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Joachim Dolomite

The Joachim Dolomite is a Middle Ordovician geologic formation in Arkansas, Illinois, and Missouri. The name was first introduced in 1894 by Arthur Winslow in his study of the geology of Missouri. Winslow designated a stratotype along Plattin Cre ...

Juana Lopez Member

Juana Lopez refers to both the uppermost member of the Carlile Shale formation and to the environment that cause it to form. This unit is calcareous sandstone of Turonian age, Upper/Late Cretaceous series in the southern and western Colorado and ...

Kimmswick Limestone

The Kimmswick Limestone is an Ordovician geologic formation in Arkansas, Illinois and Missouri. Fossils occurring in the Kimmswick include corals, bryozoans, brachiopods, conodonts, trilobites, crinoids and mollusks.

Kishenehn Formation

The Kishenehn Formation is a Paleogene stratigraphic unit in Montana. Fossil amiiforme and teleost fish have been found in outcrops of the formations Coal Creek Member in Glacier National Park. Mosquitos have also been found in the Coal Creek Mem ...

Kootenai Formation

The Kootenai Formation is a Lower Cretaceous geologic formation. The Kootenai was deposited in a foreland basin east of the Sevier thrust belt in western Montana. The lithology consists of a basal conglomerate with overlying non-marine sandstones ...

Ladd Formation

Dinosaur remains mainly hadrosaurid fragments are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus. In 1927 Bernard Nettleton Moore found a hadrosaur maxilla with teeth while ...

Lafferty Limestone

The Lafferty Limestone is a Middle to Late Silurian geologic formation in the Ozark Plateaus of Arkansas. The name was introduced in 1921 by Hugh Dinsmore Miser in his study of Arkansas, replacing part of the upper St. Clair Limestone. Miser desi ...

Latah Formation

The Latah Formation is a series of late Miocene lacustrine sedimentary deposits which outcrop in eastern Washington and northwestern Idaho. The lake beds are interbedded with igneous rock of the Columbia River Basalt Group. The formation was orig ...

Logan Formation

The Logan Formation is the name given to a Lower Carboniferous siltstone, sandstone and conglomeratic unit exposed in east-central Ohio and parts of western West Virginia, USA.

Lompico Sandstone

The Lompico Sandstone is a sedimentary rock formation of lower to middle Miocene age. It overlies the Salinian basement rocks of Santa Cruz County, California. It interfingers with and is overlain by the Miocene Monterey Formation. These are in t ...

Manassas Sandstone

The Manassas Sandstone is a Carnian Stage sandstone geological formation in Virginia, United States. Stage Karni is part of the Triassic system of the Mesozoic Erathem. Fossils of theropod tracks were registered in education.

Maquoketa Formation

The Maquoketa Formation is a geologic formation in Illinois, Indiana. Iowa, Kansas, Minnesota, Missouri, and Wisconsin. It preserves mollusk, coral, brachiopod and graptolite fossils dating back to the Ordovician period.

Marshalltown Formation

The Marshalltown Formation is a Mesozoic geologic formation. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.

Masuk Formation

The Masuk Formation is a Mesozoic geologic formation in the United States. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.

Mazarn Shale

The Mazarn Shale is an Early Ordovician geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. This interval was first described in 1892, but remained unnamed until 1918 as part of a study by U.S. Geological Survey geologist Hugh ...

McAlester Formation

The McAlester Formation is a Pennsylvanian geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. Early descriptions of this unit considered it to be part of the Coal Measures, part of the Upper or Western Coal Bearing Division, t ...

Meeteetse Formation

The Meeteetse Formation is a Late Cretaceous geologic formation occurring in Wyoming. The formation described by G. V. Pearce as a gray to white clayey sand, gray Sandstone, gray and brown shale, and bentonitic clays. It can form the Badlands. Di ...

Meramec (series)

Included are the St. Louis Limestone, Ste. Genevieve Limestone, Salem Limestone, and the Harrodsburg Limestone. All of these rocks are generally thick bedded limestones with chert, gypsum, and dolomite. Some beds consist of siltstone.

Mesa Rica Formation

The Mesa Rica Formation is a Mesozoic geologic formation in New Mexico, United States. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.

Mesaverde Formation

The Mesaverde Formation is a Late Cretaceous geologic formation found in areas of Colorado, New Mexico, Utah, and Wyoming, in the Western United States.

Missouri Mountain Shale

The Missouri Mountain Shale is a Silurian geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. First described in 1892, this unit was not named until 1909 by Albert Homer Purdue in his study of the Ouachita Mountains of Arkansas ...

Moreno Formation

The Moreno Formation is a Mesozoic geologic formation. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.

Morrill Limestone

The Morrill Limestone is a stratigraphic unit in east-central Kansas, northeast-central Oklahoma, and southeastern Nebraska in the Midwestern United States. It preserves fossils dating to the Permian period.

Mount Laurel Formation

The Mount Laurel Formation is a Mesozoic geologic formation located in New Jersey. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation. Dinosaur teeth recovered from this formation incl ...

Mountain Springs Formation

The Mountain Springs Formation is Devonian stratigraphic unit in Arizona. The remains of both antiarch and arthrodire placoderms are known from the formation.

Mowry Shale

The Mowry Shale is a Late Cretaceous geologic formation. The formation was named for Mowrie Creek, northwest of Buffalo in Johnson County, Wyoming. The Mowry crops out or occurs at depth in parts of Colorado, Montana, North Dakota, South Dakota, ...

Newark Canyon Formation

The Newark Canyon Formation is a Mesozoic geologic formation in Nevada in the United States. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.

Nugget Sandstone

The Nugget Sandstone is a Late Triassic geologic formation that outcrops in Utah, western United States. Fossil theropod tracks have been reported from the formation.

Ojinaga Formation

The Ojinaga Formation is a Mesozoic geologic formation. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.

Oronto Group

The Oronto Group is a thick group of arkose sandstone and shale located beneath the Bayfield Group in northern Wisconsin, along the northwestern side of the Keweenaw Peninsula and southern Isle Royale, and believed to extend into Minnesota. Becau ...

Patuxent Formation

The Patuxent formation was first described by W. B. Clark in 1897. The formation is primarily unconsolidated white-grey or orange-brown sand and gravel, with minor clay and silt. The sand often contains kaolinized feldspar, making it an arkose. C ...

Penters Chert

The Penters Chert is a Devonian geologic formation in the Ozark Plateaus of Arkansas. The name was introduced in 1921 by Hugh Dinsmore Miser in his study of Arkansas. Miser designated a type locality near the old Penters Bluff railroad station in ...

Pictured Cliffs Formation

The Pictured Cliffs Formation is a Campanian geologic formation in New Mexico. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.

Plattin Limestone

The Plattin Limestone is a Middle Ordovician geologic formation in Arkansas, Illinois, and Missouri. The name was first introduced in 1904 by Edward Oscar Ulrich in his study of the geology of Missouri. A type locality was designated at the mouth ...

Polk Creek Shale

The Polk Creek Shale is a Late Ordovician geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. First described in 1892, this unit was not named until 1909 by Albert Homer Purdue in his study of the Ouachita Mountains of Arkansas ...

Popo Agie Formation

The Popo Agie Formation is a Triassic geologic formation that outcrops in western Wyoming, western Colorado, and Utah. It was deposited during the Late Triassic in fluvial and lacustrine environments that existed across much of what is now the Am ...

Powell Formation

The Powell Formation or Powell Dolomite is a geologic formation in northern Arkansas, southeast Missouri and Virginia. It contains gastropod, cephalopod, and trilobite fossils dating back to the Ordovician Period.

Reedsville Formation

The Ordovician Reedsville Formation is a mapped surficial bedrock unit in Pennsylvania, Maryland, Virginia, West Virginia, and Tennessee, that extends into the subsurface of Ohio. This rock is a slope-former adjacent to the prominent ridge-formin ...

Salem Limestone

The Salem Formation is a geologic formation in Illinois, Indiana, Kentucky, and Missouri. It preserves fossils dating back to the Mississippian subperiod.

Sand Wells Formation

The Sand Wells Formation is a Mesozoic geologic formation in the United States. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.

Santa Rosa Formation, New Mexico

The Santa Rosa Formation is a Mesozoic geologic formation. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.

Savanna Sandstone

The Savanna Sandstone or Savanna Formation is a Pennsylvanian geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. Early descriptions of this unit have considered it to be part of the Coal Measures, part of the Upper or Western ...

Severn Formation

The Severn Formation is a Mesozoic geologic formation in Maryland. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.

Sheep Pen Sandstone Formation

The Sheep Pen Sandstone Formation is a Mesozoic geologic formation in the United States. Fossil theropod tracks have been reported from the formation.

Shellenberger Canyon Formation

The Shellenberger Canyon Formation is a Mesozoic geologic formation. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.

St. Louis Limestone

The St. Louis Limestone is a large geologic formation covering a wide area of the midwest of the United States. It is named after an exposure at St. Louis, Missouri. It consists of sedimentary limestone with scattered chert beds, including the he ...

Stanley Shale

The Stanley Shale, or Stanley Group, is a Mississippian stratigraphic unit in the Ouachita Mountains of Arkansas and Oklahoma. First described in Arkansas in 1892, this unit was not named until 1902 by J.A. Taff in his study of the Ouachita Mount ...

Tippecanoe sequence

The Tippecanoe sequence was the cratonic sequence--that is, the marine transgression--that followed the Sauk sequence, it extended from roughly the Middle Ordovician to the Early Devonian.

Tokio Formation

The Tokio Formation is a Late Cretaceous geologic formation in Arkansas and Oklahoma. Named in 1919 by Hugh Dinsmore Miser and Albert Homer Purdue in their study of Arkansas. They assigned the town of Tokio, Hempstead County, Arkansas as the type ...

Transcontinental Arch

The Transcontinental Arch refers to the islands of North America which extended from New Mexico to Minnesota and the Great Lakes region. These islands were present during the Sauk sequence, the earliest cratonic sequence. As a result of the Sauk ...