Cutler formation

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The Cutler Formation , also Cutler Group , is a rock formation of sedimentary origin located in the United States in the states of Arizona , northwestern New Mexico , southeastern Utah and southwestern Colorado . It was deposited in the Paleozoic from the late Carboniferous ( Gzhelian ) to the end of the Lower Permian ( Kungurian ).

stratigraphy

Stratigraphic positioning of the Cutler Formation in the Canyonlands

In Arizona and Utah, the rock unit is usually referred to as the Cutler Group , but the USGS prefers the Cutler Formation .

The formation can be divided into the following members (from young to old):

The Cutler Formation transgresses the marine Honaker Trail Formation from Upper Pennsylvania with their Halgaito member . It is in turn overlaid by the Black Box Dolomite , the lateral equivalent of the Kaibab Limestone in the Grand Canyon (upper Permian), and the subsequent Triassic Moenkopi Formation .

Lateral equivalents are the Supai Group in the Grand Canyon area of ​​Arizona in the southwest and the Abo formation in New Mexico in the southeast .

The total thickness of the Cutler Formation in the Paradox Basin reaches 3700 meters.

The Cutler formation has no type locality . It was named in 1905 by Cross and Howe after the Cutler Creek, which flows into the Uncompahgre River about 6 kilometers north of Ouray . In a revision of Cross and Howe's research in 1929, Baker and Reeside divided the formation as follows:

  • White Rim Sandstone Member
  • Organ Rock Tongue
  • Cedar Mesa Sandstone
  • Halgaito tongue at the base

In 1946, Wood and Northrop mapped the formation and determined its geographic extent. Wengerd and Matheny raised the formation to a group in 1958 , but this is not recognized by the USGS (as of 2005).

distribution

The Cutler Formation occurs in the following sedimentation spaces:

Geological framework

The sub-Permian red sediments of the Cutler Formation are a direct consequence of the continued tectonic unrest that led to the collision of Laurasia with Gondwana in the Upper Carboniferous . Ultimately, the result was the creation of the supercontinent Gondwana . On the south and east side of North America, the Ouachita marathon orogen formed during the Ouachita mountain formation , the continental thrust movements continued into the lower Permian. The subduction on the western edge of North America continued during its continued so that the deposition space of the Cutler-formation was exposed on both sides severe tectonic stresses. The continental crust reacted brittle and broke into several large clods. The Ancestral Rocky Mountains were created , a series of raised basement blocks with basins and troughs in between (see the sedimentation rooms mentioned above). The tectonic movements were accompanied by a general rise in sea level, which led to the Absaroka transgression .

At the time of the deposition of the Cutler Formation, the peak of the transgression had already been passed, and marine sediments were now being replaced by continental alluvial fan sediments . The main delivery area for the Cutler sediments was the so-called Uncompahgre Uplift , which had gradually lifted the block of the Uncompahgre Mountains . On the southwestern edge of the Uncompahgre Mountains, the Paradox Basin was created , which absorbed the rubble from the protruding basement block - the Cutler Formation was formed.

Sedimentary development

Monument Valley . The Halgaito Shale Member forms the valley floor, the slopes of the Buttes and Mesas consist of the Organ Rock Pipe Member, the steep walls of the De Chelly Sandstone Member and the uppermost layers of the layers of the Moenkopi Formation and the Shinarump formation

The Cutler Formation reaches its maximum thickness in the Paradox Basin - 3700 meters near Moab . In the immediate vicinity of the Uncompahgre Mountains, the sediments are red-colored, iron-containing ( hematite- bearing ), coarse-grained arkoses and polymictic conglomerates that were formed under semi-arid to arid paleoclimate conditions. With increasing distance from the delivery area, they lose their grain size , in order to finally be deposited as fine-grained sandstones , siltstones and claystones near the coast to the southwest of their original area. It is these finer-grained, more distal sediments that enable the Cutler Formation to be subdivided into its individual members; this is not the case in the immediate vicinity of the Uncompahgre Mountains, here the formation remains undivided.

Nevertheless, up to three major cycles can also be excreted in the undivided alluvial fan sediments, which reflect the pulsating uplift of the Uncompahgre Mountains. In New Mexico, for example, the El Cobre Canyon Formation and the younger Arroyo del Agua Formation are excreted - both world-famous for their rich tetrapod fauna (see below).

Overall, the Cutler Formation is a very complex sediment body, the members of which usually interlock with one another several times. Further complications are caused by extensive salt tectonics , which can be traced back to the underlying evaporites of the Paradox formation .

The subdivided Cutler Formation begins with a transgression from the northwest, which deposited the carbonate sediments of the Elephant Canyon member . On the basis of fusulinides , the Elephant Canyon member can be assigned an Upper Carboniferous age ( Gzhelium ). Towards the southeast, it interlocks with the siliciclastic, fluvial red sediments and loess deposits of the Halgaito shale member . These two basal members are then overlaid by the Cedar-Mesa-Sandstone-Member , a relatively fine-grained, white sandstone that forms distinctive steep walls. The Cedar-Mesa-Sandstone-Member partly contains fossilized sandbanks including a barrier island (northwest section), but essentially consists of the aeolian deposits of a coastal erg (main wind direction northwest) and subordinate Sabchas sediments (southeast section). For its part, it interlocks towards the east and south-east with the fluvial red sediments of the organ rock shale members , relatively fine-grained, erosion-prone arcs from the Uncompahgre Mountains. Since only fine-grained sediments were delivered from the Uncompahgre Mountains, this suggests that the basement block is already largely leveling. The Cedar-Mesa-Sandstone-Member then gradually changes into the White-Rim-Sandstone-Member , a white, diagonally layered, very compact sandstone of Aeolian origin (coastal sand dune facies, main wind direction also northwest). The White-Rim-Sandstone-Member also interlocks in an easterly direction with the red-colored Organ-Rock-Shale-Member, creating very impressive color contrasts. The Cutler formation closes with the De-Chelly-Sandstone-Member , who is only slightly younger than the White-Rim-Sandstone-Member. These are orange-red, obliquely layered sandstones, which also formed a very large erg in the southwest part of the deposit area. The orientation of the dune fields suggests north to north-easterly winds, which blew the sand fraction out of the area of ​​the now almost leveled Uncopahgre Mountains towards the shallow sea.

Natural resources

In addition to hematite , the Cutler Formation contains uranium , vanadium , copper , barium and rare earths . The uranium is found as intraformational enrichment in fluvial sandstones, but can also be bound to fissures of laramic age (around 60 million years). The latter type was found in Kane Creek in Utah.

Fossil content

The Cutler Formation houses a rich Tetrapodenfauna and their trace fossils and contains two fish , plant remains , brachiopods , bryozoans , crinoids , corals , and the already mentioned above Fusuliniden .

Fishes:

Tetrapods :

Tetrapod tracks :

Plants :

(The Tetrapodenfunde made in New Mexico made it possible for Lucas, three land vertebrate biozones English. LVF to distinguish - "land vertebrate faunachron") that can be used for the global correlation of terrestrial deposits (from young to old):

Individual evidence

  1. ↑ GEOLEX database entry for 'Cutler'. Accessed March 18, 2006
  2. ^ Krainer, K. Pennsylvanian-Permian Depositional Break in the Cutler Formation, El Cobre Canyon, New Mexico
  3. ↑ Hunt, A. Nonmarine Fossils from late Paleozoic Redbeds in New Mexico and the timing of the Ancestral Rocky Mountain Orogeny
  4. ↑ Lucas, SG 2005d. Permian tetrapod faunachrons. In: Lucas, SG & Zeigler, KE (eds) The Nonmarine Permian. New Mexico Museum of Natural History and Science Bulletin, 30, 192-196.

swell

  • Baars, DL (2000) The Colorado Plateau. University of New Mexico Press. ISBN 978-0-8263-2301-9
  • Baker, AA and Reeside, JB, Jr., 1929, "Correlation of the Permian of southern Utah, northern Arizona, northwestern New Mexico, and southwestern Colorado," American Association of Petroleum Geologists Bulletin, v. 13, no.11, p. 1413-1448
  • Baldridge, WS (2004) Geology of the American Southwest. Cambridge University Press. ISBN 0-521-01666-5
  • Cross, CW and Howe, Ernest, 1905, "Geography and general geology of the quadrangle, In: Description of the Silverton quadrangle [Colorado]", US Geological Survey Geologic Atlas of the United States , Silverton folio, no. 120, 34 p .
  • Lucas, SG (2006) Global Permian tetrapod biostratigraphy and biochronology. In: Lucas, SG, Cassinis, G., Schneider, JW Non-marine Permian biostratigraphy and biochronology. Geological Society of London. Special Publication N ° 265.
  • Wengerd, SA and Matheny, ML, 1958, "Pennsylvanian system of the Four Corners region," American Association of Petroleum Geologists Bulletin, v. 42, no.9, p. 2048-2106
  • Wood, GH and Northrop, SA, 1946, "Geology of Nacimiento Mountains, San Pedro Mountain, and adjacent plateaus in parts of Sandoval and Rio Arriba Counties, New Mexico," US Geological Survey Oil and Gas Investigations Map, OM-57, 1 sheet, scale 1: 95.040

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