| Hoback Formation | |
|---|---|
| Stratigraphic range: Paleogene | |
| Type | Formation |
| Underlies | Pass Peak Conglomerate |
| Thickness | 4572 m |
| Location | |
| Region | Wyoming |
| Country | United States |
| Type section | |
| Named for | Hoback River |
The Hoback Formation is a geologic formation in west-central Wyoming, located within the Hoback Basin (directly north of the Green River Basin). It formed as a result of increased sedimentation rates from the Laramide Orogeny [1] and preserves fossils dating back to the late Paleogene period, through the early Eocene.
The Hoback Formation was likely formed in a forested floodplain environment during a period of humid climate, as indicated by plentiful coal, carbonaceous shale, and fossilized plant remains. Many of the beds observed are dull in color, indicating that they formed in a reducing environment - another sign of a floodplain depositional environment, as standing water and waterlogged soil would be present for a substantial portion of the year. A prominent sandstone facies (with crossbedding, overbank deposits, and large pebbly deposits), thought to represent a large stream, is also present through much of the formation. [2]
Fossils found within the Hoback Formation include bone fragments, turtles, larger mammals, molluscs, scales, fish teeth, and a wide variety of fossilized plant material (including fossilized wood). Signs of early Cenozoic crocodiles have also been found. [1]
The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in the dry season. Each pair of layers is called a varve and represents one year. The sediments of the Green River Formation present a continuous record of six million years. The mean thickness of a varve here is 0.18 mm, with a minimum thickness of 0.014 mm and maximum of 9.8 mm.
The Florissant Formation is a sedimentary geologic formation outcropping around Florissant, Teller County, Colorado. The formation is noted for the abundant and exceptionally preserved insect and plant fossils that are found in the mudstones and shales. Based on argon radiometric dating, the formation is Eocene in age and has been interpreted as a lake environment. The fossils have been preserved because of the interaction of the volcanic ash from the nearby Thirtynine Mile volcanic field with diatoms in the lake, causing a diatom bloom. As the diatoms fell to the bottom of the lake, any plants or animals that had recently died were preserved by the diatom falls. Fine layers of clays and muds interspersed with layers of ash form "paper shales" holding beautifully-preserved fossils. The Florissant Fossil Beds National Monument is a national monument established to preserve and study the geology and history of the area.
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 Laramie Formation is a geologic formation of Late Cretaceous (Maastrichtian) age, named by Clarence King in 1876 for exposures in northeastern Colorado, in the United States. It was deposited on a coastal plain and in coastal swamps that flanked the Western Interior Seaway. It contains coal, clay and uranium deposits, as well as plant and animal fossils, including dinosaur remains.
The Cloverly Formation is a geological formation of Early and Late Cretaceous age that is present in parts of Montana, Wyoming, Colorado and Utah in the western United States. It was named for a post office on the eastern side of the Bighorn Basin in Wyoming by N.H. Darton in 1904. The sedimentary rocks of formation were deposited in floodplain environments and contain vertebrate fossils, including a diverse assemblage of dinosaur remains. In 1973, the Cloverly Formation Site was designated as a National Natural Landmark by the National Park Service.
The Geology of Bangladesh is affected by the country's location, as Bangladesh is mainly a riverine country. It is the eastern two-thirds of the Ganges and Brahmaputra river delta plain stretching to the north from the Bay of Bengal. There are two small areas of slightly higher land in the north-centre and north-west composed of old alluvium called the Madhupur Tract and the Barind Tract, and steep, folded, hill ranges of older (Tertiary) rocks along the eastern border.
The Chuckanut Formation in northwestern Washington, its extension in southwestern British Columbia, and various related formations in central Washington are fluvial sedimentary formations of Eocene age, deposited from about 54 million years ago to around 34 million years ago. The nature of the deposits and included plant fossils indicate a low-lying coastal plain with a subtropical climate; the nature of the sediments indicates metamorphic sources in northeastern Washington.
Didymictis is an extinct genus of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in North America and Europe from the late Paleocene to middle Eocene.
Bahndwivici is an extinct genus of lizard known from a nearly complete and articulated skeleton discovered in rocks of the Green River Formation of Wyoming, United States. The skeleton is very similar to that of the modern Chinese crocodile lizard, Shinisaurus.
Afairiguana avius is an extinct iguanid lizard known from a nearly complete and articulated skeleton discovered in rocks of the Early Eocene-aged Green River Formation of Wyoming, United States. As of the initial description, the skeleton represents the oldest complete iguanian from the Western Hemisphere, and is the oldest representative of the extant iguanid family of anoles, Polychrotidae.
Paleontology in Tennessee refers to paleontological research occurring within or conducted by people from the U.S. state of Tennessee. During the early part of the Paleozoic era, Tennessee was covered by a warm, shallow sea. This sea was home to brachiopods, bryozoans, cephalopods, corals, and trilobites. Tennessee is one of the best sources of Early Devonian fossils in North America. During the mid-to-late Carboniferous, the state became a swampy environment, home to a rich variety of plants including ferns and scale trees. A gap in the local rock record spans from the Permian through the Jurassic. During the Cretaceous, the western part of the state was submerged by seawater. The local waters were home to more fossil gastropods than are known from anywhere else in the world. Mosasaurs and sea turtles also inhabited these waters. On land the state was home to dinosaurs. Western Tennessee was still under the sea during the early part of the Cenozoic. Terrestrial portions of the state were swampy. Climate cooled until the Ice Age, when the state was home to Camelops, horses, mammoths, mastodons, and giant ground sloths. The local Yuchi people told myths of giant lizard monsters that may have been inspired by fossils either local or encountered elsewhere. In 1920, after local fossils became a subject of formal scientific study, a significant discovery of a variety of Pleistocene creatures was made near Nashville. The Cretaceous bivalve Pterotrigonia thoracica is the Tennessee state fossil.
Paleontology in Wyoming includes research into the prehistoric life of the U.S. state of Wyoming as well as investigations conducted by Wyomingite researchers and institutions into ancient life occurring elsewhere. The fossil record of the US state of Wyoming spans from the Precambrian to recent deposits. Many fossil sites are spread throughout the state. Wyoming is such a spectacular source of fossils that author Marian Murray noted in 1974 that "[e]ven today, it is the expected thing that any great museum will send its representatives to Wyoming as often as possible." Murray has also written that nearly every major vertebrate paleontologist in United States history has collected fossils in Wyoming. Wyoming is a major source of dinosaur fossils. Wyoming's dinosaur fossils are curated by museums located all over the planet.
Paleontology in Colorado refers to paleontological research occurring within or conducted by people from the U.S. state of Colorado. The geologic column of Colorado spans about one third of Earth's history. Fossils can be found almost everywhere in the state but are not evenly distributed among all the ages of the state's rocks. During the early Paleozoic, Colorado was covered by a warm shallow sea that would come to be home to creatures like brachiopods, conodonts, ostracoderms, sharks and trilobites. This sea withdrew from the state between the Silurian and early Devonian leaving a gap in the local rock record. It returned during the Carboniferous. Areas of the state not submerged were richly vegetated and inhabited by amphibians that left behind footprints that would later fossilize. During the Permian, the sea withdrew and alluvial fans and sand dunes spread across the state. Many trace fossils are known from these deposits.
Paleontology in Utah refers to paleontological research occurring within or conducted by people from the U.S. state of Utah. Utah has a rich fossil record spanning almost all of the geologic column. During the Precambrian, the area of northeastern Utah now occupied by the Uinta Mountains was a shallow sea which was home to simple microorganisms. During the early Paleozoic Utah was still largely covered in seawater. The state's Paleozoic seas would come to be home to creatures like brachiopods, fishes, and trilobites. During the Permian the state came to resemble the Sahara desert and was home to amphibians, early relatives of mammals, and reptiles. During the Triassic about half of the state was covered by a sea home to creatures like the cephalopod Meekoceras, while dinosaurs whose footprints would later fossilize roamed the forests on land. Sand dunes returned during the Early Jurassic. During the Cretaceous the state was covered by the sea for the last time. The sea gave way to a complex of lakes during the Cenozoic era. Later, these lakes dissipated and the state was home to short-faced bears, bison, musk oxen, saber teeth, and giant ground sloths. Local Native Americans devised myths to explain fossils. Formally trained scientists have been aware of local fossils since at least the late 19th century. Major local finds include the bonebeds of Dinosaur National Monument. The Jurassic dinosaur Allosaurus fragilis is the Utah state fossil.
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The Yegua Formation is a geologic formation in Texas. It preserves fossils dating back to the Paleogene period.
The Wasatch Formation (Tw) is an extensive highly fossiliferous geologic formation stretching across several basins in Idaho, Montana Wyoming, Utah and western Colorado. It preserves fossils dating back to the Early Eocene period. The formation defines the Wasatchian or Lostcabinian, a period of time used within the NALMA classification, but the formation ranges in age from the Clarkforkian to Bridgerian.
The San Jose Formation is an Early Eocene geologic formation in the San Juan Basin of New Mexico and Colorado.
The Beaver Mines Formation is a stratigraphic unit of Early Cretaceous (Albian) age in the Western Canada Sedimentary Basin that is present in southwestern Alberta and southeastern British Columbia, Canada. It was established by G.B. Mellon in 1967 who named it for the hamlet of Beaver Mines, Alberta. It contains a variety of plant fossils.
The Kootenay Group, originally called the Kootenay Formation, is a geologic unit of latest Jurassic to earliest Cretaceous age in the Western Canada Sedimentary Basin that is present in the southern and central Canadian Rockies and foothills. It includes economically important deposits of high-rank bituminous and semi-anthracite coal, as well as plant fossils and dinosaur trackways.
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