1.
National Park Service
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It was created on August 25,1916, by Congress through the National Park Service Organic Act and is an agency of the United States Department of the Interior. As of 2014, the NPS employs 21,651 employees who oversee 417 units, the National Park Service celebrated its centennial in 2016. National parks and national monuments in the United States were originally individually managed under the auspices of the Department of the Interior, the movement for an independent agency to oversee these federal lands was spearheaded by business magnate and conservationist Stephen Mather, as well as J. Horace McFarland. With the help of journalist Robert Sterling Yard, Mather ran a publicity campaign for the Department of the Interior and they wrote numerous articles that praised the scenic and historic qualities of the parks and their possibilities for educational, inspirational, and recreational benefits. This campaign resulted in the creation of a National Park Service, Mather became the first director of the newly formed NPS. On March 3,1933, President Herbert Hoover signed the Reorganization Act of 1933, the act would allow the President to reorganize the executive branch of the United States government. It wasnt until later that summer when the new President, Franklin D. Roosevelt, President Roosevelt agreed and issued two Executive orders to make it happen. In 1951, Conrad Wirth became director of the National Park Service, the demand for parks after the end of the World War II had left the parks overburdened with demands that could not be met. In 1952, with the support of President Dwight D. Eisenhower, he began Mission 66, New parks were added to preserve unique resources and existing park facilities were upgraded and expanded. In 1966, as the Park Service turned 50 years old, emphasis began to turn from just saving great and wonderful scenery, Director George Hartzog began the process with the creation of the National Lakeshores and then National Recreation Areas. Since its inception in 1916, the National Park Service has managed each of the United States national parks, Yellowstone National Park was the first national park in the United States. In 1872, there was no government to manage it. Yosemite National Park began as a park, the land for the park was donated by the federal government to the state of California in 1864 for perpetual conservation. Yosemite was later returned to federal ownership, at first, each national park was managed independently, with varying degrees of success. In Yellowstone, the staff was replaced by the U. S. Army in 1886. Due to the irregularities in managing these national treasures, Stephen Mather petitioned the government to improve the situation. In response, Secretary of the Interior Franklin K. Lane challenged him to lobby for creating a new agency, Mather was successful with the ratification of the National Park Service Organic Act in 1916. Later, the agency was given authority over other protected areas, the National Park System includes all properties managed by the National Park Service
2.
National Monument (United States)
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Historically, some national monuments were managed by the War Department. National monuments can be so designated through the power of the Antiquities Act of 1906, President Theodore Roosevelt used the act to declare Devils Tower in Wyoming as the first national monument. The Antiquities Act of 1906 resulted from concerns about protecting mostly prehistoric Native American ruins, the Act authorized permits for legitimate archaeological investigations and penalties for taking or destroying antiquities without permission. Among the next three monuments he proclaimed in 1906 was Petrified Forest in Arizona, another natural feature, in 1908, Roosevelt used the act to proclaim more than 800,000 acres of the Grand Canyon as a national monument. In 1918, President Woodrow Wilson proclaimed Katmai National Monument in Alaska, Katmai was later enlarged to nearly 2,800,000 acres by subsequent Antiquities Act proclamations and for many years was the largest national park system unit. Petrified Forest, Grand Canyon, and Katmai were among the national monuments later converted to national parks by Congress. Substantial opposition did not materialize until 1943, when President Franklin D. Roosevelt proclaimed Jackson Hole National Monument in Wyoming. He did this to accept a donation of lands acquired by John D. Rockefeller, roosevelts proclamation unleashed a storm of criticism about use of the Antiquities Act to circumvent Congress. A bill abolishing Jackson Hole National Monument passed Congress but was vetoed by Roosevelt, the proclamation authority was not used again anywhere until 1996, when President Bill Clinton proclaimed the Grand Staircase-Escalante National Monument in Utah. This action was unpopular in Utah, and bills were introduced to further restrict the presidents authority. To date, none of them have been enacted, presidents have used the Antiquities Acts proclamation authority not only to create new national monuments but to enlarge existing ones. For example, Franklin D. Roosevelt significantly enlarged Dinosaur National Monument in 1938, lyndon B. Johnson added Ellis Island to Statue of Liberty National Monument in 1965, and Jimmy Carter made major additions to Glacier Bay and Katmai National Monuments in 1978. Marine National Monument List of U. S. National Forests List of areas in the National Park System of the United States List of U. S
3.
Colorado
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Colorado is a state in the United States encompassing most of the Southern Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains. Colorado is part of the Western United States, the Southwestern United States, Colorado is the 8th most extensive and the 21st most populous of the 50 United States. The United States Census Bureau estimates that the population of Colorado was 5,540,545 on July 1,2016, the state was named for the Colorado River, which Spanish travelers named the Río Colorado for the ruddy silt the river carried from the mountains. The Territory of Colorado was organized on February 28,1861, Colorado is nicknamed the Centennial State because it became a state in the same year as the centennial of the United States Declaration of Independence. Colorado is noted for its landscape of mountains, forests, high plains, mesas, canyons, plateaus, rivers. Denver is the capital and the most populous city of Colorado, residents of the state are properly known as Coloradans, although the term Coloradoan has been used archaically and lives on in the title of Fort Collins newspaper, the Coloradoan. Colorado, Wyoming and Utah are the states which have boundaries defined solely by lines of latitude and longitude. The summit of Mount Elbert at 14,440 feet elevation in Lake County is the highest point in Colorado, Colorado is the only U. S. state that lies entirely above 1,000 meters elevation. The point where the Arikaree River flows out of Yuma County, Colorado and this point, which holds the distinction of being the highest low elevation point of any state, is higher than the high elevation points of 18 states and the District of Columbia. A little less than one half of the area of Colorado is flat, East of the Rocky Mountains are the Colorado Eastern Plains of the High Plains, the section of the Great Plains within Nebraska at elevations ranging from roughly 3,350 to 7,500 feet. The Colorado plains were mostly prairies, but they have many patches of forests, buttes. Eastern Colorado is presently covered in farmland and rangeland, along with small farming villages. Precipitation is fair, averaging from 15 to 25 inches annually, corn, wheat, hay, soybeans, and oats are all typical crops, and most of the villages and towns in this region boast both a water tower and a grain elevator. Irrigation water is available from the South Platte, the Arkansas River, and a few other streams, however, heavy use of ground water from wells for irrigation has caused underground water reserves to decline. As well as agriculture, eastern Colorado hosts considerable livestock, such as cattle ranches. Roughly 70% of Colorados population resides along the edge of the Rocky Mountains in the Front Range Urban Corridor between Cheyenne, Wyoming, and Pueblo, Colorado. This region is protected from prevailing storms that blow in from the Pacific Ocean region by the high Rockies in the middle of Colorado. The Front Range includes Denver, Boulder, Fort Collins, Loveland, Colorado Springs, Pueblo, Greeley and other townships, on the other side of the Rockies, the significant population centers in Western Colorado are the cities of Grand Junction, Durango, and Montrose
4.
Utah
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Utah is a state in the western United States. It became the 45th state admitted to the U. S. on January 4,1896, Utah is the 13th-largest by area, 31st-most-populous, and 10th-least-densely populated of the 50 United States. Utah has a population of more than 3 million, approximately 80% of whom live along the Wasatch Front, Utah is bordered by Colorado to the east, Wyoming to the northeast, Idaho to the north, Arizona to the south, and Nevada to the west. It also touches a corner of New Mexico in the southeast, approximately 62% of Utahns are reported to be members of The Church of Jesus Christ of Latter-day Saints or LDS, which greatly influences Utahn culture and daily life. The LDS Churchs world headquarters is located in Salt Lake City, Utah is the only state with a majority population belonging to a single church. The state is a center of transportation, education, information technology and research, government services, mining, in 2013, the U. S. Census Bureau estimated that Utah had the second fastest-growing population of any state. St. George was the metropolitan area in the United States from 2000 to 2005. Utah also has the 14th highest median income and the least income inequality of any U. S. state. A2012 Gallup national survey found Utah overall to be the best state to live in based on 13 forward-looking measurements including various economic, lifestyle, the name Utah is derived from the name of the Ute tribe. It means people of the mountains in the Ute language, according to other sources Utah is derived from the Apache name Yudah which means Tall. These Native American tribes are subgroups of the Ute-Aztec Native American ethnicity and were sedentary, the Ancestral Pueblo people built their homes through excavations in mountains, and the Fremont people built houses of straw before disappearing from the region around the 15th century. Another group of Native Americans, the Navajo, settled in the region around the 18th century, in the mid-18th century, other Uto-Aztecan tribes, including the Goshute, the Paiute, the Shoshone, and the Ute people, also settled in the region. These five groups were present when the first European explorers arrived, the southern Utah region was explored by the Spanish in 1540, led by Francisco Vásquez de Coronado, while looking for the legendary Cíbola. A group led by two Catholic priests—sometimes called the Dominguez-Escalante Expedition—left Santa Fe in 1776, hoping to find a route to the coast of California, the expedition traveled as far north as Utah Lake and encountered the native residents. The Spanish made further explorations in the region, but were not interested in colonizing the area because of its desert nature, in 1821, the year Mexico achieved its independence from Spain, the region became known as part of its territory of Alta California. European trappers and fur traders explored some areas of Utah in the early 19th century from Canada, the city of Provo, Utah was named for one, Étienne Provost, who visited the area in 1825. The city of Ogden, Utah was named after Peter Skene Ogden, in late 1824, Jim Bridger became the first known English-speaking person to sight the Great Salt Lake. Due to the salinity of its waters, Bridger thought he had found the Pacific Ocean
5.
Green River (Colorado River tributary)
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The Green River, located in the western United States, is the chief tributary of the Colorado River. The watershed of the river, known as the Green River Basin, covers parts of Wyoming, Utah, and Colorado. The Green River is 730 miles long, beginning in the Wind River Mountains of Wyoming and flowing through Wyoming and Utah for most of its course, much of the route is through the Colorado Plateau and through some of the most spectacular canyons in the United States. It is only smaller than the Colorado when the two rivers merge, but typically carries a larger load of silt. The average yearly mean flow of the river at Green River, the status of the Green River as a tributary of the Colorado River came about for mainly political reasons. In earlier nomenclature, the Colorado River began at its confluence with the Green River, above the confluence the Colorado was called the Grand River. Representative Edward T. Taylor petitioned the Congressional Committee on Interstate and it rises in western Wyoming, in northern Sublette County, on the western side of the Continental Divide in the Bridger-Teton National Forest in the Wind River Range. It flows south through Sublette County and western Wyoming in a known as the Upper Green River Valley. At the town of La Barge, it flows into Fontenelle Reservoir, prior to the creation of the reservoir, the Blacks Fork joined the Green River south of Green River, today the mouth of Blacks Fork is submerged by the reservoir. It turns westward back into Utah along the edge of the Uintas in Whirlpool Canyon. In Utah it meanders southwest across the Yampa Plateau and through the Uintah and Ouray Indian Reservation, two miles south of Ouray, Utah, it is joined by Duchesne River, and three miles downstream by the White River. Ten miles farther downstream it is joined by the Willow River, south of the plateau, it is joined by Nine Mile Creek, then enters the Roan Cliffs where it flows south through the back-to-back Desolation and Gray Canyons, with a combined length of 120 mi. In Gray Canyon, it is joined by the Price River, south of the canyon it passes the town of Green River, Utah and is joined by the San Rafael River in southern Emery County. In eastern Wayne County it meanders through Canyonlands National Park where it joins the Colorado, the Flaming Gorge Dam in Utah is a significant regional source of water for irrigation and mining, as well as for hydroelectric power. Begun in the 1950s and finished in 1963, it was highly controversial, originally, a dam was to be built in Whirlpool Canyon, but the conservationist movement traded the Flaming Gorge dam for halting that proposal. Apocryphally, the Sierra Club, an environmental organization, lost its tax-exempt status for political action in opposing the proposed dam. The Green is a large, deep, powerful river and it ranges from 100 to 300 feet wide in the upper course to 300 to 1,500 feet wide in its lower course and ranges from 3 to 50 feet in depth. It is navigable by small craft throughout its course and by large motorboats upstream to Flaming Gorge Dam, near the areas where the Oregon Trail crosses, the river is 400 -500 feet wide and averages about 20 feet deep at normal flow
6.
Yampa River
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The Yampa River flows 250 miles through northwestern Colorado in the United States. Rising in the Rocky Mountains, it is a tributary of the Green River, the Yampa is one of the few free-flowing rivers in the western United States, with only a few small dams and diversions. The name is derived from the Snake Indians word for the Perideridia plant, frémont was among the first to record the name Yampah in entries of his journal from 1843, as he found the plant was particularly abundant in the watershed. The headwaters of the Yampa are in the Park Range in Routt County, Colorado as the confluence of the Bear River and Phillips Creek, the Bear River, larger of the two, flows from a source of 11, 600-foot at Derby Peak in the Flat Tops Wilderness. The Yampa River then flows north through a mountain valley, through Stagecoach Reservoir and Lake Catamount, before reaching Steamboat Springs. Below Steamboat Springs, the Yampa flows through a valley in the western foothills of the Rockies. It receives the Elk River from the north, then passes the towns of Milner, after entering Moffat County the Yampa passes Craig and is joined by the Williams Fork. Below Cross Mountain the Yampa enters the valley of Lily Park, where it is joined by its largest tributary. Further west it enters Dinosaur National Monument, where it more than 40 miles of rugged canyons. The Yampa joins the Green in Echo Park deep within the national monument, the Yampa drains 7,660 square miles of mostly semi-arid plateau country in northwestern Colorado and a small portion of southern Wyoming. The bulk of the watershed is located between the Park Range, to the east, the Flat Tops, to the south, the Great Divide Basin, an area of closed drainage, borders the Yampa River basin to the north. The Continental Divide runs along the north and east sides of the Yampa basin, separating it from the headwaters of the North Platte River, which flows into the Mississippi River system. On the south, the Yampa River basin is bordered by that of the White River, the Yampa River is a typical Western snow-fed stream, and unlike other rivers in the western U. S. its seasonal discharge patterns are not affected by large dams and water projects. The river forms a wide, shallow braided stream throughout much of its course. The lower three fourths of the Yampa, from the Elk River down, are navigable by small craft, however the meandering, shallow nature of the river can render the river unnavigable during late summer in low water years. The upper section of the river freezes over between December and March, according to a U. S. Geological Survey stream gage at Deerlodge Park, about 50 miles above the mouth, the average river flow was 2,082 cu ft/s between 1983 and 2013. The highest annual mean was 4,431 cu ft/s in 2011, monthly average flows were highest in May at 8,200 cu ft/s and lowest in September at 342 cu ft/s. The highest recorded flow was 33,200 cu ft/s during the record snowment of May 18,1984
7.
Dinosaur
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Dinosaurs are a diverse group of reptiles of the clade Dinosauria that first appeared during the Triassic. Although the exact origin and timing of the evolution of dinosaurs is the subject of active research and they became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago. Their dominance continued through the Jurassic and Cretaceous periods and ended when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups 66 million years ago, until the late 20th century, all groups of dinosaurs were believed to be extinct. As such, birds were the dinosaur lineage to survive the mass extinction event. This article deals primarily with non-avian dinosaurs, Dinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints. Birds, at over 10,000 living species, are the most diverse group of vertebrates besides perciform fish, using fossil evidence, paleontologists have identified over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs. Dinosaurs are represented on every continent by both extant species and fossil remains, while dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species, and some were able to shift between these stances. Elaborate display structures such as horns or crests are common to all dinosaur groups, evidence suggests that egg laying and nest building are additional traits shared by all dinosaurs.7 meters and heights of 18 meters and were the largest land animals of all time. Still, the idea that dinosaurs were uniformly gigantic is a misconception based in part on preservation bias, as large. Many dinosaurs were small, Xixianykus, for example, was only about 50 cm long. Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the community believed dinosaurs to have been sluggish. Most research conducted since the 1970s, however, has indicated that all dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction. The large sizes of some groups, as well as their seemingly monstrous and fantastic nature, have ensured dinosaurs regular appearance in best-selling books and films. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, the term is derived from the Greek words δεινός and σαῦρος. Though the taxonomic name has often interpreted as a reference to dinosaurs teeth, claws. Instead, dinosaurs, like many forms of reptile sub-groups, did not exhibit characteristics which were traditionally regarded as reptilian. Under phylogenetic nomenclature, dinosaurs are usually defined as the group consisting of Triceratops, Neornithes, their most recent common ancestor, Birds are now recognized as being the sole surviving lineage of theropod dinosaurs. In traditional taxonomy, birds were considered a class that had evolved from dinosaurs
8.
Allosaurus
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Allosaurus is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period. The name Allosaurus means different lizard and it is derived from the Greek ἄλλος/allos and σαῦρος/sauros. The first fossil remains that could definitively be ascribed to this genus, were described in 1877 by paleontologist Othniel Charles Marsh and these remains became known as Antrodemus. As one of the first well-known theropod dinosaurs, it has attracted attention outside of paleontological circles. Indeed, it has been a top feature in several films, Allosaurus was a large bipedal predator. Its skull was large and equipped with dozens of sharp, serrated teeth and it averaged 8.5 m in length, though fragmentary remains suggest it could have reached over 12 m. Relative to the large and powerful hindlimbs, its forelimbs were small. It is classified as an allosaurid, a type of carnosaurian theropod dinosaur, the genus has a complicated taxonomy, and includes an uncertain number of valid species, the best known of which is A. fragilis. The bulk of Allosaurus remains have come from North Americas Morrison Formation, with also known from Portugal. Potential prey included ornithopods, stegosaurids, and sauropods and it may have attacked large prey by ambush, using its upper jaw like a hatchet. Allosaurus was a large theropod, having a massive skull on a short neck. Allosaurus fragilis, the species, had an average length of 8.5 m, with the largest definitive Allosaurus specimen estimated at 9.7 meters long. In his 1976 monograph on Allosaurus, James Madsen mentioned a range of sizes which he interpreted to show a maximum length of 12 to 13 m. As with dinosaurs in general, weight estimates are debatable, several gigantic specimens have been attributed to Allosaurus, but may in fact belong to other genera. Another potential specimen of Allosaurus, once assigned to the genus Epanterias, a more recent discovery is a partial skeleton from the Peterson Quarry in Morrison rocks of New Mexico, this large allosaurid may be another individual of Saurophaganax. The skull and teeth of Allosaurus were modestly proportioned for a theropod of its size, paleontologist Gregory S. Paul gives a length of 845 mm for a skull belonging to an individual he estimates at 7.9 m long. Each premaxilla, held five teeth with D-shaped cross-sections, and each maxilla had between 14 and 17 teeth, the number of teeth does not exactly correspond to the size of the bone, each dentary had between 14 and 17 teeth, with an average count of 16. The teeth became shorter, narrower, and more curved toward the back of the skull, all of the teeth had saw-like edges
9.
Deinonychus
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Deinonychus is a genus of carnivorous dromaeosaurid coelurosaurian dinosaurs, with one described species, Deinonychus antirrhopus. This species, which could grow up to 3.4 metres long, lived during the early Cretaceous Period, fossils have been recovered from the U. S. Before this, the conception of dinosaurs had been one of plodding. Ostrom noted the small body, sleek, horizontal posture, ratite-like spine, and especially the enlarged raptorial claws on the feet, terrible claw refers to the unusually large, sickle-shaped talon on the second toe of each hind foot. The fossil YPM5205 preserves a large, strongly curved ungual, in life, archosaurs have a horny sheath over this bone, which extends the length. Ostrom looked at crocodile and bird claws and reconstructed the claw for YPM5205 as over 120 millimetres long, the species name antirrhopus means counter balance, which refers to Ostroms idea about the function of the tail. As in other dromaeosaurids, the vertebrae have a series of ossified tendons. This suggests that, in life, the tail could bend to the sides with a degree of flexibility. In both the Cloverly and Antlers formations, Deinonychus remains have been closely associated with those of the ornithopod Tenontosaurus. Teeth discovered associated with Tenontosaurus specimens imply they were hunted, or at least scavenged upon, the skull was equipped with powerful jaws lined with around seventy curved, blade-like teeth. Studies of the skull have progressed a great deal over the decades, Ostrom reconstructed the partial, imperfectly preserved skulls that he had as triangular, broad, and fairly similar to Allosaurus. The skull of Deinonychus was different from that of Velociraptor, however, in that it had a more robust skull roof, like that of Dromaeosaurus, both the skull and the lower jaw had fenestrae which reduced the weight of the skull. In Deinonychus, the fenestra, a skull opening between the eye and nostril, was particularly large. Deinonychus possessed large hands with three claws on each forelimb, the first digit was shortest and the second was longest. Each hind foot bore a claw on the second digit. No skin impressions have ever found in association with fossils of Deinonychus. Nonetheless, the evidence suggests that the Dromaeosauridae, including Deinonychus, had feathers, the genus Microraptor is both older geologically and more primitive phylogenetically than Deinonychus, and within the same family. Multiple fossils of Microraptor preserve pennaceous, vaned feathers like those of birds on the arms, legs
10.
Cedar Mountain Formation
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The Cedar Mountain Formation is the name given to a distinctive sedimentary geologic formation in eastern Utah. The formation was named for Cedar Mountain in northern Emery County, Utah, the formation occurs between the underlying Morrison Formation and overlying Naturita Formation. It is composed of sediments, that is, sediments deposited in rivers, lakes. Based on various fossils and radiometric dates, the Cedar Mountain Formation was deposited during the last half of the Early Cretaceous Epoch and it has lithography similar to the Burro Canyon Formation in the region. Dinosaurs occur throughout the formation, but their study has only occurred since the early 1990s, the dinosaurs in the lower part of the formation differ from those in the upper part. A middle dinosaur assemblage may be present, but the record is not clear. The Cedar Mountain Formation is sandwiched between the Morrison Formation below and the Naturita Formation and Mancos Shale above, the youngest date for Morrison just below the Cedar Mountain Formation is 148.1 ±0.5 Ma. or lower Tithonian. Typically, the Jurassic-Cretaceous boundary in western North America is marked by an unconformity of variable length and this boundary between the Morrison and Cedar Mountain is commonly marked by a horizon of carbonate nodules or by highly polished pebbles that are allegedly gastroliths. Although not part of the Cedar Mountain Formation, the Naturita Formation immediately overlies the Cedar Mountain, the Naturita is not uniformly distributed and was eroded away in places by the advancing Seaway so that the marine shales of the Mancos Formation lay directly on the Mussentuchit or its equivalent. The name Dakota Formation has been used for these strata. Only recently did the 125 m thick formation get subdivided into smaller, in ascending order the remaining members are the Yellow Cat Member, Poison Strip Sandstone, Ruby Ranch Member, and the Mussentuchit Member. Each of these members are named after an area where they were first studied. The Buckhorn Conglomerate is considered the lowermost member of the Cedar Mountain Formation in the region of the San Raphael Swell by Stokes and it is named for exposures near Buckhorn Reservoir near Cedar Mountain. Its position immediately below the Ruby Ranch Member suggests that it may be equivalent to the sandstones in the Yellow Cat Member. This idea is strengthened by the composition of the gravels in these members. The Yellow Cat Member is named for exposures near the Yellow Cat mining area north of Arches National Park and it is limited to the eastern portions of the formation and is thickest near Arches National Monument. The member is composed of drab greyish mudstones and some lenses of sandstone, the mudstones were deposited on flood plains, and show evidence of ancient soil development called paleosols. The mudstones originated as flood deposits from river channels that are marked by the sandstone lenses, radiometric dating places the Yellow Cat Member at 126 ±2.5 Ma
11.
Morrison Formation
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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 gray, greenish gray. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the Jurassic period. It is centered in Wyoming and Colorado, with outcrops in Montana, North Dakota, South Dakota, Nebraska, Kansas, the panhandles of Oklahoma and Texas, New Mexico, Arizona, Utah, equivalent rocks under different names are found in Canada. It covers an area of 1.5 million square km, although only a fraction is exposed. Over 75% is still buried under the prairie to the east and it was named after Morrison, Colorado, where the first fossils in the formation were discovered by Arthur Lakes in 1877. That same year, it became the center of the Bone Wars, in Colorado, New Mexico, and Utah, the Morrison Formation was a major source of uranium ore. This is similar in age to the Solnhofen Limestone Formation in Germany, throughout the western United States, it variously overlies the Middle Jurassic Summerville, Sundance, Bell Ranch, Wanakah, and Stump Formations. At the time, the supercontinent of Laurasia had recently split into the continents of North America and Eurasia, North America moved north and was passing through the subtropical regions. In the north, the Sundance Sea, an extension of the Arctic Ocean, coal is found in the Morrison Formation of Montana, which means that the northern part of the formation, along the shores of the sea, was wet and swampy, with more vegetation. Aeolian, or wind-deposited sandstones are found in the southwestern part, in the Colorado Plateau region, the Morrison Formation is further broken into four sub-divisions, or members. From the oldest to the most recent, they are, Windy Hill Member, at the time, the Morrison basin was characterized by shallow marine and tidal flat deposition along the southern shore of the Sundance Sea. Tidwell Member, The Sundance Sea receded to Wyoming during this member and was replaced by lakes, Salt Wash Member, The first purely terrestrial member. The basin was an alluvial plain, with seasonal mudflats. Brushy Basin Member, Much finer-grained than the Salt Wash Member, rivers flowed from the west into a basin that contained a giant, saline alkaline lake called Lake Toodichi and extensive wetlands that were located just west of the modern Uncompahgre Plateau. Deposition in the Morrison Formation ended about 147 Ma, the latest Morrison strata are followed by a thirty-million year gap in the geologic record. The overlying units are the Lower Cretaceous Cedar Mountain, Burro Canyon, Lytle, though many of the Morrison Formation fossils are fragmentary, they are sufficient to provide a good picture of the flora and fauna in the Morrison Basin during the Kimmeridgian. Overall, the climate was dry, similar to a savanna but, since there were no angiosperms, conifers, the dominant plants of the time, were to be found with ginkgos, cycads, tree ferns, and horsetail rushes
12.
Sandstone
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Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earths crust, like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, quartz-bearing sandstone is converted into quartzite through heating and pressure, usually related to tectonic compression within orogenic belts. They are formed from cemented grains that may either be fragments of a rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, clays, grain sizes in sands are defined within the range of 0.0625 mm to 2 mm. The formation of sandstone involves two principal stages, first, a layer or layers of sand accumulates as the result of sedimentation, either from water or from air. Typically, sedimentation occurs by the settling out from suspension. The most common cementing materials are silica and calcium carbonate, which are derived either from dissolution or from alteration of the sand after it was buried. Colours will usually be tan or yellow, a predominant additional colourant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red, with additional manganese imparting a purplish hue. Red sandstones are seen in the Southwest and West of Britain, as well as central Europe. The regularity of the latter favours use as a source for masonry, either as a building material or as a facing stone. These physical properties allow the grains to survive multiple recycling events. Quartz grains evolve from rock, which are felsic in origin. Feldspathic framework grains are commonly the second most abundant mineral in sandstones, Feldspar can be divided into two smaller subdivisions, alkali feldspars and plagioclase feldspars. The different types of feldspar can be distinguished under a petrographic microscope, below is a description of the different types of feldspar. Alkali feldspar is a group of minerals in which the composition of the mineral can range from KAlSi3O8 to NaAlSi3O8. Plagioclase feldspar is a group of solid solution minerals that range in composition from NaAlSi3O8 to CaAl2Si2O8. Lithic framework grains are pieces of ancient source rock that have yet to weather away to individual mineral grains, accessory minerals are all other mineral grains in a sandstone, commonly these minerals make up just a small percentage of the grains in a sandstone
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