Moenkopi Formation | |
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Stratigraphic range: | |
![]() Moenkopi at its reference section along the Little Colorado River west of Cameron, Arizona | |
Type | Geological formation |
Sub-units | See "Members" section |
Underlies | Chinle Formation |
Overlies | Kaibab Limestone |
Lithology | |
Primary | Sandstone |
Other | Shale |
Location | |
Coordinates | 35°55′05″N111°29′20″W / 35.918°N 111.489°W |
Region | Northern Arizona Southeast California East-central Nevada Southern Utah Northwestern New Mexico Southwestern Colorado |
Country | Southwestern United States |
Type section | |
Named for | Moenkopi Wash |
Named by | Ward |
Year defined | 1901 |
The Moenkopi Formation is a geological formation that is spread across the U.S. states of New Mexico, northern Arizona, Nevada, southeastern California, eastern Utah and western Colorado. This unit is considered to be a group in Arizona. Part of the Colorado Plateau and Basin and Range, this red sandstone was laid down in the Lower Triassic [1] and possibly part of the Middle Triassic, around 240 million years ago. [2]
There is no designated type locality for this formation. It was named for a development at the mouth of Moencopie Wash in the Grand Canyon area by Ward in 1901. [3] In 1917 a 'substitute' type locality was located by Gregory in the wall of the Little Colorado Canyon, about 5 miles below Tanner Crossing in Coconino County, Arizona. [4] While in the Great Basin, Bassler and Reeside characterized and named the Rock Canyon Conglomerate, Virgin Limestone, and Shnabkaib Shale members in 1921. [5] Salt Creek (later replaced by Wupatki and Moqui Members) and the Holbrook Member were found and named in the Black Mesa basin by Hager in 1922. [6]
The Sinbad Limestone Member was named in the Paradox Basin by Gilluly and Reeside in 1928. Williams and Gregory named the Timpoweap Member in the Plateau sedimentary province in 1947. [7]
The Wupatki Member was first used in the Plateau Sedimentary Province and its age was modified to Early and Middle(?) Triassic by McKee in 1951. [8] Contacts were revised by Robeck in 1956 and Cooley in 1958. The Tenderfoot, Ali Baba, Sewemup, and Pariott Members were named in the Piceance and Uinta Basins by Shoemaker and Newman in 1959. [9] The Hoskinnini Member was assigned in the Black Mesa and Paradox basins by Stewart in 1959. [10] Contacts were revised again by Schell and Yochelson in 1966. Blakey named the Black Dragon, Torrey, and Moody Canyon members in the Paradox Basin and Plateau Sedimentary Province in 1974. [11] Contacts were revised yet again by Welsh and others in 1979.
Kietzke modified the age to Early and Middle Triassic using biostratigraphic dating in 1988. The Anton Chico Member was assigned in the Palo Duro Basin and areal limits set by Lucas and Hunt in 1989. [12] In 1991 areal limits were set again by Lucas and Hayden. An overview was completed by Lucas in 1991, Sprinkel in 1994, Hintze and Axen in 1995 and later, Huntoon and others. [13]
The Moenkopi consists of thinly bedded sandstone, mudstone, and shale, with some limestone in the Capitol Reef area. It has a characteristic deep red color and tends to form slopes and benches. The depositional environment varies from fluvial channel and floodplain deposits in the eastern exposures to tidal mudflats in the Cedar Mesa area to deltaic sandstones and shallow marine limestones at Capitol Reef. In eastern Nevada and northwestern Utah, it thickens dramatically, then transitions to the Woodside, Thaynes, and Mahogany formations. [14]
The general deposition setting was sluggish rivers traversing a flat, featureless coastal plain to the sea. The low relief meant that the shoreline moved great distances with changes of sea level or even with the tides. Thickness varies from a feather edge against the Uncompahgre highlands to the east to over 600 metres (2,000 ft) in southwestern Utah. The thickness varies greatly in the Paradox Basin, where the Moenkopi is thin to nonexistent on the crests of salt anticlines and over 400 meters (1,300 feet) thick in the corresponding synclines. [14] [2]
The Moenkopi rests unconformably on Paleozoic beds and the Chinle Formation in turn rests unconformably on the Moenkopi. Both unconformities are locally angular unconformities. [15] The lower unconformity corresponds to the regional Tr-1 unconformity and the upper to the regional Tr-3 unconformity. The Tr-1 unconformity represents a hiatus of at least 20 million years while Tr-2 represents a hiatus of about 10 million years. [16]
Members differ considerably from east to west, in part because sandstone beds corresponding to marine transgressions are used to define members to the west but cannot be traced to the east. [17] In different regions, by ascending stratigraphic order, the members are:
Canyonlands and Glen Canyon area: [18]
San Juan Basin and Tucumcari: [12] [20] [21]
Other members listed in alphabetical order, with asterisks (*) indicating usage by the U.S. Geological Survey and other usages by state geological surveys: [22]
Found in these geologic locations: [22]
Found within these parks (incomplete list):
Numerous fossils of bivalves were found in the Olenekian Virgin Limestone Member of the Moenkopi Formation, in south-western Utah. The discovery of 27 species from 18 genera of two subclasses in these sites in 2013 cast doubt on previous claims that the bivalve fauna only recovered in the Middle Triassic after the end-Permian mass extinction. [23] The first subclass, Pteriomorphia, includes mainly genera that survived the mass extinction, while the second, Heteroconchia, is represented mainly by genera that evolved in the Early Triassic. [23]
Pteriomorphs reported from the Moenkopi Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Member | Material | Notes | Images |
Bakevellia | B. cf. exporrecta | South-western Utah |
| Numerous specimens. | ||
B. costata | South-western Utah |
| Numerous left valves. | The absence of right valves may be caused by the "hydrodynamic separation of the differentially vaulted valves or to weaker calcification". [23] | ||
Eumorphotis | E. venetiana | South-western Utah |
| One left valve with shell over 18.3 mm long and 21.7 mm high. [23] | ||
E. ericius | South-western Utah |
| Several specimens with shells. | The Anisian Pseudomonotis beneckei is a possibly related species. [23] | ||
E. virginensis | South-western Utah |
| Several fragmental specimens. | |||
E. cf. multiformis | South-western Utah |
| One incomplete left valve. | |||
Leptochondria | L. nuetzeli | South-western Utah |
| "One articulated specimen and approximately 50 isolated left valves", all with external shell layer preserved. [23] | ||
L. curtocardinalis | South-western Utah |
| Several specimens. | |||
Modiolus | M. sp. | South-western Utah |
| One right valve (USNM 543477) 6.5 mm long and 4.3 mm high. | Shell interior is unknown. USNM 543477 have similarities with "Modiolus" sp. from the late Griesbachian of Russia, and Promytilus homevalensis from the early Permian of Australia. [23] | |
Parallelodon | P.? aff. beyrichii | South-western Utah |
| Two right valves. | ||
Promyalina | P. putiatinensis | South-western Utah |
| Numerous medium-sized specimens, mostly with outer shell layer but eroded to varying degrees. | ||
Pernopecten | P.? sp. | South-western Utah |
| One left valve 27 mm long and 27.6 mm high. [23] | ||
Heteroconchs reported from the Moenkopi Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Member | Material | Notes | Images |
Arcomya | A.? sp. | South-western Utah |
| Two steinkerns. | ||
Heminajas | H.? cf. balatonis | South-western Utah |
| Few specimens. | Possibly belong to Neoschizodus thaynesianus. [23] | |
Myoconcha | M. cf. plana | South-western Utah |
| Several specimens. | Slightly differs from the holotype by greater divergence of the dorsal and ventral margins. [23] | |
Neoschizodus | N. laevigatus | South-western Utah |
| One left valve. | ||
N. praeorbicularis | South-western Utah |
| One steinkern. | |||
Permophorus | P. triassicus | South-western Utah |
| Several specimens (steinkerns). | ||
Pleuromya | P. prima | South-western Utah |
| One steinkern. | Tre earliest specimen of the genus. [23] | |
Protopis | P.? aff. waageni | South-western Utah |
| One left valve over 10 mm long and 10 mm high. [23] | ||
Sementiconcha | S. recuperator | South-western Utah |
| 119 steinkerns. | ||
Trigonodus | T. cf. orientalis | South-western Utah |
| Several specimens. | ||
T. cf. sandbergeri | South-western Utah |
| Several specimens. | |||
Unicaridum | U.? sp. | South-western Utah |
| One left valve. | Assigned to Unicaridum due to subelliptical shape and slightly concave central part of the umbo. [23] | |
Unionites | U.? fassaensis | South-western Utah |
| Three steinkerns. | ||
U.? canalensis | South-western Utah |
| Four steinkerns. | |||
U.? cf. borealis | South-western Utah |
| Numerous specimens. | Specimens look similar to the Griesbachian U. borealis from East Greenland, but the type material is poorly preserved, which makes comparison with published specimens difficult. [23] | ||
This section needs additional citations for verification .(May 2020) |
A diverse fossil vertebrate fauna has been described from the Moenkopi Formation, mainly from the Wupatki Member and Holbrook Member of northern Arizona. Described basal vertebrates include freshwater hybodont sharks, coelacanths, and lungfish. Temnospondyl amphibians are a common component of the fauna. Temnospondyli include Eocyclotosaurus , Quasicyclotosaurus , Wellesaurus , Vigilius , and Cosgriffius . The rhynchosaur Ammorhynchus is known, but rare. Anisodontosaurus is an enigmatic reptile only known from a few tooth-bearing jaws. The poposauroid archosaur Arizonasaurus is known from one relatively complete skeleton and a significant amount of other isolated material. Footprints and several fragmentary body fossils are known from dicynodonts. The footprints of Cheirotherium and Rhynchosauroides are common in the Wupatki Member.
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: CS1 maint: multiple names: authors list (link)The Entrada Sandstone is a formation in the San Rafael Group found in the U.S. states of Wyoming, Colorado, northwest New Mexico, northeast Arizona, and southeast Utah. Part of the Colorado Plateau, this formation was deposited during the Jurassic Period sometime between 180 and 140 million years ago in various environments, including tidal mudflats, beaches, and sand dunes. The Middle Jurassic San Rafael Group was dominantly deposited as ergs in a desert environment around the shallow Sundance Sea.
The exposed geology of the Capitol Reef area presents a record of mostly Mesozoic-aged sedimentation in an area of North America in and around Capitol Reef National Park, on the Colorado Plateau in southeastern Utah.
The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone, and limestone and is light gray, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the Jurassic period.
The Cutler Formation or Cutler Group is a rock unit that is exposed across the U.S. states of Arizona, northwest New Mexico, southeast Utah and southwest Colorado. It was laid down in the Early Permian during the Wolfcampian epoch.
The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In New Mexico, it is often raised to the status of a geological group, the Chinle Group. Some authors have controversially considered the Chinle to be synonymous to the Dockum Group of eastern Colorado and New Mexico, western Texas, the Oklahoma panhandle, and southwestern Kansas. The Chinle Formation is part of the Colorado Plateau, Basin and Range, and the southern section of the Interior Plains. A probable separate depositional basin within the Chinle is found in northwestern Colorado and northeastern Utah. The southern portion of the Chinle reaches a maximum thickness of a little over 520 meters (1,710 ft). Typically, the Chinle rests unconformably on the Moenkopi Formation.
The Kaibab Limestone is a resistant cliff-forming, Permian geologic formation that crops out across the U.S. states of northern Arizona, southern Utah, east central Nevada and southeast California. It is also known as the Kaibab Formation in Arizona, Nevada, and Utah. The Kaibab Limestone forms the rim of the Grand Canyon. In the Big Maria Mountains, California, the Kaibab Limestone is highly metamorphosed and known as the Kaibab Marble.
The Glen Canyon Group is a geologic group of formations that is spread across the U.S. states of Nevada, Utah, northern Arizona, north west New Mexico and western Colorado. It is called the Glen Canyon Sandstone in the Green River Basin of Colorado and Utah.
The San Rafael Group is a geologic group or collection of related rock formations that is spread across the U.S. states of New Mexico, Arizona, Utah and Colorado. As part of the Colorado Plateau, this group of formations was laid down in the Middle Jurassic during the Bajocian, Bathonian and Callovian Stages.
The Carmel Formation is a geologic formation in the San Rafael Group that is spread across the U.S. states of Wyoming, Utah, Colorado, north east Arizona and New Mexico. Part of the Colorado Plateau, this formation was laid down in the Middle Jurassic during the late Bajocian, through the Bathonian and into the early Callovian stages.
The Summerville Formation is a geological formation in New Mexico, Colorado, and Utah of the Southwestern United States. It dates back to the Oxfordian stage of the Late Jurassic.
Cedar Mesa Sandstone is a sandstone member of the Cutler Formation, found in southeast Utah, southwest Colorado, northwest New Mexico, and northeast Arizona.
In geology, the Paradox Formation Is a Pennsylvanian age formation which consists of abundant evaporites with lesser interbedded shale, sandstone, and limestone. The evaporites are largely composed of gypsum, anhydrite, and halite. The formation is found mostly in the subsurface, but there are scattered exposures in anticlines in eastern Utah and western Colorado. These surface exposures occur in the Black Mesa, San Juan and Paradox Basins and the formation is found in the subsurface in southwestern Colorado, southeastern Utah, northeastern Arizona and northeastern New Mexico.
The Supai Group is a slope-forming section of red bed deposits found in the Colorado Plateau. The group was laid down during the Pennsylvanian to Lower Permian. Cliff-forming interbeds of sandstone are noticeable throughout the group. The Supai Group is especially exposed throughout the Grand Canyon in northwest Arizona, as well as local regions of southwest Utah, such as the Virgin River valley region. It occurs in Arizona at Chino Point, Sycamore Canyon, and famously at Sedona as parts of Oak Creek Canyon. In the Sedona region, it is overlain by the Hermit Formation, and the colorful Schnebly Hill Formation.
The Shinarump Conglomerate is a geologic formation found in the Four Corners region of the United States. It was deposited in the early part of the Late Triassic period.
The Bright Angel Shale is one of five geological formations that comprise the Cambrian Tonto Group. It and the other formations of the Tonto Group outcrop in the Grand Canyon, Arizona, and parts of northern Arizona, central Arizona, southeast California, southern Nevada, and southeast Utah. The Bright Angel Shale consists of locally fossiliferous, green and red-brown, micaceous, fissile shale (mudstone) and siltstone with local, thicker beds of brown to tan sandstone and limestone. It ranges in thickness from 57 to 450 feet. Typically, its thin-bedded shales and sandstones are interbedded in cm-scale cycles. They also exhibit abundant sedimentary structures that include current, oscillation, and interference ripples. The Bright Angel Shale also gradually grades downward into the underlying Tapeats Sandstone. It also complexly interfingers with the overlying Muav Limestone. These characters make the upper and lower contacts of the Bright Angel Shale often difficult to define. Typically, its thin-bedded shales and sandstones erode into green and red-brown slopes that rise from the Tonto Platform up to cliffs formed by limestones of the overlying Muav Limestone and dolomites of the Frenchman Mountain Dolostone.
The San Pedro Arroyo Formation is a geologic formation in south-central New Mexico. It preserves fossils dating back to the late Triassic period.
The Curtis Formation is a geologic formation in Utah. It preserves fossils dating back to the Callovian age of the Jurassic period.
The Sinbad Formation is a geologic formation in Utah initially named and described by James Gilluly and J. B. Reeside Junior in the 1920s. It is known for preserving fossils dating back to the Early Triassic epoch.
The Virgin Formation is a geologic formation in Utah. It preserves fossils dating back to the Triassic period.
The Bluff Formation is a geological formation found in the Four Corners area. It was deposited in the late Jurassic Period.
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