Helms Formation | |
---|---|
Stratigraphic range: | |
Type | Formation |
Underlies | La Tuna Formation |
Overlies | Rancheria Formation |
Thickness | 30 m (98 ft) |
Lithology | |
Primary | Shale |
Other | Sandstone, limestone |
Location | |
Coordinates | 31°46′05″N106°01′34″W / 31.768°N 106.026°W |
Region | Texas, New Mexico |
Country | United States |
Type section | |
Named for | Helms West Well |
Named by | J.W. Beede |
Year defined | 1920 |
The Helms Formation is a geologic formation in Texas and New Mexico. It preserves fossils dating back to the Chesterian (Serpukhovian) Age of the Carboniferous period. [1]
At its type section in the Hueco Mountains, the formation consists of 30 meters (98 ft) of olive-gray shale, shaly sandstone, and dirty limestone. It is unconformably underlain by the Rancheria Formation [2] and unconformably overlain by the La Tuna Formation. The formation also crops out in the Organ Mountains of New Mexico. [1]
The formation is interpreted as having been deposited during a marine regression (withdrawal of the sea from the continent) to the south. [3]
The formation contains fossils characteristic of the Chesterian (Serpukhovian) Age of the Carboniferous period. [2] [1] These include abundant specimens of the ostracod Graphiadactyllis arkansana, as well as specimens of the bryozoan Archimedes terebriformis, the echinoderm Pentremites , the brachiopods Composita subquadrata, Spiriferina transversa, Diaphragmus elegans, and several species of Dictyoclostus , [2] and the trilobite Paladin helmensis. [4]
The formation was first designated as the Helms Group by J.W. Beeded in 1920 for outcrops near Helms Well West near the Hueco Mountains. [5] The original definition included the entire set of beds between Silurian and Pennsylvanian in age. In 1949, L.R. Laudon and A.L. Bowsher restricted Helms Formation to only the uppermost beds of the original section. [2]
The Bear Gulch Limestone is a limestone-rich geological lens in central Montana, renowned for the quality of its late Mississippian-aged fossils. It is exposed over a number of outcrops northeast of the Big Snowy Mountains, and is often considered a component of the more widespread Heath Formation. The Bear Gulch Limestone reconstructs a diverse, though isolated, marine ecosystem which developed near the end of the Serpukhovian age. It is a lagerstätte, a particular type of rock unit with exceptional fossil preservation of both articulated skeletons and soft tissues. Bear Gulch fossils include a variety of fish, invertebrates, and algae occupying a number of different habitats within a preserved shallow bay.
The Fayetteville Shale is a geologic formation of Mississippian age composed of tight shale within the Arkoma Basin of Arkansas and Oklahoma. It is named for the city of Fayetteville, Arkansas, and requires hydraulic fracturing to release the natural gas contained within.
Paleontology in Oklahoma refers to paleontological research occurring within or conducted by people from the U.S. state of Oklahoma. Oklahoma has a rich fossil record spanning all three eras of the Phanerozoic Eon. Oklahoma is the best source of Pennsylvanian fossils in the United States due to having an exceptionally complete geologic record of the epoch. From the Cambrian to the Devonian, all of Oklahoma was covered by a sea that would come to be home to creatures like brachiopods, bryozoans, graptolites and trilobites. During the Carboniferous, an expanse of coastal deltaic swamps formed in areas of the state where early tetrapods would leave behind footprints that would later fossilize. The sea withdrew altogether during the Permian period. Oklahoma was home a variety of insects as well as early amphibians and reptiles. Oklahoma stayed dry for most of the Mesozoic. During the Late Triassic, carnivorous dinosaurs left behind footprints that would later fossilize. During the Cretaceous, however, the state was mostly covered by the Western Interior Seaway, which was home to huge ammonites and other marine invertebrates. During the Cenozoic, Oklahoma became home to creatures like bison, camels, creodonts, and horses. During the Ice Age, the state was home to mammoths and mastodons. Local Native Americans are known to have used fossils for medicinal purposes. The Jurassic dinosaur Saurophaganax maximus is the Oklahoma state fossil.
Paleontology in Texas refers to paleontological research occurring within or conducted by people from the U.S. state of Texas. Author Marian Murray has said that "Texas is as big for fossils as it is for everything else." Some of the most important fossil finds in United States history have come from Texas. Fossils can be found throughout most of the state. The fossil record of Texas spans almost the entire geologic column from Precambrian to Pleistocene. Shark teeth are probably the state's most common fossil. During the early Paleozoic era Texas was covered by a sea that would later be home to creatures like brachiopods, cephalopods, graptolites, and trilobites. Little is known about the state's Devonian and early Carboniferous life. Evidence indicates that during the late Carboniferous the state was home to marine life, land plants and early reptiles. During the Permian, the seas largely shrank away, but nevertheless coral reefs formed in the state. The rest of Texas was a coastal plain inhabited by early relatives of mammals like Dimetrodon and Edaphosaurus. During the Triassic, a great river system formed in the state that was inhabited by crocodile-like phytosaurs. Little is known about Jurassic Texas, but there are fossil aquatic invertebrates of this age like ammonites in the state. During the Early Cretaceous local large sauropods and theropods left a great abundance of footprints. Later in the Cretaceous, the state was covered by the Western Interior Seaway and home to creatures like mosasaurs, plesiosaurs, and few icthyosaurs. Early Cenozoic Texas still contained areas covered in seawater where invertebrates and sharks lived. On land the state would come to be home to creatures like glyptodonts, mammoths, mastodons, saber-toothed cats, giant ground sloths, titanotheres, uintatheres, and dire wolves. Archaeological evidence suggests that local Native Americans knew about local fossils. Formally trained scientists were already investigating the state's fossils by the late 1800s. In 1938, a major dinosaur footprint find occurred near Glen Rose. Pleurocoelus was the Texas state dinosaur from 1997 to 2009, when it was replaced by Paluxysaurus jonesi after the Texan fossils once referred to the former species were reclassified to a new genus.
The Bluestone Formation is a geologic formation in West Virginia. It is the youngest unit of the Upper Mississippian-age Mauch Chunk Group. A pronounced unconformity separates the upper boundary of the Bluestone Formation from sandstones of the overlying Pennsylvanian-age Pocahontas Formation.
The Pennington Formation is a geologic formation named for Pennington Gap, Virginia. It can be found in outcrops along Pine Mountain and Cumberland Mountain in Kentucky, Virginia, and Tennessee, where it is the uppermost Mississippian-age formation. The name has also been applied to similar Mississippian strata in the Cumberland Escarpment of eastern Kentucky, though the rocks in that area were later renamed to the Paragon Formation.
The Hale Formation is a geologic formation in northern Arkansas that dates to the Morrowan Series of the early Pennsylvanian. The Hale Formation has two named members: the Cane Hill and the Prairie Grove Members. The lower member is the Cane Hill, a primarily sandstone and shale interval that unconformably overlies the Mississippian-age Pitkin Formation. The upper member, the Prairie Grove Member, is predominately limestone and conformably underlies the Bloyd Formation.
The Imo Formation, or Imo Shale, is a geologic unit in northern Arkansas that dates to the Chesterian Series of the late Mississippian. The Imo is considered to be a member of the upper Pitkin Formation, and is the most recent Mississippian age rock in Arkansas. The Imo Shale unconformably underlies the Pennsylvanian age Hale Formation
The Bloyd Formation, or Bloyd Shale, is a geologic formation in Arkansas. It preserves fossils dating back to the Carboniferous period.
The Pitkin Formation, or Pitkin Limestone, is a fossiliferous geologic formation in northern Arkansas that dates to the Chesterian Series of the late Mississippian. This formation was first named the "Archimedes Limestone" by David Dale Owen in 1858, but was replaced in 1904. The Pitkin conformably overlies the Fayetteville Shale and unconformably underlies the Pennsylvanian-age Hale Formation. Some workers have considered the top of the Pitkin Formation to be a separate formation called the Imo Formation. However more recently, others have considered it as an informal member of the Pitkin Formation.
The Bishop Cap Formation is a geologic formation in the Franklin Mountains of southern New Mexico and western Texas and the Hueco Mountains of western Texas. It preserves fossils dating back to the Moscovian to Kasimovian Ages of the early Pennsylvanian.
The Hueco Formation is a geologic formation in west Texas and southern New Mexico. It preserves fossils dating back to the early Permian period.
The Lake Valley Limestone is a geologic formation widely exposed in southwestern New Mexico. It preserves fossils dating back to the lower to middle Mississippian.
The Tererro Formation is a geologic formation in Sangre de Cristo Mountains of New Mexico. It preserves fossils dating back to the early Mississippian.
The Caballero Formation is a geologic formation found in the highlands flanking the southern Rio Grande River valley in New Mexico. It preserves fossils dating back to the Tournasian Age of the Carboniferous period.
The Laborcita Formation is a geologic formation in the Sacramento Mountains of New Mexico. It preserves fossils dating back to the late Pennsylvanian to early Permian.
The La Tuna Formation is a geologic formation in the Franklin Mountains of southern New Mexico and western Texas and the Hueco Mountains of western Texas. It preserves fossils dating back to the Bashkirian Age of the early Pennsylvanian.
The Rancheria Formation is a geologic formation in the Sacramento and San Andres Mountains of New Mexico, the Franklin Mountains of southern New Mexico and western Texas, and the Hueco Mountains of western Texas. It preserves fossils dating back to the Visean Age of the Mississippian.
Diaphragmus is an extinct genus of brachiopod belonging to the order Productida and family Linoproductidae. Specimens have been found in Carboniferous beds in North America.
The Canutillo Formation is a geologic formation that is exposed in the Franklin Mountains near El Paso, Texas. The formation is Middle Devonian in age.