Coconino Sandstone

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Coconino Sandstone
Schnebly Hill formations. It also interfingers laterally with the Schnebly Hill Formation.
AreaColorado and Coconino plateaus.
Thickness65 feet (20 m) to 300 feet (91 m) in Grand Canyon region.
Lithology
Primarycross-bedded sandstone[3]
Location
RegionArizona–(northern) and Utah–(southern)
CountryUnited States – (Southwestern United States)
Type section
Named forIt is named for the Coconino Plateau, northern Arizona[4]
Named byDarton (1910)[4]
The Coconino Sandstone forms the two prominent white cliffs in the middle distance in this view from the South Rim of the Grand Canyon.

The Coconino Sandstone is a geologic

vertebrates and large-scale cross-stratification.[5]

Eastward of a north–south line from Monument Creek to

De Chelly Sandstone in Utah. In this area, it underlies the Kaibab Limestone. Further eastward, the Coconino Sandstone likely correlates with and is contemporaneous with the Glorieta Sandstone of New Mexico. Westward of this line, the upper part of Coconino Sandstone is known as the White Rim Sandstone in Utah and the Cave Springs Member in Arizona. It interfingers and merges westward into the Toroweap Formation. The remaining lower part of the Coconino Formation is known as the Harding Point Member and underlies the Toroweap Formation and uncomfortablyy overlies the Hermit Formation. Between the Toroweap and Hermit formations, the Harding Point Member thins westward until it disappears.[2][6]

Nomenclature

In 1910, Darton[4] named and mapped the Coconino sandstone as a member of the now abandoned Aubrey group for its widespread distribution in the Coconino Plateau. He named the Coconino sandstone for the cross-bedded gray to white sandstones that form a conspicuous sheer cliff in walls of Grand Canyon and underlies entire Coconino Plateau and the extensive Colorado Plateau north of the Grand Canyon. As defined at that time, it lay between the overlying Kaibab (Aubre) limestone and the underlying Supai formation. The Kaibab limestone was later divided onto the Kaibab Limestone and Toroweap Formation and the Supai formation was later subdivided into the Hermit Formation and Supai Group.[7] Later, the Coconino Sandstone was recognized and mapped in the San Rafael Swell in the Emery County, Utah, region.[8]

In 1982, Hamilton recognized the fine-grained vitreous quartzites exposed in the Salton basin as the metamorphosed equivalent of Coconino Sandstone in the Big Maria Mountains of southeast California. Because of change in lithology, named and mapped these fine-grained quartzite as the Coconino Quartzite. In the Big Maria Mountains exposures, the Coconino Quartzite lies between the Hermit Schist and Kaibab Marble.[9]

Hermit Shale upon resistant & sloping Supai Group – "redbeds"
.

Description

The Coconino Sandstone consists predominately of buff to white, well-sorted, uniformly fine grained 0.0045–0.98 in (0.11–24.89 mm), nearly pure quartz sand held together by siliceous cement. It contains a few scattered potassium feldspar grains and traces of heavy minerals. Many of the sand grains are frosted or pitted and nearly all of them are rounded to subangular. Typically, iron oxide staining and cements are commonly absent, which is reflect in its pale, white to buff color. However, locally, the Coconino Sandstone is iron-stained and, as a result, is either a brownish color, as in Marble Canyon, or bright red, as near Flagstaff, Arizona.[10][11]

The Coconino Sandstone exhibits a number of primary

sedimentary structures. The most conspicuous of these is ubiquitous large-scale, wedge-planar, cross-stratification. It consists of long sweeping layers that often are 30–40 ft (9.1–12.2 m) long and as much as long as 80 ft (24 m). The cross-stratification dip mostly at 25°- 30° with few at a maximum of about 34°. Their dip is generally unimodal southward, but with a spread of readings ranging between southwest and southeast. Truncated by overlying beds, they form large, irregular wedges. In addition to the wedge-planar, cross-stratification, the Coconino Sandstone exhibits rare, large-scale, low-angle, less than 15°, cross-stratification that dip in the opposite direction. They are only found in limited numbers in a few localities within in exposures of this sandstone. The basal 3–6 ft (0.91–1.83 m) of the Coconino Sandstone at many outcrops exhibits horizontal laminae. A distinctive characteristic of this sandstone is that the cross-stratification readily splits into thin plates.[11]

Although

ripple marks are not abundant within the Coconino Sandstone, they are distinctive and locally numerous. They consist typically of low, wide, and asymmetrical ripples with ripple indexes, the ratio of wavelength to amplitude, greater than 17 with most considerably higher. Typically, the ripple crests and troughs lie parallel to the direction of dip of the foreset slopes. The ripple crest are rounded and generally had the concentration of coarser sand grains on or about their crests. The crests and troughs of these ripple are straight and parallel and, where exposed, exhibit little change in direction for distances of 3 ft (0.91 m) or more. They are less common in the Coconino Sandstone than in modern sand dunes because of the general lack of preservation of both the windward-side deposits of sand dunes and of ripple marks formed in dry sand without special circumstances.[11][12]

On the bedding planes of Coconino Sandstone, the small, crater-like pits of raindrop impressions are recognized at several outcrops. They are oriented in respect to the sloping surface of laminations such that these circular pits tend to face upward, or vertically, with a raised downslope rim. Rain pits have been reproduced in the laboratory on sloping surfaces of fine dry sand to provide positive evidence of subaerial formation by brief rain showers.[11][12]

Slump marks from mass movement or avalanching when lee-side slopes of dunes near the angle of repose are oversteepened are also found in the Coconino Sandstone. The slump marks range from those resulting from "successive discontinuous jerks with miniature landslides" to series of variable and irregular lines that are roughly parallel to the lee side's slope and mark the edge of a slumped sand mass, miniature terrace-and-cliff structures, and other types of dry-sand slump marks.[11][12]

The Coconino Sandstone uncommonly exhibits deformed bedding in the form of penecontemporaneously deformed cross-strata. In the few outcrops in which they are found, they can be quite abundant as near Doney Crater northeast of Flagstaff, Arizona. Typically, they consist of dipping foresets within a bed that for many feet in length have been folded locally, while the cross-strata above and below them are undisturbed.[11]

The thickness of the Coconino Sandstone varies due to regional structural features. In the Grand Canyon area, it is only 65 feet (20 m) thick in the west, thickens to over 600 feet (180 m) in the middle and then thins to 57 feet (17 m) in the east.[5]

Fossils

Fossil trackway in Coconino Sandstone.

The only known fossils found in the Coconino Sandstone are

trace fossils. Plant fossils have yet to be reported from the Coconino Sandstone. The body fossils of invertebrates and vertebrates are also lacking. However, it is a common occurrence, especially in continental desert deposits, that trace fossils provide the only available paleontologic and palaeobotanic information for paleoenvironmental reconstructions.[13][14]

The invertebrate trace fossils are known from the Coconino Sandstone include possible producers, such as worms, millipedes, isopods, spiders, scorpions. Paleohelcura, a possible scorpion track, is the most common invertebrate trace fossil. Other arthropod tracks, meniscate horizontal burrows, and conical pits have also been documented in the Coconino Sandstone. Many of the invertebrate trace specimens been collected from it include long, complete, and beautifully preserved trackways and burrows. Typically, these trace fossils are reported from the lower half of the Coconino Sandstone. They are commonly preserved on the surfaces of foreset laminae of eolian sand dunes. The invertebrate tracks were likely made on dry sand that was then moistened and covered by sand before the surface dried out, or on dunes dampened by dew. Because of the preservation of so much extramorphological variation, the effects of the trackmaker's travels across inclined sand, foreset beds can be recognized and studied. The number of valid ichnotaxa known from the Coconino Sandstone is low and consists of only 6 ichnogenera: Diplichnites, Diplopodichnus, Lithographus, Octopodichnus, Palaeohelcura, and Taenidium.[13]

One fossil specimen from the Mogollon Rim area consists of two trackways, one composed of two parallel rows of tracks, Lithographus isp (possibly insect such as blattoids). The insect trackway ends abruptly after a change its path in at a tetrapod trackway trending transverse to it at a quite high pace. This association of insect and tetrapod trackways is interpreted as predation behavior by the tetrapod relative to an insect prey.[15] This interpretation has been questioned, although predation cannot be excluded.[1]

Because of its abundant and well-preserved vertebrate tracks and trackways, the Coconino Sandstone is one of the most famous track-bearing formation of the Grand Canyon and a standard for the description of tetrapod tracks from Paleozoic eolian strata.

synapsid), cf. Tambachichnium isp. (synapsid), and Varanopus curvidactylus (reptile). The presence of Ichniotherium and Erpetopus together in the Coconino Sandstone suggests a late Artinskian–Kungurian age for the Coconino Sandstone. Because of its stratigraphic position, Kungurian age is more likely.[1]

Depositional environments

It consists primarily of fine, well-sorted sand deposited by eolian processes (wind-deposited) approximately 275 million years ago. Primary sedimentary structures such as large-scale cross-stratification, ripple marks, rain impressions, slump marks, and fossil tracks are well preserved within it and contribute evidence of its eolian origin. Its composition, along with its well-sorted, uniformly fine grained sand and stratigraphic relationships, are also consistent with an eolian origin[2][5][11]

Meteor crater

Lechatelierite (silica glass), as well as coesite and stishovite (high pressure forms of SiO2) were formed during the impact of a meteorite into the Coconino Sandstone at Barringer Crater in Arizona.[21][22]

See also

Wikimedia Commons has media related to Coconino Sandstone.

References

  1. ^ a b c d e Marchetti, L., Francischini, H., Lucas, S. G., Voigt, S., Hunt, A. P., and Santucci, V.L., Chapter 9. Paleozoic Vertebrate Ichnology of Grand Canyon National Park In: Santucci, V.L., Tweet, J.S., ed., pp. 333-379, Grand Canyon National Park: Centennial Paleontological Resource Inventory (Non-sensitive Version)'. Natural Resource Report NPS/GRCA/NRR—2020/2103. National Park Service, Fort Collins, Colorado, 603 pp.
  2. ^ a b c 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.
  3. ^ Connors, T.B., Tweet, J.S., and Santucci, V.L., 2020. Chapter 3. Stratigraphy of Grand Canyon National Park. In: Santucci, V.L., Tweet, J.S., ed., pp. 54–74, Grand Canyon National Park: Centennial Paleontological Resource Inventory (Non-sensitive Version). Natural Resource Report NPS/GRCA/NRR—2020/2103. National Park Service, Fort Collins, Colorado, 603 pp.
  4. ^ a b c Darton, N. H., 1910, A reconnaissance of parts of northwestern New Mexico and northern Arizona. Bulletin no. 435. U.S. Geological Survey, Reston, Virginia. 88 pp.
  5. ^
    ISBN 0-19-512299-2
  6. ^ Blakey, R.C., and Knepp, R., 1989. Pennsylvanian and Permian geology of Arizona, in: Jenney, J.P., and Reynolds S.J., eds., Geologic Evolution of Arizona, Arizona Geological Society Digest, 17. pp. 313-347.
  7. ^ Noble, L.F., 1922. A section of the Paleozoic formations of the Grand Canyon at the Bass Trail. U.S. Geological Survey Bulletin. 131-B, pp. B23-B73.
  8. ^ Gilluly, J., and Reeside, J.B., Jr., 1928, Sedimentary rocks of the San Rafael Swell and some adjacent areas in eastern Utah. in Shorter contributions to general geology, 1927, U.S. Geological Survey Professional Paper, 150-D, p. D61-D110.
  9. ^ Hamilton, W. H., 1982, Structural evolution of the Big Maria Mountains, northeastern Riverside County, southeastern California. in E. G. Frost and D. L. Martin, eds., pp. 1–27, Mesozoic-Cenozoic tectonic evolution of the Colorado River region, California, Arizona, and Nevada. Cordilleran Publishers, San Diego, California, United States. 608 pp.
  10. ^ McKee, E.D., 1934. The Coconino sandstone--its history and origin, in Papers concerning the Palaeontology of California, Arizona, and Idaho. Carnegie Institution of Washington Publication, 440, pp. 77-115.
  11. ^ a b c d e f g McKee, E.D. (1979) A study of global sand seas. Professional Paper 1052. U.S. Geological Survey, Reston, Virginia. 429 pp.
  12. ^ a b c McKee, E.D. (1945) "Small-scale structures in the Coconino Sandstone of northern Arizona". "The Journal of Geology". 53(5):313–325.
  13. ^ a b Miller, A.E., Marchetti, L., Francischini, H., and Lucas, S.G., 2020. Chapter 8. Paleozoic invertebrate ichnology of Grand Canyon national Park. In: Santucci, V.L., Tweet, J.S., ed., pp. 277–331, Grand Canyon National Park: Centennial Paleontological Resource Inventory (Non-sensitive Version). Natural Resource Report NPS/GRCA/NRR—2020/2103. National Park Service, Fort Collins, Colorado, 603 pp.
  14. ^ Spamer, E.E., 1984. Paleontology in the Grand Canyon of Arizona: 125 years of lessons and enigmas from the late Precambrian to the present. The Mosasaur. 2, pp. 45–128.
  15. ^ Kramer, J.M., Erickson, B.R. Lockley, M.G. Hunt, A.P., and Braddy, S., 1995. Pelycosaur predation in the Permian: Evidence from Laoporus trackways from the Coconino Sandstone with description of a new species of Permichnium. New Mexico Museum of Natural History and Science Bulletin. 6, pp. 245–249.
  16. ^ Lull, R.S., 1918. Fossil footprints from the Grand Canyon of the Colorado. American Journal of Science (4th series) 45, pp. 337–346.
  17. ^ Gilmore, C.W., 1926. Fossil footprints from the Grand Canyon. Smithsonian Miscellaneous Collections, 77(9), 55 pp.
  18. ^ Gilmore, C. W. 1928. Fossil footprints from the Grand Canyon: Third contribution. Smithsonian Miscellaneous Collections 80(8), 22 pp.
  19. ^ Brand, L.R., and Tang, T., 1991. Fossil vertebrate footprints in the Coconino Sandstone (Permian) of northern Arizona: Evidence for underwater origin. Geology, 19(12), pp. 1201–1204.
  20. ^ Helble, T., 2024. Flood Geology and Conventional Geology Face Off over the Coconino Sandstone. Perspectives on Science & Christian Faith, 76(2), 86-106.
  21. ^ Kieffer, S.W. (1971) Shock metamorphism of the Coconino sandstone at Meteor Crater. Arizona, Journal of Geophysical Research. 76(23):5449-5473.
  22. ^ Kieffer, S.W. (1971) I, Shock Metamorphism of the Coconino Sandstone at Meteor Crater, Arizona; II, The Specific Heat of Solids of Geophysical Interest. Unpublished PhD. dissertation. Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California. 253 pp.
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