassic(?) Cretaceous-Late)
MESOZOIC AND PALEOZOIC ROCKS (north Wyoming). Shown in small areas of complex structure. East Flank of Absaroka Range--Dinwoody Formation, Phosphoria Formation and related rocks., Tensleep Sandstone, and Amsden Formation (Lower Triassic through Upper Mississippian). East flank of Bighorn Mountains--Cloverly, Morrison, Sundance, Gypsum Spring, Chugwater and Gypsum Spring Formations (Lower Cretaceous through Permian). MESOZOIC AND PALEOZOIC ROCKS (south Wyoming). Shown in small areas of complex structure. South side of Granite Mountains north of Green Mountain--Nugget Sandstone, Chugwater and Goose Egg Formations, Tensleep Sandstone, and Amsden Formation (Jurassic? through Upper Mississippian). South flank of Ferris Mountains--Nugget Sandstone and Chugwater and Goose Egg Formation (Jurassic? through Permian). Northeast flank of Seminoe Mountians--Cloverly, Morrison, Sundance, Chugwater, and Goose Egg Formations (Lower Cretaceous through Permain). West flank of Sierra Madre--Chugwater, Goose Egg, Casper, and Fountain Formations (Upper Triassic through Middle Pennsylvanian). East Flank of Laramie Mountains--Cloverly, Morrison, Sundance, Chugwater, and Goose Egg Formations, and, east of fault in T. 19 N., Casper Formation (Lower Creatceous through Middle Pennsylvanian). NUGGET SANDSTONE in south--Gray to dull-red, massive to coarsely crossbedded quartz sandstone.
Middle and Lower Eocene Rocks (Phanerozoic | Cenozoic | Tertiary | Eocene-Early Eocene-Middle)
MIDDLE AND LOWER EOCENE ROCKS--Equivalent to Aycross (Ta) and Wind River (Twdr) Formations. AYCROSS FORMATION (ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP)--Brightly variegated bentonitic claystone and tuffaceous sandstone, grading laterally into greenish-gray sandstone and claystone. In and east of Jackson Hole contains gold-bearing lenticular quartzite conglomerate. WIND RIVER FORMATION--Variegated claystone and sandstone; lenticular conglomerate.
Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early)
MOWRY (Kmr) AND THERMOPOLIS SHALES. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. THERMOPOLIS SHALE--Black soft fissile shale; Muddy Sandstone Member at top.
Niobrara and Frontier Formations, and Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late)
NIOBRARA (Kn) AND FRONTIER (Kf) FORMATIONS, AND MOWRY (Kmr) AND THERMOPOLIS SHALES. NIOBRARA FORMATION (AGE ABOUT 83 Ma)--Light-colored limestone and gray to yellow speckled limy shale. FRONTIER FORMATION--Gray sandstone and sandy shale. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. THERMOPOLIS SHALE--Black soft fissile shale; Muddy Sandstone Member at top.
Oligocene and (or) Upper and Middle Eocene rocks (Phanerozoic | Cenozoic | Tertiary | Eocene Oligocene)
OLIGOCENE AND (OR) UPPER AND MIDDLE EOCENE ROCKS--Light-gray tuff, arkosic sandstone, and lenticular conglomerate.
Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late)
PIERRE SHALE (AGE 72 TO 78 Ma)--Dark-gray concretionary marine shale; contains several bentonite beds.
Salt Lake Formation (Phanerozoic | Cenozoic | Tertiary | Miocene Pliocene)
SALT LAKE FORMATION--White, gray, and green limy tuff, siltstone, sandstone, and conglomerate.
Shooting Iron Formation (Phanerozoic | Cenozoic | Tertiary | Pliocene)
SHOOTING IRON FORMATION--Greenish-gray to pink tuffaceous lacustrine and fluviatile claystone and siltstone, fine-grained sandstone, and conglomerate.
Steele Shale (Phanerozoic | Mesozoic | Cretaceous-Late)
STEELE SHALE (AGE ABOUT 78 TO 82 Ma)--Gray soft marine shale containing numerous bentonite beds and thin lenticular sandstone.
Steele Shale and Niobrara Formations (Phanerozoic | Mesozoic | Cretaceous-Late)
STEELE SHALE (Ks) AND NIOBRARA FORMATIONS (Kn). STEELE SHALE (AGE ABOUT 78 TO 82 Ma)--Gray soft marine shale containing numerous bentonite beds and thin lenticular sandstone. NIOBRARA FORMATION (AGE ABOUT 83 Ma)--Light-colored limestone and gray to yellow speckled limy shale.
Teewinot Formation (Phanerozoic | Cenozoic | Tertiary | Miocene)
TEEWINOT FORMATION (AGE ABOUT 9 Ma)--White lacustrine clay, tuff, and limestone. In thrust belt includes conglomerate.
Volcanic Conglomerate (Phanerozoic | Cenozoic | Tertiary | Eocene)
VOLCANIC CONGLOMERATE--Dark-brown to black conglomerate, poorly bedded, composed chiefly of basalt clasts in a basaltic tuff matrix.
Washakie Formation (Phanerozoic | Cenozoic | Tertiary | Eocene (43-44 Ma))
WASHAKIE FORMATION (AGE ABOUT 43 TO 44 Ma)--Gray, green, tan, and dull-red tuffaceous arkosic sandstone and claystone.
White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene (31-35 Ma))
WHITE RIVER FORMATION (AGE 31 TO 35 Ma)--White to pale-pink blocky tuffaceous claystone and lenticular arkosic conglomerate.
White River Formation--Brule Member (Phanerozoic | Cenozoic | Tertiary | Oligocene )
WHITE RIVER FORMATION Brule Member--Pale-pink to white blocky tuffaceous claystone and lenticular sandstone. Locally includes the Upper Conglomerate Member (Twru).
White River Formation--Chadron Member (Phanerozoic | Cenozoic | Tertiary | Oligocene )
WHITE RIVER FORMATION Chadron Member--Light-gray to dark-red tuffaceous claystone, sandstone, and lenticular conglomerate.
White River Formation--Upper conglomerate member (Phanerozoic | Cenozoic | Tertiary | Oligocene )
WHITE RIVER FORMATION Upper conglomerate member--Light-gray soft conglomeratic tuffaceous sandstone and conglomerate of Precambrian clasts.

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