Geologic units in Iron county, Utah

Additional scientific data in this geographic area

Alluvium and colluvium (Quaternary) at surface, covers 46 % of this area

Alluvium and colluvium

Miocene volcanic rocks, undivided (Late Oligocene to Middle Miocene) at surface, covers 14 % 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.

Tertiary volcanic rocks, undivided (Tertiary) at surface, covers 9 % of this area

Tertiary volcanic rocks, undivided.

Isom Fm, Needles Range Fm, Escalante Desert Fm, Sawtooth Peak Fm, and Tunnel Springs Tuff (Late Eocene to Oligocene) at surface, covers 6 % of this area

Isom Fm (tuff), Needles Range Fm (ash-flow tuff), Escalante Desert Fm (ash-flow tuff), Sawtooth Peak Fm (ash-flow tuff), and Tunnel Springs Tuff.

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).

Claron Formation (Late Paleocene to Early Oligocene) at surface, covers 3 % of this area

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

Lake Bonneville deposits (Quaternary) at surface, covers 3 % of this area

Lake Bonneville deposits

Sevier River Formation (Miocene to Pliocene) at surface, covers 2 % of this area

Sevier River Formation.

Isom Fm, Needles Range Fm, and Bullion Canyon Volcanics (Late Eocene to Oligocene) at surface, covers 2 % of this area

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

Basalts (Quaternary) at surface, covers 2 % of this area

Basalts

Eolian deposits (Quaternary) at surface, covers 1 % of this area

Eolian deposits

Quartz Monzonite and granite (Oligocene to Miocene) at surface, covers 0.8 % of this area

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

Muddy Creek Formation (Miocene) at surface, covers 0.7 % of this area

Muddy Creek Formation (in Cedar City area).

Entrada and Carmel Formations (Middle Jurassic) at surface, covers 0.7 % of this area

Entrada and Carmel Formations (Arapien Shale at Marysvale).

Iron Springs Formation of Cedar City Area (Tropic Shale and Dakota Sandstone) (Late Cretaceous) at surface, covers 0.7 % of this area

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

Iron Springs Formation of Cedar City Area (Kaiparowits Fm) (Late Cretaceous) at surface, covers 0.7 % of this area

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

Rhyolites (Middle to Late Miocene) at surface, covers 0.5 % of this area

In Northwestern Utah: Dacitic tuff (8.5 my). In Logan-Huntsville Allochthon: rhyolite.

Older alluvial deposits (Quaternary) at surface, covers 0.5 % of this area

Older alluvial deposits

Navajo Sandstone, Kayenta and Moenave Formations (Early to Middle Jurassic) at surface, covers 0.4 % of this area

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

Basalts (Early to Middle Miocene) at surface, covers 0.3 % of this area

In Southwestern Utah: In Cedar City area: Page Ranch Fm, Rencher Fm and Quichapa Group (24my). In Marysvale area: Joe Lott Tuff, Mt. Belknap Volcanics, Osiris Tuff and Mt. Dutton Formation.

Notch Peak, Orr, Lamb, Weeks, and Wah Wah Summit Formations (Middle Cambrian to Early Ordovician) at surface, covers 0.3 % of this area

Notch Peak, Orr, Lamb, Weeks, and Wah Wah Summit Formations.

Alluvial materials, Axtell and Harkers Formations (Pliocene to Quaternary) at surface, covers 0.2 % of this area

Alluvial materials, Axtell and Harkers Formations

Landslides (Quaternary) at surface, covers 0.2 % of this area

Landslides

Moenkopi Formation (Early Triassic) at surface, covers 0.2 % of this area

Moenkopi Formation.

Playa (Holocene) at surface, covers 0.2 % of this area

Playa

Chinle Formation and Shinarump Conglomerate Member (Late Triassic) at surface, covers < 0.1 % of this area

Chinle Formation and Shinarump Conglomerate Member.

Ely Springs Dm, Eureka Qtz, Crystal Peak Dm, Watson Ranch Qzt, and the Pogonip Group (Ordovician) at surface, covers < 0.1 % of this area

Ely Springs Dm, Eureka Qtz, Crystal Peak Dm, Watson Ranch Qzt, and the Pogonip Group (Lehman Formation, Kanosh Shale, Juab, Wah Wah, Fillmore, and House Limestones).

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.

Navajo Sandstone (Star Range and Blue Mountain) (Early Jurassic) at surface, covers < 0.1 % of this area

Navajo Sandstone (Star Range and Blue Mountain).

Intrusions, chiefly granitic, of various dates (Late Eocene to Early Miocene) at surface, covers < 0.1 % of this area

Intrusions, chiefly granitic, of various dates.

Joana Limestone (Mississippian) at surface, covers < 0.1 % of this area

Joana Limestone.

Laketown Dolomite (Silurian) at surface, covers < 0.1 % of this area

Laketown Dolomite.

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.

Callville Limestone (Pennsylvanian) at surface, covers < 0.1 % of this area

Callville Limestone.

Nopah and Bonanza King Formations, Muav Limestone, and Pioche Shale (Middle Cambrian) at surface, covers < 0.1 % of this area

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

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.

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.

Mud and salt flats (Holocene) at surface, covers < 0.1 % of this area

Mud and salt flats

Green River Formation (Eocene) at surface, covers < 0.1 % of this area

Green River Formation.

Pilot Shale, Guilmette Formation, and Simonson and Sevy Dolomites (Devonian to Mississippian) at surface, covers < 0.1 % of this area

Pilot Shale, Guilmette Formation, and Simonson and Sevy Dolomites.

Coconino Sandstone, Supai Group, and Pakoon Formation (Early Permian) at surface, covers < 0.1 % of this area

Coconino Sandstone, Supai Group, and Pakoon Formation.

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.