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Nebraskan Glaciation
The Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America from ~2.5–0.2 Ma (million years ago). North America As the oldest stage in the North American regional subdivision of the Quaternary, the Pre-Illinoian precedes the Illinoian Stage. Researchers have identified 11 distinct glacial stages during the Pre-Illinoian Stage. The Pleistocene prior to the Illinoian stage had previously been subdivided into the Nebraskan, Aftonian, Kansan, and Yarmouthian stages (ages). However, detailed studies of these stages revealed that the assumptions and criteria on which they were defined proved to be wrong to such a point that these stages became meaningless in terms of the actual glacial–interglacial record. For example, instead of two glaciations having occurred prior to the Illinoian Stage, researchers found that 11 distinct glaciations had occurred. In addition, what was p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek grc, label=none, πλεῖστος, pleīstos, most and grc, label=none, καινός, kainós (latinized as ), 'new'. At the end of the preceding Pliocene, the previously isolated North and South American continents were joined by the Isthmus of Panama, causing Great American Interchang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anglian Stage
The Anglian Stage is the name used in the British Isles for a middle Pleistocene glaciation. It precedes the Hoxnian Stage and follows the Cromerian Stage in the British Isles. The Anglian Stage is correlated to Marine Isotope Stage 12 (MIS 12), which started about 478,000 years ago and ended about 424,000 years ago. Lisiecki, L.E. (2005Ages of MIS boundaries. Boston MA:Boston University Description The Anglian stage has often been correlated to the Elsterian Stage of northern Continental Europe and the in the |
Ice Age
An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and greenhouse periods, during which there are no glaciers on the planet. Earth is currently in the Quaternary glaciation. Individual pulses of cold climate within an ice age are termed ''glacial periods'' (or, alternatively, ''glacials, glaciations, glacial stages, stadials, stades'', or colloquially, ''ice ages''), and intermittent warm periods within an ice age are called '' interglacials'' or ''interstadials''. In glaciology, ''ice age'' implies the presence of extensive ice sheets in both northern and southern hemispheres. By this definition, Earth is currently in an interglacial period—the Holocene. The amount of anthropogenic greenhouse gases emitted into Earth's oceans and atmosphere is predicted to prevent the next glacial period for th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Isotope Stage
Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data reflecting changes in temperature derived from data from deep sea core samples. Working backwards from the present, which is MIS 1 in the scale, stages with even numbers have high levels of oxygen-18 and represent cold glacial periods, while the odd-numbered stages are lows in the oxygen-18 figures, representing warm interglacial intervals. The data are derived from pollen and foraminifera (plankton) remains in drilled marine sediment cores, sapropels, and other data that reflect historic climate; these are called proxies. The MIS timescale was developed from the pioneering work of Cesare Emiliani in the 1950s, and is now widely used in archaeology and other fields to express dating in the Quaternary period (the last 2.6 million years), as well as providing the fullest and best data ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Illinoian Glacial Lobe
The Illinoian Stage is the name used by Quaternary geologists in North America to designate the period c.191,000 to c.130,000 years ago, during the middle Pleistocene, when sediments comprising the Illinoian Glacial Lobe were deposited. It precedes the Sangamonian Stage and follows the Pre-Illinoian Stage in North America. The Illinoian Stage is defined as the period of geologic time during which the glacial tills and outwash, which comprise the bulk of the Glasford Formation, accumulated to create the Illinoian Glacial Lobe.Willman, H.B., and J.C. Frye, 1970, ''Pleistocene Stratigraphy of Illinois.'' Bulletin no. 94, Illinois State Geological Survey, Champaign, Illinois. It occurs at about the same time as the penultimate glacial period. Definition At its type exposure in Peoria County, Illinois, the Illinoian deposits consist of three till members of the Glasford Formation. They overlay Pre-Illinoian tills of the Banner Formation, in which the Yarmouth Soil (paleosol) has deve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pearl Formation
A pearl is a hard, glistening object produced within the soft tissue (specifically the mantle) of a living shelled mollusk or another animal, such as fossil conulariids. Just like the shell of a mollusk, a pearl is composed of calcium carbonate (mainly aragonite or a mixture of aragonite and calcite) in minute crystalline form, which has deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes, known as baroque pearls, can occur. The finest quality of natural pearls have been highly valued as gemstones and objects of beauty for many centuries. Because of this, ''pearl'' has become a metaphor for something rare, fine, admirable and valuable. The most valuable pearls occur spontaneously in the wild, but are extremely rare. These wild pearls are referred to as ''natural'' pearls. ''Cultured'' or ''farmed'' pearls from pearl oysters and freshwater mussels make up the majority of those currently sold. Imitation pearls are also widely ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Outwash
An outwash plain, also called a sandur (plural: ''sandurs''), sandr or sandar, is a plain formed of glaciofluvial deposits due to meltwater outwash at the terminus of a glacier. As it flows, the glacier grinds the underlying rock surface and carries the debris along. The meltwater at the snout of the glacier deposits its load of sediment over the outwash plain, with larger boulders being deposited near the terminal moraine, and smaller particles travelling further before being deposited. Sandurs are common in Iceland where geothermal activity accelerates the melting of ice flows and the deposition of sediment by meltwater. Formation Sandurs are found in glaciated areas, such as Svalbard, Kerguelen Islands, and Iceland. Glaciers and icecaps contain large amounts of silt and sediment, picked up as they erode the underlying rocks when they move slowly downhill, and at the snout of the glacier, meltwater can carry this sediment away from the glacier and deposit it on a broad plai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glasford Formation
Glasford is a village in Peoria County, Illinois, United States. The population was 1,022 at the 2010 census. Glasford is part of the Peoria, Illinois Metropolitan Statistical Area. History Glasford or Glasco as it was called in 1868, was named for its founder, Samual Alexander Glasford/Glassford (1824-1896). Samuel A. Glasford whom arrived in Peoria County in 1842 from Ohio and was one of the early settlers of Timber Twp., had the foresight to off lots where cornfields once stood. When the railroad was built by his farm residence, Mr. Glasford had the hindsight to realize Lancaster, IL would seek the railroad and laid out the town December 9, 1868 which became incorporated as a village in 1889.Glasford Gazette. The Birth of Glasford; History of Eighty Years Glasco would become a center of trade and population along the new route of the Toledo, Peoria and Warsaw Railroad, bringing many new settlers and stores to Glasco in 1868. The town has been called by many names in differen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Till
image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is diagnostic of till. image:Glacial till exposed in roadcut-750px.jpg, Glacial till with tufts of grass Till or glacial till is unsorted glacier, glacial sediment. Till is derived from the erosion and entrainment of material by the moving ice of a glacier. It is deposited some distance down-ice to form terminal, lateral, medial and ground moraines. Till is classified into primary deposits, laid down directly by glaciers, and secondary deposits, reworked by fluvial transport and other processes. Description Till is a form of '' glacial drift'', which is rock material transported by a glacier and deposited directly from the ice or from running water emerging from the ice. It is distinguished from other forms of drift in that it is depos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optically Stimulated Luminescence
In physics, optically stimulated luminescence (OSL) is a method for measuring doses from ionizing radiation. It is used in at least two applications: * Luminescence dating of ancient materials: mainly geological sediments and sometimes fired pottery, bricks etc., although in the latter case thermoluminescence dating is used more often * Radiation dosimetry, which is the measurement of accumulated radiation dose in the tissues of health care, nuclear, research and other workers, as well as in building materials in regions of nuclear disaster The method makes use of electrons trapped between the valence and conduction bands in the crystalline structure of certain minerals (most commonly quartz and feldspar). The trapping sites are imperfections of the lattice — impurities or defects. The ionizing radiation produces electron-hole pairs: Electrons are in the conduction band and holes in the valence band. The electrons that have been excited to the conduction band may become entrap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Isotope Stage 9
Marine Isotope Stage 9 (MIS 9) is a Marine Isotope Stage in the geological record. It is the final period of the Lower Paleolithic, and lasts from 337,000 to 300,000 years ago according to Lisiecki and Raymo's LR04 Benthic Stack, which has been adopted by the Subcommission on Quaternary Stratigraphy of the International Commission on Stratigraphy. It was an interglacial (warm period) which corresponds to the Purfleet Interglacial in Britain, and falls within the Pre-Illinoian in North America. Some authorities regard it as corresponding to the Holstein Interglacial in continental Europe. Europe was then occupied by ''Homo heidelbergensis'', but they had probably retreated from Britain during the preceding glacial period. Populations returned as the climate warmed and sea levels rose around 330,000 years ago, and thousands of hand axes and other artefacts have been found along the terraces of the Thames and former Solent rivers. In Southern England, the summers were similar to or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
