Geologic units in Washington county, Utah

Additional scientific data in this geographic area

Alluvium and colluvium (Quaternary) at surface, covers 20 % of this area

Alluvium and colluvium

Navajo Sandstone, Kayenta and Moenave Formations (Early to Middle Jurassic) at surface, covers 18 % of this area

Navajo Sandstone, Kayenta and Moenave Formations. Includes Zion National Park (Navajo Ss).

Miocene volcanic rocks, undivided (Late Oligocene to Middle Miocene) at surface, covers 10 % of this area

In Western Utah: Quichapa Group and other volcanic rocks (Tmb,Tmr,Tma). In Central Utah: Silver Shield Latite (17 my) and Pinyon Creek Conglomerate.

Basalts (Quaternary) at surface, covers 9 % of this area

Basalts

Moenkopi Formation (Early Triassic) at surface, covers 7 % of this area

Moenkopi Formation.

Tertiary volcanic rocks, undivided (Tertiary) at surface, covers 6 % of this area

Tertiary volcanic rocks, undivided.

Chinle Formation and Shinarump Conglomerate Member (Late Triassic) at surface, covers 6 % of this area

Chinle Formation and Shinarump Conglomerate Member.

Iron Springs Formation of Cedar City Area (Wahweap Ss and Straight Cliffs Fm) (Late Cretaceous) at surface, covers 4 % of this area

Iron Springs Formation of Cedar City Area (Wahweap Ss and Straight Cliffs Fm).

Quartz Monzonite and granite (Oligocene to Miocene) at surface, covers 3 % of this area

Quartz Monzonite (in Cedar City area) and monzonite and granite (in Marysvale area).

Entrada and Carmel Formations (Middle Jurassic) at surface, covers 3 % of this area

Entrada and Carmel Formations (Arapien Shale at Marysvale).

Kaibab Limestone and Toroweap Formation (Early Permian) at surface, covers 3 % of this area

Kaibab Limestone and Toroweap Formation.

Muddy Creek Formation (Miocene) at surface, covers 2 % of this area

Muddy Creek Formation (in Cedar City area).

Claron Formation (Late Paleocene to Early Oligocene) at surface, covers 2 % of this area

Claron Formation. Includes Bryce Canyon/Cedar Breaks Nat. Park.

Callville Limestone (Pennsylvanian) at surface, covers 1 % of this area

Callville Limestone.

Iron Springs Formation of Cedar City Area (Tropic Shale and Dakota Sandstone) (Late Cretaceous) at surface, covers 1.0 % of this area

Iron Springs Formation of Cedar City Area (Tropic Shale and Dakota Sandstone).

Coconino Sandstone, Supai Group, and Pakoon Formation (Early Permian) at surface, covers 1.0 % of this area

Coconino Sandstone, Supai Group, and Pakoon Formation.

Redwall Limestone (Mississippian) at surface, covers 0.6 % of this area

Redwall Limestone (chert).

Alluvial materials, Axtell and Harkers Formations (Pliocene to Quaternary) at surface, covers 0.6 % of this area

Alluvial materials, Axtell and Harkers Formations

Vishnu Schist and granitic intrusions (Precambrian) at surface, covers 0.5 % of this area

Vishnu Schist and granitic intrusions (1650 my).

Nopah and Bonanza King Formations, Muav Limestone, and Pioche Shale (Middle Cambrian) at surface, covers 0.4 % of this area

Nopah and Bonanza King Formations, Muav Limestone, and Pioche Shale

Older alluvial deposits (Quaternary) at surface, covers 0.4 % of this area

Older alluvial deposits

Iron Springs Formation of Cedar City Area (Kaiparowits Fm) (Late Cretaceous) at surface, covers 0.3 % of this area

Iron Springs Formation of Cedar City Area (Kaiparowits Fm).

Granitic intrusions (Precambrian) at surface, covers 0.3 % of this area

Granitic intrusions

Temple Butte and Muddy Peak Limestones (Devonian) at surface, covers 0.2 % of this area

Temple Butte and Muddy Peak Limestones.

Isom Fm, Needles Range Fm, and Bullion Canyon Volcanics (Late Eocene to Oligocene) at surface, covers 0.2 % of this area

In Cedar City area: Isom Fm and Needles Range Fm (29 my). In Marysvale area: Bullion Canyon Volcanics.

Landslides (Quaternary) at surface, covers 0.1 % of this area

Landslides

Sevier River Formation (Miocene to Pliocene) at surface, covers 0.1 % of this area

Sevier River Formation.

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

Eolian deposits

Prospect Mountain Quartzite (Early to Middle Cambrian) at surface, covers < 0.1 % of this area

Prospect Mountain Quartzite.

Intermediate andesite and intermediate flows and breccias (lower Miocene and Oligocene) at surface, covers < 0.1 % of this area

Andesite flows and breccias and other related rocks of intermediate composition such as dacite, rhyodacite, quartz latite, and biotite-hornblende porphyries. This unit includes units mapped as the South Willow Formation on the Washoe North map, the Milltown Andesite on the Nye South and Esmeralda County maps, the Mizpah Trachyte on the Nye North map, and other units. It corresponds to unit Ta2 on the 1978 State map. It crops out in all counties except Clark, Eureka, Lyon, Douglas, and Carson.

Younger tuffaceous sedimentary rocks (Pliocene and Miocene) at surface, covers < 0.1 % of this area

Tuffaceous and other young Tertiary sedimentary rocks. Most of these rocks are sedimentary with a strong volcanic component - a few are tuffaceous with a strong sedimentary component. This unit includes rocks originally mapped as the High Rock sequence in Washoe County; the Horse Camp Formation in northern Nye County; the Esmeralda Formation in Mineral and Esmeralda Counties; older lake beds in Lincoln County; the Belted Range Tuff; the Indian Trail Formation (now abandoned); Timber Mountain, Paintbrush, and Crater Flat Tuffs; Wahmonie and Salyer Formations in southern Nye County; the Siebert Tuff in Esmeralda County; the Muddy Creek Formation in Clark County; and the Thousand Creek and Virgin Valley “beds” in Humboldt County; and other unnamed units. It corresponds to units Ts3 and Tts from the 1978 State map. It is present in all counties.

Alluvium, undifferentiated (Holocene and Pleistocene) at surface, covers < 0.1 % of this area

Unit is present in all counties. Some counties divided the alluvium into younger and older units, and some did not. For those that did not, or used other generalized terms for Quaternary rocks, the unit Qal has been used for the general undivided alluvium. Additionally, when polygons have been edited and changed to alluvium, Qal was used as the general value; hence it now is present in all counties. Qya-Younger alluvium: Map unit is used in Churchill, Elko, Esmeralda, Eureka, Humboldt, Lander, and Lincoln Counties where geologic information suggests better-defined younger versus older alluvium. It is mostly interchangeable with Qal, except that it implies some specifically younger Quaternary deposits.

Younger rhyolitic flows and shallow intrusive rocks (Miocene) at surface, covers < 0.1 % of this area

Rhyolitic flows, domes, plugs, breccias, quartz latite, rhyodacite, quartz porphyry dikes, and other shallow intrusive rocks. This unit includes rocks mapped as the Cañon Rhyolite on the Washoe North map, the Jarbidge Rhyolite and phenorhyolitic and phenodacitic flows and domes on the Elko County map, and other unnamed units. It has a distribution similar to Tt3, with exposures in the northern and southern parts of the State, but only crops out in a few places in the central region. It corresponds to unit Tr3 on the 1978 State map, and also includes a few rocks mapped as Trt on the 1978 State map. This unit is exposed in every county except White Pine.

Younger silicic ash flow tuffs (Miocene) at surface, covers < 0.1 % of this area

Includes units mapped as the High Rock sequence on the Washoe North map; the Timber Mountain, Paintbrush, Crater Flat, and Belted Range Tuffs, and Indian Trail Formation (now abandoned) on the Nye South map; the Thirsty Canyon Tuff on the Nye South and Esmeralda maps; and other unnamed units. Locally it includes tuffaceous sedimentary rocks interstratified with tuffs. It is present in the northernmost part and southernmost parts of the State, and is not exposed in the central region. It corresponds to unit Tt3 on the 1978 State map, although a few rocks also mapped as Trt on the 1978 State map also are included. It is present in Clark, Churchill, Washoe, Nye, Lincoln, Lyon, Douglas, Carson, Esmeralda, Elko, Humboldt, Pershing, and Mineral Counties.

Pliocene to middle Miocene deposits (Middle Miocene to Pliocene) at surface, covers < 0.1 % of this area

Moderately to strongly consolidated conglomerate and sandstone deposited in basins during and after late Tertiary faulting. Includes lesser amounts of mudstone, siltstone, limestone, and gypsum. These deposits are generally light gray or tan. They commonly form high rounded hills and ridges in modern basins, and locally form prominent bluffs. Deposits of this unit are widely exposed in the dissected basins of southeastern and central Arizona. (2-16 Ma)

Intermediate silicic ash flow tuff (lower Miocene and Oligocene) at surface, covers < 0.1 % of this area

Welded and nonwelded silicic ash flow tuffs. Aside from alluvium, this unit covers more of Nevada than any other rock, with over 4,000 polygons representing it on this map. It is principally exposed in the central regions of the State. It locally includes thin units of air fall tuff and sedimentary rocks. It includes rocks mapped on the Washoe South, Lyon, Douglas, and Carson Counties maps as the Hartford Hill Rhyolite Tuff (now abandoned); on the Nye South map as the tuff of White Blotch Spring, the tuffs of Antelope Springs, and the tuff of Monotony Valley; in Lander County it is mapped as the Bates Mountain Tuff, Caetano Tuff, Edwards Creek Tuff, New Pass Tuff, tuff of Hall Creek, and the tuff of McCoy Mine; in Lander and Pershing Counties it is the Fish Creek Mountains Tuff; on both of the Nye County maps it is the Fraction Tuff; it also includes the Pancake Summit Tuff, Northumberland Tuff, Shingle Pass Tuff, some outcrops of Darrough Felsite shown to be Tertiary (other outcrops have been shown to be Mesozoic or Paleozoic), tuffs of Moores station, tuffs of Peavine Canyon, tuffs of the Pancake caldera complex, the Stone Cabin Formation, tuff of Saulsbury Wash, tuff of Kiln Canyon, the Tonopah Formation, tuffs of Hannapah, tuff of Bald Mountain, the Needles Range Formation, and the Calloway Well Formation on the Nye North map; in Esmeralda County it is the Kendall Tuff and latite; and in northern Nye and Lander Counties it is the Toiyabe Quartz Latite (now abandoned), and other unnamed units. It corresponds to unit Tt2 on the 1978 State map. It crops out in every county except Clark.

Carbonate Shelf Sequence - Limestone (Mississippian) at surface, covers < 0.1 % of this area

This unit is present in southern Nye, Lincoln, and Clark Counties. Unit includes the Monte Cristo Limestone, and Lower Mississippian rocks referred to as the Joana, Mercury, Bristol Pass, and Rogers Spring Limestones. It generally lies depositionally above Devonian carbonate rocks and beneath Pennsylvanian carbonate and clastic rocks. In the Meadow Valley Mountains in southern Lincoln County it is also shown sitting on a thin horizon of Pilot Shale and overlain by a thin Mississippian clastic unit assigned to unit IPMcl.

Early Pleistocene to latest Pliocene surficial deposits (Late Pliocene to Early Pleistocene) at surface, covers < 0.1 % of this area

Coarse relict alluvial fan deposits that form rounded ridges or flat, isolated surfaces that are moderately to deeply incised by streams. These deposits are generally topographically high and have undergone substantial erosion. Deposits are moderately to strongly consolidated, and commonly contain coarser grained sediment than younger deposits in the same area. (0.75-3 Ma)

Carbonate Shelf Sequence - Limestone, dolomite, siltstone, sandstone, and shale (Lower Permian and Pennsylvanian) at surface, covers < 0.1 % of this area

Present in Elko, White Pine, Lincoln, and Clark Counties. This unit represents mostly Upper Pennsylvanian and Lower Permian rocks that have not otherwise been separated into units Psc or IPMbc. Unit includes unnamed Pennsylvanian and Lower Permian limestone and sandstone beds in Lincoln County, the Bird Spring Formation in Clark County, the Riepe Spring and Ely Limestones (undivided) in White Pine County, and limestone and dolomite rocks not otherwise assigned in Elko County. This unit lies depositionally below unit Psc and above the Ely Limestone (IPMbc) where it is mapped separately. Where unit IPMbc is not mapped separately in southern Nevada, the unit lies directly on Mississippian carbonate (Mc) and in White Pine County it rests on undivided Chainman and Pilot Shales and Joana Limestone (shown as either unit IPMcl or MDcl).

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

Basalt flows, plugs and dikes, some olivine basalt, and andesite and latitic rocks. This unit corresponds with unit Tb on the 1978 State map. It is present on the Washoe North, Washoe South, Lincoln, Clark, Elko, Eureka, Humboldt, Nye South, and Lander County maps.

Carbonate Shelf Sequence - Cherty limestone, dolomite, shale, and sandstone (Middle to Lower Permian) at surface, covers < 0.1 % of this area

These Permian rocks include cherty limestone, dolomite, shale, sandstone, bioclastic limestone, and phosphatic limestone exposed in Elko, White Pine, Lincoln, and Clark counties. This unit includes rocks mapped as the Phosphoria Formation; the Gerster Limestone, Plympton Formation, Kaibab Limestone, and Grandeur Formation of the Park City Group; the Park City Group undivided; the Toroweap Formation; and the Coconino Sandstone. Unit Pc is disconformably overlain by Triassic unit TRmt in scattered places in eastern and southern Nevada. It depositionally overlies unit Psc. It matches closely with unit Pc of Stewart and Carlson (1978).