Pottery is the craft of making ceramic material into pots or potterywares using mud. Major types of potterywares include earthenware and porcelain, the place where such wares are made by a potter is called a pottery. Early Neolithic pottery have found in places such as Jomon Japan. A clay body can be decorated before or after firing, prior to shaping processes. Kneading helps to ensure an even moisture content throughout the body, air trapped within the clay body needs to be removed. This is called de-airing and can be accomplished either by a called a vacuum pug or manually by wedging. Wedging can produce an even moisture content. Once a clay body has been kneaded and de-aired or wedged, after shaping, it is dried and fired. Clay ware takes on varying physical characteristics during the making of pottery, at sufficient moisture content, bodies at this stage are in their most plastic form. Leather-hard refers to a body that has been dried partially. At this stage the clay object has approximately 15% moisture content, clay bodies at this stage are very firm and only slightly pliable.
Trimming and handle attachment often occurs at the leather-hard state, bone-dry refers to clay bodies when they reach a moisture content at or near 0%. It is now ready to be bisque fired, bisque refers to the clay after the object is shaped to the desired form and fired in the kiln for the first time, known as bisque fired or biscuit fired. This firing changes the body in several ways. Mineral components of the body will undergo chemical changes that will change the colour of the clay. Glaze fired is the stage of some pottery making. A glaze may be applied to the form and the object can be decorated in several ways. After this the object is glazed fired, which causes the material to melt
Bison antiquus, the Ancient or Antique bison, was the most common large herbivore of the North American continent for over 10,000 years, and is a direct ancestor of the living American bison. During the Pleistocene epoch, between 240,000 and 220,000 years ago, steppe wisent migrated from Siberia into Alaska and this species inhabited parts of northern North America throughout the remainder of the Pleistocene. In midcontinent North America, however, B. priscus was replaced by the long-horned bison, B. latifrons, the larger B. latifrons appears to have died out by about 20,000 years ago. B. antiquus is the most commonly recovered large mammalian herbivore from the La Brea tar pits, B. antiquus was taller, had larger bones and horns, and was 15-25% larger overall than modern bison. It reached up to 2.27 m tall,4.6 m long, from tip to tip, the horns of B. antiquus measured about 3 ft. A number of paleo-Indian spear and projectile points have been recovered in conjunction with the skeletons at the site.
Individuals of B. antiquus of both sexes and a range of ages have been found at the site. According to internationally renowned archaeologist George Carr Frison, B. occidentalis and Rocky Mountain First Nations peoples depended on these bison as their major food source. Frison noted that the oldest, well-documented bison kills by pedestrian human hunters in North America date to about 11,000 years ago, the Loess Hills of the Lower Mississippi Valley
National Park Service
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 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 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 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 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
New Mexico is a state located in the southwestern region of the United States of America. It was admitted to the Union as the 47th state on January 6,1912 and it is usually considered one of the Mountain States. New Mexico is fifth by area, the 36th-most populous, inhabited by Native Americans for thousands of years before European exploration, New Mexico was colonized by the Spanish in 1598 Imperial Spanish viceroyalty of New Spain. Later, it was part of independent Mexico before becoming a U. S. territory and eventually a U. S. state as a result of the Mexican–American War. Among U. S. states, New Mexico has the highest percentage of Hispanics, the major Native American nations in the state are Navajo and Apache peoples. The demography and culture of the state are shaped by these strong Hispanic and Native American influences and its scarlet and gold colors are taken from the royal standards of Spain, along with the ancient sun symbol of the Zia, a Pueblo-related tribe. New Mexico, or Nuevo México in Spanish, is incorrectly believed to have taken its name from the nation of Mexico.
The name simply stuck, even though the area had no connection to Mexico or the Mexica Indian tribes, formerly a part of New Spain, adopted its name centuries in 1821, after winning independence from Spanish rule. New Mexico was a part of the independent Mexican Empire and Federal Republic of Mexico for 27 years,1821 through 1848, New Mexico and Mexico developed as neighboring Spanish-speaking communities under Spanish rule, with relatively independent histories. The states total area is 121,412 square miles, the eastern border of New Mexico lies along 103° W longitude with the state of Oklahoma, and 2.2 miles west of 103° W longitude with Texas. On the southern border, Texas makes up the eastern two-thirds, while the Mexican states of Chihuahua and Sonora make up the western third, the western border with Arizona runs along the 109°03 W longitude. The southwestern corner of the state is known as the Bootheel, the 37° N latitude parallel forms the northern boundary with Colorado. The states New Mexico, Colorado and Utah come together at the Four Corners in the corner of New Mexico.
New Mexico, although a state, has very little water. Its surface water area is about 250 square miles, the New Mexican landscape ranges from wide, rose-colored deserts to broken mesas to high, snow-capped peaks. Despite New Mexicos arid image, heavily forested mountain wildernesses cover a significant portion of the state, the Sangre de Cristo Mountains, the southernmost part of the Rocky Mountains, run roughly north-south along the east side of the Rio Grande in the rugged, pastoral north. The most important of New Mexicos rivers are the Rio Grande, Canadian, San Juan, the Rio Grande is tied for the fourth-longest river in the United States. Tourists visiting these sites bring significant money to the state, other areas of geographical and scenic interest include Kasha-Katuwe Tent Rocks National Monument and the Gila Wilderness in the southwest of the state
New York City
The City of New York, often called New York City or simply New York, is the most populous city in the United States. With an estimated 2015 population of 8,550,405 distributed over an area of about 302.6 square miles. Located at the tip of the state of New York. Home to the headquarters of the United Nations, New York is an important center for international diplomacy and has described as the cultural and financial capital of the world. Situated on one of the worlds largest natural harbors, New York City consists of five boroughs, the five boroughs – Brooklyn, Manhattan, The Bronx, and Staten Island – were consolidated into a single city in 1898. In 2013, the MSA produced a gross metropolitan product of nearly US$1.39 trillion, in 2012, the CSA generated a GMP of over US$1.55 trillion. NYCs MSA and CSA GDP are higher than all but 11 and 12 countries, New York City traces its origin to its 1624 founding in Lower Manhattan as a trading post by colonists of the Dutch Republic and was named New Amsterdam in 1626.
The city and its surroundings came under English control in 1664 and were renamed New York after King Charles II of England granted the lands to his brother, New York served as the capital of the United States from 1785 until 1790. It has been the countrys largest city since 1790, the Statue of Liberty greeted millions of immigrants as they came to the Americas by ship in the late 19th and early 20th centuries and is a symbol of the United States and its democracy. In the 21st century, New York has emerged as a node of creativity and entrepreneurship, social tolerance. Several sources have ranked New York the most photographed city in the world, the names of many of the citys bridges, tapered skyscrapers, and parks are known around the world. Manhattans real estate market is among the most expensive in the world, Manhattans Chinatown incorporates the highest concentration of Chinese people in the Western Hemisphere, with multiple signature Chinatowns developing across the city. Providing continuous 24/7 service, the New York City Subway is one of the most extensive metro systems worldwide, with 472 stations in operation.
Over 120 colleges and universities are located in New York City, including Columbia University, New York University, and Rockefeller University, during the Wisconsinan glaciation, the New York City region was situated at the edge of a large ice sheet over 1,000 feet in depth. The ice sheet scraped away large amounts of soil, leaving the bedrock that serves as the foundation for much of New York City today. Later on, movement of the ice sheet would contribute to the separation of what are now Long Island and Staten Island. The first documented visit by a European was in 1524 by Giovanni da Verrazzano, a Florentine explorer in the service of the French crown and he claimed the area for France and named it Nouvelle Angoulême. Heavy ice kept him from further exploration, and he returned to Spain in August and he proceeded to sail up what the Dutch would name the North River, named first by Hudson as the Mauritius after Maurice, Prince of Orange
The prefix paleo- comes from the Greek adjective palaios, meaning old or ancient. The term Paleo-Indians applies specifically to the period in the Western Hemisphere and is distinct from the term Paleolithic. Evidence suggests big-animal hunters crossed the Bering Strait from Eurasia into North America over a land and ice bridge, small isolated groups of hunter-gatherers migrated alongside herds of large herbivores far into Alaska. From c. 16,500 – c. 13,500 BCE, ice-free corridors developed along the Pacific coast and this allowed animals, followed by humans, to migrate south into the interior. The people went on foot or used primitive boats along the coastline, the precise dates and routes of the peopling of the New World are subject to ongoing debate. Stone tools, particularly projectile points and scrapers, are the evidence of the earliest human activity in the Americas. Crafted lithic flaked tools are used by archaeologists and anthropologists to classify cultural periods, scientific evidence links Indigenous Americans to Asian peoples, specifically eastern Siberian populations.
There is evidence for at least two separate migrations, between 8000–7000 BCE the climate stabilized, leading to a rise in population and lithic technology advances, resulting in more sedentary lifestyle. The specifics of Paleo-Indian migration to and throughout the Americas, including the dates and routes traveled, are subject to ongoing research. These people are believed to have followed herds of now-extinct pleistocene megafauna along ice-free corridors that stretched between the Laurentide and Cordilleran ice sheets, another route proposed is that, either on foot or using primitive boats, they migrated down the Pacific coast to South America. Evidence of the latter would since have been covered by a sea rise of hundreds of meters following the last ice age. Archaeologists contend that Paleo-Indians migration out of Beringia, ranges from c. 40,000 – c. 16,500 years ago and this time range is a source of debate and promises to continue as such for years to come. However, alternative theories about the origins of Paleoindians exist, including migration from Europe, the Paleo-Indian would eventually flourish all over the Americas.
These peoples were spread over a geographical area, thus there were regional variations in lifestyles. However, all the groups shared a common style of stone tool production, making knapping styles. Food would have been plentiful during the few months of the year. Lakes and rivers were teeming with many species of fish, nuts and edible roots could be found in the forests and marshes. The fall would have been a time because foodstuffs would have to be stored
Cynthia Irwin-Williams was an archaeologist of the prehistoric American Southwest. She received a B. A. in Anthropology from Radcliffe College in 1957, in 1963 she completed her educational career in Anthropology with a PhD. from Harvard University. Beginning her career in the 1950s, Irwin-Williams was considered a ground-breaker in the field for women, like her friend. She worked with her brother, Henry Irwin, a fellow archaeologist, in 1966 Irwin-Williams and her brother published a book of her findings from the Magic Mountain Site excavation performed for the Peabody Museum of Harvard University in 1959-1960. They worked on the nearby and related LoDaisKa Site between 1958-1960, in the 1960s she defined the Picosa culture, an Archaic culture of people from three locations with interconnected artifacts and lifestyles. It was named by Irwin-Williams for those areas, Pinto Basin, Cochise Tradition and San Jose, Irwin-Williams developed the sequence of Archaic culture for the Oshara Tradition, which followed the Picosa culture, during her work in the Arroyo Cuervo area of northwestern New Mexico.
Irwin contended that the Ancient Pueblo People, or Anasazi, developed, at least in part, in 1962, Irwin-Williams led the team that first excavated the Hueyatlaco site in Mexico. The site became mired in controversy about the age of human habitation in the site, Cynthia Irwin-Williams was born April 14,1936 in Denver, Colorado. After a long illness, Irwin-Williams died on June 15,1990 in Reno. Irwin, Henry J. Irwin, Cynthia C, excavations at Magic Mountain, A Diachronic Study of Plains-Southwest Relations. Denver Museum of Natural History Proceedings Number 12, Irwin-Williams, and C. Vance Haynes, Jr. Climatic Change and Early Population Dynamics in the Southwestern United States. The Oshara Tradition, Origins of Anasazi Culture, Eastern New Mexico University Contributions in Anthropology. 5 Portales, Eastern New Mexico University Paleo-Indian Institute, post-Pleistocene Archaeology, 7000-2000 B. C. in Handbook of North American Indians. Investigations at the Salmon Site, The Structure of Chacoan Society in the Northern Southwest, Eastern New Mexico University Publications in Anthropology.
Irwin-Williams, Baker, Larry L. Baker, Anasazi Puebloan Adaptation in Response to Climatic Stress, Prehistory of the Middle Rio Puerco Valley. On file, Bureau of Land Management, Albuquerque, NM
In archaeology, excavation is the exposure and recording of archaeological remains. An excavation site or dig is a site being studied, such a site excavation concerns itself with a specific archaeological site or a connected series of sites, and may be conducted over as little as several weeks to over a number of years. Numerous specialized techniques each with its features are used. Resources and other practical issues do not allow archaeologists to carry out excavations whenever and wherever they choose and these constraints mean many known sites have been deliberately left unexcavated. This is with the intention of preserving them for generations as well as recognising the role they serve in the communities that live near them. Excavation involves the recovery of types of data from a site. These data include artifacts, ecofacts and, most importantly, data from the excavation should suffice to reconstruct the site completely in three-dimensional space. The presence or absence of remains can often be suggested by remote sensing.
Indeed, grosser information about the development of the site may be drawn from this work, the history of excavation began with a crude search for treasure and for artifacts which fell into the category of curio. These curios were the subject of interest of antiquarians and it was appreciated that digging on a site destroyed the evidence of earlier peoples lives which it had contained. Once the curio had been removed from its context, most of the information it held was lost and it was from this realization that antiquarianism began to be replaced by archaeology, a process still being perfected. Archaeological material tends to accumulate in events, a gardener swept a pile of soil into a corner, laid a gravel path or planted a bush in a hole. A builder built a wall and back-filled the trench, years later, someone built a pig sty onto it and drained the pig sty into the nettle patch. Later still, the original wall blew over and so on, each event, which may have taken a short or long time to accomplish, leaves a context.
This layer cake of events is referred to as the archaeological sequence or record. It is by analysis of sequence or record that excavation is intended to permit interpretation. As he remarked, waiting for animals to hunt represented 24% of the total man-hours of activity recorded, no tools left on the site were used, and there were no immediate material byproducts of the primary activity. All of the activities conducted at the site were essentially boredom reducers
Nebraska /nᵻˈbræskə/ is a state that lies in both the Great Plains and the Midwestern United States. Its area is just over 77,220 sq mi with almost 1.9 million people and its largest city is Omaha, which is on the Missouri River. The state is crossed by many trails and was explored by the Lewis. Nebraska was admitted as the 37th state of the United States in 1867 and it is the only state in the United States whose legislature is unicameral and officially nonpartisan. Nebraska is composed of two major regions, the Dissected Till Plains and the Great Plains. The Dissected Till Plains is a region of rolling hills. The Great Plains occupy most of western Nebraska, characterized by treeless prairie, the state has a large agriculture sector and is a major producer of beef, pork and soybeans. Two major climatic zones are represented in Nebraska, the half of the state has a humid continental climate, and the western half. Indigenous peoples lived in the region of present-day Nebraska for thousands of years before European exploration.
The historic tribes in the state included the Omaha, Ponca, Otoe, when European exploration and settlement began, both Spain and France sought to control the region. In the 1690s, Spain established trade connections with the Apaches, by 1703, France had developed a regular trade with the native peoples along the Missouri River in Nebraska, and by 1719 had signed treaties with several of these peoples. After war broke out between the two countries, Spain dispatched an expedition to Nebraska under Lieutenant General Pedro de Villasur in 1720. The party was attacked and destroyed near present-day Columbus by a force of Pawnees and Otoes. The massacre of the Villasur expedition effectively put an end to Spanish exploration of Nebraska for the remainder of the 18th century, in 1762, during the Seven Years War, France ceded the Louisiana territory to Spain. Frances withdrawal from the area left Britain and Spain competing for dominance along the Mississippi, by 1773, that year, Mackays party built a trading post, dubbed Fort Carlos IV, near present-day Homer.
In 1819, the United States established Fort Atkinson as the first U. S. Army post west of the Missouri River, the army abandoned the fort in 1827 as migration moved further west. European-American settlement did not begin in any numbers until after 1848, on May 30,1854, the US Congress created the Kansas and the Nebraska territories, divided by the Parallel 40° North, under the Kansas–Nebraska Act. The Nebraska Territory included parts of the current states of Colorado, North Dakota, South Dakota, the territorial capital of Nebraska was Omaha
Mastodons lived in herds and were predominantly forest dwelling animals that fed on a mixed diet obtained by browsing and grazing with a seasonal preference for browsing, similar to living elephants. M. americanum, the American mastodon, is the youngest, the first remnant of Mammut, a tooth some 2.2 kilograms in weight, was discovered in the village of Claverack, New York, in 1705. The mystery animal became known as the incognitum, in 1806 the French anatomist Georges Cuvier named the incognitum mastodon. The name mastodon means breast tooth, and was assigned by the French naturalist Georges Cuvier in 1817, Mastodon as a genus name is obsolete, the valid name is Mammut, a name that preceded Cuviers description, making Mastodon a junior synonym. The change was met with resistance, and authors sometimes applied Mastodon as a name so it became the common term for members of the genus. Species include, M. americanum, the American mastodon, the best known, the American mastodon resembled a woolly mammoth in appearance, with a thick coat of shaggy hair.
It had tusks that sometimes exceeded 5 meters in length, they curved upwards and its main habitat was cold spruce woodlands, and it is believed to have browsed in herds. It became extinct at the end of the Pleistocene approximately 11,000 years ago, M. matthewi—found in the Snake Creek Formation of Nebraska, dating from the late Hemphillian. Some authors consider it practically indistinguishable from M. americanum, M. raki—Its remains were found in the Palomas Formation, near Truth or Consequences, New Mexico, dating from the early-middle Pliocene, between 4.5 and 3.6 Ma. However, like M. matthewi, some authors do not consider it distinct from M. americaum to warrant its own species. M. cosoensis—found in the Coso Formation of California, dating from the late Pliocene, originally a species of Pliomastodon, it was assigned to Mammut. Since a tentative 1977 report of M. matthewi in China, the status of Mammut or Zygolophodon borsoni in the literature appears equivocal. Mammut is a genus of the extinct family Mammutidae, related to the proboscidean family Elephantidae, named from remains found in the Juntura Formation of Oregon, dating from the late Miocene.
However, it is no longer considered valid, leaving only four valid species, a complete mtDNA sequence has been obtained from the tooth of an M. americanum skeleton found in permafrost in northern Alaska. The remains are thought to be 50,000 to 130,000 years old and this sequence has been used as an outgroup to refine divergence dates in the evolution of the Elephantidae. The rate of mtDNA sequence change in proboscideans was found to be lower than in primates. Compared to mammoths, mastodons had shorter legs, a body and were more heavily muscled. The average body size of the species M. americanum was around 2.3 m in height at the shoulders, corresponding to a female or a small male
U.S. Route 285
U. S. Route 285 is a north–south United States highway, running 846 miles through the states of Texas, New Mexico and Colorado. The highways southern terminus is in Sanderson, Texas at an intersection with U. S. Route 90, US285 has always had an endpoint in Denver, although the original US285 went north from Denver. Today the highways northern terminus is in Denver, at exit 201 on Interstate 25, US285 is a secondary route of US85, which it crosses in metro Denver, and historically crossed again in Santa Fe, New Mexico. US285 intersects a sibling route, US385, in Fort Stockton, trucking makes up a large portion of the routes traffic, but along much of its route the road is used for local travel from one town to the next. The northern section of US285, from Santa Fe to Denver, traverses mountainous and rocky terrain, with that in mind, the southern terminus of US285 is at US90 in Sanderson. Proceeding north from there, it crosses I-10 at Fort Stockton, as 285 traverses north on the eastern plains of New Mexico, it passes through Carlsbad and Roswell.
In Artesia the route intersects with U. S. Route 82, in Roswell, the route intersects with U. S. Route 70 and U. S. Route 380. The route next heads northwest to Vaughn where it has a concurrency with U. S. Route 54. The route continues northwest and has a junction with Interstate 40 at Clines Corners, heading north out of Clines Corners, the route continues towards the state capital. After exiting I-25, US285 follows Saint Francis Drive through Santa Fe, the route continues north by northwest to Española and Chamita, where the concurrency with US84 ends. The route traverses the Carson National Forest where 285 now makes a long climb up to the Colorado Plateau, passing though Ojo Caliente as it ascends to the San Luis Valley. After crossing US64, the passes through the village of Tres Piedras, New Mexico at the south end of the valley. Heading north from the Colorado border, US285 passes through the part of the San Luis Valley. The highway brushes Salida and follows the Arkansas River north up the valley,285 climbs over Trout Creek Pass, elevation 9,346 feet, and enters the high-altitude South Park basin.
A few miles north, the passes through Fairplay and the historic South Park City site, reaches its highest elevation,10,051 feet. As the highway leaves the Rocky Mountains and reaches Denvers southwest suburbs, it becomes Hampden Avenue, on March 14,2008 both houses of the Colorado legislature, in a unanimous vote, named the section between Kenosha Pass and C-470 the Ralph Carr Memorial Highway. Between Denver and Como, US285 mostly follows the route of the Denver, South Park and Pacific Railroad, the route skirts the south side of the Mount Evans massif, descends into and crosses the South Park. Como in Colorados South Park still houses one of the few remaining narrow gauge roundhouses, Texas US90 in Sanderson US385 in Fort Stockton
Fossils are the preserved remains or traces of animals and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record. The study of fossils across geological time, how they were formed, such a preserved specimen is called a fossil if it is older than some minimum age, most often the arbitrary date of 10,000 years. The observation that fossils were associated with certain rock strata led early geologists to recognize a geological timescale in the 19th century. The development of dating techniques in the early 20th century allowed geologists to determine the numerical or absolute age of the various strata. Like extant organisms, fossils vary in size from microscopic, even single bacterial cells one micrometer in diameter, to gigantic, such as dinosaurs, Fossils may consist of the marks left behind by the organism while it was alive, such as animal tracks or feces.
These types of fossil are called trace fossils, as opposed to body fossils, past life leaves some markers that cannot be seen but can be detected in the form of biochemical signals, these are known as chemofossils or biosignatures. The process of fossilization varies according to type and external conditions. Permineralization is a process of fossilization that occurs when an organism is buried, the empty spaces within an organism become filled with mineral-rich groundwater. Minerals precipitate from the groundwater, occupying the empty spaces and this process can occur in very small spaces, such as within the cell wall of a plant cell. Small scale permineralization can produce very detailed fossils, for permineralization to occur, the organism must become covered by sediment soon after death or soon after the initial decay process. The degree to which the remains are decayed when covered determines the details of the fossil, some fossils consist only of skeletal remains or teeth, other fossils contain traces of skin, feathers or even soft tissues.
This is a form of diagenesis, in some cases the original remains of the organism completely dissolve or are otherwise destroyed. The remaining organism-shaped hole in the rock is called an external mold, if this hole is filled with other minerals, it is a cast. An endocast or internal mold is formed when sediments or minerals fill the cavity of an organism. This is a form of cast and mold formation. If the chemistry is right, the organism can act as a nucleus for the precipitation of minerals such as siderite, if this happens rapidly before significant decay to the organic tissue, very fine three-dimensional morphological detail can be preserved. Nodules from the Carboniferous Mazon Creek fossil beds of Illinois, USA, are among the best documented examples of such mineralization, replacement occurs when the shell, bone or other tissue is replaced with another mineral