Glen Canyon Group

The Glen Canyon Group consists of extensive eolian deposits of latest Triassic to Early Jurassic age on the Colorado Plateau. These form the spectacular orange canyon walls of Canyonlands National Park and Paria Canyon as well as the unflooded portions of Glen Canyon. Deposition of the Glen Canyon Group ceased in the Middle Jurassic with the transgression of the Sundance Sea, which separated deposition of the Glen Canyon Group from deposition of the overlying San Rafael Group.[6] The Glen Canyon Group is separated from the underlying Chinle Formation by the regional J-0 unconformity, which represents a time of widespread erosion across western North America. The group is likewise separated from the overlying San Rafael Group by the regional J-2 conformity, representing a renewal of widespread erosion.[7]

The Glen Canyon Group was deposited in a foreland basin created by the uplift of the Sevier Mountains in what is now Nevada and eastern Utah. As a result, the formations of the group thicken to the west.[8]

The Kayenta Formation pinches out and disappears to the north, in the Uintah Basin, and the Wingate Sandstone and Navajo Sandstone become indistinguishable. These remaining eolian beds have sometimes been mapped as simply Glen Canyon Formation, but they correlate with the Nugget Sandstone further north, and it has been recommended that they be assigned to the Nugget Sandstone.[9]

The Permian through Jurassic stratigraphy of the Colorado Plateau area of southeastern Utah that makes up much of the famous prominent rock formations in protected areas such as Capitol Reef National Park and Canyonlands National Park. From top to bottom: Rounded tan domes of the Navajo Sandstone, layered red Kayenta Formation, cliff-forming, vertically-jointed, red Wingate Sandstone, slope-forming, purplish Chinle Formation, layered, lighter-red Moenkopi Formation, and white, layered Cutler Formation sandstone. Picture from Glen Canyon National Recreation Area, Utah.

Group rank (stratigraphic order):[2]

• Navajo Sandstone (AZ*,[10] CO*,[11] NM*,[12] UT*[13]),
• Kayenta Formation (AZ,[10] CO*,[14] UT*[13]),
• Moenave Formation (AZ*,[10] NV*,[15] UT*[13]),
• Wingate Sandstone (AZ*,[10] CO*,[16] NM*,[2] UT*[17])

There is no designated type locality for this group. It was named by Gregory and Moore prior to 1928 for exposures in walls that form the Glen Canyon of the Colorado River in Coconino County, Arizona and San Juan County, Utah, though their report was not published until 1931.[18] The name had by then been published by Gilluly and Reeside, who gave an overview of the group.[19]

In 1936, A.A. Baker reexamined the group and named the Kayenta Formation.[20] The work was revised again in 1955 by Averitt and others. They assigned the Shurtz Sandstone Tongue (new) and Lamb Point Tongue (new) to the Navajo Sandstone, and Cedar City Tongue (new) and Tenney Canyon Tongue (new) to the Kayenta Formation.[17] In 1957 Harshbarger and others created an overview and revision that assigned the Moenave Formation and divided the Wingate Sandstone into the newly named Rock Point and Lukachukai members.[2] In 1963, the upper contact was revised by Phoenix, who moved the uppermost silstone beds of the Navajo Sandstone into the Judd Hollow Tongue of the Carmel Formation.[21] Poole and Stewart mapped the group into the Green River Basin in 1964, treating it here as a single formation.[22] Areal extent limits were revised by Wilson and Stewart in 1967[23] and again by Green in 1974, who added the Iyanbito Member.[24] Peterson and Pipiringos revised the upper contact and created an overview in 1979.[13] In 1989 the age of the group was reexamined by Padian[10] and separately by Dubiel (who also revised the lower contact).[25]

Alcove in the Navajo Sandstone near Moab, Utah.

Geologic Province:

• Black Mesa Basin[25]
• Great Basin province[13]
• Green River Basin[22]
• Paradox Basin[2]
• Piceance Basin[22]
• Plateau Sedimentary Province[2]
• San Juan Basin[2]
• Uinta Uplift[22]

Prehistoric animals from the various formations of the Glen Canyon Group include several types of dinosaurs, known from both skeletal remains and tracks. Dinosaur finds in the Wingate and Moenave formations are presently almost entirely tracks. The Kayenta Formation has a diverse skeletal fauna including the theropods "Syntarsus" kayentakatae and Dilophosaurus, the prosauropod Sarahsaurus, an unnamed heterodontosaurid, and the armored dinosaurs Scelidosaurus and Scutellosaurus. The Navajo Sandstone has body fossils of the theropod Segisaurus and an Ammosaurus-like prosauropod, and tracks.[5]

The following summarizes vertebrate fossils and tracks reported in the Glen Canyon Group:

Navajo Sandstone:

Body fossils

Tritylodontidae indet.[26]

Protosuchidae indet.[26]

Segisaurus hallii Camp[26]

Ammosaurus[26]

Trace fossils

Actinopterygii[27]

Anchisauripus[28]

Anomoepus?[28]

Brasilichnium[26][28]

Eubrontes[26][28]

Grallator[28]

Tetrasauropus[26]

Otozoum[26]

Anomoepus[26]

Kayenta Formation:

Body fossils

Hybodontidae incert.[26]

Osteichthyes incert.[26]

Prosalirus bitis Shubin and Jenkins[26]

Eocaecilia micropodia Jenkins and Wash[26]

Kayentachelys aprix Gaffney et al.[26]

Trace fossils

Brasilichnium?[28]

Eubrontes[28]

Grallator[28]

Otozoum[29]

Moenave Formation:

Body fossils

Semionotidae incert.[26]

Reptilia indet.[26]

Protosuchus[26]

Lepidosauria indet.[26]

Megapnosaurus[26]

Trace fossils

Brasilichnium[26]

Grallator[28]

Tetrasauropus[26]

Eubrontes[28]

Wingate Sandstone:

Trace fossils:

Brasilichnium[26]

Tetrasauropus[26]

Grallator[26]

Wikimedia Commons has media related to Glen Canyon Group.

• Lists of dinosaur-bearing stratigraphic units
• List of stratigraphic units with few dinosaur genera