Virgin Formation | |
---|---|
Stratigraphic range: Spathian | |
Type | Formation |
Unit of | Thaynes Group |
Thickness | 150 m (490 ft) |
Lithology | |
Primary | Limestone |
Other | Siltstone, shale |
Location | |
Coordinates | 37°12′6″N113°11′23″W / 37.20167°N 113.18972°W |
Region | Utah |
Country | United States |
Type section | |
Named for | Virgin, Utah |
Named by | Bassler and Reeside |
Year defined | 1921 |
The Virgin Formation is a geologic formation in Utah. It preserves fossils dating back to the Triassic period (Spathian substage). [1]
The Virgin Formation consists of gray to yellowish gray to greenish gray limestone, occasionally fossiliferous, alternating with greenish yellow to reddish brown to gray shale or siltstone. The limestone beds are up to 20 feet (6.1 m) thick. [2] [3] Total thickness of the formation is up to 150 meters (490 ft). [4] About 30% of the total section of the formation is limestone. [5]
The formation rests on the "lower red member" of the Moenkopi Group and underlies the Shnabkaib Member of the Moenkopi Group. [4] More recently, the Virgin Formation is interpreted as a formation of the Thaynes Group. [6]
The formation is interpreted as having been deposited in a near-shore shallow marine environment. The lower part shows cyclic sedimentation, while the upper part of the formation to the southeast was deposited in lagoons in an arid climate while marine deposition continued to the north. [5]
The formation contains marine fossils, including crinoids, pelecypods, gastropods, worms, crustaceans, and the ammonoid Tirolites . The latter is characteristic of the early Spathian stage of the Early Triassic. [3] [1]
The unit was first named as the Virgin limestone member of the Moenkopi Formation in 1922, by Harvey Bassler and John Reeside. [2] The unit was promoted to formation rank (and the Moenkopi Formation to group rank) in southwestern Utah) by S.J. Poborski in 1954. [5]
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.
The Moenkopi Formation is a geological formation that is spread across the U.S. states of New Mexico, northern Arizona, Nevada, southeastern California, eastern Utah and western Colorado. This unit is considered to be a group in Arizona. Part of the Colorado Plateau and Basin and Range, this red sandstone was laid down in the Lower Triassic and possibly part of the Middle Triassic, around 240 million years ago.
The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In New Mexico, it is often raised to the status of a geological group, the Chinle Group. Some authors have controversially considered the Chinle to be synonymous to the Dockum Group of eastern Colorado and New Mexico, western Texas, the Oklahoma panhandle, and southwestern Kansas. The Chinle Formation is part of the Colorado Plateau, Basin and Range, and the southern section of the Interior Plains. A probable separate depositional basin within the Chinle is found in northwestern Colorado and northeastern Utah. The southern portion of the Chinle reaches a maximum thickness of a little over 520 meters (1,710 ft). Typically, the Chinle rests unconformably on the Moenkopi Formation.
The Kaibab Limestone is a resistant cliff-forming, Permian geologic formation that crops out across the U.S. states of northern Arizona, southern Utah, east central Nevada and southeast California. It is also known as the Kaibab Formation in Arizona, Nevada, and Utah. The Kaibab Limestone forms the rim of the Grand Canyon. In the Big Maria Mountains, California, the Kaibab Limestone is highly metamorphosed and known as the Kaibab Marble.
The Glen Canyon Group is a geologic group of formations that is spread across the U.S. states of Nevada, Utah, northern Arizona, north west New Mexico and western Colorado. It is called the Glen Canyon Sandstone in the Green River Basin of Colorado and Utah.
The San Rafael Group is a geologic group or collection of related rock formations that is spread across the U.S. states of New Mexico, Arizona, Utah and Colorado. As part of the Colorado Plateau, this group of formations was laid down in the Middle Jurassic during the Bajocian, Bathonian and Callovian Stages.
The Carmel Formation is a geologic formation in the San Rafael Group that is spread across the U.S. states of Wyoming, Utah, Colorado, north east Arizona and New Mexico. Part of the Colorado Plateau, this formation was laid down in the Middle Jurassic during the late Bajocian, through the Bathonian and into the early Callovian stages.
The Mancos Shale or Mancos Group is a Late Cretaceous geologic formation of the Western United States.
The Thaynes Formation is a geologic formation in Montana and Idaho, United States. It was recently elevated to group status, as the Thaynes Group.
The San Pedro Arroyo Formation is a geologic formation in south-central New Mexico. It preserves fossils dating back to the late Triassic period.
The Deseret Limestone, also known as the Pine Canyon Formation, is a geologic formation in Utah. It was formed by the Panthalassa ocean around 340 Ma. It preserves marine fossils dating back to the Carboniferous period or Mississippian age, mostly consisting of tabulate and rugose corals, and other marine invertebrates; vertebrates are represented by conodonts. The Deseret is a 500-foot thick layer of dolomitic limestone with chert, with a basal layer of black shale that is host rock for many Utah caves such as Timpanogos Cave National Monument.
The Ely Limestone is a geologic formation in Nevada and Utah. It preserves fossils dating back to the Carboniferous period.
The Curtis Formation is a geologic formation in Utah. It preserves fossils dating back to the Callovian age of the Jurassic period.
The Sinbad Formation is a geologic formation in Utah initially named and described by James Gilluly and J. B. Reeside Junior in the 1920s. It is known for preserving fossils dating back to the Early Triassic epoch.
The Rock Point Formation is a geologic formation in New Mexico, Arizona, and Utah. It preserves fossils dating back to the late Triassic.
The Thaynes Group, Thaynes Formation in older literature, is a geologic group in eastern Idaho, western Wyoming, Utah and eastern Nevada. It includes the Sinbad Formation, Virgin Formation and Shnabkaib Formation. The Thaynes Group is of marine origin. Its formations are interbedded with layers of the non-marine Moenkopi Group.
The Johnson Spring Formation is a geologic formation in California. It preserves fossils dating back to the Ordovician period.
The Mesaverde Group is a Late Cretaceous stratigraphic group found in areas of Colorado, New Mexico, Utah, and Wyoming, in the Western United States.
The Spray River Group is a stratigraphic unit of Triassic age. It is present on the western edge of the Western Canada Sedimentary Basin in the foothills and Rocky Mountains of western Alberta. It was originally described as the Spray River Formation by E.M. Kindle in 1924 and was later raised to group status. Its type section is located in the Spray River gorge at the southern end of Sulphur Mountain.
The Horquilla Formation is a geologic formation exposed in southern Arizona and New Mexico. It preserves fossils dating back to the Pennsylvanian.