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Geologic units containing basalt

Earth material > Volcanic rock > Mafic volcanic rock
Basalt
A volcanic rock defined modally by Q/(Q+A+P) < 20% or F/(F+A+P) < 10%, P/(A+P) > 90%, and M > 35.
Subtopics:
Tholeiite
Hawaiite
Alkaline basalt

Arizona - California - Colorado - Connecticut - Idaho - Massachusetts - Maine - Michigan - Minnesota - North Carolina - New Hampshire - New Jersey - New Mexico - Nevada - New York - Oklahoma - Oregon - South Dakota - Tennessee - Texas - Utah - Virginia - Washington - Wisconsin - Wyoming
Arizona
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 Tertiary to Late Cretaceous volcanic rocks (Late Cretaceous to Early Tertiary)
Rhyolite to andesite and closely associated sedimentary and near-surface intrusive rocks; commonly dark gray to dark greenish gray or greenish brown. In the ranges west of Tucson, this unit includes thick welded ash-flow tuffs. Volcanic rocks of this unit are inferred to be derived from vents and volcanoes above magma chambers that solidified to form the granitic rocks of map unit TKg. These rocks are restricted to southeastern Arizona except for a small outcrop near Bagdad. (50-82 Ma)
Holocene to middle Pliocene basaltic rocks (Middle Pliocene to Holocene)
Mostly dark-colored basaltic lava and cinders young enough that some original volcanic landforms are still apparent. Includes a small amount of andesite, dacite, and rhyolite. Rocks of this map unit are largely restricted to six areas widely distributed in Arizona: San Francisco and Uinkaret volcanic fields in northern Arizona (0-4 Ma); Springerville (0-4 Ma) and San Carlos (0-2 Ma) volcanic fields in east-central Arizona; and San Bernardino (0-1 Ma) and Sentinel (1-4 Ma) volcanic fields in southern Arizona. Rocks of this unit are also present in the extreme southwestern part of Arizona where they were erupted at the edge of the Pinacate volcanic field (0-2 Ma) in northwestern Sonora. (0-4 Ma)
Holocene to middle Pliocene volcanic rocks (Middle Pliocene to Holocene)
Rhyolite to andesite deposited as a sequence of lava flows and associated rocks; generally light to medium gray, tan, or reddish brown. These rocks are part of the San Francisco volcanic field. (0-4 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)
Late to middle Miocene basaltic rocks (Middle to Late Miocene)
Mostly dark, mesa-forming basalt deposited as lava flows. Rocks of this unit are widely exposed south of Camp Verde (Hickey Formation basalts), in the Mohon Mountains north of Bagdad, "The Mesa" east of Parker, and at other scattered locations in western Arizona. Rocks of this unit were not tilted by middle-Tertiary normal faulting except in a narrow belt from north of Phoenix to the northwest corner of the state. (8-16 Ma)
Middle Miocene to Oligocene volcanic and sedimentary rocks, undivided (Oligocene to Middle Miocene)
Sequences of diverse volcanic rocks with abundant interbedded sedimentary rocks. (11-32 Ma)
Middle Miocene to Oligocene volcanic rocks (Oligocene to Middle Miocene)
Lava, tuff, fine-grained intrusive rock, and diverse pyroclastic rocks. These compositionally variable volcanic rocks include basalt, andesite, dacite, and rhyolite. Thick felsic volcanic sequences form prominent cliffs and range fronts in the Black (Mohave County), Superstition, Kofa, Eagletail, Galiuro, and Chiricahua Mountains. This unit includes regionally extensive ash-flow tuffs, such as the Peach Springs tuff of northwestern Arizona and the Apache Leap tuff east of Phoenix. Most volcanic rocks are 20-30 Ma in southeastern Arizona and 15 to 25 Ma in central and western Arizona, but this unit includes some late Eocene rocks near the New Mexico border in east-central Arizona. (11-38 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)
Oligocene to Paleocene[?] sedimentary rocks (Paleocene(?) to Oligocene)
Light colored, weakly to moderately consolidated conglomerate and sandstone deposited largely or entirely before mid-Tertiary volcanism and extensional faulting. Most sediment was deposited by early Cenozoic streams that flowed northeastward onto the Colorado Plateau from areas to the southwest that are now lower in elevation than the Plateau. Sediments of this map unit, other than the Chuska Sandstone in northeasternmost Arizona, are commonly referred to as "rim gravels" because they now rest on or near the Mogollon Rim, which is the southwestern edge of the Colorado Plateau. (30-65 Ma)
Pliocene to late Miocene basaltic rocks (Late Miocene to Pliocene)
Mostly dark, inconspicuously flat, low-lying or mesa-forming basalt deposited as lava flows. Rocks included in this unit are located almost entirely in the large volcanic fields south and west of Flagstaff, in smaller fields in northwesternmost Arizona, and in the Hopi Buttes volcanic field on the Navajo and Hopi Indian Reservations north of Holbrook. Original volcanic landforms have been obscured by erosion. (4-8 Ma)
Pliocene to middle Miocene volcanic rocks (Middle Miocene to Pliocene)
Rhyolite to andesite deposited as lava flows and related rocks associated with basaltic rocks of map units Tby and Tb. (2-12 Ma)
California
Cretaceous marine rocks (in part nonmarine), unit 3 (Mescal Range) (Middle Jurassic to late Early Cretaceous)
Undivided Cretaceous sandstone, shale, and conglomerate; minor nonmarine rocks in Peninsular Ranges
Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains) (Triassic to Late Jurassic)
Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks
Mesozoic volcanic rocks, unit 1 (Coast Ranges) (Jurassic to Cretaceous)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Mesozoic volcanic rocks, unit 3 (Mojave Desert, Death Valley area, and Eastern Sierra Nevada) (Triassic to Cretaceous)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Miocene nonmarine rocks (Oligocene to Pleistocene)
Sandstone, shale, conglomerate, and fanglomerate; in part Pliocene and Oligocene.
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 metavolcanic rocks, unit 2 (Northeastern Sierra Nevada) (Devonian and Permian)
Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks
Quaternary pyroclastic and volcanic mudflow deposits, unit 1 (Cascade Volcanic Field) (Quaternary)
Quaternary pyroclastic and volcanic mudflow deposits.
Quaternary pyroclastic and volcanic mudflow deposits, unit 1, questionably identified (Cascade Volcanic Field) (Quaternary)
Quaternary pyroclastic and volcanic mudflow deposits.
Quaternary pyroclastic and volcanic mudflow deposits, unit 4 (Sierra Nevada) (Quaternary)
Quaternary pyroclastic and volcanic mudflow deposits.
Quaternary volcanic flow rocks, unit 1 (Cascade Volcanic Field) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 1, questionably identified (Cascade Volcanic Field) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 2 (Long Valley Caldera) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 3 (Clear Lake Volcanic Field) (Quaternary (0-4 Ma))
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 5 (Coso Volcanic Field) (Quaternary (0-4 Ma))
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 6 (Sierra Nevada) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 7 (Mojave Desert) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 7, questionably identified (Mojave Desert) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Quaternary volcanic flow rocks, unit 8 (Peninsular Ranges) (Quaternary)
Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.
Recent (Holocene) volcanic flow units, unit 4 (Mojave Desert) (Holocene)
Recent (Holocene) volcanic flow rocks; minor pyroclastic deposits; in part Pleistocene.
Tertiary-Cretaceous Coastal Belt Rocks (Late Cretaceous to Pliocene)
Sandstone, shale and minor conglomerate in coastal belt of northwestern California; included by some in Franciscan Complex. Previously considered Cretaceous, but now known to contain early Tertiary microfossils in places.
Tertiary intrusive rocks (hypabyssal), unit 1 (Cascades Volcanic Field) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 2 (Quien Sabe Volcanic Field) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 4 (Tranquillon-Obispo) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 5 (Southern California Basin) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 6 (Southern Mojave Desert) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary intrusive rocks (hypabyssal), unit 7 (Northern Mojave Desert) (Tertiary)
Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.
Tertiary pyroclastic and volcanic mudflow deposits, unit 2 (Berkeley Hills) (Tertiary (8-12 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 5 (Southern California Basin) (Tertiary (8-25 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 6 (Jacumba) (Tertiary (12-19 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 7 (Southern Mojave Desert) (Tertiary (8-28 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 8 (Northern Mojave Desert) (Tertiary (4-22 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary pyroclastic and volcanic mudflow deposits, unit 9 (Cascade Range) (Tertiary (2-24 Ma))
Tertiary pyroclastic and volcanic mudflow deposits.
Tertiary volcanic flow rocks, unit 10 (Alverson) (Tertiary (14-18 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 11 (Jacumba) (Tertiary (12-19 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 12 (Sam Emigdio) (Tertiary (22-25 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 13 (Plush Ranch-Vasquez-Diligencia) (Tertiary (19-23 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 14 (Tranquillon-Obispo) (Tertiary (16-18 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 15 (Southern Mojave Desert) (Tertiary (8-28 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 16 (Northern Mojave Desert) (Tertiary (4-22 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 17 (Cascade Range) (Tertiary (2-24 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 19 (Lovejoy) (Tertiary (14-16 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 1 (Quien Sabe-Burdell Mountain) (Tertiary (9.5-13 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 3 (Sonoma Volcanic Field) (Tertiary (3-7 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 4 (Berkeley Hills) (Tertiary (8-12 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 5 (San Luis Reservoir) (Tertiary (7.5-9.5 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 6 (Page Mill-Mindego) (Tertiary (12-15 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 8 (Southern California Basin) (Tertiary (8-25 Ma; most near 15))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Tertiary volcanic flow rocks, unit 9 (Caliente) (Tertiary (14-18 Ma))
Tertiary volcanic flow rocks; minor pyroclastic deposits.
Undivided pre-Cenozoic metavolcanic rocks, unit 1 (Southwestern Sierra Nevada) (Ordovician(?) to Permian(?))
Undivided pre-Cenozoic metavolcanic rocks. Includes latite, dacite, tuff, and greenstone; commonly schistose.
Upper Cretaceous marine rocks (?) (Cretaceous)
Upper Cretaceous sandstone, shale, and conglomerate (?)
Colorado
Basalt flows (Phanerozoic | Cenozoic | Quaternary)
Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary)
Includes basalts of Hinsdale Fm in San Juan Mountains - Servilleta Fm in San Luis Valley and many other occurrences
Basaltic flows in Denver Fm near Golden (Phanerozoic | Cenozoic | Tertiary)
Basaltic intrusive rocks related to basalt flows (Phanerozoic | Cenozoic | Tertiary)
In dikes and plugs
Felsic and hornblendic gneisses, either separate or interlayered (Proterozoic | Paleoproterozoic)
Includes metabasalt, metatuff, and interbedded metagraywacke; locally contains interlayered biotite gneiss. Derived principally from volcanic rocks
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
Connecticut
Buttress Dolerite (Middle? Jurassic)
Buttress Dolerite - Dark-gray to greenish-gray (weathers brown or gray), medium- to fine-grained, commonly porphyritic, generally massive with well-developed columnar jointing, grading from basalt near contacts to fine-grained gabbro in the interior, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.
Buttress Dolerite (uncertain) (Middle? Jurassic)
Buttress Dolerite (uncertain)- Dark-gray to greenish-gray (weathers brown or gray), medium- to fine-grained, commonly porphyritic, generally massive with well-developed columnar jointing, grading from basalt near contacts to fine-grained gabbro in the interior, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.
Hampden Basalt (Lower Jurassic)
Hampden Basalt - Greenish-gray to black (weathers bright orange to brown), fine- to medium-grained, grading from basalt near contacts to fine-grained gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass.
Holyoke Basalt (Lower Jurassic)
Holyoke Basalt - Greenish-gray to black (weathers bright orange to brown), fine- to coarse-grained, grading from basalt near contacts to gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass.
Talcott Basalt (Lower Jurassic)
Talcott Basalt - Greenish-gray to black (weathers bright orange to brown), fine- to medium-grained, grading from basalt near contacts to fine-grained gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass. Pillows in many places; volcanic breccia with fragmentary pillows in others.
West Rock Dolerite (Lower Jurassic)
West Rock Dolerite - Dark-gray to greenish-gray (weathers bright orange to brown), medium- to fine-grained, grading from basalt near contacts to fine-grained gabbro in the interior, generally massive with well-developed columnar jointing, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.
West Rock Dolerite (uncertain) (Lower Jurassic)
West Rock Dolerite (uncertain) - Dark-gray to greenish-gray (weathers bright orange to brown), medium- to fine-grained, grading from basalt near contacts to fine-grained gabbro in the interior, generally massive with well-developed columnar jointing, composed of plagioclase and pyroxene with accessory opaques and locally devitrified glass, quartz, or olivine.
Idaho
Basalt dikes; Miocene basaltic feeder dikes of subunit ib; Columbia Plateau (Miocene)
Miocene intrusions including basalt feeder dikes and sills of western Idaho.
Basalt flows and incidental andesite, and latite flows; Miocene mafic to intermediate volcanics; subunits are Tmib, Tm1b, Tm2b, Tm3b; Columbia Plateau, Owyhee Plateau (Miocene)
Miocene plateau basalt flows of western Idaho; subdivisions are (Tm3b, Tm2b, Tm1b).
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.
Basalt lava flows; Middle Miocene flood-basalt flows of subunit 2b; Columbia Plateau (Miocene)
Miocene basalt flows of western Idaho; commonly finely crystalline and exposed on upper slopes.
Basalt lava flows; Middle to Late Miocene local basalt flows of subunit 3b; Columbia Plateau (Late Miocene)
Upper Miocene valley-filling basalt flows of western 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.
Intrusive andesite, basalt, and diorite; Quaternary to Pliocene subvolcanic intrusions; southeastern Idaho (Quaternary to Pliocene)
Rhyolite ignimbrites, basalt flows, andesitic flows and tuffs, mudstone, conglomerate, and limestone; Quaternary to Tertiary volcanics and sediments; east-central Idaho (Pliocene)
Pliocene silicic welded tuff, ash, and flow rock; most common in southwestern Idaho.
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.
Trachyandesite, latite, trachybasalt flows, dikes, and volcaniclastic debris; Eocene intermediate volcanics; central Idaho, southern Challis volcanic field (Eocene)
Eocene mixed silicic and basaltic volcanic ejecta, flows and reworked debris.
Massachusetts
Newbury Volcanic Complex (Lower Devonian and Upper Silurian)
Newbury Volcanic Complex - Lower members. Basalt, andesite, rhyolite, and tuff.
Washington Gneiss (Proterozoic Y)
Washington Gneiss - Coarse- to medium-grained hornblende-garnet amphibolite, hornblende-plagioclase gneiss and phlogopite-hornblende-plagioclase amphibolite (metabasalt).
Maine
Cambrian Caucomgomoc Lake Formation, basalt member (Cambrian)
Cambrian Caucomgomoc Lake Formation, basalt member
Cambrian Hurricane Mountain Formation, Amphibolite and Greenschist (Cambrian)
Cambrian Hurricane Mountain Formation, amphibolite and greenschist
Devonian Eastport Formation basalt member (Devonian)
Devonian Eastport Formation basalt member
Devonian Perry Formation basalt member (Devonian)
Devonian Perry Formation basalt member - Matagamon Sandstone, Perry Formation, Basalt Member
Devonian - Silurian Allagash Lake Formation, basalt and mixed sedimentary rocks (Devonian - Silurian)
Devonian - Silurian Allagash Lake Formation, basalt and mixed sedimentary rocks
Ordovician Bluffer Pond formation (Ordovician)
Ordovician Bluffer Pond formation
Ordovician - Cambrian Hurd Mountain formation basalt member (Ordovician - Cambrian)
Ordovician - Cambrian Hurd Mountain formation basalt member
Ordovician Dry Wall Volcanic rocks (Ordovician)
Ordovician Dry Wall Volcanic rocks
Ordovician Kamankeag Formation basalt and graywacke member (Ordovician)
Ordovician Kamankeag Formation basalt and graywacke member
Ordovician Lobster Mountain volcanic complex basalt member (Ordovician)
Ordovician Lobster Mountain volcanic complex basalt member
Ordovician Munsungun Lake Formation (Ordovician)
Ordovician Munsungun Lake Formation
Ordovician Winterville Formation (Ordovician)
Ordovician Winterville Formation
Penobscot Formation, Basalt Member (Ordovician - Cambrian)
Penobscot Formation, Basalt Member
Precambrian Z rocks of Islesboro (Precambrian Z)
Precambrian Z rocks of Islesboro
Silurian Dennys formation basalt member (Silurian)
Silurian Dennys formation basalt member
Silurian Leighton Formation basalt member (Silurian)
Silurian Leighton Formation basalt member
Silurian - Ordovician Frontenac Formation Canada Falls volcanic member (Silurian - Ordovician)
Silurian - Ordovician Frontenac Formation Canada Falls volcanic member
Silurian rocks of the Fivemile Brook sequence (Silurian)
Silurian rocks of the Fivemile Brook sequence
Michigan
Badwater Greenstone (Early Proterozoic)
Badwater Greenstone - Dark-greenish-gray, pillowed to massive tholeiitic basalt and pyroclastic rocks. Correlated with the Hemlock Formation on basis of geology and similarity in chemical composition.
Mafic metavolcanic rocks (Early Proterozoic)
Mafic metavolcanic rocks - Dominantly tholeiitic basalt and basaltic andesite flows and tuffs; associated with sheet dikes, massive and layered metagabbro, and ultramafic rocks. In northeastern Wisconsin, rocks have been named the Quinnesec Formation.
Menominee Group; Blair Creek Formation (Early Proterozoic)
Menominee Group; Blair Creek Formation - Dominantly dark-gray, massive, porphyritic tholeiitic basalt. Includes a basal conglomerate and a lean iron-formation in middle of formation
Menominee Group; Hemlock Formation (Early Proterozoic)
Menominee Group; Hemlock Formation - Predominantly mafic to intermediate volcanic flows and pyroclastic rocks with interlayered slate and tuff beds
Porcupine Volcanics (Middle Proterozoic)
Porcupine Volcanics - Generally dark-gray basalt, andesite, and felsite flows and subordinate interflow sedimentary rocks
Portage Lake Volcanics (Middle Proterozoic)
Portage Lake Volcanics - Lava flows, mostly basalt, andesite and felsite flows and subordinate interflow sedimentary rocks.
Powder Mill Group; Kallander Creek Volcanics (Middle Proterozoic)
Powder Mill Group; Kallander Creek Volcanics - Basalt, andesite and lesser rhyolite flows. Basalt flows near base of the formation contain plagioclase phenocrysts, some in radiating clusters
Powder Mill Group; Siemens Creek Volcanics (Middle Proterozoic)
Powder Mill Group; Siemens Creek Volcanics - Dark-gray basalt and minor porphyritic andesite. Generally strongly magnetic with reversed remanent magnetism. Underlain by a thin unit of quartzose sandstone (Bessemer Quartzite).
Minnesota
Chengwatana Volcanic Group (Middle Proterozoic)
Chengwatana Volcanic Group - Basalt and related volcanogenic and interflow sedimentary rocks in east-central Minnesota
Mafic metavolcanic rocks (Late Archean)
Mafic metavolcanic rocks - Dominantly basalt that contains thin sedimentary units, including iron-formation. Includes parts of the Ely Greenstone and the Newton Lake Formation in northeastern Minnesota. Also includes metabasalt exposed in the Minnesota River Valley.
Migmatitic gneiss, amphibolite, and granite (Middle to Early Archean)
Migmatitic gneiss, amphibolite, and granite - Montevideo and Morton Gneisses (3600-3000 m.y.) in the Minnesota River Valley, southwestern Minnesota; McGrath Gneiss (2750 m.y.) east of Mille Lacs Lake; components of Hillman Migmatite southwest of Mille Lacs Lake; and Sartell Gneiss in Stearns County. Inferred to include various younger rocks, including granitoid intrusions in the Hillman Migmatite and pillowed basalt in poorly exposed areas of southwestern Minnesota.
North Shore Volcanic Group; Normally polarized volcanic rocks, undivided (Middle Proterozoic)
North Shore Volcanic Group; Normally polarized volcanic rocks, undivided - Basalt, andesitic basalt, rhyolite and related volcanogenic interflow sedimentary rocks along and inland from the North Shore of Lake Superior.
North Shore Volcanic Group; Reversely polarized volcanic rocks, undivided (Middle Proterozoic)
North Shore Volcanic Group; Reversely polarized volcanic rocks, undivided - Mixed tholeiitic diabasic and porphyritic basalt, trachybasalt, and rhyolite in far northeastern Minnesota and porphyritic and diabasic basalt near Duluth. Includes units of a basal quartz arenite, Puckwunge Sandstone and Nopeming Formation, in northeastern Minnesota and near Duluth, respectively.
North Shore Volcanic Group; Schroeder-Lutsen basalts (Middle Proterozoic)
North Shore Volcanic Group; Schroeder-Lutsen basalts - Predominantly ophitic olivine tholeiitic basalt unconformably over older, normally polarized volcanic rocks. Based on its stratigraphic position and geochemical affinities, the unit may be correlative with the Lake Shore traps of northern Michigan
North Carolina
Amphibolite (Cambrian/Late Proterozoic)
Amphibolite - equigranular, massive to well foliated, dioritic to basaltic dikes and sills; variably metamorphosed.
Amphibolite (Cambrian/Late Proterozoic)
Amphibolite - equigranular, massive to well foliated, dioritic to basaltic dikes and sills; variably metamorphosed.
Grandfather Mountain Formation; Metasiltstone (Late Proterozoic)
Greenstone - schistose to massive, amygdaloidal; interlayered with metasedimentary rocks. Includes Montezuma Member (metabasalt) in upper part.
New Hampshire
Basalt (Cretaceous )
Basalt - Black, chiefly massive to porphyritic. Includes minor rhyolitic ignimbrite and andesitic tuff. Part of Ossipee Mountain Complex of Kingsley (1931)
Ironbound Mountain Formation, Basaltic to andesitic member (Lower Devonian)
Ironbound Mountain Formation, Basaltic to andesitic member.
New Jersey
Hook Mt. Basalt (Lower Jurassic)
Hook Mt. Basalt (Olsen, 1980) - Light- to dark-greenish-gray, medium- to coarse-grained, amygdaloidal basalt composed of plagioclase (typically An65 and commonly porphyritic), clinopyroxene (augite and pigeonite), and iron-titanium oxides such as magnetite and ilmenite. Locally contains small spherical to tubular cavities (gas-escape vesicles), some filled by zeolite minerals or calcite. Consists of two major flows. Base of lowest flow is intensely vesicular. Tops of flows are weathered and vesicular. Maximum thickness is about 110 m (360 ft) (Olsen and others, 1989).
Metabasalt (Late Proterozoic)
Metabasalt - Sequence of conformably layered volcanic rocks of fine-grained to aphanitic, greenish-gray, retrogressively metamorphosed greenstone, greenschist, and basalt. Greenschist contains clots and lenses of blue quartz and abundant sulfide. Unit does not crop out and is known only from subsurface borings and artificial exposures. Interpreted to be Late Proterozoic by Volkert and Drake (1993) on the basis of geochemical similarity to Late Proterozoic metadiabase dikes in New Jersey Highlands.
Orange Mountain Basalt (Lower Jurassic)
Orange Mountain Basalt (Olsen, 1980) - Dark-greenish-gray to greenish-black basalt composed mostly of calcic plagioclase (typically An65) and clinopyroxene (augite and pigeonite); crystals are generally less than 1 mm (0.04 in) long. Consists of three major flows. The flows are separated in places by a weathered zone or by a thin, up to 3-m- (10-ft-) thick bed of red siltstone (not shown on map) or volcaniclastic rock. Lowest flow is generally massive and has widely spaced curvilinear joints; columnar joints in lowest flow become more common toward the northeast. Middle flow is massive or has columnar jointing. Lower part of the uppermost flow has pillow structures; upper part has pahoehoe flow structures. Tops and bottoms of flow layers are vesicular. Maximum thickness is about 182 m (597 ft).
Orange Mountain Basalt (Lower Jurassic)
Orange Mountain Basalt - Basalt, fine-grained to aphanitic, dark-greenish-gray, composed mostly of calcic plagioclase and augite; crystals smaller than 1 mm (0.04 in). Unit consists of three major tholeiitic lava-flow sequences, each about 80 m (262 ft) thick. Lowest flow is generally massive with widely spaced curvilinear joints; middle flow is massive or has columnar joints; lower part of uppermost flow has pillow structures and upper part has pahoehoe flow structures. Thickness in map area is about 160 m (525 ft).
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
andesites and basaltic andesites (Phanerozoic | Cenozoic | Tertiary)
Upper Oligocene andesites and basaltic andesites (26-29 Ma); includes La Jara Peak Basaltic Andesite, Uvas Basalt, the basaltic andesite of Poverty Creek, and Squirrel Springs Andesite, the Razorback, Bear Springs Canyon, Salt Creek, Gila Flat, and Middle Mountain Formations, and the Alum Mountain Group; locally includes more silicic flows
basalt and andesite flows and vent deposits (Phanerozoic | Cenozoic | Quaternary)
Basalt and andesite flows and locally vent deposits
basalt and andesite flows, Miocene (Phanerozoic | Cenozoic | Tertiary)
Basalt and andesite flows; Miocene
basalt and andesite flows, Neogene (Phanerozoic | Cenozoic | Tertiary)
Basalt and andesite flows; Neogene. Includes flows interbedded with Santa Fe and Gila Groups
basalt and andesite flows, Pliocene (Phanerozoic | Cenozoic | Tertiary)
Basalt and andesite flows; Pliocene
basaltic and andesitic volcanics interbedded with sedimentary units (Phanerozoic | Cenozoic | Tertiary Quaternary)
Basaltic and andesitic volcanics interbedded with Pleistocene and Pliocene sedimentary units
basaltic andesites (Phanerozoic | Cenozoic | Tertiary)
Lower Miocene and uppermost Oligocene basaltic andesites (22-26 Ma). Includes Bearwallow Mountain Andesite and basaltic andesite of Mangas Mountain
basaltic volcanics (Phanerozoic | Cenozoic | Quaternary)
Basaltic volcanics; tuff rings, cinders, and proximal lavas
basalt or basaltic andesite (Phanerozoic | Cenozoic | Quaternary)
Basalt or basaltic andesite; middle and lower Pleistocene
Gila Group (Phanerozoic | Cenozoic | Tertiary Quaternary)
Gila Group. Includes Mimbres Formation and several informal units in southwestern basins; Middle Pleistocene to uppermost Oligocene
Hinsdale Basalt (Phanerozoic | Cenozoic | Tertiary)
Hinsdale Basalt; northern Taos and eastern Rio Arriba Counties; basalt flows interbedded with Los Pinos Formation
Los Pinos Formation of Lower Santa Fe Group (Phanerozoic | Cenozoic | Tertiary)
Los Pinos Formation of Lower Santa Fe Group (Miocene and upper Oligocene); includes Carson Conglomerate (Dane and Bachman, 1965) in Tusas Mountains-San Luis Basin area
Nevada
Andesite and basalt flows (Early Miocene to Early Pliocene)
ANDESITE AND BASALT FLOWS-Mostly in about 17 to about 6 m.y. age range. In Humboldt County, locally includes rocks as old as 21 m.y. May include rocks younger than 6 m.y. in places
Banbury Formation (Middle Miocene to Late Miocene)
BANBURY FORMATION-Basalt, gravel, and tuffaceous sediments locally. Northeast Humboldt County and northwest Elko County
Basalt flows (Late Miocene to Middle Miocene)
BASALT FLOWS
Basalt flows (Miocene to Quaternary)
BASALT FLOWS-Locally includes maar deposits
Gabbroic complex (Early Jurassic to Middle Jurassic)
GABBROIC COMPLEX (Lower and Middle Jurassic)-Includes gabbro, basalt, and synorogenic quartz sandstone (Boyer Ranch Formation). Churchill and Pershing Counties
Intrusive rocks of mafic and intermediate composition (Miocene to Quaternary)
INTRUSIVE ROCKS OF MAFIC AND INTERMEDIATE COMPOSITION
Koipato Group and related rocks (Permian to Early Triassic)
KOIPATO GROUP AND RELATED ROCKS (Lower Triassic)-Altered andesitic flows, rhyolitic tuffs and flows, and clastic rocks. Includes rocks mapped by Silberling (1959) as Pablo Formation and originally considered to be Permian in the Shoshone Mountains, Nye County. Includes Tallman Fanglomerate (Permian?) in Humboldt County
Older basalt rocks (Early Oligocene to Early Miocene)
OLDER BASALT ROCKS
Shale, sandstone, volcanogenic clastic rocks, andesite, rhyolite, and locally thick carbonate units (Late Triassic to Early Cretaceous)
SHALE, SANDSTONE, VOLCANOGENIC CLASTIC ROCKS, ANDESITE, RHYOLITE, AND LOCALLY THICK CARBONATE UNITS-Undivided sequence locally containing recognizable equivalents of the Luning and Dunlap Formations
Volcanic flows and flow breccias, chiefly of andesitic composition, tuffs, sparse sandstone and graywacke (Permian to Jurassic)
VOLCANIC FLOWS AND FLOW BRECCIAS, CHIEFLY OF ANDESITIC COMPOSITION, TUFFS, SPARSE SANDSTONE AND GRAYWACKE-Includes Happy Creek Volcanic Series and related rocks in Humboldt County and similar rocks in Washoe and Pershing Counties; includes andesite breccias and volcanogenic sedimentary rocks in Mineral County
New York
Greenstones and tuffs and/or basalt (Cambrian?)
Greenstones and tuffs and/or basalt
Ladentown diabase and baslatic lava (Upper Triassic)
Ladentown diabase and basaltic lava
Lamprophyre, diabase, and albite-basalt dikes (Jurassic - Lower Cretaceous)
Lamprophyre, diabase, and albite-basalt dikes - not shown in Proterozoic terrane.
Oklahoma
Basalt (Phanerozoic | Cenozoic | Tertiary | Pliocene)
CIMARRON- Dark, dense to vesicular volcanic rock 50 to 85 +/- feet thick forming cap rock of Black Mesa.
Oregon
Andesite (Holocene and Pleistocene) (Quaternary)
Forms major stratovolcanoes dominantly of aphyric to porphyritic basaltic andesite and andesite; phenocrysts are principally pyroxene, olivine, plagioclase, and, rarely, hornblende. Locally includes dacite and minor basalt
Andesitic and basaltic rocks on Steens Mountain (Miocene)
Called Steens Mountain Volcanic Series by Walker (1977); Steens Mountain Andesitic Series of Fuller (1931) and Williams and Compton (1953)
Basalt and andesite intrusions (Pliocene, Miocene, and Oligocene?) (Oligocene(?) to Pliocene)
Sills, plugs and dikes of basaltic andesite, basalt, and andesite. Mostly represents feeders, exposed by erosion, for flows and flow breccias of units Tba and Trb. Includes a few dikes of hornblende and plagioclase porphyritic andesite, commonly altered, and aphyric basaltic andesite that probably were feeders for parts of unit Tub
Basalt and basaltic andesite (Holocene and Pleistocene) (Pleistocene to Holocene)
Thin flows of aphyric and porphyritic basalt and basaltic andesite, and open-textured (dikytaxitic), generally nonporphyritic, subophitic olivine basalt that commonly is highly feldspathic. Also includes some dissected intracanyon flows of porphyritic basalt and related vent complexes. Pressure ridges and tumuli on upper surfaces well preserved. Occurs principally along crest of Cascade Range; also in areas near and east of Newberry volcano, along southeast margin of Harney Basin, and in Rome Basin. Older than Mazama ash deposits (Qma, Qmp; approximately 6,800 yr old; 14C)
Basalt and basaltic andesite (Pleistocene and Pliocene) (Pliocene to Pleistocene)
Flows, flow breccia, and pyroclastic deposits. Flows are aphanitic to finely crystalline, commonly diktytaxitic, and aphyric to porphyritic. Textures are mostly intergranular grading to intersertal; some andesite flows are finely trachytic and a few basalt flows are subophitic. Phenocrysts, mostly unaltered, include bytownite and labradorite, olivine, calcic augite, and hypersthene. Flows and breccia form shields, lava cones, and valley fill; in places greatly dissected and modified by fluvial erosion. Includes Boring Lava of Trimble (1963) and Hampton (1972) and Battle Ax Basalts of Thayer (1936). Potassium-argon ages from this unit range from about 1.2 to 3.9 Ma; in places difficult to distinguish from youngest flows of unit Trb
Basaltic and andesitic rocks (upper and middle Miocene) (Middle to Late Miocene)
Lava flows and flow breccia of hypersthene and olivine andesite, basaltic andesite containing plagioclase and pyroxene phenocrysts, and basalt; many flows contain phenocrysts of both hypersthene and augite. Includes interbedded volcaniclastic and epiclastic rocks mostly of andesitic composition, but partly of dacitic or rhyodacitic composition. Includes really restricted flows of silicic andesite or dacite. Upper part of unit mostly unaltered, although olivine crystals are locally altered to clay minerals. Lower parts commonly altered; secondary minerals include nontronite and saponite, chalcedony, calcite, and zeolites. Older parts of this unit locally are propylitically altered adjacent to larger intrusions. Erupted mostly from widespread, northwest- and north-trending dikes and dike swarms and related plugs and lava cones. Potassium-argon ages range from about 10 Ma to about 17 Ma. Much of this unit was previously assigned to the Sardine Formation (Peck and others, 1964), although the type locality of the Sardine Formation ("Sardine Series" as mapped by Thayer, 1939) may be older. Includes Elk Lake Formation (White, 1980a, 1980b), part of the Rhododendron Formation (Trimble, 1963; Wise, 1969), and andesite of Nohorn Creek of Hammond and others (1982)
Basaltic andesite and basalt (Holocene? and Pleistocene) (Quaternary)
Flows and flow breccia dominantly of basaltic andesite containing plagioclase, olivine, and pyroxene phenocrysts and olivine-bearing basalt representing part of the volcanic sequence of the High Cascade Range (Thayer, 1937). Unit mostly forms small shield volcanoes, gentle-sided lava cones, and, in places, intracanyon flows
Basaltic lava flows (Oligocene to Miocene)
Basaltic and basaltic andesite lava flows and breccia; grades laterally into rare bedded palagonitic tuff and breccia
Basaltic lava flows (Oligocene to Miocene)
Basaltic and basaltic andesite lava flows and breccia; grades laterally into rare bedded palagonitic tuff and breccia
Basaltic rocks (Late Eocene to Oligocene)
Probably part of Fisher Formation
Basalt (Pleistocene and Pliocene) (Pliocene to Pleistocene)
Thin flows and minor flow breccia of open--textured (diktytaxitic) olivine basalt in southeastern part of map area. Locally contains thin interbeds of sedimentary rocks. Grades laterally through palagonite tuff and breccia into sedimentary rocks (unit QTs)
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)
Clastic rocks and andesite flows (lower Oligocene?, Eocene, and Paleocene?) (Paleocene to Early Oligocene)
Mostly andesitic lava flows, domes, breccia, and small intrusive masses and lesser basaltic to rhyolitic rocks; interlayered saprolite, bedded volcaniclastic and epiclastic mudstone, claystone, siltstone, sandstone, conglomerate, and mudflow (lahar) deposits. Mostly consists of Clarno Formation of central Oregon and unnamed rocks of Basin and Range Province in south-central Oregon. Fossil plants and vertebrates in these rocks are Eocene in age. Andesite and basalt lava flows are typically slightly altered; most glass is devitrified and altered to clay minerals, zeolites, and secondary feldspar. Reliable K-Ar ages of rocks from unit range from about 54 Ma to about 37 Ma (Evernden and James, 1964; Fiebelkorn and others, 1983). A number of K-Ar ages on rocks shown on source maps as part of the Clarno Formation are in the range of about 36 to 19 Ma (Fiebelkorn and others, 1983). Although these rocks are lithologically similar to, but generally less altered than, rocks of the Clarno Formation, they are coeval with the John Day Formation. Most of these enigmatic rocks of Oligocene and early Miocene age are included in unit Tas. At base of unit in Blue Mountains Province, locally includes quartzose and feldspathic sandstone, siltstone, and shale largely of granitic or metamorphic provenance; fossil plants in these sedimentary rocks indicate an early Eocene or Paleocene age
Columbia River Basalt Group and related flows (Miocene) (Miocene)
Subaerial basalt and minor andesite lava flows and flow breccia; submarine palagonitic tuff and pillow complexes of the Columbia River Basalt Group (Swanson and others, 1979); locally includes invasive basalt flows. Flows locally grade laterally into subaqueous pillow-palagonite complexes and bedded palagonitic tuff and breccia. In places includes tuffaceous sedimentary interbeds. Joints commonly coated with nontronite and other clayey alteration products. Occurs principally in the Willamette Valley from Salem north to the Columbia River, and in the northern Coast Range. Unit includes correlative Cape Foulweather and Depoe Bay Basalts in the Coast Range (Snavely and others, 1973, 1976a, 1976b; Swanson and others, 1979; Wells and others, 1983). In Eastern Oregon, occurs principally in Deschutes-Umatilla Plateau and in the Blue Mountains. K-Ar ages range from about 6 to about 16.5 Ma (McKee and others, 1977; Swanson and others, 1979; Sutter, 1978; Lux, 1982). Locally separated into Tcs, Tcw, Tcg, Tcp, and Tci
Flows and clastic rocks, undifferentiated (Miocene) (Miocene)
Chiefly basaltic andesite and andesite lava flows and flow breccia containing plagioclase and pyroxene (hypersthene and augite) phenocrysts, mudflows (lahars), and volcanic conglomerates; locally includes some dacite flows. Includes lesser, coarse- to fine-grained epiclastic volcanic sedimentary rocks and ash-flow and air-fall tuffs. Partly equivalent in age to unit Tba and may be partly coeval with younger parts of unit Tstb. Locally altered adjacent to larger intrusions. The oldest radiometrically dated rocks assigned to this unit are about 17 Ma (Sutter, 1978); in part lapped by flows questionably assigned to unit Tba, radiometrically dated at about 10 Ma, and unconformably overlain by flows of unit Trb. Includes some of rocks formerly mapped as Sardine Formation and some mapped as Rhododendron Formation
Grande Ronde Basalt (middle and lower Miocene) (Early to Middle Miocene)
Flows of dark-gray to black, aphyric tholeiitic basalt, including both high- and low-Mg chemical types (Swanson and others, 1979). Potassium-argon ages mostly in the range of 15 to 17 Ma (Lux, 1982; Watkins and Baksi, 1974; Fiebelkorn and others, 1983)
Imnaha Basalt (lower Miocene) (Early Miocene)
Mostly coarse-grained, plagioclase porphyritic basalt; flows commonly contain zeolite amygdules and montmorillonitic alteration is widespread. Potassium-argon ages mostly 16 to 17 Ma (McKee and others, 1981)
Intrusive basalt and andesite (Pleistocene, Pliocene, and Miocene) (Miocene to Pleistocene)
Sills, plugs and dikes of basaltic andesite, basalt, and andesite. In the Cascade Range most of these represent feeders, exposed by erosion, for flows and flow breccias of units Tba and Trb and a few are feeders for units QTba and QTa; in foothills of western Cascades includes several sins and dikes that may represent feeders for flows in unit Tu. May include some invasive flows. Includes a few dikes of hornblende and plagioclase porphyritic andesite, commonly altered, that probably were feeders for parts of unit Tu
Late basalt (Holocene or upper Pleistocene) (Late Pleistocene to Holocene)
Thin flows of scoriaceous, mostly olivine-bearing basalt in southeast Oregon; upper surfaces of flows characterized by blocky, spiny, or pahoehoe structures and by pressure ridges and tumuli, all essentially unmodified by erosion. Occurs at Diamond and Jordan Craters, the Devils Garden (Peterson, 1965), Lava Mountain, east flank of Green Mountain, and Pumice Desert
Mafic and intermediate intrusive rocks (Pliocene and Miocene) (Miocene to Pliocene)
Dikes, plugs, and sills of basalt, diabase, gabbro, and lesser andesite that fed many of the Miocene basalt and andesite flows in units Tc and Tba. Some intrusions are rootless and are invasive into sedimentary sequences; includes related breccia and peperite. Includes the Monument dike swarm of northwestern Grant County (OR061), the Chief Joseph dike swarm principally in Baker and Wallowa Counties (OR093), the Steens Mountain dike swarm in Harney County (OR005; OR094; OR095) and numerous isolated intrusive bodies in southern Lake County and several intrusive masses in and near-vent flows in southern Malheur County (OR023;OR024). May also include some lower Pleistocene(?) rocks
Mafic and intermediate vent rocks (Pliocene? and Miocene) (Miocene to Pliocene)
Basaltic and andesitic agglomerate, breccia, scoria, cinders, flows, and intrusive masses forming lava cones and small shields
Mafic and intermediate vent rocks (Pliocene? and Miocene) (Miocene to Pliocene)
Basaltic and andesitic agglomerate, breccia, scoria, cinders, flows, and intrusive masses forming lava cones and small shields
Mafic vent and intrusive rocks (Eocene?) (Eocene)
Mostly plugs, dikes, and irregular intrusive bodies of basaltic andesite and porphyritic hornblende or pyroxene andesite. Represents some of vents for unit Tca and possibly for unit Tas
Mafic vent complexes (Miocene) (Miocene)
Intrusive plugs and dike swarms and related near-vent flows, breccias, cinders, and agglutinate of basaltic andesite, basalt, and andesite; commonly in the form of eroded piles of red, iron-stained thin flows, cinders, and agglutinate cut by mafic intrusions
Mafic vent complexes (Pleistocene, Pliocene, and Miocene?) (Late Miocene to Pleistocene)
Plugs, dikes, and related near-vent flows, breccia, cinders, and agglutinate of basalt, basaltic andesite, and andesite; commonly in the form of either little-modified lava cones or partly eroded piles of reddish, iron-stained thin flows and fragmental ejecta cut by mafic intrusions. May also include rocks of late Miocene(?) age
Mafic vent deposits (Pleistocene, Pliocene, and Miocene?) (Miocene to Pleistocene)
Mostly in small stratovolcanoes or shield volcanoes and lava cones of basalt and andesite. Includes agglomerate, breccia, scoria, cinders, ash, restricted flows, and small basaltic intrusive bodies. Transitional into pyroclastic rocks of cinder cones (QTp). May also include rocks of late Miocene(?) age
Marine facies (Middle Eocene to Late Eocene)
Basaltic clastic rocks and pillow lavas, locally mapped separately by Wells and others (1983). Foraminiferal assemblages are assigned to the lower part of the Narizian Stage of Mallory (1959); see Wells and others (1983) for summary
Marine facies (Middle Eocene to Late Eocene)
Basaltic clastic rocks and pillow lavas, locally mapped separately by Wells and others (1983). Foraminiferal assemblages are assigned to the lower part of the Narizian Stage of Mallory (1959); see Wells and others (1983) for summary
Melange (Jurassic) (Jurassic)
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)
Olivine basalt (Pliocene and Miocene) (Miocene to Pliocene)
Thin, commonly open-textured (diktytaxitic), subophitic to intergranular olivine basalt flows, intercalated with and grades laterally through palagonite breccia and tuff into tuffaceous sedimentary rocks (unit Ts). In places includes flows of platy olivine andesite or basaltic andesite. Several potassium-argon ages ranging from about 4 to 7 Ma indicate unit is mostly of early Pliocene and late Miocene age. Includes Shumuray Ranch Basalt and Antelope Flat Basalt of Kittleman and others (1965), Grassy Mountain Basalt of Corcoran and others (1962), Drinkwater Basalt of Bowen and others (1963), basalt formerly assigned to Danforth Formation by Piper and others (1939) (see Walker, 1979), Hayes Butte Basalt of Hampton (1964), Pliocene and upper Miocene basalt flows capping and interstratified with the Madras (or Deschutes) Formation, and basalt flows interstratified in the Dalles Formation of Newcomb (1966; 1969)
Olivine basalt (Pliocene and Miocene) (Miocene to Pliocene)
Thin, commonly open-textured (diktytaxitic), subophitic to intergranular olivine basalt flows, intercalated with and grades laterally through palagonite breccia and tuff into tuffaceous sedimentary rocks (unit Ts). In places includes flows of platy olivine andesite or basaltic andesite. Several potassium-argon ages ranging from about 4 to 7 Ma indicate unit is mostly of early Pliocene and late Miocene age. Includes Shumuray Ranch Basalt and Antelope Flat Basalt of Kittleman and others (1965), Grassy Mountain Basalt of Corcoran and others (1962), Drinkwater Basalt of Bowen and others (1963), basalt formerly assigned to Danforth Formation by Piper and others (1939) (see Walker, 1979), Hayes Butte Basalt of Hampton (1964), Pliocene and upper Miocene basalt flows capping and interstratified with the Madras (or Deschutes) Formation, and basalt flows interstratified in the Dalles Formation of Newcomb (1966; 1969)
Picture Gorge Basalt (middle and lower Miocene) (Early to Middle Miocene)
Flows of aphyric and plagioclase porphyritic flood basalt. Potassium-argon ages mostly 15.0 to 16.4 Ma (Watkins and Baksi, 1974; Fiebelkorn and others, 1983)
Porphyritic basalt (upper Eocene) (Late Eocene)
Subaerial lava flows and breccia of porphyritic basalt, minor basaltic andesite, and rare dacite. Includes basalt of Cascade Head (Wells and others, 1983), Yachats Basalt (Snavely and others, 1976c) and Goble Volcanic Series (Warren and others, 1945). Also includes camptonitic extrusive rocks (tuff breccia, lapilli tuff, and minor pillow flows) interbedded in Nestucca Formation
Pyroclastic ejecta of basaltic and andesitic cinder cones (Holocene, Pleistocene, Pliocene, and Miocene?) (Miocene to Holocene)
Mostly unconsolidated, oxidized, fine to coarse, scoriaceous cinders, bombs, and agglutinate deposited in subaerial environment
Pyroclastic ejecta of basaltic cinder cones (lower Pliocene? and Miocene?) (Miocene to Early Pliocene)
Mostly unconsolidated, oxidized, fine to course, scoriaceous cinders, bombs, and agglutinate deposited in subaerial environment
Rhyolitic tuff, tuffaceous sedimentary rocks, and lava flows (lower Miocene, Oligocene, and uppermost Eocene?) (Late Eocene to Early Miocene)
Rhyolitic to dacitic varicolored bedded tuff, lapilli tuff, and fine- to medium-grained tuffaceous sedimentary rocks with interstratified welded and nonwelded ash-flow tuff and interbedded basalt and andesite flows. Also includes minor rhyolite and dacite flows and domes. Glass in tuff and tuffaceous sedimentary rocks is commonly altered to zeolites, clay minerals, and small amounts of opal, chalcedony, orthoclase, and calcite. Fossil plants and vertebrates indicate an Oligocene and Miocene age. Locally a late Hemingfordian age indicated by mammalian fauna (Woodburn and Robinson, 1977). May include some rocks of middle Miocene age in the area west and northwest of Lakeview. Potassium-argon ages on rocks from unit range from about 36 Ma (Swanson and Robinson, 1968) to about 20 Ma. Includes Pike Creek Formation of Walker and Repenning (1965), originally identified as Pike Creek Volcanic Series by Fuller (1931), and unnamed volcanic and volcaniclastic rocks of southern Lake County, some of which have been correlated with the Miocene and Oligocene Cedarville Formation of northeastern California
Saddle Mountains Basalt (upper and middle Miocene) (Middle to Late Miocene)
Petrographically diverse flows of basalt erupted between about 13.5 and 6 Ma (McKee and others, 1977; Swanson and others, 1979)
Sedimentary rocks (Jurassic) (Late Jurassic )
Black and gray mudstone, shale, siltstone, graywacke, andesitic to dacitic water-laid tuff, porcelaneous tuff, and minor interlayers and lenses of limestone and fine-grained sediments metamorphosed to phyllite or slate. Locally includes some felsite, andesite and basalt flows, breccia, and agglomerate. Marine invertebrate fauna indicates age range from Early Jurassic (Hettangian) to early Late Jurassic (Oxfordian). In Klamath Mountains of southwest Oregon, includes Galice Formation (Wells and Peck, 1961) and unnamed, hornblende- and (or) pyroxene-bearing clastic rocks of Jurassic age (Smith and others, 1982)
Strawberry Volcanics (Pliocene? and Miocene) (Miocene to Pliocene)
Flows and flow breccia of basalt, basaltic andesite, and andesite; includes restricted domal complexes and related flows and breccia of rhyolite and dacite (Thayer, 1957; Brown and Thayer, 1966). Potassium-argon ages are mostly in the range of 12 to 20 Ma (Robyn, 1977; Fiebelkorn and others, 1983)
Subaqueous pyroclastic ejecta of basaltic and andesitic cinder cones (Holocene, Pleistocene, Pliocene, and Miocene?) (Miocene to Holocene)
Partly consolidated, palagonitized, fine to coarse, scoriaceous altered cinders, bombs, breccia, and minor agglutinate, mostly deposited in subaqueous environment. Commonly with some interlayers and intermixed lacustrine sedimentary rocks. Forms palagonitic tuff and breccia cones and rings (maars) and, in places, palagonitic tuff ridges
Thin flows of basalt and andesite (Late Eocene to Early Miocene)
Part of unit Tsfj; exact age uncertain
Tillamook Volcanics (upper and middle Eocene) (Middle Eocene to Late Eocene)
Subaerial basaltic flows and breccia and submarine basaltic breccia, pillow lavas, lapilli and augite-rich tuff with interbeds of basaltic sandstone, siltstone, and conglomerate. Includes some basaltic andesite and, near the top of the sequence, some dacite. Potassium-argon ages on middle and lower parts of sequence range from about 43 to 46 Ma (Magill and others, 1981): one potassium-argon age from dacite near top of sequence is about 40 Ma (see Wells and others, 1983)
Ultramafic and related rocks of ophiolite sequences; Basaltic volcanic and sedimentary rocks (Jurassic) (Jurassic)
Basalt flows, flow breccia, agglomerate, pillow basalt and pillow breccia, and lesser shale, chert, siltstone, and mudstone of ophiolitic complexes
Undifferentiated tuffaceous sedimentary rocks, tuffs, and basalt (Miocene and Oligocene) (Oligocene to Miocene)
Heterogeneous assemblage of continental, largely volcanogenic deposits of basalt and basaltic andesite, including flows and breccia, complexly interstratified with epiclastic and volcaniclastic deposits of basaltic to rhyodacitic composition. Includes extensive rhyodacitic to andesitic ash-flow and air-fall tuffs, abundant lapilli tuff and tuff breccia, andesitic to dacitic mudflow (lahar) deposits, poorly bedded to well-bedded, fine- to coarse-grained tuffaceous sedimentary rocks, and volcanic conglomerate. Originally included in Little Butte Volcanic Series (Peck and others, 1964); includes Mehama Volcanics and Breitenbush Tuffs or Series of Thayer (1933, 1936, 1939), Breitenbush Formation of Hammond and others (1982), Mehama Formation of Eubanks (1960), and Molalla Formation of Miller and Orr (1984a). In Columbia River Gorge, includes Miocene and older rocks previously assigned to the Skamania Volcanic Series (Trimble, 1963), or to the Eagle Creek Formation (Waters, 1973). Lower parts of unit exhibit low-grade metamorphism with primary constituents altered to clay minerals, calcite, zeolites (stilbite, laumontite, heulandite), and secondary silica minerals. In contact aureoles adjacent to stocks and larger dikes of granitic and dioritic composition or in areas of andesitic dike swarms, both wallrocks and intrusions are pervasively propylitized; locally rocks also have been subjected to potassic alteration. Epiclastic part of assemblage locally contains fossil plants assigned to the Angoonian Stage (Wolfe, 1981) or of Oligocene age. A regionally extensive biotite-quartz rhyodacite ash-flow tuff, the ash-flow tuff of Bond Creek of Smith and others (1982), is exposed in southern part of Western Cascade Range near and at base of unit. A K-Ar age of 34.9 Ma was determined on biotite from the tuff (Smith, 1980). Ash-flow tuffs, higher in the section and in the same area, have been radiometrically dated at 22 to 32 Ma by potassium-argon methods (J.G. Smith, unpublished data; Evernden and James, 1964; Fiebelkorn and others, 1983). In the central part of the Western Cascade Range, the unit has yielded a number of K-Ar ages in the range of about 32 to 19 Ma (Verplanck, 1985, p. 53-54). A fission-track age of 23.8 +/- 1.4 Ma was obtained on a red, crystal-rich ash-flow tuff (J.A. Vance, oral communication, 1983) collected at an elevation of about 3,000 ft on U.S. Highway 20 west-southwest of Echo Mountain. Most ages from basalt and basaltic andesite lava flows are in the range of about 35 to 18 Ma. Locally intruded by small stocks of granitoid rocks and by dikes, sills, plugs, and invasive flows of basaltic andesite and basalt; in many places, the intrusions are indistinguishable from poorly exposed interbedded lava flows; K-Ar ages on several of the mafic intrusions or invasive flows are about 27 to 31 Ma. In places subdivided into Tus, Tut, and Tub
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
Volcanic rocks (Jurassic) (Late Jurassic)
Lava flows, flow breccia, and agglomerate dominantly of plagioclase, pyroxene, and hornblende porphyritic and aphyric andesite. Includes flow rocks that range in composition from basalt to rhyolite as well as some interlayered tuff and tuffaceous sedimentary rocks. Commonly metamorphosed to greenschist facies; locally foliated, schistose or gneissic. Includes the Rogue Formation and volcanic rocks commonly assigned to the Galice Formation (Wells and Walker, 1953; Wells and Peck, 1961). Considered to be accreted island-arc terrane
Volcanic rocks of the Dothan Formation and related rocks (Lower Cretaceous and Upper Jurassic) (Late Jurassic to Early Cretaceous)
Basaltic pillow lavas, volcanic breccia, and silicified basalt lava flows
Volcanic rocks (Triassic and Permian) (Triassic and (or) Jurassic)
Massive flows of porphyritic meta-andesite, metabasalt, spilite, and keratophyre, volcanic breccia, and subordinate amounts of fine-grained volcaniclastic rocks. In southwest Oregon includes hornblende, pyroxene, and plagioclase porphyritic andesite flows, breccia, agglomerate, tuff, and locally, some basalt flows and dacitic tuffs of the Applegate Group
Wanapum Basalt (middle Miocene) (Middle Miocene)
Flows of gray to dark-gray, medium-grained, commonly plagioclase porphyritic basalt of Frenchman Springs petrochemical type (Wright and others, 1973). Generally exhibits blocky to platy jointing. Potassium-argon ages mostly about 15 Ma (Lux, 1982; Fiebelkorn and others, 1983)
Yamhill Formation and related rocks (upper and middle Eocene) (Middle Eocene to Late Eocene)
Massive to thin-bedded concretionary marine siltstone and thin interbeds of arkosic, glauconitic, and basaltic sandstone; locally contains interlayered basalt lava flows and lapilli tuff. Foraminiferal assemblages in siltstone referred to the Ulatisian and lower Narizian Stages (Snavely and others, 1969; McKeel, 1980) Includes the Elkton Formation of Baldwin (1974; also see Beaulieu and Hughes, 1975), which consists of thin-bedded siltstone and minor sandstone interbeds
Youngest basalt and basaltic andesite (Holocene) (Holocene)
Little-modified flows and associated breccia of basaltic andesite and some basalt in both central part of Cascade Range and on slopes of Newberry Volcano. Relations to Mazama pumice deposits indicate most of these rocks are less than 6,800 yr old (14C); isotopic ages on flows range from about 1,000 to 6,000 yr B.P. (14C)
South Dakota
Metabasalt (Proterozoic | Paleoproterozoic)
Alkalic basalt, greenstone, and actinolite schist. Includes metamorphosed volcanoclastic rocks and iron-rich schist.
Tennessee
Bakersville Gabbro (Precambrian)
Bakersville Gabbro - Metagabbro, dark, porphyritic; contains diorite, basalt, anorthosite, and diabase; occurs as thin to massive dikes and lenticular masses.
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.
Mount Rogers Group including Bakersville Gabbro, Beech Granite, Cranberry Granite, and Roan Gneiss (Precambrian)
Mount Rogers Group - Metavolcanics, typically purplish and reddish; massive lavas and tuffs, altered rhyolites and quartz latites; strongly foliated; interbedded arkose, shale, and conglomerate. Thickness 1,000 to 3,000 feet; Includes Bakersville Gabbro - Metagabbro, dark, porphyritic; contains diorite, basalt, anorthosite, and diabase; occurs as thin to massive dikes and lenticular masses; Beech Granite - Granite, porphyritic, light-gray to reddish; coarse potash feldspar crystals and clustered interstitial mafics (chloritized biotite and hornblende) give spotted appearance; includes Max Patch Granite; Cranberry Granite - Complex of intertonguing rock types including migmatite, granitic gneisses, monzonite, quartz diorite, greenstone, mica and hornblende schists, abundant granitic pegmatite; and Roan Gneiss - Layered hornblende and garnet gneiss and granitic migmatite with zones of mica schist and amphibolite, foliation commonly contorted; contains numerous granitic and gabbroic dikes.
Unicoi Formation (Cambrian)
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.
Texas
Black Gap area volcanic rocks (Phanerozoic | Cenozoic | Tertiary | Miocene)
Black Gap area volcanic rocks
Bofecillos volcano volcanic rocks, including units 1-8 of Rawls Formation and lava flows in upper part of Fresno Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene)
Bofecillos volcano volcanic rocks, including units 1-8 of Rawls Formation and lava flows in upper part of Fresno Formation
Chinati Mountains caldera volcanic rocks, including Chinati Mountains Group, Mitchell Mesa Ignimbrite, and type area of Petan Basalt (Phanerozoic | Cenozoic | Tertiary | Oligocene)
Chinati Mountains caldera volcanic rocks, including Chinati Mountains Group, Mitchell Mesa Ignimbrite, and type area of Petan Basalt
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
Delaho and Rawls Formations, undivided (Phanerozoic | Cenozoic | Tertiary | Oligocene Miocene)
Delaho and Rawls Formations, undivided NOTE: This unit is represented within the map unit explanation of (Geol. Map of Texas, 1992, Bur. Econ. Geol.) but does not occur on the map and is NOT included in the spatial data.
Delaho Formation and unit 9 of Rawls Formation (Phanerozoic | Cenozoic | Tertiary | Miocene)
Delaho Formation and unit 9 of Rawls Formation NOTE: This unit is represented within the map unit explanation of (Geol. Map of Texas, 1992, Bur. Econ. Geol.) but does not occur on the map and is NOT included in the spatial data.
Devils Graveyard volcanic rocks (Phanerozoic | Cenozoic | Tertiary | Eocene Oligocene)
Devils Graveyard volcanic rocks
Duff Formation (with Decie Member from Paisano caldera shown separately), Cottonwood Springs Basalt, Potato Hill Andesite, Sheep Canyon Basalt, Crossen Trachyte, and Pruett Formation, undivided (Phanerozoic | Cenozoic | Tertiary | Eocene-Late Oligocene-Early)
Duff Formation (with Decie Member from Paisano caldera shown separaetly), Cottonwood Springs Basalt, Potato Hill Andesite, Sheep Canyon Basalt, Crossen Trachyte, and Pruett Formation, undivided
Eocene intrusive rocks (Phanerozoic | Cenozoic | Tertiary | Eocene)
Eocene intrusive rocks
igneous rocks of Austin age (Phanerozoic | Mesozoic | Cretaceous-Late)
igneous rocks of Austin age
Infiernito caldera volcanic rocks including Capote Mountain Tuff, Tsh2 of Shely Group, Buckshot Ignimbrite, and Tm1 of Morita Ranch Formation (Phanerozoic | Cenozoic | Tertiary | Eocene-Late)
Infiernito caldera volcanic rocks including Capote Mountain Tuff, Tsh2 of Shely Group, Buckshot Ignimbrite, and Tm1 of Morita Ranch Formation
Jones Basalt (Phanerozoic | Cenozoic | Tertiary | Oligocene)
Jones Basalt
Miocene intrusive rocks (Phanerozoic | Cenozoic | Tertiary | Miocene)
Miocene intrusive rocks
Mundy Breccia and Castner Limestone, undivided (preCambrian-Proterozoic)
Mundy Breccia and Castner Limestone, undivided
Oligocene intrusive rocks (Phanerozoic | Cenozoic | Tertiary | Oligocene)
Oligocene intrusive rocks
Quitman Mountains caldera volcanic rocks and volcanic rocks of sneed (Cox) Mountain and west of Victorio Peak (Phanerozoic | Cenozoic | Tertiary | Oligocene)
Quitman Mountains caldera volcanic rocks and volcanic rocks of sneed (Cox) Mountain and west of Victoria Peak
Tarantula Gravel (Phanerozoic | Cenozoic | Tertiary | Miocene)
Tarantula Gravel
Tm2 and Tm3 units of Morita Ranch Formation (possibly from Cienega Mountain area) (Phanerozoic | Cenozoic | Tertiary | Oligocene)
Tm2 and Tm3 units of Morita Ranch Formation (possibly from Cienega Mountain area)
upper part of Shely Group, including Tm4 or Morita Ranch Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene)
upper part of Shely Group, including Tm4 or Morita Ranch Formation
Van Horn Mountains caldera volcanic rocks (Phanerozoic | Cenozoic | Tertiary | Eocene)
Van Horn Mountains caldera volcanic rocks
Utah
Miocene basalts (Early to Middle Miocene)
Miocene volcanic rocks (Late Oligocene to Middle Miocene)
Oligocene volcanic rocks (Late Eocene to Oligocene)
Pliocene basalts (Pliocene)
Quaternary basalts (Quaternary)
Tertiary (4) sedimentary rocks in Salt Lake City-Coalville-Randolph region (Middle Miocene to Late Pliocene)
Tertiary (4) sedimentary rocks in western Utah (Middle Miocene to Late Pliocene)
Triassic (2) sedimentary rocks in western Utah (Late Triassic)
Younger Precambrian metamorphic rocks in Logan-Huntsville Allochthon (Proterozoic Z)
Virginia
Newark Supergroup; Jurassic Basalt (Lower Jurassic)
basalt
Unicoi Formation (Cambrian)
Unicoi Formation - Sandstone and quartzite with phyllite, tuffaceous phyllite, conglomerate, and minor basalt.
Valley and Ridge Igneous Intrusions; Basalt (Jurassic-Tertiary)
Valley and Ridge Igneous Intrusions; b: Basalt - Dikes in Augusta and Rockingham Counties: nepheline syenite, teschenite-syenite, and teschenite-picrite. Igneous bodies in Highland County: andesite and basalt.
Washington
Carboniferous and Permian volcanic rocks (Devonian to Permian; Triassic in Asotin 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.
Eocene nonmarine rocks (Eocene)
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.
Eocene-Oligocene volcanic rocks (Eocene-Oligocene)
Predominantly light-green, bedded andesite breccia with interbedded andesite and basalt flows, mudflows, and tuff beds; becomes more tuffaceous near top of unit. Includes tuffaceous and arkosic sandstone, shale, and carbonaceous shale beds in central and southern Cascade Mountians. Rhyodacite and quartz latite flows in northwestern Ferry County.
Eocene volcanic rocks (Eocene )
Predominantly andesite flows and breccia; includes interbedded sedimentary rocks south of Startup in Snohomish and King Counties.
Lower Tertiary volcanic rocks, undivided (Eocene)
Predominantly andesite flows and flow breccia; includes basalt flows, minor rhyolitic rocks, and some sedimentary rocks.
Mesozoic-Tertiary marine rocks, undivided (Miocene to Eocene)
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.
Mesozoic-Tertiary volcanic rocks, undivided (Oligocene to Eocene)
Altered basalt, pillow lavas, and flow breccia of inner volcanic belt of Olympic Peninsula; includes minor interbedded red limy argillite and associated manganese ore.
Mesozoic volcanic rocks, undivided (Jurassic)
Includes latite, andesite and basalt flows, tuff, and agglomerate. Interbedded sedimentary rocks in Orient area of Stevens County.
Miocene-Pliocene nonmarine rocks (Miocene-Pliocene)
Tuffaceous and pumiceous andesitic sandstone and siltstone with interbedded conglomerate and claystone. Conglomerate beds chiefly andesitic, but also quartzitic, granitic, and basaltic; includes basalt flows locally.
Miocene-Pliocene volcanic rocks (Miocene-Pliocene)
Dark-gray, fine-grained, dense, porphyritic in part, basalt flows in central and south-central part of State; commonly interbedded with conglomerate, sandstone, and siltstone. Includes small areas of rhyolite north of Cle Elum in Kittitas County, and andesite north of Leavenworth in Chelan County.
Oligocene-Miocene volcanic rocks (Miocene)
Andesite flow breccia, andesite flows, and minor tuff beds; includes some basalt flows and flow breccia. Commonly more massive and less altered than similar-appearing Eocene-Oligocene volcanic rocks. Clastic flows and flows of black glass, and course to fine-grained clastic and pyroclastic rocks in the Republic and Curlew areas of Ferry County.
Oligocene nonmarine rocks (Oligocene)
Andesite conglomerate, tuff beds, and mudflow material. Includes some interbedded andesite flows in Columbia River Gorge. Lake sediments with Oligocene flora in Republic area in Ferry County. Massive tuffaceous sandstone and siltstone with beds of coal and high-alumina clay in Castle Rock-Toledo coal district in Cowlitz and Lewis Counties; include local interbedded basalt flows and some marine and late Eocene rocks.
Pleistocene-Recent volcanic rocks (Pleistocene to Holocene)
Predominantly dark-gray to black vesicular basalt; olivine-rich in part. Includes andesite flows and pyroclastic rocks of Mount Baker, Glacier Peak, Mount Rainier, Mount Adams, Mount St. Helens, and all cinder cones in southern part of the State. Also includes some Recent flows southeast of Mount St. Helens.
Pliocene-Pleistocene volcanic rocks (Mostly Pleistocene)
Light-gray andesite, andesite porphyry, and open-textured basalt flows with minor associated mudflows and breccia. Includes restricted areas of valley flow basalt in Snake River Canyon in southeastern Washington and in Spokane area.
Pre-Carboniferous intrusive rocks (Paleozoic)
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.
Pre-Tertiary basic intrusive rocks (Triassic-Permian)
Predominantly gabbro and metagabbro; includes hornblendite, peridotite, and pyroxenite. In Nighthawk district and near 49th Parallel in Okanogan County and in Orient district of Stevens County.
Pre-Tertiary sedimentary and metasedimentary rocks, undivided (Mostly Early Cretaceous to Middle Jurassic, possibly includes minor Eocene rocks)
Graywacke, argillite, phyllite, chert, talc, and graphite schist; some faulted-in blocks of serpentinite and greenstone. Includes minor limestone on San Juan Island.
Pre-upper Eocene rocks (Eocene (Olympic Peninsula); Cretaceous(?) (Yakima County))
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.
Tertiary dikes, sills, and small intrusive bodies (Middle to Late Tertiary)
Dikes are commonly diabase; plugs and sills are generally andesite porphyry and dacite.
Upper Eocene volcanic rocks (Late Eocene)
Andesite and basalt flows and associated breccia in central Lewis County. Pyroclastic rocks, mudflows, flow breccia, and volcanic-rich sedimentary rocks in King and Pierce Counties.
Upper Eocene volcanic rocks (Late-Middle Eocene)
Rhyolite flows and some interbedded tuff beds in Cle Elum area, Kittitas County.
Upper Eocene volcanic rocks (Late Eocene to Oligocene)
Predominantly basalt flows and flow breccia; includes some pyroclastic and andesite rocks. Chiefly in western Washington.
Upper Eocene volcanic rocks (Late Eocene)
Predominantly andesite flows and breccia; includes some basalt flows. Contains basaltic conglomerate, pyroclastic rocks, tuff beds, and sandstone in Chehalis-Centralia coal district, Lewis County.
Wisconsin
Badwater Greenstone (Early Proterozoic)
Badwater Greenstone - Dark-greenish-gray, pillowed to massive tholeiitic basalt and pyroclastic rocks. Correlated with the Hemlock Formation on basis of geology and similarity in chemical composition.
Bimodal mafic and felsic metavolcanic rocks (Early Proterozoic)
Bimodal mafic and felsic metavolcanic rocks - High-aluminum basalt to low-silica andesite pillowed flows and interlayered dacite to rhyolite tuffs and porphyries in Monico and Mountain areas, northeastern Wisconsin. A rhyolite porphyry at Jennings (Oneida County) has an age of 1869 +/- 6 Ma. Rocks are host to massive sulfide deposits (Crandon and Pelican River)
Chengwatana Volcanic Group (Middle Proterozoic)
Chengwatana Volcanic Group - Gray basalt flows, interflow breccia, tuff, and minor sedimentary rocks
Copper Harbor Conglomerate (Middle Proterozoic)
Copper Harbor Conglomerate - Red lithic conglomerate and sandstone; mafic to felsic volcanic flows similar to those of the unnamed formation (unit Yu) are interlayered with the sedimentary rocks.
Mafic metavolcanic rocks (Early Proterozoic)
Mafic metavolcanic rocks - Dominantly tholeiitic basalt and basaltic andesite flows and tuffs; associated with sheet dikes, massive and layered metagabbro, and ultramafic rocks. In northeastern Wisconsin, rocks have been named the Quinnesec Formation.
Menominee Group; Blair Creek Formation (Early Proterozoic)
Menominee Group; Blair Creek Formation - Dominantly dark-gray, massive, porphyritic tholeiitic basalt. Includes a basal conglomerate and a lean iron-formation in middle of formation
Porcupine Volcanics (Middle Proterozoic)
Porcupine Volcanics - Generally dark-gray basalt, andesite, and felsite flows and subordinate interflow sedimentary rocks
Portage Lake Volcanics (Middle Proterozoic)
Portage Lake Volcanics - Lava flows, mostly basalt, andesite and felsite flows and subordinate interflow sedimentary rocks.
Powder Mill Group; Kallander Creek Volcanics (Middle Proterozoic)
Powder Mill Group; Kallander Creek Volcanics- Basalt, andesite and lesser rhyolite flows. Basalt flows near base of the formation contain plagioclase phenocrysts, some in radiating clusters
Powder Mill Group; Siemens Creek Volcanics (Middle Proterozoic)
Powder Mill Group; Siemens Creek Volcanics- Dark-gray basalt and minor porphyritic andesite. Generally strongly magnetic with reversed remanent magnetism. Underlain by a thin unit of quartzose sandstone (Bessemer Quartzite).
Wyoming
Absaroka Volcanic Supergroup: Sunlight Group (Phanerozoic | Cenozoic | Tertiary | Eocene)
ABSAROKA VOLCANIC SUPERGROUP: SUNLIGHT GROUP--including Trout Peak Trachyandesite, Wapiti Formation (andesitic volcaniclastic rocks), Crescent Hill Basalt, and Mount Wallace Formation (felsic and mafic volcaniclastic rocks).
Absaroka Volcanic Supergroup: Thoroughfare Creek and Sunlight Groups (Phanerozoic | Cenozoic | Tertiary | Eocene (44-49 Ma))
ABSAROKA VOLCANIC SUPERGROUP: THOROFARE CREEK GROUP (AGE 44 TO 49 Ma)--Light-colored volcaniclastic strata, andesite lava flows, and dark-brown breccia AND SUNLIGHT GROUP--including Trout Peak Trachyandesite, Wapiti Formation (andesitic volcaniclastic rocks), Crescent Hill Basalt, and Mount Wallace Formation (felsic and mafic volcaniclastic rocks).
Basalt flows and intrusive igneous rocks (Phanerozoic | Cenozoic | Quaternary | Pleistocene)
BASALT FLOWS AND INTRUSIVE IGNEOUS ROCKS. Yellowstone area--Includes Osprey, Madison River, Swan Lake Flat, and Falls River Basalts, basalts of Mariposa Lake, Undine Falls Basalt, and gravels, sands, silts, and basalts of The Narrows. In and adjacent to Absaroka and Washakie Ranges--Includes basalt of Lava Mountain (age about 0.5 Ma).
Basalt flows and intrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Miocene)
BASALT FLOWS AND INTRUSIVE IGNEOUS ROCKS (AGE ABOUT 11 Ma).
Intrusive and extrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Miocene Pliocene)
INTRUSIVE AND EXTRUSIVE IGNEOUS ROCKS--Composition ranges from hornblende monzonite to basalt. In Yellowstone area includes andesite and basalt of Emerald Lake (age about 2 Ma), rhyolite of Broad Creek, Pliocene Junction Butte Basalt, and gravel of Mount Everts. Age of basalt on Crescent Mountain 3.6 Ma.

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