The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah and Arizona. Specifically, the basin occupies space in the San Juan, Rio Arriba, Sandoval, and McKinley counties in New Mexico, and La Plata and Archuleta counties in Colorado. The basin extends roughly 100 miles (160 km) N-S and 90 miles (140 km) E-W.
The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Interior Seaway. The usage of the name Dakota for this particular Albian-Cenomanian strata is exceptionally widespread; from British Columbia and Alberta to Montana and Wisconsin to Colorado and Kansas to Utah and Arizona. It is famous for producing massive colorful rock formations in the Rocky Mountains and the Great Plains of the United States, and for preserving both dinosaur footprints and early deciduous tree leaves.
The Point Lookout Sandstone is a Cretaceous bedrock formation occurring in New Mexico and Colorado.
The Plainview Formation is an Early Cretaceous (Albian) geologic formation of the Dakota Group in Colorado. Fossil ankylosaur tracks and tracks of Caririchnium sp. have been reported from the formation.
The Pajarito Formation is a geologic formation in eastern New Mexico and west Texas. It preserves fossils dating back to the Albian Age of the Cretaceous Period.
The Kiowa Formation or Kiowa Shale is a Cretaceous geologic formation in Kansas, diminishing to member status in Colorado and Oklahoma. In Colorado, the Kiowa Shale was classified as a member of the now abandoned Purgatoire Formation. In the vicinity of Longford, Kansas, the local Longford member comprises thinly bedded siltstone, clay, polished gravel, lignite, and sandstone suggests a river and estuary environment.
The Graneros Shale is a geologic formation in the United States identified in the Great Plains as well as New Mexico that dates to the Cenomanian Age of the Cretaceous Period. It is defined as the finely sandy argillaceous or clayey near-shore/marginal-marine shale that lies above the older, non-marine Dakota sand and mud, but below the younger, chalky open-marine shale of the Greenhorn. This definition was made in Colorado by G. K. Gilbert and has been adopted in other states that use Gilbert's division of the Benton's shales into Carlile, Greenhorn, and Graneros. These states include Kansas, Texas, Oklahoma, Nebraska, and New Mexico as well as corners of Minnesota and Iowa. North Dakota, South Dakota, Wyoming, and Montana have somewhat different usages — in particular, north and west of the Black Hills, the same rock and fossil layer is named Belle Fourche Shale.
The Mesa Rica Sandstone is a geologic formation in Oklahoma and New Mexico. It preserves fossils dating back to the Cretaceous period.
The Purgatoire Formation is an abandoned (1987) Cretaceous period geologic formation classification. The classification was used in Colorado, New Mexico, and Oklahoma, with mentions in older geologic literature in neighboring states.
The Sheep Pen Sandstone is a late Triassic geologic formation exposed in northeastern New Mexico. Fossil theropod tracks have been reported from the formation.
The Sandia Formation is a geologic formation in New Mexico, United States. Its fossil assemblage is characteristic of the early 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 Mesilla Valley Shale is a geologic formation in southern New Mexico, northern Chihuahua, and far west Texas. It preserves fossils dating back to the Albian age of the early Cretaceous period.
The Muleros Formation is a geologic formation in New Mexico, which is particularly well exposed at Cerro de Cristo Rey near El Paso, Texas. It preserves fossils dating back to the early Cretaceous period.
The Tucumcari Formation is a geologic formation in New Mexico. It preserves fossils dating back to the Albian Age of the early Cretaceous period.
The Travesser Formation is a geologic formation in northeastern New Mexico, southeastern Colorado, westernmost Oklahoma, and northwestern Texas, particularly in the Dry Cimarron valley. It preserves fossils dating back to the late Triassic period.
Juana Lopez refers to both the uppermost member of the Carlile Shale formation and to the environment that caused it to form. The Juana Lopez Member is calcareous sandstone dated to the Turonian age of the Upper Cretaceous and is exposed in the southern and western Colorado, northern and central New Mexico, and northeastern Utah. The unit has been described as "the most enigmatic" member of the Carlile Shale.
The Lytle Formation or Lytle Sandstone is a geologic formation found in Wyoming, Colorado, and New Mexico.
The Romeroville Sandstone is a geologic formation in northeastern New Mexico. It likely was deposited in the Cenomanian Age of the Cretaceous Period.
Texigryphaea is an extinct genus of oyster belonging to the order Ostreida and family Gryphaeidae. It dates to the Albian to Cenomanian Ages of the Cretaceous period and is primarily found in Texas and the southern Western Interior of North America. However, specimens have been identified from northern Spain.
