San Pedro Arroyo Formation | |
---|---|
Stratigraphic range: | |
Type | Formation |
Unit of | Chinle Group |
Sub-units | Ojo Huelos Member |
Underlies | Morrison Formation |
Overlies | Santa Rosa Formation |
Thickness | 123 meters (404 ft) |
Lithology | |
Primary | Mudstone, sandstone |
Other | Conglomerate, siltstone, limestone |
Location | |
Coordinates | 33°53′35″N106°45′00″W / 33.893°N 106.750°W |
Region | New Mexico |
Country | United States |
Type section | |
Named for | San Pedro Arroyo |
Named by | Spencer G. Lucas |
Year defined | 1991 |
The San Pedro Arroyo Formation is a geologic formation in south-central New Mexico. It preserves fossils dating back to the late Triassic period. [1]
The formation consists of variegated bentonitic mudstone, sandstone, conglomerate, siltstone, and minor limestone, with a total thickness of 123 meters (404 ft). The sandstones are purple to red in color and are crossbedded, laminar, ripple laminated and micaceous. They are interbedded with conglomerates composed of mudstone and calcrete clasts. The formation rests on the Santa Rosa Formation and underlies either the Morrison Formation or, where that is not present, the Mesa Rica Formation or Dakota Group. [1]
A set of limestone beds near the base of the formation have been designated the Ojo Huelos Member. [1] This consists of brown-weathering limestone beds a few meters thick, interbedded with meter-thick yellowish to greenish mudstone. [2]
The formation was defined by Lucas et al. in 1991 to resolve an inconsistency in the stratigraphy of south-central New Mexico. Previous work had separated the Shinarump Formation from the Chinle Formation, but the Shinarump is a member of the Chinle Formation on the Colorado Plateau. [1] Lucas further rationalized the stratigraphy by promoting the Chinle to group rank in New Mexico in 1993. [3] However, other New Mexico stratigraphers have criticized the formation as a junior synonym for the Cooper Canyon Formation. [4]
Fossils of amphibians and phytosaurs have been found in the formation. [1]
The exposed geology of the Capitol Reef area presents a record of mostly Mesozoic-aged sedimentation in an area of North America in and around Capitol Reef National Park, on the Colorado Plateau in southeastern Utah.
The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone, and limestone and is light gray, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the Jurassic period.
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 Dockum is a Late Triassic geologic group found primarily on the Llano Estacado of western Texas and eastern New Mexico with minor exposures in southwestern Kansas, eastern Colorado, and Oklahoma panhandle. The Dockum reaches a maximum thickness of slightly over 650 m but is usually much thinner. The Dockum rests on an unconformity over the Anisian aged Anton Chico Formation.
The Triassic Lockatong Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and New York. It is named after the Lockatong Creek in Hunterdon County, New Jersey.
The Garita Creek Formation is a geologic formation in New Mexico that contains vertebrate fossils characteristic of the Carnian Age of the late Triassic.
The Santa Rosa Formation is a geologic formation exposed in New Mexico that was deposited in the Carnian Age of the late Triassic Period.
The Shinarump Conglomerate is a geologic formation found in the Four Corners region of the United States. It was deposited in the early part of the Late Triassic period.
The Baldy Hill Formation is a geologic formation in northeastern New Mexico and western Oklahoma. It preserves fossils dating back to the late Triassic period.
The Trujillo Formation is a geologic formation in Texas and New Mexico. It preserves fossils dating back to the upper Triassic period. It is also known as the Trujillo Sandstone.
The Gray Mesa Formation is a geologic formation in New Mexico. Its fossil assemblage dates the formation to the Moscovian age of the Pennsylvanian.
The Del Norte Formation is a geologic formation in Mexico, New Mexico and Texas near the city of El Paso. It preserves fossils dating back to the early Cretaceous period.
The Atrasado Formation is a geologic formation in New Mexico. Its fossil assemblage dates the formation to the Kasimovian age of the Pennsylvanian. It was formerly known locally as the Wild Cow Formation or the Guadelupe Box Formation.
The Bluewater Creek Formation is a geologic formation in west-central New Mexico. It preserves fossils dating back to the late Triassic period.
The Petrified Forest Member is a stratigraphic unit of the Chinle Formation in Arizona, Colorado, New Mexico, Nevada, and Utah. It preserves fossils dating back to the Triassic period.
The Salitral Formation is a Late Triassic geologic formation found in north-central New Mexico, primarily the northwestern Jemez Mountains. It is an older subunit of the Chinle Group, overlying the Shinarump Conglomerate and underlying the Poleo Formation.
The Rock Point Formation is a geologic formation in New Mexico, Arizona, and Utah. It preserves fossils dating back to the late Triassic.
The Blairmore Group, originally named the Blairmore Formation, is a geologic unit of Early Cretaceous age in the Western Canada Sedimentary Basin that is present in southwestern Alberta and southeastern British Columbia. It is subdivided into four formations: Cadomin Formation, Gladstone, Beaver Mines and Ma Butte, all of which are defined by type sections, most of which contain plant fossils. In some areas the Blairmore contains significant reservoirs of natural gas.
The Poleo Formation is a geologic formation in northern New Mexico. Its stratigraphic position corresponds to the late Triassic epoch.