Geologic units in Humboldt county, Nevada

Mineral Resources On-Line Spatial Data

Tuffaceous sedimentary rocks (Late Eocene to Late Miocene) at surface, covers 2 % of this area

TUFFACEOUS SEDIMENTARY ROCKS-Locally includes minor amounts of tuff

Lithology: sandstone; limestone; siltstone; conglomerate; mudstone; dolostone (dolomite); felsic volcanic rock; intermediate volcanic rock; mafic volcanic rock; tuff

Rhyolite and dacite (Pliocene? and Miocene) (Miocene to Pliocene) at surface, covers < 0.1 % of this area

Ash-flow tuff, lava flows, pumice-lapilli tuff, coarse pumicite, flow breccia, and domal complexes of rhyolitic, rhyodacitic, and dacitic composition; in places includes peralkaline rhyolite and some andesite and andesite breccia. Locally porphyritic with phenocrysts of alkali feldspar, plagioclase, and minor augite, ferro-hedenbergite, hornblende, hypersthene, or biotite. Commonly flow banded; locally glassy. Many of the ash--flow tuffs exhibit flow features and only obscure vitro-clastic textures. In places includes interlayers of silicic volcaniclastic rocks and tuffaceous sedimentary rocks. Includes rhyolite at Owyhee Dam, Jump Creek Rhyolite, and Littlefield Rhyolite, all of Kittleman and others (1965); Dooley Rhyolite Breccia of Gilluly (1937), radiometrically dated at 14.7 +/- 0.4 Ma by potassium-argon methods (Fiebelkorn and others, 1983); resurgent domal masses in McDermitt caldera area; and extensive unnamed flows and ash-flow tuffs in the central and southern part of the Owyhee Upland. Also includes isolated masses of dacitic and rhyodacitic flows, breccia, and ash-flow tuff along eastern slope of Cascade Range that are lapped by flows and sediments of the Madras (or Deschutes) Formation. Potassium-argon ages on rocks in unit from southeast Oregon range from about 13 to 16 Ma; lenses of interbedded tuffaceous sedimentary rocks locally contain a Miocene (Barstovian) vertebrate fauna

Lithology: rhyolite; dacite; andesite

Sedimentary rocks (Late Cretaceous to Oligocene) at surface, covers < 0.1 % of this area

SEDIMENTARY ROCKS-Includes Sheep Pass Formation (Eocene) and related units and unnamed tuffaceous sedimentary rocks

Lithology: sandstone; conglomerate; limestone; siltstone; claystone; mudstone; shale; tuff; oil shale

Dune sand (Holocene) (Holocene) at surface, covers < 0.1 % of this area

Large areas of windblown sand composed of rock-forming minerals, mostly feldspar and small amounts of quartz, and, in southeastern Oregon, also pumice

Lithology: sand

Continental sedimentary rocks (Late Cretaceous to Eocene) at surface, covers < 0.1 % of this area

CONTINENTAL SEDIMENTARY ROCKS-Includes units such as Pansy Lee Conglomerate in Humboldt County, part of Cretaceous(?) and Tertiary rocks of Kleinhampl and Ziony (1967) in northern Nye County, and part of "older clastic rocks" of Tschanz and Pampeyan (1970) in Lincoln County

Lithology: conglomerate; sandstone; siltstone; mudstone; limestone

Alluvial deposits (Holocene) (Holocene) at surface, covers < 0.1 % of this area

Sand, gravel, and silt forming flood plains and filling channels of present streams. In places includes talus and slope wash. Locally includes soils containing abundant organic material, and thin peat beds

Lithology: sand; gravel; silt; peat

Shale, mudstone, siltstone, sandstone, and carbonate rock; sparse volcanic rock (Late Triassic to Early Jurassic) at surface, covers 4 % of this area

SHALE, MUDSTONE, SILTSTONE, SANDSTONE, AND CARBONATE ROCK; SPARSE VOLCANIC ROCK (Upper Triassic and Lower Jurassic)-Includes Auld Lang Syne Group, Nightingale sequence of Bonham (1969), and Gabbs and Sunrise Formations

Lithology: claystone; shale; sandstone; siltstone; carbonate; volcanic rock (aphanitic); conglomerate

Harmony Formation (Late Cambrian) at surface, covers 0.8 % of this area

HARMONY FORMATION (Upper Cambrian)-Feldspathic and arkosic sandstone and minor amounts of shale, limestone, and chert.

Lithology: sandstone; shale; limestone; chert; conglomerate

Continental deposits of siltstone, shale, conglomerate, and limestone (Cretaceous) at surface, covers 0.1 % of this area

CONTINENTAL DEPOSITS OF SILTSTONE, SHALE, CONGLOMERATE, AND LIMESTONE-Includes units such as King Lear Formation in Humboldt County, Newark Canyon Formation in Eureka County, Willow Tank Formation and baseline Sandstone in Clark County

Lithology: conglomerate; sandstone; limestone; mudstone; siltstone

Olivine basalt (Pliocene and Miocene) (Miocene to Pliocene) at surface, covers < 0.1 % of this area

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)

Lithology: basalt; andesite

Granitic rocks (Paleocene to Late Miocene) at surface, covers < 0.1 % of this area

GRANITIC ROCKS-Mostly quartz monzonite and granodiorite

Lithology: granodiorite; quartz monzonite; granite; monzonite

Basalt flows (Miocene to Quaternary) at surface, covers 1 % of this area

BASALT FLOWS-Locally includes maar deposits

Lithology: basalt; andesite; trachybasalt; latite; andesite

Basalt flows, pyroclastic debris, clastic sediments, and diatomite; Pliocene basaltic volcanics and clastic sediments; Snake River Plain and vicinity (Pliocene) at surface, covers < 0.1 % of this area

Pliocene olivine basalt flows and associated tuff and detritus of southern Idaho.

Lithology: basalt; lava flow; tuff; mixed clastic/volcanic

Landslide deposits (Quaternary) at surface, covers 0.8 % of this area

LANDSLIDE DEPOSITS

Lithology: landslide; colluvium; sedimentary rock

Intrusive rocks of mafic to intermediate composition (Eocene to Miocene) at surface, covers < 0.1 % of this area

INTRUSIVE ROCKS OF MAFIC TO INTERMEDIATE COMPOSITION

Lithology: diorite; monzodiorite; quartz diorite; quartz monzogabbro; tonalite; gabbro

Rhyolitic flows and shallow intrusive rocks (Early Oligocene to Early Miocene) at surface, covers 1 % of this area

RHYOLITIC FLOWS AND SHALLOW INTRUSIVE ROCKS

Lithology: rhyolite; dacite; trachyte

Andesite and related rocks of intermediate composition (Late Eocene to Middle Eocene) at surface, covers < 0.1 % of this area

ANDESITE AND RELATED ROCKS OF INTERMEDIATE COMPOSITION-Flows and breccias

Lithology: andesite; latite

Andesite and related rocks of intermediate composition (Early Oligocene to Early Miocene) at surface, covers 1.0 % of this area

ANDESITE AND RELATED ROCKS OF INTERMEDIATE COMPOSITION-Flows and breccias

Lithology: andesite; trachyte; dacite

Welded and nonwelded silicic ash-flow tuffs (Middle Miocene to Late Miocene) at surface, covers 8 % of this area

WELDED AND NONWELDED SILICIC ASH-FLOW TUFFS-Locally includes thin units of air-fall tuff and sedimentary rock

Lithology: rhyolite

Granitic rocks (Cretaceous) at surface, covers 3 % of this area

GRANITIC ROCKS-Mostly quartz monzonite and granodiorite

Lithology: granodiorite; quartz monzonite; granite; peraluminous granite

Siliceous and volcanic rocks (Ordovician to Devonian) at surface, covers 0.8 % of this area

SILICEOUS AND VOLCANIC ROCKS-Chert, shale, quartzite, greenstone, and minor amounts of limestone. Includes units such as Valmy Formation of north-central Nevada and some rocks mapped as Palmetto Formation in northern part of Esmeralda County and adjacent parts of Mineral and Nye Counties. Locally includes rocks of Silurian and Devonian age.

Lithology: chert; quartzite; shale; greenstone; limestone; conglomerate; siltstone; chemical

Andesite and related rocks of intermediate composition (Late Miocene to Middle Miocene) at surface, covers 0.7 % of this area

ANDESITE AND RELATED ROCKS OF INTERMEDIATE COMPOSITION-Flows and breccias

Lithology: andesite; latite; trachyte; dacite

Tuffaceous sedimentary rocks and tuff (Pliocene and Miocene) (Miocene to Pliocene) at surface, covers < 0.1 % of this area

Semiconsolidated to well-consolidated mostly lacustrine tuffaceous sandstone, siltstone, mudstone, concretionary claystone, conglomerate, pumicite, diatomite, air-fall and water-deposited vitric ash, palagonitic tuff and tuff breccia, and fluvial sandstone and conglomerate. Palagonitic tuff and breccia grade laterally into altered and unaltered basalt flows of unit Tob. In places includes layers of fluvial conglomerate and, in parts of the Deschutes-Umatilla Plateau, extensive deposits of fanglomerate composed mostly of Miocene basalt debris and silt. Also includes thin, welded and nonwelded ash-flow tuffs. Vertebrate and plant fossils indicate rocks of unit are mostly of Clarendonian and Hemphillian (late Miocene and Pliocene) age. Potassium-argon ages on interbedded basalt flows and ash-flow tuffs range from about 4 to 10 Ma. Includes the Drewsey Formation of Shotwell and others (1963); sedimentary parts of the Rattlesnake Formation of Brown and Thayer (1966); an interstratified ash-flow tuff has been radiometrically dated by potassium-argon methods at about 6.6 Ma (see Fiebelkorn and others, 1983); Bully Creek Formation of Kittleman and others (1967); Dalles Formation of Newcomb (1966, 1969); Shutler Formation of Hodge (1932), McKay beds of Hogenson (1964) and Newcomb (1966) (see also Shotwell, 1956); Kern Basin Formation of Corcoran and others (1962); Rome beds of Baldwin (1976); parts of the (now obsolete) Danforth Formation of Piper and others (1939), Idaho Group of Malde and Powers (1962), Thousand Creek Beds of Merriam (1910); the Madras (or Deschutes) Formation, the "Simtustus formation" of Smith (1984), and the Yonna Formation (Newcomb, 1958). In areas west of Cascade crest, includes the Sandy River Mudstone and the Troutdale Formation of Trimble (1963) and the lower Pliocene Helvetia Formation of Schlicker and Deacon (1967)

Lithology: sandstone; siltstone; mudstone; conglomerate; pumice; diatomite; tuff; conglomerate

Morainal deposits (Quaternary) at surface, covers < 0.1 % of this area

MORAINAL DEPOSITS

Lithology: glacial drift

Rhyolitic intrusive rocks (Eocene to Miocene) at surface, covers < 0.1 % of this area

RHYOLITIC INTRUSIVE ROCKS

Lithology: granitoid

Volcanic flows and flow breccias, chiefly of andesitic composition, tuffs, sparse sandstone and graywacke (Permian to Jurassic) at surface, covers 2 % of this area

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

Lithology: andesite; basalt; dacite; graywacke; sandstone; shale; chert; limestone; conglomerate

Limestone, minor amounts of dolomite, shale, and sandstone; locally thick conglomerate units (Triassic) at surface, covers < 0.1 % of this area

LIMESTONE, MINOR AMOUNTS OF DOLOMITE, SHALE, AND SANDSTONE; LOCALLY THICK CONGLOMERATE UNITS (Lower, Middle, and Upper Triassic)-Includes Tobin, Dixie Valley, Favret, Augusta Mountain, and Cane Spring Formations and Star Peak Group in central Nevada and Grantsville and Luning Formations in west-central Nevada

Lithology: limestone; dolostone (dolomite); shale; sandstone; conglomerate; siltstone; andesite; chert

Granitic rocks (Jurassic) at surface, covers 0.2 % of this area

GRANITIC ROCKS-Mostly quartz monzonite and granodiorite

Lithology: quartz monzonite; granodiorite; granite; monzonite; quartz diorite; peraluminous granite

Playa deposits (Holocene) (Holocene) at surface, covers < 0.1 % of this area

Clay, silt, sand, and some evaporites

Lithology: clay or mud; silt; sand; evaporite

Welded and nonwelded silicic ash-flow tuffs (Early Oligocene to Early Miocene) at surface, covers 0.5 % of this area

WELDED AND NONWELDED SILICIC ASH-FLOW TUFFS-Locally includes thin units of air-fall tuff and sedimentary rock

Lithology: rhyolite; dacite; trachyte

Intrusive rocks (Cretaceous and Jurassic) (Jurassic to Cretaceous) at surface, covers < 0.1 % of this area

Hornblende and biotite quartz diorite (tonalite), trondhjemite, granodiorite, and small amounts of norite, in batholithic masses and large dikelike bodies. Includes Bald Mountain Tonalite and Anthony Lake Granodiorite of Taubeneck (1957), tonalite and trondhjemite of Wallowa batholith and Cornucopia stock (Taubeneck, 1964; Nolf, 1966), quartz diorite intrusion in the Snake River area (Morrison, 1963), quartz diorite and minor other intrusive rocks in the Caviness quadrangle (Wolff, 1965), quartz diorite northeast of John Day and southeast of Ironside Mountain (Thayer and Brown, 1964), quartz diorite in the Sparta and Durkee quadrangles (Prostka, 1962; 1967), and granodiorite and related rocks of the Pueblo Mountains (Roback and others, 1987). Rubidium-strontium and potassium-argon ages indicate an age range from about 94 to 160 Ma (Taubeneck, 1963; Thayer and Brown, 1964; Armstrong and others, 1976)

Lithology: quartz diorite; trondhjemite; granodiorite

Alluvial deposits (Quaternary) at surface, covers 38 % of this area

ALLUVIAL DEPOSITS-Locally includes beach and sand dune deposits

Lithology: alluvium; mass wasting; dune sand; lake or marine deposit (non-glacial)

Terrace, pediment, and lag gravels (Holocene and Pleistocene) (Pleistocene to Holocene) at surface, covers < 0.1 % of this area

Unconsolidated deposits of gravel, cobbles, and boulders intermixed and locally interlayered with clay, silt, and sand. Mostly on terraces and pediments above present flood plains. Includes older alluvium of Smith and others (1982) in the Klamath Mountains and both high- and low-level terraces along Oregon coast. Includes dissected alluvial fan deposits northeast of Lebanon, and Linn and Leffler Gravels of Allison and Felts (1956)

Lithology: gravel; terrace; clay or mud; silt; sand

Basalt flows (Late Miocene to Middle Miocene) at surface, covers 2 % of this area

BASALT FLOWS

Lithology: basalt

Quartzite and minor amounts of conglomerate, phyllitic siltstone, limestone, and dolomite (Late Proterozoic to Early Cambrian) at surface, covers 0.3 % of this area

QUARTZITE AND MINOR AMOUNTS OF CONGLOMERATE, PHYLLITIC SILTSTONE, LIMESTONE, AND DOLOMITE-Includes Prospect Mountain Quartzite, Osgood Mountain Quartzite, and Gold Hill Formation in northern Nevada, and Stirling Quartzite, Wood Canyon Formation, and Zabriskie Quartzite in southern Nevada.

Lithology: quartzite; siltstone; dolostone (dolomite); limestone; phyllite; shale; conglomerate; sandstone

Siliceous and volcanic rocks (Mississippian) at surface, covers < 0.1 % of this area

SILICEOUS AND VOLCANIC ROCKS-In Humboldt County, consists of altered pillow lavas, coarse volcanic breccias, clastic limestone, and minor amounts of sandstone, shale, siliceous shale, and chert of the Goughs Canyon Formation (Lower and Upper Mississippian). In the East Range, Pershing County, consists of quartzite, conglomerate, slate, limestone, chert, and greenstone of the Inskip Formation (Mississippian?).

Lithology: metavolcanic rock; sandstone; siltstone; limestone; shale; chert; conglomerate; quartzite

Banbury Formation (Middle Miocene to Late Miocene) at surface, covers 3 % of this area

BANBURY FORMATION-Basalt, gravel, and tuffaceous sediments locally. Northeast Humboldt County and northwest Elko County

Lithology: basalt; gravel; sandstone

Basalt and andesite (Miocene) (Miocene) at surface, covers < 0.1 % of this area

Lava flows and breccia of aphyric and plagioclase porphyritic basalt and aphyric andesite; locally includes flow breccia, peperite, some palagonite tuff and breccia, and minor silicic ash-flow tuff and interbeds of tuffaceous sedimentary rocks. In Basin and Range and Owyhee Upland provinces unit grades upward into more silicic, andesitic, and quartz latitic flows and flow breccia, as well as some interbedded tuffs and ash-flow tuffs; also in this region includes aphyric and highly porphyritic, plagioclase-rich basalt. Interfingers with and grades laterally into units Tit and Tts. Commonly contains montmorillonite clays, zeolites, calcite, and secondary silica minerals as alteration products on fractures and in pore spaces. Age, mostly middle Miocene, but includes some rocks of early Miocene age based on vertebrate fossils from related sedimentary units and on potassium-argon ages that range from about 13 Ma to about 19 Ma; most isotopic ages are about 13 to 16 Ma. Includes Steens Basalt (Steens Mountain Basalt of Fuller, 1931) Owyhee Basalt of Corcoran and others (1962) and Kittleman and others (1967), Hunter Creek Basalt and "unnamed igneous complex" of Kittleman and others (1965, 1967), and flows of Prineville chemical type (Uppuluri, 1974; Swanson and others, 1979), which previously were considered part of the Columbia River Basalt Group (Swanson, 1969a)

Lithology: basalt ; andesite; tuff; ignimbrite; mixed clastic/volcanic

Antler Sequence of Silberling and Roberts (1962) (Pennsylvanian to Late Permian ) at surface, covers 0.3 % of this area

ANTLER SEQUENCE OF SILBERLING AND ROBERTS (1962) (Middle Pennsylvanian to Early or Late Permian) (Guadalupian)-Conglomerate, sandy to conglomeratic limestone, limestone, sandstone, and calcareous shale. Thin detrital and carbonate sequence within main part of Antler orogenic belt. Includes units such as Sunflower Formation of Bushnell (1967) in Elko County, Battle Formation, Antler Peak Limestone, and Edna Mountain Formation in Lander and western Eureka Counties, and Wildcat Peak Formation in northern Nye County

Lithology: conglomerate; limestone; sandstone; siltstone; shale

Shale and thin-bedded or laminated limestone; also thinly interbedded limestone and chert (Middle Cambrian to Late Cambrian) at surface, covers 0.4 % of this area

SHALE AND THIN-BEDDED OR LAMINATED LIMESTONE; ALSO THINLY INTERBEDDED LIMESTONE AND CHERT-Includes units such as Preble and Emigrant Formations

Lithology: shale; limestone; chert; siltstone; quartzite; diorite; conglomerate

Older alluvial deposits (Miocene to Quaternary) at surface, covers 1 % of this area

OLDER ALLUVIAL DEPOSITS

Lithology: alluvium; lake or marine deposit (non-glacial)

Havallah sequence of Silberling and Roberts (1962) (Mississippian to Permian) at surface, covers 1 % of this area

HAVALLAH SEQUENCE OF SILBERLING AND ROBERTS (1962)-Chert, argillite, shale, greenstone, and minor amounts of siltstone, sandstone, conglomerate, and limestone. Includes Schoonover Formation of Fagan (1962) and Reservation Hill Formation in Elko County, Farrel Canyon Formation in southwestern Humboldt County, Havallah and Pumpernickel Formations in Pershing, Lander, and parts of Humboldt Counties, and rocks originally considered a part of the Pablo and Excelsior Formations in northern Nye, northern Esmeralda, and southern Mineral Counties. Assignment of some rocks to the Havallah sequence in the East Range, Pershing County, is highly uncertain. Includes rocks ranging in age from Late Mississippian to Early Permian

Lithology: shale; metavolcanic rock; chert; siltstone; sandstone; conglomerate; limestone

Older basalt rocks (Early Oligocene to Early Miocene) at surface, covers 0.2 % of this area

OLDER BASALT ROCKS

Lithology: basalt; andesite

Koipato Group and related rocks (Permian to Early Triassic) at surface, covers < 0.1 % of this area

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

Lithology: rhyolite; andesite; clastic; basalt

Andesite and basalt flows (Early Miocene to Early Pliocene) at surface, covers 5 % of this area

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

Lithology: basalt; andesite; shoshonite

Olivine basalt (Pliocene and Miocene) (Miocene to Pliocene) at surface, covers < 0.1 % of this area

Lithology: basalt; andesite

Diorite (Jurassic to Cretaceous) at surface, covers 0.3 % of this area

Lithology: diorite; quartz diorite; gabbro; granite; granodiorite; serpentinite

Rhyolitic flows and shallow intrusive rocks (Middle Miocene to Late Miocene) at surface, covers 8 % of this area

RHYOLITIC FLOWS AND SHALLOW INTRUSIVE ROCKS

Lithology: rhyolite; dacite; trachyte

Serpentinite (Late Devonian to Early Triassic) at surface, covers < 0.1 % of this area

SERPENTINITE (Paleozoic)-Mineral, northwestern Nye, and eastern Humboldt counties

Lithology: serpentinite

Shale, chert, and minor amounts of quartzite, greenstone, and limestone (Ordovician) at surface, covers < 0.1 % of this area

SHALE, CHERT, AND MINOR AMOUNTS OF QUARTZITE, GREENSTONE, AND LIMESTONE-Includes units such as Vinini Formation of north-central Nevada, Palmetto Formation in southern and central parts of Esmeralda County, and Comus Formation in Humboldt County. Locally includes rocks of Silurian and Devonian age.

Lithology: chert; shale; limestone; quartzite; andesite; siltstone; sandstone; chemical; greenstone; dolostone (dolomite)

Granitic rocks, western Nevada (Jurassic to Cretaceous) at surface, covers 0.2 % of this area

GRANITIC ROCKS, WESTERN NEVADA (Mesozoic)-Mostly quartz monzonite and granodiorite. Inconclusively dated or not dated radiometrically

Lithology: granodiorite; quartz monzonite; granite; quartz diorite; gabbro

Ash-flow tuffs and tuffaceous sedimentary rocks (Middle Miocene to Late Miocene) at surface, covers 2 % of this area

ASH-FLOW TUFFS AND TUFFACEOUS SEDIMENTARY ROCKS

Lithology: ash-flow tuff; rhyolite; sandstone; dacite; trachyte

Playa, marsh, and alluvial-flat deposits, locally eroded (Quaternary) at surface, covers 10 % of this area

PLAYA, MARSH, AND ALLUVIAL-FLAT DEPOSITS, LOCALLY ERODED

Lithology: playa; alluvium

Welded tuffs and tuffaceous sedimentary rocks (upper? and middle Miocene) (Middle to Late Miocene) at surface, covers < 0.1 % of this area

Partly to densely welded vitric and vitric-crystal tuff of soda-rhyolitic, rhyolitic, and rhyodacitic composition that interfingers with and grades laterally into unit Tit. Includes some nonwelded ash-flow tuff and tuffaceous sedimentary rocks. Potassium-argon ages range from about 13 to 16 Ma. In Harney and Malheur Counties, it commonly overlies unit Tmb. Includes Dinner Creek Welded Tuff of Haddock (1965; 1967) and middle and upper Miocene ash-flow tuffs of Rytuba and others (1982; 1983a, b), widely exposed in the Trout Creek Mountains and adjacent areas, erupted from the McDermitt caldera complex, west and southwest of McDermitt, Nevada-Oregon, the White Horse caldera, northwest of McDermitt, and several other vent areas

Lithology: rhyolite; dacite; mudstone

Accessibility FOIA Privacy Policies and Notices

U.S. Department of the Interior | U.S. Geological Survey
URL: http://mrdata.usgs.gov/geology/state/fips-unit.php?code=f32013
Page Contact Information: pschweitzer@usgs.gov
Page Last modified: 10:03 on 08-May-2012