Organ Rock Formation

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Organ Rock Formation
Stratigraphic range: Early to Middle Permian:
290–272  Ma
Organ Rock Towers.jpg
Towers of red Organ Rock capped with White Rim Sandstone in Shafer Canyon in Canyonlands National Park
Type Geological formation
Unit of Cutler Formation
Underlies De Chelly Sandstone
Overlies Cedar Mesa Sandstone
Lithology
Primary sandstones, siltstones, conglomerates, and mudstones. [1]
Location
Coordinates 37°07′26″N110°22′41″W / 37.124°N 110.378°W / 37.124; -110.378
Region Colorado Plateau
ExtentFlag of the State of Utah.svg  Utah
Flag of Colorado.svg  Colorado
Flag of Arizona.svg  Arizona
Flag of New Mexico.svg  New Mexico
Usa edcp relief location map.png
Red pog.svg
Organ Rock Formation (the United States)
USA Utah relief location map.svg
Red pog.svg
Organ Rock Formation (Utah)

The Organ Rock Formation or Organ Rock Shale is a formation within the late Pennsylvanian to early Permian Cutler Group and is deposited across southeastern Utah, northwestern New Mexico, and northeastern Arizona. This formation notably outcrops around Canyonlands National Park, Natural Bridges National Monument, and Monument Valley of northeast Arizona, southern Utah. The age of the Organ Rock is constrained to the latter half of the Cisuralian epoch by age dates from overlying and underlying formations. Important early terrestrial vertebrate fossils have been recovered from this formation in northern Arizona, southern Utah, and northern New Mexico. These include the iconic Permian terrestrial fauna: Seymouria , Diadectes , Ophiacodon , and Dimetrodon . The fossil assemblage present suggests arid environmental conditions. This is corroborated with paleoclimate data indicative of global drying throughout the early Permian.

Contents

Geographic extent

The Organ Rock Formation is present across southeastern Utah, U.S.A. It outcrops around Canyonlands National Park, Natural Bridges National Monument, and Monument Valley. [1] In these areas the Organ Rock typically outcrops as a dark-red/brown siltstone to mudstone gently dipping towards the southeast. Within Canyonlands N.P. it forms towers which are meters to tens of meters tall. These are protected by caps of the White Rim Sandstone. In general, the Organ Rock Formation records the evolution of terminal fluvial fans, which dry up into sections of overlying formations. [2] Animals living during the time of the Organ Rock's deposition had the capacity to travel across most of earth's landmass, as at the time, land was all concentrated into the supercontinent Pangea.

Stratigraphy and age

The Organ Rock Formation is conformably underlain by the Cedar Mesa Sandstone. [3] [1] It is conformably overlain by the De Chelly Sandstone around Monument Valley and by the White Rim Sandstone in the Canyonlands National Park. In locations where the De Chelly and White Rim are absent, the Organ Rock is unconformably overlain by the Triassic Moenkopi or Chinle Formations by an erosional contact. Toward its eastern extent, the Organ Rock Formation grades into the Cutler Formation, undivided. This transition occurs to the southwest of Moab, UT. The age of the Organ Rock Formation is unconfirmed. [4] The preceding Cedar Mesa Sandstone is dated to the Wolfcampian (ICS stage: Artinskian). [5] The anteceding De Chelly and White Rim Sandstones are dated to the Leonardian (ICS stage: Kungurian). [6] [7] These formations constrain the age of the Organ Rock Formation to the latter part of the Cisuralian Epoch, approximately 290.1 to 272.3 Ma. The Organ Rock Formation may contain the Artinskian/Kungurian boundary. This is during the early to mid-Permian, a time where synapsids and temnospondyl amphibians are the dominant players in terrestrial ecosystems. These animals predate the advent of archosaur reptiles which give rise to dinosaurs in the Triassic.

Depositional environments

The Organ Rock Formation is composed of sandstones, siltstones, conglomerates, and mudstones. [1] These rocks occur in two primary facies: floodplain and channel, as well as eolian dunes and sand sheets.

Floodplain and channel

In these deposits, mixed reddish-brown sands and silts dominate with minor mudstones and conglomerates interspersed. [1] Interpreted channel deposits grade from laterally accreting coarse sands – into conglomerates of pebble-sized carbonate clasts. Channels are 0.5 meter to 7 meters thick and may extend laterally for a few hundred meters. Fine-grained silt to mudstone deposits are proximal to interpreted channels. These deposits are interpreted as meandering streams with associated floodplains.

Eolian dune and sand sheet

Deposits are characterized by pale red fine- to medium-grained sandstones. [1] These units are cross-bedded. Each cross-bed is composed of thin, consistently spaced laminations. These strata are interpreted as those made by migrating dunes. This facies is marked by a sharp contact at the top of the preceding floodplain and channel facies. Mud cracks found at the top of the facies are filled by fine-grained sand from the overlying dune facies. This facies is most common at the western extent of the Organ Rock Formation.

Plant fossils

Plant fossils include Supaia , Walchi and Yakia which lived in semi-arid conditions.

Vertebrate fossils

Fossil vertebrates represent the majority of the faunal assemblage present in the Organ Rock Formation. [8] [9] [10] [11] [12] Animal remains are most commonly preserved within ancient stream channels of the floodplain and channel facies. Within this facies, fossilized bone occurs proximal to conglomeratic lenses. Taxa recovered include: freshwater actinopterygian fishes, temnospondyl amphibians, diadectomorphs, seymouriamorphs, and early synapsids.

Freshwater Actinopterygian fishes

Fossil fish material, either bone or scale, is infrequent within the Organ Rock Formation. [8] Scales from the extinct group of fishes Palaeoniscoidea are present. These scales, however, are only found preserved in fossilized feces (coprolites). Some coprolites are interpreted to be from fish; others from indeterminate terrestrial vertebrates.

Temnospondyls

Temnospondyl amphibian remains are present within the Organ Rock Formation. [8] Three taxa have been reported. These include: Trimerorhachis , Eryops , and Zatrachys . Of these three taxa, fragments of Eryops are the most commonly recovered. Remains of this animal are very common in other formations of the Cutler Group and in general during the Early Permian of southwestern North America.

Diadectomorphs

Diadectomorphs are medium to large (2–3 meters), heavily-built reptiliomorphs with robust limbs. These animals are thought to be the closest outgroup to the clade Amniota. Two taxa are present within the Organ Rock Formation: Diadectes , and Tseajaia campi . Diadectes is more abundant in the Organ Rock than the other formations of the Cutler Group. Fragments of the animal are most commonly reported. The most complete two specimens include pectoral girdles and limbs. These were collected in San Juan County, Utah. Diadectes is an important animal as it is the first terrestrial vertebrate to demonstrate characteristics necessary for obligatory herbivory. These include: peg-shaped teeth in the front of the mouth, as well as broad blunt teeth used to more effectively process vegetation. Tseajaia campi is a very rare taxon known from one nearly complete specimen recovered from the Organ Rock. Originally described by Vaughn, [8] this animal was first assigned to the group Seymouriamorpha, however, upon reassessment of the holotype it was demonstrated to have a closer affinity to Diadectomorpha. [13]

Seymouriamorphs

Seymouriamorphs are small- to medium- sized (0.5 to 1.5 meters), reptiliomorphs. These animals have a generalized early amphibian body plan with a large “u”-shaped head and a sprawling lizard-like posture. The taxon Seymouria sanjuanensis is the only seymouriamorph found in the Organ Rock Formation. Seymouria sanjuanensis is a unique taxon because of its extensive geographic range. This particular animal was first described by Vaughn (1966) [9] from the Organ Rock Formation. Since this initial find, a number of these individuals have been recovered from localities as distant as Germany. [14]

Early Synapsids

Four early synapsid taxa are present within the Organ Rock Formation. These include Ophiacodon , as well as three sphenacodontids: Ctenospondylus , Dimetrodon , and Sphenacodon ferocior . [12] Most taxa are known from fragmentary material. Early synapsids were dominant members of the terrestrial Permian ecosystem. [14] Some early synapsids adapted an herbivorous diet, however, the Organ Rock Formation only preserves carnivorous animals; these were likely the apex predators of this ecosystem. The three sphenacodontids were terrestrial predators consuming other tetrapods, while Ophiacodon likely hunted fishes and other aquatic animals.

Coprolites

Coprolites associated with a labyrinthodont tooth as well as “Pelycosaur” and didectid remains have been recovered from this formation.

Paleoecological significance

The vertebrate faunal assemblage found in the Organ Rock Formation is diverse with respect to taxonomic groups, body plans, and diets. This material represents a decent cross-section of what terrestrial vertebrate life was like during the early Permian. It is noteworthy that no diapsid material has been definitively recovered from this formation. [12] As one moves younger in time through the Organ Rock Formation, temnospondyls become less abundant with respect to other major groups such as diadectomorphs and early synapsids. [8] This could track the general trend of aridification as indicated by sedimentology of the formation. This trend is globally recognized during the Early Permian, supported by many lines of geologic evidence including significant deposits of calcretes, eolianites, and evaporites. [15]

Related Research Articles

Diadectomorpha Extinct clade of tetrapods

Diadectomorpha is a clade of large tetrapods that lived in Euramerica during the Carboniferous and Early Permian periods and in Asia during Late Permian (Wuchiapingian), They have typically been classified as advanced reptiliomorphs positioned close to, but outside of the clade Amniota, though some recent research has recovered them as the sister group to the traditional Synapsida within Amniota, based on inner ear anatomy. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully terrestrial. The diadectomorphs seem to have originated during late Mississippian times, although they only became common after the Carboniferous rainforest collapse and flourished during the Late Pennsylvanian and Early Permian periods.

Cutler Formation Geologic formation in the Four Corners, US

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.

Caseasauria Extinct clade of synapsids

Caseasauria is one of the two main clades of early synapsids, the other being the Eupelycosauria. Caseasaurs are currently known only from the Late Carboniferous and the Permian, and include two superficially different families, the small insectivorous or carnivorous Eothyrididae, and the large, herbivorous Caseidae. These two groups share a number of specialised features associated with the morphology of the snout and external naris.

<i>Ophiacodon</i> Extinct genus of synapsids

Ophiacodon is an extinct genus of synapsid belonging to the family Ophiacodontidae that lived from the Late Carboniferous to the Early Permian in North America and Europe. The genus was named along with its type species O. mirus by paleontologist Othniel Charles Marsh in 1878 and currently includes five other species. As an ophiacodontid, Ophiacodon is one of the most basal synapsids and is close to the evolutionary line leading to mammals.

<i>Ctenospondylus</i> Extinct genus of synapsids

Ctenospondylus is an extinct genus of sphenacodontid synapsid

Wingate Sandstone

The Wingate Sandstone is a geologic formation in the Glen Canyon Group of the Colorado Plateau province of the United States which crops out in northern Arizona, northwest Colorado, Nevada, and Utah.

New Red Sandstone

The New Red Sandstone, chiefly in British geology, is composed of beds of red sandstone and associated rocks laid down throughout the Permian to the end of the Triassic, that underlie the Jurassic-Triassic age Penarth Group. The name distinguishes it from the Old Red Sandstone which is largely Devonian in age, and with which it was originally confused due to their similar composition.

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 and Arizona. Specifically, the basin occupies space in the San Juan, Rio Arriba, Sandoval, and McKinley counties in New Mexico, and La Plata and Archuleta counties in Colorado. The basin extends roughly 100 miles (160 km) N-S and 90 miles (140 km) E-W.

<i>Limnoscelis</i> Genus of diadectomorphs

Limnoscelis was a genus of large diadectomorph tetrapods from the Late Carboniferous of western North America. It includes two species: the type species Limnoscelis paludis from New Mexico, and Limnoscelis dynatis from Colorado, both of which are thought to have lived concurrently. No specimens of Limnoscelis are known from outside of North America. Limnoscelis was carnivorous, and likely semiaquatic, though it may have spent a significant portion of its life on land. Limnoscelis had a combination of derived amphibian and primitive reptilian features, and its placement relative to Amniota has significant implications regarding the origins of the first amniotes.

Cedar Mesa Sandstone

Cedar Mesa Sandstone is a sandstone member of the Cutler Formation, found in southeast Utah, southwest Colorado, northwest New Mexico, and northeast Arizona.

Tambach Formation

The Tambach Formation is an Early Permian-age geologic formation in central Germany. It consists of red to brown-colored sedimentary rocks such as conglomerate, sandstone, and mudstone, and is the oldest portion of the Upper Rotliegend within the Thuringian Forest Basin.

Red Beds of Texas and Oklahoma Geologic strata in the southwestern United States

The Red Beds of Texas and Oklahoma are a group of Early Permian-age geologic strata in the southwestern United States cropping out in north-central Texas and south-central Oklahoma. They comprise several stratigraphic groups including the Clear Fork Group, the Wichita Group, and the Pease River Group. The Red Beds were first explored by American paleontologist Edward Drinker Cope starting in 1877. Fossil remains of many Permian tetrapods have been found in the Red Beds, including those of Dimetrodon, Edaphosaurus, Seymouria, Platyhystrix, and Eryops. A recurring feature in many of these animals is the sail structure on their backs.

Wescogame Formation Geological formation in the Grand Canyon

The (Upper) Late Pennsylvanian Wescogame Formation is a slope-forming, sandstone, red-orange geologic unit, formed from an addition of eolian sand, added to marine transgression deposits,, and found throughout sections of the Grand Canyon, in Arizona, Southwest United States. It is one of the upper members of the Supai Group 'redbeds', with the Supai Group found in other sections of Arizona, especially in the Verde Valley region, or as a basement unit below the Mogollon Rim, just eastwards or part of the basement Supai Group of the southwest & south Colorado Plateau.

Supai Group Section of red bed deposits at the Colorado Plateau

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.

White Rim Sandstone

The White Rim Sandstone is a sandstone geologic formation located in southeastern Utah. It is the last member of the Permian Cutler Group, and overlies the major Organ Rock Formation and Cedar Mesa Sandstone; and again overlies thinner units of the Elephant Canyon and Halgaito Formations.

The Waggoner Ranch Formation is a geologic formation in northern Texas. It preserves fossils dating back to the Artinskian to Kungurian stages of the Permian period.

The Arroyo Formation is a geologic formation in Texas. It preserves fossils dating back to the Kungurian stage of the Permian period. It is the lower-most portion of the Clear Fork Group, part of a series of fossiliferous Permian strata in the south-central United States known as the red beds.

El Cobre Canyon Formation Geologic formation in New Mexico, United States

The El Cobre Canyon Formation is a geologic formation in New Mexico. It preserves fossils dating back to the late Pennsylvanian to early Permian periods.

The Halgaito Formation is the basal Permian geologic member of the Cutler Group in southern Utah. The member consists of silty sandstone, siltstone and limestone. The Elephant Canyon may grade into the Halgaito and grades northward into the Cedar Mesa Formation.

The Ntawere Formation is a Middle Triassic (Anisian) geological formation in Zambia, preserving fossils of synapsids, archosaurs, and temnospondyls.

References

  1. 1 2 3 4 5 6 Stanesco, J.D.; Dubiel, R.F.; Huntoon, J.E. (2000). "Depositional Environments and Paleotectonics of the Organ Rock Formation of the Permian Cutler Group, Southeastern Utah". Utah Geological Association Publication. 28: 1–15.
  2. ↑ Cain, S.A.; Mountney, N.P. (2009). "Spatial and temporal evolution of a terminal fluvial fan system: the Permian Organ Rock Formation, South‐east Utah, USA". Sedimentology. 56 (6).
  3. ↑ Condon, S.M. (1997). "Geology of the Pennsylvanian and Permian Cutler Group and Permian Kaibab Limestone in the Paradox Basin, Southeastern Utah and Southwestern Colorado". U.S. Geological Survey Bulletin. 2000: 1–46.
  4. ↑ Baars, D.L. (1962). "Permian System of Colorado Plateau". American Association of Petroleum Geologists Bulletin. 46 (2): 1–46.
  5. ↑ Stanesco, J.D.; Campbell, J.A. (1989). "Eolian and noneolian facies of the Lower Permian Cedar Mesa Sandstone Member of the Cutler Formation, southeastern Utah". U.S. Geological Survey Bulletin. 1808 (2): F1-F13.
  6. ↑ Blakey, R.C. (1974). "Stratigraphic and depositional analysis of the Moenkopi Formation, southeastern Utah". Utah Geological and Mineral Survey Bulletin. 104: 81.
  7. ↑ Blakey, R.C. (1990). "Stratigraphy and geologic history of Pennsylvanian and Permian rocks, Mogollon Rim region, central Arizona and vicinity". Geological Society of America Bulletin. 102 (9): 1189–1217. doi:10.1130/0016-7606(1990)102<1189:saghop>2.3.co;2.
  8. 1 2 3 4 5 Vaughn, P.P. (1964). "Vertebrates from the Organ Rock Shale of the Cutler Group, Permian of Monument Valley and Vicinity, Utah and Arizona". Journal of Paleontology. 38 (3): 567–583.
  9. 1 2 Vaughn, P.P. (1966). "Comparison of the early Permian vertebrate faunas of the Four Corners region and North Central Texas". Los Angeles County Museum Contributions in Science. 105: 1–13.
  10. ↑ Vaughn, Peter P., 1973, Vertebrates from the Cutler Group of Monument Valley and vicinity in Monument Valley (Arizona, Utah and New Mexico), James, H.L.: New Mexico Geological Society 24th Annual Fall field Guidebook, 232 p.
  11. ↑ Sumida, Stuart S., Walliser, James B.D., and Lombard, B. Eric, 1999a, Late Paleozoic amphibian-grade tetrapods of Utah: Miscellaneous Publication- Utah Geological Survey, v. 99(1), p. 21 – 30.
  12. 1 2 3 Sumida, Stuart S., Lombard, B. Eric, Berman, David S., Henrici, Amy C., 1999b, Late Paleozoic amniotes and their near relatives from Utah and northeastern Arizona, with comments on the Permian – Pennsylvanian boundary in Utah and northern Arizona: Miscellaneous Publication- Utah Geological Survey, v. 99(1), p. 21 – 30.
  13. ↑ Sumida, Stuart S., Lombard, R. E., and Berman, D. S, 1992, Morphology of the atlas axis complex of the late Palaeozoic tetrapod suborders Diadectomorpha and Seymouriamorpha: Philosophical Transactions of the Royal Society of London, v. 336, p. 259-273.
  14. 1 2 Benton, Michael J., 2015, Vertebrate Palaeontology: Wiley-Blackwell, Oxford, 4th edition.
  15. ↑ Tabor, Neil J., and Poulsen, Christopher J., 2008, Palaeoclimate across the Late Pennsylvanian _ early Permian tropical palaeolatitudes: A review of climate indicators, their distribution, and relation to palaeophysiographic climate factors: Palaeogeography, Palaeoclimatology, Palaeoecology, 268, p. 293 – 310.
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