Moenkopi-Formation

The Moenkopi Formation is a rock association ( formation of sedimentary origin ), which in many parts of the U.S. states of New Mexico, Arizona (north), Nevada, California ( south east), Utah and Colorado ( west) may be encountered. In Arizona, the rock group association status is granted. Geologically, the Moenkopi Formation on Colorado Plateau and the Basin and Range. Your red-colored shales and sandstones were deposited during the Lower Triassic and possibly even during the Middle Triassic period about 240 million years ago.

  • 3.1 Trace Fossils

Stratigraphy

Layer members (Member)

The Moenkopi Formation is because of their wide distribution and their different facies training in a myriad of layer members (Member) divided ( in alphabetical order):

  • Ali Baba Member ( CO, UT)
  • Anton Chico Member ( NM)
  • Black -Dragon- Member ( UT)
  • Holbrook Sandstone Member ( AZ)
  • Hoskinnini Members (AZ, CO, UT) also Hoskinnini Tongue (AZ, CO, UT)
  • Moody Canyon Member ( UT)
  • Moqui Members ( AZ)
  • Pariott Members (CO, UT)
  • Rock Canyon Conglomerate Member ( AZ, NV, UT)
  • Sinbad Limestone Member ( UT)
  • Sewemup Members (CO, UT)
  • Shnabkaib Members (AZ, NV, UT)
  • Tenderfoot Member ( CO, UT)
  • Timpoweap Members (AZ, NV, UT)
  • Torrey Member ( UT)
  • Virgin Limestone Member ( AZ, NV, UT)
  • Winslow member ( AZ)
  • Wupatki Member ( AZ)

Local profiles

To better illustrate the rather complex stratigraphic relationships follow some local profiles ( sequence from young to old):

Northern Utah ( Uinta Basin):

  • Pariott Members
  • Sewemup Members
  • Ali Baba Members
  • Tenderfoot member

Southeastern Utah ( Canyonlands ) - 300 meters:

  • Moody Canyon Member
  • Torrey Members
  • Sinbad Limestone Member
  • Black Dragon Members
  • Hoskinnini Members

Northeastern Arizona ( near Holbrook ) - 100 to 150 meters:

  • Holbrook Member ( identical to the Anton Chico Members in New Mexico)
  • Moqui Members
  • Wupatki Member ( upper part identical with Shnabkaib Members in SW Utah)

Southwestern Utah (Virgin River) - 700 meters:

  • Upper Red Members
  • Shnabkaib Members
  • Middletown -Red Members
  • Virgin Limestone Member
  • Lower Red Member
  • Timpoweap Members

Note: The Timpoweap Members will be eliminated, more recently, since it is identical with the Rock Canyon Conglomerate Members and the subsequent Sinbad Limestone Members.

The southwestern Utah is a facies transition area where the marine layer kalkbetonten members of Thaynes formation or Thaynes group interlock with the continental red beds of the actual Moenkopi formation. At the Thaynes group include the Sinbad Limestone Member, the Virgin Limestone Member and the Shnabkaib Members.

Equivalent formations

The predominantly siliciclastic Moenkopi Formation is equivalent to the following formations:

  • Alcova lineup - Wyoming
  • Chugwater Formation - Wyoming
  • Crow Mountain Formation - Wyoming
  • Red Peak Formation - Wyoming
  • State Bridge Formation - Colorado

History

The Moenkopi Formation has no type locality. Your Erstbeschreiber Ward named it in 1901 after lying at the mouth of " Moencopie Wash " in the territory of the Grand Canyon settlement. As a substitute Gregory behalf in 1917 with a profile in the rock wall of the Little Colorado Canyon, about 8 kilometers down from Tanner Crossing in Coconino County.

During your stay in the Great Basin in 1921 Bassler and Reeside divided the formation for the first time, that they separated the Rock Canyon Conglomerate Members, the Virgin Limestone Member and the Members of Shnabkaib. Hager was 1922 ( later replaced by the Wupatki Member and Moqui Members ) and the Holbrook - Sandstone Members Disconnect the Black Mesa Basin, the Salt Creek Members. In the Paradox Basin Gilluly James and John Bernard Reeside 1928 the Sinbad Limestone Member established. Gregory described in 1948 for the first time Timpoweap Members. The Wupatki Member was introduced by McKee in 1951, who made a revision on age under-or Middle Triassic time.

Layer boundaries were revised for the first time by Robeck in 1956 and Cooley in 1958. Shoemaker and Newman could then disconnect the Tenderfoot member that Ali Baba member that Sewemup Members and Pariott Members in the Piceance Basin and the Uinta Basin in 1959. The Hoskinnini Members was introduced in 1959 by Stewart in Black Mesa Basin and in the Paradox Basin.

1966 took Schell and Ellis Yochelson a new layer boundaries revision. 1974 named Blakey in the Paradox Basin, the Black Dragon Members, the Members Torrey and Moody Canyon Member. 1979 was again a layer boundaries revision. Kietzke confirmed in 1988 by biostratigraphic methods a lower or middle Triassic sian age. 1989 Finally, the Anton Chico Member was introduced by Lucas and Hunt in the Palo Duro Basin, at the same time it revised the geographic expansion. Also, Lucas and Hayden 1991 edited geographical circumstances. Summary overviews in 1991 by Lucas, 1994 by Sprinkel, 1995 by Hintze and Axen, and then by Huntoon, among others published.

General Overview

The depositional environment of the Moenkopi Formation was a very wide area sedimentation basin, stretching from Wyoming, Montana and Idaho over Colorado and Utah to New Mexico, Arizona and Nevada. It was this to be a ramped Kratonrand which gradually dived to the northwest. He had a long stretch of 650 kilometers, was 160-500 kilometers wide. An inland sea transgredierte over him, handed this from southern Utah to British Columbia at its peak. In three major pulses is toothed with continental siliciclastic red beds, the origin of which areas were high areas like the Uncompahgre Plateau, the Defiance Uplift, the Mogollon Rim and a tectonic barrier in western Nevada and those from the north-west flowing rivers, the sediment load verfrachteten into deeper basin parts.

The formation is generally discordant contact with their Paleozoic ground so she grabs example, in northeastern Arizona to the Coconino Sandstone, Grand Canyon down to the Kaibab Limestone and in the Canyonlands to the Cutler Formation down. It ends with an erosive unconformity and is in turn covered by the Shinarump Conglomerate of the Chinle formation. The widths of the Moenkopi Formation vary greatly in the East it is only made ​​very thin ( about 100 meters), but towards the west it grows gradually, to reach at its western and north-western edge of up to 700 meters. Similar to the thickness changes are associated facies changes. In the eastern part of their depositional environment, the Moenkopi Formation has fluvial character, in the central part it is increasingly intertidal to tidal, and finally on the western edge to accept entirely marine character. So she goes into the cephalopodenführende Thaynes lineup for example, in the north- west and west.

Age

Due to the fossil content, the Moenkopi Formation can assign an under trias sian age, comprising the steps of indusium, Olenekian and lower Anisian, ie approximately the period of 250 bis 245 million years BP. Your vertebrate fauna and in particular its trace fossils suggest an equivalence with the German Middle and Upper Bunter ( Volpriehausen Formation) and sediments from the eastern Massif Central of France.

Occurrence

The Moenkopi Formation occurs in the following Sedimentationsräumen:

  • Black Mesa Basin
  • Great Basin
  • Green River Basin
  • Las-Vegas-Becken/Raton-Becken
  • Orogrande Basin
  • Palo Duro Basin
  • Paradox Basin
  • Piceance Basin
  • San Juan Basin
  • Uinta Basin

Also available in other national parks it is found:

  • Canyonlands National Park
  • Capitol Reef National Park
  • Grand Canyon National Park
  • Zion National Park

Furthermore, in:

Fossil content

From the Moenkopi Formation a very diversified vertebrate fauna, especially the Wupatki Member and Holbrook Members originates in northeastern Arizona have become known for their rich vertebrate finds. To name Among the invertebrates have ammonite, Conchostraca, gastropods, Kahnfüßer, ostracods, echinoderms, stromatolites and spirorbide worms. Charophyta, green algae ( Codiaceen ) and the remains of plants are also available.

To be mentioned among the basal vertebrate groups are Hybodontiformes ( Haiartige ), coelacanth and lungfish. Also temnospondyle amphibians are very common. Among the Temnospondyli to Eocyclotosaurus, Quasicyclotosaurus, Wellesaurus, Vigilius and Cosgriffius find. Chance also occur Rhynchosaurier. Anisodontosaurus is an enigmatic reptile, present of which only some dental occupied jaw fragments. From Arizonasaurus, a poposauriden archosaurs, are a nearly complete skull and other isolated bones.

The findings are as follows:

Vertebrates:

Archosaurs

  • Anisodontosaurus greeri - Proterosuchia
  • Arizonasaurus babbitti

Temnospondyli

  • Cosgriffius campi
  • Cyclotosaurus randalli
  • Eocyclotosaurus wellesi
  • Haddrokkosaurus bradyi
  • Parotosuchus
  • Quasicyclotosaurus campi
  • Vigilius wellesi
  • Wellesaurus peabodyi

Invertebrates

Ammonites:

  • Anasibirites kingianus
  • Columbites
  • Meekoceras gracilitatis
  • Tirolites
  • Wasatchites

Ostracods:

  • Darwinula
  • Darwinuloides
  • Gerdalia

Trace fossils

The Moenkopi Formation is very rich in trace fossils. In addition to numerous vertebrate tracks, there are also traces of invertebrates such as horseshoe crabs. Also worth mentioning is the presence of coprolites.

From Dicynodontiern besides some remains of bones and their footprints were discovered. Especially in the Wupatki Member traces of Chirotherium and Rhynchosauroides are quite common.

The following ichnotaxa occur in the Moenkopi Formation:

  • Capitosauroides bernburgani
  • Chirotherium
  • Isochirotherium cotteri
  • Isochirotherium marshalli
  • Rhynchosauroides
  • Rotadactylus brady
  • Rotodactylus Cursorius
  • Rotadactylus mckeei
  • Synaptichnium cameronense
  • Synaptichnium diabloense
  • Therapsipus cumminsi

Swell

  • GEOLEX database entry for the Moenkopi Formation, USGS ( Retrieved on March 18, 2006 - text from the public domain )
  • Bibliography of Moenkopi Formation ( Accessed on March 18, 2006)
Group (stratigraphy) Colorado-Plateau Basin and Range Province Holbrook (Arizona) Coconino County, Arizona Cutler-Formation Chinle-Formation Buntsandstein Canyonlands-Nationalpark Grand-Canyon-Nationalpark Grand Staircase-Escalante National Monument Clam shrimp Shark Proterosuchidae
577882
de