Grand Canyon and Grand Staircase

A showcase of the history of sedimentary rock

The Grand Canyon and the layered formations north of it to Zion Canyon and Bryce Canyon display the history of sedimentary rock through much of Earth's history. The formations rise in what is often called the "grand staircase". The multiple layers offer an opportunity to survey many types of sedimentary formations. The illustration below will be used as a key to the discussion of the multiple formations. This illustration is patterned after one in "The Grand Canyon", C. Hill, et al., eds, Figure 3-2 and a similar color scheme is followed for organization of the comments.

Active Graphic

Claron Formation

The Claron Formation is a lake deposit (limestone) from the Cenozoic Era containing fossils of freshwater fish and an abundance of fossils of freshwater snails.(Hill,et al.,Ch3) The unique pillars of Bryce Canyon, called hoodoos, are carved into this formation. There are fossils of animals like bison and of flowering plants, but none of the extinct species such as trilobites and dinosaurs.(Hill,et al.,Ch4)

Caanan Peak Formation

Named for exposures of this formation around Caanan Peak, this formation is mostly a coarse clastic unit characterized by gray, tan, light-brown and pink conglomerates and conglomeratic sandstones. The material is thought to be associated with river and stream deposition and varies in thickness from about 40ft to 1000 ft. It sits atop the Kaiparowits Formation but is mostly absent in the Bryce Canyon area. It is associated with the Paleocene epoch. USGS report, Wiki

Kaiparowits Formation

The Kaiparowits Formation is placed in the Mesozoic Era, Cretaceous Period. The fossils found there are terrestrial fossils: frogs, lizards, turtles, crocodiles, duckbill dinosaurs, horned dinosaurs, theropod dinosaurs, and marsupial mammals. (Hill,et al.,Ch13) It is characterized by gray sandstones and mudstones, and is in the neighborhood of 100ft (30m) thick in the Bryce Canyon area. Wiki

Wahweap Formation

The Wahweap Formation is placed in the Mesozoic Era, Cretaceous Period. It has sandstone and siltstone and is the source of a significant variety of invertebrate fossils: insect burrows in petrified logs, mollusks, crabs, gastropods. Freshwater fish fossils have been recovered: bowfin, rays, probable lungfish burrows. Several dinosaur fossils have been found: hadrosaur, ceratopsian, theropod. Wiki.

Straight Cliffs Formation

The Straight Cliffs Formation is placed in the Mesozoic Era, Cretaceous Period. The fossils found there are terrestrial fossils: frogs, lizards, turtles, crocodiles, duckbill dinosaurs, horned dinosaurs, theropod dinosaurs, and marsupial mammals. (Hill,et al.,Ch13)

Tropic Shale

The Tropic Shale formation is placed in the Mesozoic Era, Cretaceous Period. Fossils found there include ammonites, sharks and plesiosaurs. (Hill,et al.,Ch13)

Dakota Formation

The Dakota Formation is placed in the Mesozoic Era, Cretaceous Period. Fossil pollen and spores have been collected here. (Hill,et al.,Ch14)

Entrada Formation

The Entrada Formation is placed in the Mesozoic Era, Jurassic Period. The fossils found there are dinosaur bones and tracks. (Hill,et al.,Ch13)

Carmel Formation

The Carmel Formation (limestone) dating to the Mesozoic Era, Jurassic Period, contains many fossil examples of marine fauna. There are many marine invertebrates including corals, crinoids, oysters and other bivalves, and the extinct cephalopods known as ammonites. (Hill,et al.,Ch13)

Temple Cap Formation

Navajo Sandstone

The Navajo Sandstone is placed in the Mesozoic Era, Jurassic Period. The fossils found there are dinosaur bones and tracks. (Hill,et al.,Ch13)

Kayenta Formation

The Kayenta Formation is placed in the Mesozoic Era, Jurassic Period. The fossils found there are dinosaur bones and tracks. (Hill,et al.,Ch13)

Moenave Formation

Wingate Sandstone

Chinle Formation

"The Chinle Formation s placed in the Mesozoic Era, Triassic Period. It consists of colorful mudstones and siltstones that erode to form the low, rounded hills of Arizona's Painted Desert and Petrified Forest National Park."(Hill,et al.,Ch13) Fossils preserved here are many primitive conifer trees and several groups of plants that do not appear in underlying Paleozoic rocks. There are also fossils of insects and scorpions, freshwater fish and a variety of tetrapods. There are fossils of early dinosaurs. Hill, et al. lists freshwater clams, crayfish, beetles, lungfish, phytosaurs, aetosaurs, and an early bipedal dinosaur, Coelophysis. No marine organisms of any kind have been found in the Chinle Formation.

Moenkopi Formation

The Moenkopi Formation is placed in the Mesozoic Era, Triassic Period. The fossils found there are mostly terrestrial fossils. Findings include large amphibians, tracks, and coelacanth fish. (Hill,et al.,Ch13)

Kaibab Formation

The Kaibab Formation is placed in the Paleozoic Era, Permian Period. The fossils found there are marine fossils: sponges, corals,brachiopods, bryozoans, gastropods, pelecypods, nautiloids, sharks and bony fish. Trilobites are found, but are rare.(Hill,et al.,Ch13) The projected age is 270 Myr.

Toroweap Formation

The Toroweap Formation is placed in the Paleozoic Era, Permian Period. The fossils found there are marine fossils: sponges, corals,brachiopods, bryozoans, gastropods, pelecypods, nautiloids, sharks and bony fish. Trilobites are found, but are rare.(Hill,et al.,Ch13) The projected age is 273 Myr.

Coconino Sandstone

The Coconino Sandstone is placed in the Paleozoic Era, Permian Period. The fossils found there are terrestrial fossils: tracks of reptiles, spiders and scorpions. No marine fossils are found there, in contrast to lower levels. (Hill,et al.,Ch13) Fossil pollen from conifer-like (non-flowering) trees is found here. (Hill,et al.,Ch14) The projected age is 275 Myr.

Photo: NPS.gov

Hermit Formation

With a projected age of about 265 Myr in Permian Period, this formation is made of soft, easily eroded shales which have formed a slope. Its softness has undermined the layers of sandstone and limestone above it and caused large blocks to fall to the lower parts of the canyon. It contains fossils of ferns, conifers and other plants, as well as fossilized tracks of reptiles and anphibians.

Supai Group

The Supai Group is placed in the Paleozoic Era, Mississippian and Pennsylvanian Periods. The fossils there are marine fossils: brachiopods, gastropods, pelecypods,corals,bryozoans, conodonts, sharks. (Hill,et al.,Ch13) Fossil pollen from conifer-like (non-flowering) trees is found here. (Hill,et al.,Ch14) The projected age is 285-315 Myr.

Redwall Limestone

The Redwall Limestone is placed in the Paleozoic Era, Mississippian and Pennsylvanian Periods. The fossils there are marine fossils: brachiopods, gastropods, pelecypods,corals,bryozoans, conodonts, sharks. (Hill,et al.,Ch13) It forms sheer cliffs 400-500 ft high which are a barrier to travel to the bottom of the canyon. There are many caves and arches in the limestone. The projected age is 340 Myr.


Photo:nps.gov

Surprise Canyon Formation

The Surprise Canyon Formation is placed in the Paleozoic Era, Mississippian and Pennsylvanian Periods. The fossils there are marine fossils: brachiopods, gastropods, pelecypods,corals,bryozoans, conodonts, sharks. (Hill,et al.,Ch13) Fossilized spores from lycopods and ferns are plentiful here and in layers above. In lower layers only the simple trilete (three-lobed) spores from now-extinct simple spore-bearing plants and algae were found.(Hill,et al.,Ch14) The projected age is 323 Myr.

Muav Limestone

The Muav Limestone is placed in the Paleozoic Era, Cambrian Period. The fossils there are marine fossils: early trilobites,brachiopods,echinoderms, sponges. (Hill,et al.,Ch13) The projected age is 505 Myr.

Temple Butte Limestone

The Temple Butte Limestone is placed in the Paleozoic Era, Devonian Period. The fossils there are marine fossils: massive stromatoporoid sponges, rugose corals, tabulate corals, brachiopods, trilobites, placoderm fish, conodonts. (Hill,et al.,Ch13) The projected age is 385 Myr.

Bright Angel Shale

The Bright Angel Shale is placed in the Paleozoic Era, Cambrian Period. The fossils there are marine fossils: early trilobites,brachiopods,echinoderms, sponges. (Hill,et al.,Ch13)The projected age is 515 Myr.

Tapeats Sandstone

The projected age is 525 Myr. This layer is composed of medium-grained and coarse-grained sandstone. Ripple marks are found in its upper layers, indicative of a sea environment. It contains fossils of trilobites and brachiopods, and trilobite trails are found there.

Vishnu Schist

The precambrian rock that forms the "basement" for the grand staircase strata is generally called Vishnu Basement Rocks, which appear to be of volcanic origin and have been lifted from deeper locations in the time period between 1750 and 1660 Myr. Vishnu Schist is one component of the crystalline basement rock. Another component of basement rock is Elves Chasm Gneiss, which is thought to date to about 1840 Myr. It is in the form of igneous intrusions (called plutons) and contains iron and magnesium rich (mafic) materials. No fossils have been found in this basement rock. It is placed in the early Proterozoic Era. The projected age is 1700-1850 Myr.

Zoroaster Granite

Zoroaster Granite intruded into the Vishnu Schist at the base of the Grand Canyon.

Great Unconformity

The term "unconformity" is used for a location where two layers of rock are in contact, but there is evidence that material is missing, i.e., the two layers were not formed at the same time. The "Great Unconformity" is perhaps the most famous unconformity. At some locations, the Tapeats Sandstone is in direct contact with the Vishnu Basement Rock where the time gap may be 1200 Myr.

Grand Canyon Supergroup

"A thick group of rocks known as the Grand Canyon Supergroup was deposited on top of the schist and granite. Though the group includes several rock types, it is considered as a single unit that experienced a similar history following deposition."Exploring Earth

The perspective for this illustration of the Supergroup was taken from Grand Canyon Explorer. The following descriptions are excerpted from that source.

  • Chuar Group: Projected age is from 825 to 1000 Myr. Includes the Sixty Mile Formation - a tan layer composed primarily of sandstone, but some shale sections. Also the Kwagunt Formation composed of shale, mudstone and some limestone. It contains some stromatolite fossils, perhaps the oldest fossils in the Grand Canyon. The Galeros Formaton contains interbedded sandstone, limestone and shale. There are also stromatolites in this layer.
  • Nankoweap Formation: Age of about 1050 Myr, composed of coarse-grained sandstone. Not included in either the Chuar Group or the Unkar Group because it is bounded by unconformities on both sides.
  • Unkar Group:
    • Cardenas Lavas - dark brown layer of basaltic lava flows. As igneous rock, it has been radiometrically dated at 1104 +/- 2 Myr by the Uranium-Lead method. (Hill, et al, Ch 9)
    • Dox Sandstone - Layer about 1190 Myr, sandstone interbedded with shale. Contains stromatolite and algae fossils.
    • Shinumo Quartzite - Layer about 1200 Myr, composed of sandstone.
    • Hakatai Shale - Layer about 1200 Myr, primarily shale with some sandstone. Its color is bright orange-red which gives Red Canyon its name.
    • Bass Formation - Layer about 1250 Myr, composed primarily of limestone with some interbedded shale. It contains stromatolite fossils. There is a volcanic ash layer at the base of the Bass Formation which has been dated at 1255 +/- 2 Myr. It is interesting that in 1986 the magnetic field direction of iron minerals at this location was measured and compared with iron minerals in strata outside the Grand Canyon. The resulting date was 1250 Myr, in agreement with the radiometric age value. (Hill, et al Ch 9).

The Grand Canyon Supergroup of formations shows no animal or multicellular fossils. It is placed in the late Proterozoic Era.

Examples of sedimentary rock
Index

References:
Hill, C., et al.
The Grand Canyon, Ch 3

Lutgens and Tarbuck
Ch 6

Grand Canyon Explorer
 
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