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Geologic units containing ash-flow tuff

California

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 2 (Long Valley Caldera) (Quaternary (0-1 Ma))

Quaternary pyroclastic and volcanic mudflow deposits.

Tertiary pyroclastic and volcanic mudflow deposits, unit 1 (Sonoma Volcanic Field) (Tertiary (3-7 Ma))

Tertiary pyroclastic and volcanic mudflow deposits.

Tertiary pyroclastic and volcanic mudflow deposits, unit 3 (Pinnacles-Neenach) (Tertiary (22-24 Ma))

Tertiary pyroclastic and volcanic mudflow deposits.

Tertiary pyroclastic and volcanic mudflow deposits, unit 4 (Tranquillon-Obispo) (Tertiary (16-18 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 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 3 (Sonoma Volcanic Field) (Tertiary (3-7 Ma))

Tertiary volcanic flow rocks; minor pyroclastic deposits.

Colorado

Ash-flow tuff of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary)

Ash-flow tuff of main volcanic sequence (Phanerozoic | Cenozoic | Tertiary)

Includes many named units

Wall Mountain Tuff (Phanerozoic | Cenozoic | Tertiary)

Early ash-flow tuff of Sawatch Range provenance

Idaho

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.

Montana

Tertiary sedimentary rocks, undifferentiated (Phanerozoic | Cenozoic | Tertiary)

Tertiary sedimentary rocks, undifferentiated: clastic deposits in western Montana, mostly in valleys, and in most places not divided into formations; mostly poorly consolidated gravel, sand, silt, and clay; includes some tuffaceous material and locally lenses of lignite and bentonite; a little hot spring tufa; and in areas not yet mapped in detail, lava may be included. These rocks were in part laid down in lakes but a large part was formed in streams and alluvial fans. These rocks are Tertiary in age and as now mapped may even include some beds of Cretaceous age. Some late Tertiary terrace deposits may be included.

New Hampshire

Moat Volcanics (Middle Jurassic?)

Moat Volcanics - Bedded and ignimbritic tuffs, flows, and breccias; also porphyritic rhyolite and minor trachyte.

Nevada

Ash-flow tuffs and tuffaceous sedimentary rocks (Middle Miocene to Late Miocene)

ASH-FLOW TUFFS AND TUFFACEOUS SEDIMENTARY ROCKS

Volcanic sandstone, felsic ash-flow tuffs, rhyolite, and rhyodacite flows (Middle Jurassic to Early Cretaceous)

VOLCANIC SANDSTONE, FELSIC ASH-FLOW TUFFS, RHYOLITE, AND RHYODACITE FLOWS (Upper? Jurassic)-Pony Trail Group of Cortez Mountains, Eureka County

Oregon

Tuff (Tertiary)

Welded to unwelded, mostly vitric crystal and vitric ash-flow tuff of several ages. Glass in tuff locally altered to clay, zeolites, and secondary silica minerals

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

Rhode Island

Esmond Igneous Suite - felsic volcaniclastic rock (Late Proterozoic)

Esmond Igneous Suite - felsic volcaniclastic rock - Light-colored to dark-gray ash flow tuff, ignimbrite, and felsite; may include some shallow-level intrusive rock. Phenocrysts of quartz, orthoclase, and plagioclase in a fine-grained matrix of quartz, feldspar, biotite, and opaque minerals. Some varieties contain fiamme and lithic fragments. Includes rock mapped formerly as Pennsylvanian felsite at Diamond Hill.

Newport Group - Price Neck Formation (Late Proterozoic? or older?)

Newport Group - Price Neck Formation - Fine-grained graded beds of feldspathic siltstone and sandstone, interstratified with carbonate conglomerate, and ash-flow and lapilli tuff; some units may be lahar deposits.

Scituate Igneous Suite - volcaniclastic rock (Devonian)

Scituate Igneous Suite - volcaniclastic rock - Dark-gray, pink, greenish, and purplish tuff and epiclastic rock (sandstone, breccia, conglomerate) containing abundant volcanic detritus. Tuff may include ignimbrite and ash-flow tuff. Fiamme common in some rock mapped formerly as Spencer Hill Volcanics.

Texas

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

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.

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

Perdiz Conglomerate, Tascotal Formation, and tuffaceous sediments of Fresno Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene)

Perdiz Conglomerate, Tascotal Formation, and tuffaceous sediments of Fresno Formation

San Carlos Tuff from San Carlos caldera in Mexico (Phanerozoic | Cenozoic | Tertiary | Oligocene)

San Carlos Tuff from San Carlos caldera in Mexico

Santana Tuff from Sierra Rica caldera in Mexico (Phanerozoic | Cenozoic | Tertiary | Oligocene)

Santana Tuff from Sierra Rica caldera in Mexico

South Rim Formation from Pine Canyon Caldera (Phanerozoic | Cenozoic | Tertiary | Oligocene)

South Rim Formation from Pine Canyon Caldera

Vieja Group, including Bracks Rhyolite, Chambers and Colmena Tuffs and Gill Breccia (Phanerozoic | Cenozoic | Tertiary | Eocene Oligocene)

Vieja Group, including Bracks Rhyolite, Chambers and Colmena Tuffs and Gill Breccia

Utah

Miocene volcanic rocks (Late Oligocene to Middle Miocene)