HOME

TheInfoList



OR:

The Moenkopi Formation is a
geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...
that is spread across the
U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...
s of
New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...
, northern
Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
,
Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...
, southeastern
California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
, eastern
Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
and western
Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...
. This unit is considered to be a
group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic iden ...
in Arizona. Part of the
Colorado Plateau The Colorado Plateau, also known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. This province covers an area of ...
and
Basin and Range Basin and range topography is characterized by alternating parallel mountain ranges and valleys. It is a result of crustal extension due to mantle upwelling, gravitational collapse, crustal thickening, or relaxation of confining stresses. The e ...
, this red
sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...
was laid down in the
Lower Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...
and possibly part of the
Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...
, around 240 million years ago.


History of investigation

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 The Grand Canyon (, yuf-x-yav, Wi:kaʼi:la, , Southern Paiute language: Paxa’uipi, ) is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is long, up to wide and attains a depth of over a m ...
area by Ward in 1901. In 1917 a 'substitute' type locality was located by Gregory in the wall of the
Little Colorado Canyon Little is a synonym for small size and may refer to: Arts and entertainment * ''Little'' (album), 1990 debut album of Vic Chesnutt * ''Little'' (film), 2019 American comedy film *The Littles, a series of children's novels by American author John P ...
, about 5 miles below Tanner Crossing in
Coconino County, Arizona Coconino County is a County (United States), county in the north-central part of the U.S. state of Arizona. Its population was 145,101 at the 2020 United States census, 2020 census. The county seat is Flagstaff, Arizona, Flagstaff. The count ...
. While in the Great Basin, Bassler and Reeside characterized and named the Rock Canyon Conglomerate, Virgin Limestone, and Shnabkaib Shale members in 1921. 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. 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. The Wupatki Member was first used in the
Plateau Sedimentary Province The Colorado Plateau, also known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. This province covers an area ...
and its age was modified to Early and Middle(?) Triassic by McKee in 1951. 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. The Hoskinnini Member was assigned in the Black Mesa and Paradox basins by Stewart in 1959. 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. 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. 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.For the whole section, except where noted: GEOLEX database Bibliographic References


Description

The Moenkopi consists of thinly bedded
sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...
,
mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...
, and
shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...
, with some
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
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 Cedar Mesa is a plateau in San Juan County in the southeastern portion of the U.S. state of Utah. It extends from Elk Ridge in the north, Comb Wash to the east, the gorge of the San Juan River to the south, and Grand Gulch to the west, an are ...
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. 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 in southwestern Utah. The thickness varies greatly in the
Paradox Basin The Paradox Basin is an asymmetric foreland basin located mostly in southeast Utah and southwest Colorado, but extending into northeast Arizona and northwest New Mexico. The basin is a large elongate northwest to southeast oriented depression for ...
, where the Moenkopi is thin to nonexistent on the crests of salt
anticline In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...
s and over thick in the corresponding
syncline In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimpose ...
s. The Moenkopi rests unconformably on
Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...
beds and the
Chinle Formation 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 Ne ...
in turn rests unconformably on the Moenkopi. Both unconformities are locally angular unconformities. 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.


Members

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. In different regions, by ascending stratigraphic order, the members are: Paradox Basin: * ''Tenderfoot Member''. This is everywhere in contact with the
Cutler Formation 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. Descript ...
on an angular unconformity. Up to thick, it consists of basal conglomerate,
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...
, massive cliff-forming mudstone and silty sandstone. * ''Ali Baba Member''. This is red conglomeratic sandstone and red siltstone and was laid down by energetic rivers. A distinctive feature is load structures. Sediment sources were apparently the crests of anticlines, and paleocurrent directions are north to northwest, along the corresponding synclines. * ''Sewemup Member''. This is thinly bedded siltstone, shale, and sandstone, with enough gypsum content to give it a light brown color that contrasts with the darker brown Ali Baba Member. * ''Parriott Member''. This is distinguished from the light brown Sewemup Member by its multihued brown, red, orange and purple strata. Exposures are geographically limited, appearing only in Richardson Amphitheater, Castle Valley, Sinbad Valley, and Big Bend meander of the Colorado River. This member may be separated from the Sewemup Member by a regional unconformity. Canyonlands and Glen Canyon area: * ''Hoskinnini Member'': Sandstone and siltstone. Found only in the southern part of the area. * ''Black Dragon Member''. Consists of a basal conglomerate; thinly bedded red sandstone, siltstone, and shale deposited in a tidal flat environment; a sandstone sheet; and a second sequence of tidal flat deposits. * ''Sinbad Limestone Member''. Named for the Sinbad region in the
San Rafael Swell The San Rafael Swell is a large geologic feature located in south-central Utah, United States about west of Green River. The San Rafael Swell, measuring approximately , consists of a giant dome-shaped anticline of sandstone, shale, and limeston ...
. Consists of yellowish limestone deposited by a brief marine transgression. * ''Torrey Member''. Red beds signifying a return to subaerial deposition. * ''Moody Canyon Member''. Thinly bedded slope forming siltstone and mudstone with minor evaporites. San Juan Basin and Tucumcari: * ''Anton Chico Member''. Described previously as the red sandstone member of the Santa Rosa Formation, but placed in its own formation after it was recognized to be middle Triassic in age. Subsequently, named as a member of the Moenkopi when its beds were traced west and demonstrated that it was deposited in a single basin with Moenkopi beds in Arizona. Other members listed in alphabetical order, with asterisks (*) indicating usage by the U.S. Geological Survey and other usages by state geological surveys:GEOLEX database: Moenkopi * ''Holbrook Sandstone Member'' (AZ*) * ''Moqui Member'' (AZ*) * ''Rock Canyon Conglomerate Member'' (AZ*, NV*, UT*) * ''Shnabkaib Member'' (AZ*, NV*, UT*) * ''Timpoweap Member'' (AZ, NV, UT*) * '' Virgin Limestone Member'' (AZ*, NV*, UT*) * ''Winslow Member'' (AZ) * ''Wupatki Member'' (AZ*)


Places visible

Found in these geologic locations: *
Black Mesa Basin Black Mesa (also called Big Mountain) is an upland mountainous mesa of Arizona, north-trending in Navajo County, west and southeast-trending in Apache County. In Navajo it is called ('Black Mountain') and during Mexican rule of Arizona it was c ...
* *
Great Basin The Great Basin is the largest area of contiguous endorheic basin, endorheic watersheds, those with no outlets, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja California ...
province* *
Green River Basin Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combina ...
* * Las Vegas-Raton Basin *
Orogrande Basin The Orogrande Basin is a geologic province in southern New Mexico and western Texas. It includes Doña Ana, Sierra, Socorro, Lincoln, and Otero Counties in New Mexico and El Paso County, Texas. The province takes its name from the community o ...
* Palo Duro Basin *
Paradox Basin The Paradox Basin is an asymmetric foreland basin located mostly in southeast Utah and southwest Colorado, but extending into northeast Arizona and northwest New Mexico. The basin is a large elongate northwest to southeast oriented depression for ...
* *
Piceance Basin The Piceance Basin is a geologic structural basin in northwestern Colorado, in the United States. It includes geologic formations from Cambrian to Holocene in age, but the thickest section is made up of rocks from the Cretaceous Period. The basi ...
* *
Plateau sedimentary province The Colorado Plateau, also known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. This province covers an area ...
* *
San Juan Basin The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah a ...
* *
Uinta Basin The Uinta Basin (also known as the Uintah Basin) is a physiographic section of the larger Colorado Plateaus province, which in turn is part of the larger Intermontane Plateaus physiographic division. It is also a geologic structural basin in ...
* Found within these parks (incomplete list): *
Grand Canyon National Park Grand Canyon National Park, located in northwestern Arizona, is the 15th site in the United States to have been named as a national park. The park's central feature is the Grand Canyon, a gorge of the Colorado River, which is often consider ...
*
Capitol Reef National Park Capitol Reef National Park is an American national park in south-central Utah. The park is approximately long on its northsouth axis and just wide on average. The park was established in 1971 to preserve of desert landscape and is open all ye ...
*
Zion National Park Zion National Park is an American national park located in southwestern Utah near the town of Springdale. Located at the junction of the Colorado Plateau, Great Basin, and Mojave Desert regions, the park has a unique geography and a variety ...
*
Monument Valley Monument Valley ( nv, Tsé Biiʼ Ndzisgaii, , meaning ''valley of the rocks'') is a region of the Colorado Plateau characterized by a cluster of sandstone buttes, the largest reaching above the valley floor. It is located on the Utah-Arizona s ...
Navajo Nation The Navajo Nation ( nv, Naabeehó Bináhásdzo), also known as Navajoland, is a Native American reservation in the United States. It occupies portions of northeastern Arizona, northwestern New Mexico, and southeastern Utah; at roughly , the ...
Tribal Park *
Dinosaur National Monument Dinosaur National Monument is an American national monument located on the southeast flank of the Uinta Mountains on the border between Colorado and Utah at the confluence of the Green and Yampa rivers. Although most of the monument area is in ...
*
Glen Canyon National Recreation Area Glen Canyon National Recreation Area (shortened to Glen Canyon NRA or GCNRA) is a national recreation area and conservation unit of the United States National Park Service that encompasses the area around Lake Powell and lower Cataract Canyon i ...
*
Walnut Canyon National Monument Walnut Canyon National Monument (Hopi: Wupatupqa) is a United States National Monument located about southeast of downtown Flagstaff, Arizona, near Interstate 40. The canyon rim elevation is ; the canyon's floor is 350 ft lower. A long loo ...
*
Wupatki National Monument The Wupatki National Monument is a United States National Monument located in north-central Arizona, near Flagstaff. Rich in Native American archaeological sites, the monument is administered by the National Park Service in close conjunction w ...


Fauna

A diverse fossil vertebrate fauna has been described from the Moenkopi Formation, mainly from the
Wupatki Member The Wupatki National Monument is a National monument (United States), United States National Monument located in north-central Arizona, near Flagstaff, Arizona, Flagstaff. Rich in Native Americans in the United States, Native American archaeolog ...
and Holbrook Member of northern Arizona. Described basal vertebrates include freshwater
hybodont Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like chondrichthyans, which existed from the late Devonian to the Late Cretaceous. They form the group of Elasmobranchii closest to neoselachians, the clade of modern shark ...
shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...
s,
coelacanth The coelacanths ( ) are fish belonging to the order Actinistia that includes two extant species in the genus ''Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off the east coast ...
s, and
lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...
. Temnospondyl
amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
s are a common component of the fauna.
Temnospondyli Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carb ...
include ''
Eocyclotosaurus ''Eocyclotosaurus'' is an extinct genus of mastodonsauroid temnospondyl from the Middle Triassic (Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from millio ...
'', '' Quasicyclotosaurus'', ''
Wellesaurus ''Wellesaurus'' is an extinct genus of mastodonsauroid temnospondyl. They were amphibious carnivores that lived in freshwater environments. ''Wellesaurus'' encompasses several species which were connected when the genus was named in 1971. The ...
'', '' Vigilius'', and ''
Cosgriffius ''Cosgriffius'' is an extinct genus of trematosaurian temnospondyl within the family Trematosauridae. It was described in 1993 by Samuel P. Welles based on a single partial skull from the well-known Meteor Crater Quarry (Early Triassic Moenkopi F ...
''. The
rhynchosaur Rhynchosaurs are a group of extinct herbivorous Triassic archosauromorph reptiles, belonging to the order Rhynchosauria. Members of the group are distinguished by their triangular skulls and elongated, beak like premaxillary bones. Rhynchosaurs ...
''
Ammorhynchus ''Ammorhynchus'' is an extinct genus of hyperodapedontid rhynchosaur from Middle Triassic (Anisian stage) deposits of Navajo County, Arizona.Anisodontosaurus'' is an enigmatic reptile only known from a few tooth-bearing jaws. The poposauroid archosaur ''
Arizonasaurus ''Arizonasaurus'' was a ctenosauriscid archosaur from the Middle Triassic (243 million years ago). ''Arizonasaurus'' is found in the Middle Triassic Moenkopi Formation of northern Arizona. A fairly complete skeleton was found in 2002 by Sterling ...
'' is known from one relatively complete skeleton and a significant amount of other isolated material. Footprints and several fragmentary body fossils are known from
dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivorous animals with a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typicall ...
s. The footprints of ''
Cheirotherium ''Chirotherium'', also known as ''Cheirotherium'' (‘hand-beast’), is a Triassic trace fossil consisting of five-fingered (pentadactyle) footprints and whole tracks. These look, by coincidence, remarkably like the hands of apes and bears, with ...
'' and ''
Rhynchosauroides ''Rhynchosauroides'' is an ichnogenus, a form taxon based on footprints. The organism producing the footprints was likely a lepidosaur and may have been a sphenodont, an ancestor of the modern tuatara. The footprint consists of five digits, of w ...
'' are common in the
Wupatki Member The Wupatki National Monument is a National monument (United States), United States National Monument located in north-central Arizona, near Flagstaff, Arizona, Flagstaff. Rich in Native Americans in the United States, Native American archaeolog ...
.


See also

*
Geology of the Grand Canyon The geology of the Grand Canyon area includes one of the most complete and studied sequences of rock (geology), rock on Earth. The nearly 40 major sedimentary rock layers exposed in the Grand Canyon and in the Grand Canyon National Park area rang ...
*


Footnotes


References

* * * * * * * * * * * * * *
GEOLEX database entry for Moenkopi
USGS ccessed 18 March 2006(public domain text)
Bibliographic References for Moenkopi
ccessed 18 March 2006


External links

{{Chronostratigraphy of Nevada Geologic formations of Arizona Geologic formations of California Geologic formations of Colorado Geologic formations of Nevada Triassic formations of New Mexico Geologic formations of Utah Triassic System of North America Early Triassic North America Middle Triassic North America Triassic Arizona Triassic California Triassic geology of Nevada Triassic geology of Utah Sandstone formations of the United States Natural history of the Grand Canyon Capitol Reef National Park Colorado Plateau Zion National Park