1.
Absolute dating
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Absolute dating is the process of determining an age on a specified chronology in archaeology and geology. Some scientists prefer the terms chronometric or calendar dating, as use of the word implies a unwarranted certainty of accuracy. Absolute dating provides an age or range in contrast with relative dating which places events in order without any measure of the age between events. Techniques include tree rings in timbers, radiocarbon dating of wood or bones, radiometric dating is based on the known and constant rate of decay of radioactive isotopes into their radiogenic daughter isotopes. Particular isotopes are suitable for different applications due to the type of atoms present in the mineral or other material, one of the most widely used and well-known absolute dating techniques is carbon-14 dating, which is used to date organic remains. This is a technique since it is based on radioactive decay. Cosmic radiation entering the earth’s atmosphere produces carbon-14, and plants take in carbon-14 as they fix carbon dioxide, carbon-14 moves up the food chain as animals eat plants and as predators eat other animals. With death, the uptake of carbon-14 stops and it takes 5,730 years for half the carbon-14 to change to nitrogen, this is the half-life of carbon-14. After another 5,730 years only one-quarter of the original carbon-14 will remain, after yet another 5,730 years only one-eighth will be left. By measuring the carbon-14 in organic material, scientists can determine the date of death of the matter in an artifact or ecofact. The relatively short half-life of carbon-14,5,730 years, an additional problem with carbon-14 dates from archeological sites is known as the old wood problem. Thus dating that particular tree does not necessarily indicate when the fire burned or the structure was built, for this reason, many archaeologists prefer to use samples from short-lived plants for radiocarbon dating. The development of mass spectrometry dating, which allows a date to be obtained from a very small sample, has been very useful in this regard. Other radiometric dating techniques are available for earlier periods, one of the most widely used is potassium-argon dating. Potassium-40 is an isotope of potassium that decays into argon-40. The half-life of potassium-40 is 1.3 billion years, far longer than that of carbon-14, potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated. Argon, a gas, is not commonly incorporated into such samples except when produced in situ through radioactive decay. The date measured reveals the last time that the object was heated past the closure temperature at which the trapped argon can escape the lattice, k-Ar dating was used to calibrate the geomagnetic polarity time scale
2.
Megaannum
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A year is the orbital period of the Earth moving in its orbit around the Sun. Due to the Earths axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the globe, four seasons are recognized, spring, summer, autumn. In tropical and subtropical regions several geographical sectors do not present defined seasons, but in the seasonal tropics, a calendar year is an approximation of the number of days of the Earths orbital period as counted in a given calendar. The Gregorian, or modern, calendar, presents its calendar year to be either a common year of 365 days or a year of 366 days, as do the Julian calendars. For the Gregorian calendar the average length of the year across the complete leap cycle of 400 years is 365.2425 days. The ISO standard ISO 80000-3, Annex C, supports the symbol a to represent a year of either 365 or 366 days, in English, the abbreviations y and yr are commonly used. In astronomy, the Julian year is a unit of time, it is defined as 365.25 days of exactly 86400 seconds, totalling exactly 31557600 seconds in the Julian astronomical year. The word year is used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year. Similarly, year can mean the period of any planet, for example. The term can also be used in reference to any long period or cycle, west Saxon ġēar, Anglian ġēr continues Proto-Germanic *jǣran. Cognates are German Jahr, Old High German jār, Old Norse ár and Gothic jer, all the descendants of the Proto-Indo-European noun *yeh₁rom year, season. Cognates also descended from the same Proto-Indo-European noun are Avestan yārǝ year, Greek ὥρα year, season, period of time, Old Church Slavonic jarŭ, Latin annus is from a PIE noun *h₂et-no-, which also yielded Gothic aþn year. Both *yeh₁-ro- and *h₂et-no- are based on verbal roots expressing movement, *h₁ey- and *h₂et- respectively, the Greek word for year, ἔτος, is cognate with Latin vetus old, from the PIE word *wetos- year, also preserved in this meaning in Sanskrit vat-sa- yearling and vat-sa-ras year. Derived from Latin annus are a number of English words, such as annual, annuity, anniversary, etc. per annum means each year, anno Domini means in the year of the Lord. No astronomical year has an number of days or lunar months. Financial and scientific calculations often use a 365-day calendar to simplify daily rates, in the Julian calendar, the average length of a year is 365.25 days. In a non-leap year, there are 365 days, in a year there are 366 days
3.
Paleogene
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The Paleogene is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago to the beginning of the Neogene Period 23.03 Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon and this period consists of the Paleocene, Eocene and Oligocene epochs. The terms Paleogene System and lower Tertiary System are applied to the rocks deposited during the Paleogene Period. By dividing the Tertiary Period into two periods instead of directly into five epochs, the periods are more comparable to the duration of periods of the preceding Mesozoic and Paleozoic Eras. The trend was caused by the formation of the Antarctic Circumpolar Current. During the Paleogene, the continued to drift closer to their current positions. India was in the process of colliding with Asia, subsequently forming the Himalayas, the Atlantic Ocean continued to widen by a few centimeters each year. Africa was moving north to meet with Europe and form the Mediterranean, inland seas retreated from North America early in the period. Australia had also separated from Antarctica and was drifting towards Southeast Asia, mammals began a rapid diversification during this period. Some of these mammals would evolve into forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial. Those that took to the oceans became modern cetaceans, while those that took to the trees became primates, the group to which humans belong. Birds, which were well established by the end of the Cretaceous. In comparison to birds and mammals, most other branches of life remained unchanged during this period. As the Earth cooled, tropical plants became less numerous and were now restricted to equatorial regions, deciduous plants, which could survive through the seasonal climates the world was now experiencing, became more common. The Paleogene is notable in the context of offshore oil drilling, and especially in Gulf of Mexico oil exploration and these rock formations represent the current cutting edge of deep-water oil discovery. Lower Tertiary explorations to date include, Kaskida Oil Field Tiber Oil Field Jack 2 Paleogene Microfossils, 180+ images of Foraminifera
4.
Paleocene
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The Paleocene or Palaeocene, the old recent, is a geologic epoch that lasted from about 66 to 56 million years ago. It is the first epoch of the Paleogene Period in the modern Cenozoic Era, as with many geologic periods, the strata that define the epochs beginning and end are well identified, but the exact ages remain uncertain. The Paleocene Epoch brackets two major events in Earths history and it started with the mass extinction event at the end of the Cretaceous, known as the Cretaceous–Paleogene boundary. This was a marked by the demise of non-avian dinosaurs, giant marine reptiles and much other fauna. The die-off of the dinosaurs left unfilled ecological niches worldwide, the Paleocene ended with the Paleocene–Eocene Thermal Maximum, a geologically brief interval characterized by extreme changes in climate and carbon cycling. The name Paleocene comes from Ancient Greek and refers to the old new fauna that arose during the epoch. The K–Pg boundary that marks the separation between Cretaceous and Paleocene is visible in the record of much of the Earth by a discontinuity in the fossil fauna. There is also evidence of abrupt changes in flora and fauna. There is some evidence that a substantial but very short-lived climatic change may have happened in the early decades of the Paleocene. The end of the Paleocene was also marked by a time of major change, the Paleocene–Eocene Thermal Maximum upset oceanic and atmospheric circulation and led to the extinction of numerous deep-sea benthic foraminifera and a major turnover in mammals on land. The Paleocene is divided into three stages, the Danian, the Selandian and the Thanetian, as shown in the table above, additionally, the Paleocene is divided into six Mammal Paleogene zones. The early Paleocene was cooler and dryer than the preceding Cretaceous, in many ways, the Paleocene continued processes that had begun during the late Cretaceous Period. During the Paleocene, the continued to drift toward their present positions. The Laramide orogeny of the late Cretaceous continued to uplift the Rocky Mountains in the American west, africa was heading north towards Europe, slowly closing the Tethys Ocean, and India began its migration to Asia that would lead to a tectonic collision and the formation of the Himalayas. The inland seas in North America and Europe had receded by the beginning of the Paleocene, making way for new land-based flora, warm seas circulated throughout the world, including the poles. The earliest Paleocene featured a low diversity and abundance of marine life, tropical conditions gave rise to abundant marine life, including coral reefs. With the demise of marine reptiles at the end of the Cretaceous, at the end of the Cretaceous, the ammonites and many species of foraminifera became extinct. Marine fauna also came to resemble modern fauna, with only the marine mammals, terrestrial Paleocene strata immediately overlying the K–Pg boundary is in places marked by a fern spike, a bed especially rich in fern fossils
5.
Danian
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With the exception of some ectothermic species like the leatherback sea turtle and crocodiles, no tetrapods weighing more than 25 kilograms survived. It marked the end of the Cretaceous period and with it, in the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows high levels of the metal iridium, which is rare in the Earths crust, the fact that the extinctions occurred at the same time as the impact provides strong situational evidence that the K–Pg extinction was caused by the asteroid. It was possibly accelerated by the creation of the Deccan Traps, however, some scientists maintain the extinction was caused or exacerbated by other factors, such as volcanic eruptions, climate change, or sea level change, separately or together. A wide range of species perished in the K–Pg extinction, the most well-known victims are the non-avian dinosaurs. However, the extinction also destroyed a plethora of other organisms, including certain mammals, pterosaurs, birds, lizards, insects. In the oceans, the K–Pg extinction killed off plesiosaurs and the giant marine lizards and devastated fish, sharks, mollusks and it is estimated that 75% or more of all species on Earth vanished. Yet the devastation caused by the extinction also provided evolutionary opportunities, mammals in particular diversified in the Paleogene, producing new forms such as horses, whales, bats, and primates. Birds, fish and perhaps lizards also radiated, the K–Pg boundary represents one of the most dramatic turnovers in the fossil record for various calcareous nanoplankton that formed the calcium deposits that gave the Cretaceous its name. The turnover in this group is marked at the species level. Statistical analysis of marine losses at this time suggests that the decrease in diversity was caused more by an increase in extinctions than by a decrease in speciation. Recent studies indicate that there were no major shifts in dinoflagellates through the boundary layer, the K–Pg extinction event was severe, global, rapid, and selective. In terms of severity, the event eliminated a vast number of species, based on marine fossils, it is estimated that 75% or more of all species were made extinct by the K–Pg extinction event. The event appears to have affected all continents at the same time, non-avian dinosaurs, for example, are known from the Maastrichtian of North America, Europe, Asia, Africa, South America and Antarctica, but are unknown from the Cenozoic anywhere in the world. Similarly, fossil pollen shows devastation of the plant communities in areas as far apart as New Mexico, Alaska, China, even though the boundary event was severe, there was significant variability in the rate of extinction between and within different clades. Species that depended on photosynthesis declined or became extinct as atmospheric particles blocked sunlight and this plant extinction caused a major reshuffling of the dominant plant groups. Omnivores, insectivores and carrion-eaters survived the event, perhaps because of the increased availability of their food sources. No purely herbivorous or carnivorous mammals seem to have survived, rather, the surviving mammals and birds fed on insects, worms, and snails, which in turn fed on dead plant and animal matter
6.
Cretaceous
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The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian, Gallic and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group also has other limestones and arenites, among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls
7.
Campanian
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The Campanian is, in the ICS geologic timescale, the fifth of six ages of the Late Cretaceous epoch. The Campanian spans the time from 83.6 ±0.7 Ma to 72.1 ±0.6 Ma and it is preceded by the Santonian and it is followed by the Maastrichtian. The Campanian was introduced in literature by Henri Coquand in 1857. It is named after the French village of Champagne in the département Charente-Maritime, the original type locality was an outcrop near the village of Aubeterre-sur-Dronne in the same region. Due to changes of the definitions, this section is now part of the Maastrichtian stage. The base of the Campanian stage is laid at the extinction of crinoid species Marsupites testudinarius, a GSSP had not yet been ratified in 2009. One possible candidate is in a section near a dam at Waxahachie, the top of the Campanian is defined as the place in the stratigraphic column were the ammonite Pachydiscus neubergicus first appears. The Campanian is sometimes subdivided into Lower, Middle and Upper subages, in the Tethys domain, the Campanian encompasses six ammonite biozones. In North America, for example, the number of dinosaur genera rises from 4 at the base of the Campanian to 48 in the upper part. This development is referred to as the Campanian Explosion. However, it is not yet if the event is artificial. The generally warm climates and large area covered in shallow sea during the Campanian probably favoured the dinosaurs. In the following Maastrichtian stage, the number of North American dinosaur genera found is 30% less than in the upper Campanian, & Smith, A. G.2004, A Geologic Time Scale 2004, Cambridge University Press. Late Cretaceous oviraptorosaur dinosaurs from Montana, pp. 42–57 in D. H. Tanke and K. Carpenter, Mesozoic Vertebrate Life. Le Loueff, J. Xu, X. Zhao, X. Sahni, A. Gomani,2004, Dinosaur distribution, in, Weishampel, D. B. The Dinosauria, University of California Press, Berkeley, ISBN 0-520-24209-2, pp 517–606
8.
Santonian
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The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series and it spans the time between 86.3 ±0.7 mya and 83.6 ±0.7 mya. The Santonian is preceded by the Coniacian and is followed by the Campanian, the Santonian stage was established by French geologist Henri Coquand in 1857. It is named after the city of Saintes in the region of Saintonge, the base of the Santonian stage is defined by the appearance of the inoceramid bivalve Cladoceramus undulatoplicatus. Its top is marked by the extinction of the crinoid Marsupites testudinarius, in 2009, a GSSP for both base and top had not yet been appointed. The Santonian is sometimes subdivided into Lower, Middle and Upper substages, in the Tethys domain the Santonian is coeval with a single ammonite biozone, that of Placenticeras polyopsis. Biostratigraphy based on inoceramids, nannoplankton or forams is more detailed, magnoliopsida Advanced dicotyledons Droseraceae, †Palaeoaldrovanda Gradstein, F. M. & Smith, A. G.2004, A Geologic Time Scale 2004, Cambridge University Press
9.
Coniacian
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The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series, the Coniacian is preceded by the Turonian and followed by the Santonian. The Coniacian is named after the city of Cognac in the French region of Saintonge and it was first defined by French geologist Henri Coquand in 1857. The base of the Coniacian stage is at the first appearance of the bivalve species Cremnoceramus rotundatus. An official reference profile for the base had in 2009 not yet been appointed, the top of the Coniacian is defined by the appearance of the inoceramid bivalve Cladoceramus undulatoplicatus. The Coniacian overlaps the regional Emscherian stage of Germany, which is coeval with the Coniacian and Santonian stages. In magnetostratigraphy, the Coniacian is part of magnetic chronozone C34, the so-called Cretaceous Magnetic Quiet Zone, after a maximum of the global sea level during the early Turonian, the Coniacian was characterized by a gradual fall of the sea level. This cycle is in sequence stratigraphy seen as a first order cycle, during the middle Coniacian a shorter, second order cycle, caused a temporary rise of the sea level on top of the longer first order trend. The following regression separates the Middle from the Upper Coniacian substage, an even shorter third order cycle caused a new transgression during the Late Coniacian. Beginning in the Middle Coniacian, an event occurred in the Atlantic Ocean. The anoxic event lasted till the Middle Santonian and is the longest and last such event during the Cretaceous period, the Coniacian is often subdivided into Lower, Middle and Upper substages. M. & Smith, A. G.2004, A Geologic Time Scale 2004, & Forster, A.2006, Origins and accumulation of organic matter in expanded Albian to Santonian black shale sequences on the Demerara Rise, South American margin, Organic Geochemistry 37, pp 1816–1830
10.
Turonian
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The Turonian is, in the ICS geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.9 ±0.8 Ma and 89.8 ±1 Ma, the Turonian is preceded by the Cenomanian stage and underlies the Coniacian stage. At the beginning of the Turonian an anoxic event took place which is called the Cenomanian-Turonian boundary event or the Bonarelli Event, the Turonian was defined by the French paleontologist Alcide dOrbigny in 1842. Orbigny named it after the French city of Tours in the region of Touraine, the base of the Turonian stage is defined as the place where the ammonite species Wutinoceras devonense first appears in the stratigraphic column. The official reference profile for the base of the Turonian is located in the Rock Canyon anticline near Pueblo, the top of the Turonian stage is defined as the place in the stratigraphic column where the inoceramid bivalve species Cremnoceramus rotundatus first appears. The Turonian is sometimes subdivided in Lower/Early, Middle and Upper/Late substages or subages, inoceramids are bivalve Mollusca related to todays mussels. & Smith, A. G.2004, A Geologic Time Scale 2004, & Cobban, W. A.2005, The Global Boundary Stratotype Section and Point for the base of the Turonian Stage of the Cretaceous, Pueblo, Colorado, U. S. A
11.
Cenomanian
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The Cenomanian is, in the ICS geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology, it is a unit of time, both age and stage bear the same name. As a unit of time measure, the Cenomanian age spans the time between 100.5 ±0.9 Ma and 93.9 ±0.8 Ma. In the geologic timescale it is preceded by the Albian and is followed by the Turonian, the Cenomanian is coeval with the Woodbinian of the regional timescale of the Gulf of Mexico and the early part of the Eaglefordian of the regional timescale of the US East Coast. At the end of the Cenomanian an anoxic event took place, called the Cenomanian-Turonian boundary event or the Bonarelli Event, the Cenomanian was introduced in scientific literature by French palaeontologist Alcide dOrbigny in 1847. Its name comes from the New Latin name of the French city of Le Mans, the base of the Cenomanian stage is placed at the first appearance of foram species Rotalipora globotruncanoides in the stratigraphic record. An official reference profile for the base of the Cenomanian is located in an outcrop at the flank of Mont Risou. The base is, in the profile, located 36 meters below the top of the Marnes Bleues Formation. The top of the Cenomanian is at the first appearance of ammonite species Watinoceras devonense, important index fossils for the Cenomanian are the ammonites Calycoceras naviculare, Acanthoceras rhotomagense and Mantelliceras mantelli. The late Cenomanian represents the highest mean sea-level observed in the Phanerozoic eon, a corollary is that the highlands were at all time lows, so the landscape on Earth was one of warm broad shallow seas inundating low-lying land areas on the precursors to todays continents. What few lands rose above the waves were made of old mountains and hills, upland plateaus, tectonic mountain building was minimal and most continents were isolated by large stretches of water. Without highlands to brake winds, the climate would have been windy and waves large, adding to the weathering, & Smith, A. G.2004, A Geologic Time Scale 2004, Cambridge University Press. & Caron, M.2004, The Global Boundary Stratotype Section and Point for the base of the Cenomanian Stage, Mont Risou, Hautes-Alpes, France, Episodes 27, pp. 21–32
12.
Albian
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The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series and its approximate time range is 113.0 ±1.0 Ma to 100.5 ±0.9 Ma. The Albian is preceded by the Aptian and followed by the Cenomanian, the Albian stage was first proposed in 1842 by Alcide dOrbigny. As of 2014, a profile for the base of the Albian stage had not yet been established. The top of the Albian stage is defined as the place where the foram species Rotalipora globotruncanoides first appears in the stratigraphic column, the Albian is sometimes subdivided in Early/Lower, Middle and Late/Upper subages or substages. In western Europe, especially in the UK, a subdivision in two substages is more often used, moffitites The following is a list of Ammonite genera whose fossils are geochronologically found first in lower Albian strata. These genera may survive into later portions of the Albian stage and this list should not be thought of in terms of the lifespan of the genera included. These genera may survive into later portions of the Albian stage and this list should not be thought of in terms of the lifespan of the genera included. These genera may survive into later portions of the Albian stage and this list should not be thought of in terms of the lifespan of the genera included. M. & Smith, A. G.2004, A Geologic Time Scale 2004, & Caron, M.2004, The Global Boundary Stratotype Section and Point for the base of the Cenomanian Stage, Mont Risou, Hautes-Alpes, France, Episodes 27, pp. 21–32. 1842, Paléontologie française, Terrains crétacés, vol. ii
13.
Aptian
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The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ±1.0 Ma to 113.0 ±1.0 Ma, approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous, the Aptian partly overlaps the upper part of the regionally used stage Urgonian. The Aptian was named after the city of Apt in the Provence region of France. The original type locality is in the vicinity of Apt, the Aptian was introduced in scientific literature by French palaeontologist Alcide dOrbigny in 1840. The base of the Aptian stage is laid at magnetic anomaly M0r, a global reference profile for the base had in 2009 not yet been appointed. The top of the Aptian is at the first appearance of coccolithophore species Praediscosphaera columnata in the stratigraphic record. M, & Smith, A. G.2004, A Geologic Time Scale 2004, Cambridge University Press. 1842, Paléontologie française, Terrains crétacés, vol. ii
14.
Barremian
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The Barremian is an age in the geologic timescale between 129.4 ±1.5 Ma and 125.0 ±1.0 Ma). It is a subdivision of the Early Cretaceous epoch and it is preceded by the Hauterivian and followed by the Aptian stage. The original type locality for the Barremian stage is in the vicinity of the village of Barrême, henri Coquand defined the stage and named it in 1873. The base of the Barremian is determined by the first appearance of the ammonites Spitidiscus hugii, the end of the Barremian is determined by the geomagnetic reversal at the start of the M0r chronozone, which is biologically near the first appearance of the ammonite Paradeshayesites oglanlensis. The Barremian falls in the Gallic epoch, a subdivision of the Cretaceous that is no longer used by the ICS and it overlaps the lower part of the Urgonian stage, which is sometimes used in western European stratigraphy. In North America, the late Coahulian and the early Comanchean correspond to the Barremian, in New Zealand, it falls within the Mokoiwian, and in Japan it corresponds to the late Aritan. The Barremian is often subdivided into two substages or subages, Lower/Early and Upper/Late Barremian, le Barrémien supérieur à faciès Urgonien de Brouzet-lès-Alais. Mémoires de la Société Géologique de France, Paléontologie 15, 5-42, a Geologic Time Scale 2004, Cambridge University Press. Assessment of diachronism of biostratigraphic boundaries by magnetochronological calibration of scales for the Lower Cretaceous of the Tethyan
15.
Hauterivian
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The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous epoch or a stage in the Lower Cretaceous series. It spans the time between 132.9 ±2 Ma and 129.4 ±1.5 Ma, the Hauterivian is preceded by the Valanginian and succeeded by the Barremian. The Hauterivian was introduced in literature by Swiss geologist Eugène Renevier in 1873. It is named after the Swiss town of Hauterive at the shore of Lake Neuchâtel, the base of the Hauterivian is defined as the place in the stratigraphic column where the ammonite genus Acanthodiscus first appears. A reference profile for the base had in 2009 not yet been established, the top of the Hauterivian is at the first appearance of ammonite species Spitidiscus hugii. M. A Geologic Time Scale 2004, Cambridge University Press
16.
Valanginian
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In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ±3.0 Ma and 132.9 ±2.0 Ma, the Valanginian stage succeeds the Berriasian stage of the Lower Cretaceous and precedes the Hauterivian stage of the Lower Cretaceous. The Valanginian was first described and named by Édouard Desor in 1853 and it is named after Valangin, a small town north of Neuchâtel in the Jura Mountains of Switzerland. The base of the Valanginian is at the first appearance of calpionellid species Calpionellites darderi in the stratigraphic column, a global reference section had in 2009 not yet been appointed. The top of the Valanginian is at the first appearance of the ammonite genus Acanthodiscus, the Valanginian is often subdivided in Lower and Upper substages. The Upper substage begins at the first appearance of ammonite species Saynoceras verrucosum, a Geologic Time Scale 2004, Cambridge University Press. GeoWhen Database - Valanginian Mid-Cretaceous timescale and ühttp, //stratigraphy. science. purdue. edu/charts/Timeslices/5_JurCret
17.
Berriasian
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In the geological timescale, the Berriasian is an age or stage of the Early Cretaceous. It is the oldest, or lowest, subdivision in the entire Cretaceous and it spanned the time between 145.0 ±4.0 Ma and 139.8 ±3.0 Ma. The Berriasian succeeds the Tithonian and precedes the Valanginian, the Berriasian Stage was introduced in scientific literature by Henri Coquand in 1869. It is named after the village of Berrias in the Ardèche department of France, the largely non-marine English Purbeck Formation is in part of Berriasian age. The base of the Berriasian, which is also the base of the Cretaceous system, has traditionally placed at the first appearance of fossils of the ammonite species Berriasella jacobi. But this is a species that has a problematic and geographically limited distribution. A global reference profile for the Berriasian has been under consideration by the International Subcommission on Cretaceous Stratigraphy of IUGS. A range of contender GSSP localities has been studied in detail by the ISCSs Berriasian Working Group including localities as far apart as Mexico, Ukraine, Tunisia, Iraq, several markers have been employed to refine correlations and to work towards defining a base for the Berriasian Stage. These include calcareous nannofossils, such as Nannoconus, calpionellids, ammonites, palynological data and magnetostratigraphy, in June 2016, the Berriasian Working Group voted to adopt Calpionella alpina as the primary marker for the base of the Berriasian Stage. This is just a little below the first appearance of the ammonite species Thurmanniceras pertransiens, a Geologic Time Scale 2004, Cambridge University Press
18.
Jurassic
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The Jurassic is a geologic period and system that spans 56.3 million years from the end of the Triassic Period 201.3 million years ago to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles, the start of the period is marked by the major Triassic–Jurassic extinction event. The Jurassic is named after the Jura Mountains within the European Alps, by the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses, Laurasia to the north and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, on land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs, other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to a mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, the chronostratigraphic term Jurassic is directly linked to the Jura Mountains. The name Jura is derived from the Celtic root jor, which was Latinised into juria, the Jurassic period is divided into the Early Jurassic, Middle, and Late Jurassic epochs. The Jurassic System, in stratigraphy, is divided into the Lower Jurassic, Middle, the separation of the term Jurassic into three sections goes back to Leopold von Buch. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous period, the Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of glaciation, as in the Triassic, there was apparently no land over either pole, and no extensive ice caps existed. In contrast, the North American Jurassic record is the poorest of the Mesozoic, the Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, the first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are found in Russia, India, South America, Japan, Australasia. As the Jurassic proceeded, larger and more groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are well represented nor well studied in Africa. Late Jurassic strata are also poorly represented apart from the spectacular Tendaguru fauna in Tanzania, the Late Jurassic life of Tendaguru is very similar to that found in western North Americas Morrison Formation. During the Jurassic period, the primary living in the sea were fish
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Tithonian
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In the geological timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 152.1 ±4 Ma and 145.0 ±4 Ma and it is preceded by the Kimmeridgian and followed by the Berriasian stage. The Tithonian was introduced in literature by German stratigrapher Albert Oppel in 1865. The name Tithonian is unusual in geological stage names because it is derived from Greek mythology, tithonus was the son of Laomedon of Troy. He fell in love with Eos, the Greek goddess of dawn and finds his place in the stratigraphy because this stage, the base of the Tithonian stage is at the base of the ammonite biozone of Hybonoticeras hybonotum. A global reference profile for the base of the Tithonian had in 2009 not yet been established, the top of the Tithonian stage is marked by the first appearance of small globular calpionellids of the species Calpionella alpina, at the base of the Alpina Subzone. The Tithonian is often subdivided into Lower/Early, Middle and Upper/Late substages or subages, the Late Tithonian is coeval with the Portlandian stage of British stratigraphy. The Solnhofen limestone of southern Germany, which is known for its fossils, is of Tithonian age, a Geologic Time Scale 2004, Cambridge University Press. 1865, Die Tithonische Etage, Zeitschrift der Deutschen Geologischen Gesellschaft,1865, pp 535–558
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Geologic time scale
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The table of geologic time spans, presented here, agrees with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy. Evidence from radiometric dating indicates that Earth is about 4.54 billion years old, the geology or deep time of Earth’s past has been organized into various units according to events which took place in each period. Older time spans, which predate the reliable record, are defined by their absolute age. Some other planets and moons within the Solar System have sufficiently rigid structures to have preserved records of their own histories, for example, Venus, Mars, dominantly fluid planets, such as the gas giants, do not preserve their history in a comparable manner. Apart from the Late Heavy Bombardment, events on other planets probably had little influence on the Earth. Construction of a scale that links the planets is, therefore, of only limited relevance to the Earths time scale. The existence, timing, and terrestrial effects of the Late Heavy Bombardment is still debated, the largest defined unit of time is the supereon, composed of eons. Eons are divided into eras, which are in turn divided into periods, epochs, the terms eonothem, erathem, system, series, and stage are used to refer to the layers of rock that correspond to these periods of geologic time in Earths history. Geologists qualify these units as early, mid, and late when referring to time, and lower, middle, for example, the lower Jurassic Series in chronostratigraphy corresponds to the early Jurassic Epoch in geochronology. The adjectives are capitalized when the subdivision is formally recognized, and lower case when not, thus early Miocene but Early Jurassic. Geologic units from the time but different parts of the world often look different and contain different fossils. For example, in North America the Lower Cambrian is called the Waucoban series that is subdivided into zones based on succession of trilobites. In East Asia and Siberia, the unit is split into Alexian, Atdabanian. A key aspect of the work of the International Commission on Stratigraphy is to reconcile this conflicting terminology, the term Anthropocene is used informally by popular culture and a growing number of scientists to describe the current epoch in which we are living. The term was coined by Paul Crutzen and Eugene Stoermer in 2000 to describe the current time, others say that humans have not even started to leave their biggest impact on Earth, and therefore the Anthropocene hasnt even started yet. Whatever the case, the ICS has not officially approved the term, leonardo da Vinci concurred with Aristotles interpretation that fossils represented the remains of ancient life. The 11th-century Persian geologist Avicenna and the 13th-century Dominican bishop Albertus Magnus extended Aristotles explanation into a theory of a petrifying fluid. Avicenna also first proposed one of the principles underlying geologic time scales, the Chinese naturalist Shen Kuo also recognized the concept of deep time
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Mesozoic
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The Mesozoic Era is an interval of geological time from about 252 to 66 million years ago. This Era is also called from a paleobotanist view the Age of Conifers, Mesozoic means middle life, deriving from the Greek prefix meso-/μεσο- for between and zōon/ζῷον meaning animal or living being. It is one of three eras of the Phanerozoic Eon, preceded by the Paleozoic and succeeded by the Cenozoic. The era is subdivided into three periods, the Triassic, Jurassic, and Cretaceous, which are further subdivided into a number of epochs. The Mesozoic was a time of significant tectonic, climate and evolutionary activity, the era witnessed the gradual rifting of the supercontinent Pangaea into separate landmasses that would eventually move into their current positions. The climate of the Mesozoic was varied, alternating between warming and cooling periods, overall, however, the Earth was hotter than it is today. Birds first appeared in the Jurassic, having evolved from a branch of theropod dinosaurs, the first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg —until the Cenozoic. Following the Paleozoic, the Mesozoic extended roughly 186 million years and this time frame is separated into three geologic periods. It is also known as the Great Dying because it is considered the largest mass extinction in the Earths history, the upper boundary of the Mesozoic is set at the Cretaceous–Paleogene extinction event, which may have been caused by the impactor that created Chicxulub Crater on the Yucatán Peninsula. Towards the Late Cretaceous large volcanic eruptions are believed to have contributed to the Cretaceous–Paleogene extinction event. Approximately 50% of all genera became extinct, including all of the non-avian dinosaurs, the Triassic ranges roughly from 252 million to 201 million years ago. The Triassic is a time in Earths history bracketed between the Permian Extinction and the Triassic–Jurassic extinction event, two of the big five, and precedes the Jurassic Period and it has three major epochs, the Early Triassic, the Middle Triassic and the Late Triassic. The Early Triassic was between about 252 million to 247 million years ago and was dominated by deserts as Pangaea had not yet broken up, thus the interior was nothing, the Earth had just witnessed a massive die-off in which 95% of all life became extinct. The most common life on earth were Lystrosaurus, labyrinthodonts. Temnospondyls evolved during this time and would be the dominant predator for much of the Triassic, the Middle Triassic spans roughly from 247 million to 237 million years ago. The Middle Triassic featured the beginnings of the breakup of Pangaea, the ecosystem had recovered from the devastation that was the Great Dying. Algae, sponge, corals, and crustaceans all had recovered, new aquatic reptiles evolved, such as ichthyosaurs and nothosaurs. Meanwhile, on land, pine forests flourished, as did groups of insects like mosquitoes, the first ancient crocodilians evolved, which sparked competition with the large amphibians that had since ruled the freshwater world
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Extinction event
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An extinction event is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a change in the diversity. It occurs when the rate of extinction increases with respect to the rate of speciation, Extinction occurs at an uneven rate. Based on the record, the background rate of extinctions on Earth is about two to five taxonomic families of marine animals every million years. Marine fossils are used to measure extinction rates because of their superior fossil record. The Great Oxygenation Event was probably the first major extinction event, since the Cambrian explosion five further major mass extinctions have significantly exceeded the background extinction rate. In addition to the five mass extinctions, there are numerous minor ones as well. Mass extinctions seem to be a mainly Phanerozoic phenomenon, with extinction rates low before large complex organisms arose, estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from the chosen for describing an extinction event as major. In a landmark paper published in 1982, Jack Sepkoski and David M. Raup identified five mass extinctions, the Big Five cannot be so clearly defined, but rather appear to represent the largest of a relatively smooth continuum of extinction events. Cretaceous–Paleogene extinction event,66 Ma at the Cretaceous -Paleogene transition interval, the event formerly called the Cretaceous-Tertiary or K–T extinction or K-T boundary is now officially named the Cretaceous–Paleogene extinction event. About 17% of all families, 50% of all genera and 75% of all species became extinct, in the seas all the ammonites, plesiosaurs and mosasaurs disappeared and the percentage of sessile animals was reduced to about 33%. All non-avian dinosaurs became extinct during that time, the boundary event was severe with a significant amount of variability in the rate of extinction between and among different clades. Mammals and birds, the latter descended from dinosaurs, emerged as dominant large land animals. Triassic–Jurassic extinction event,201.3 Ma at the Triassic-Jurassic transition, about 23% of all families, 48% of all genera and 70% to 75% of all species became extinct. Most non-dinosaurian archosaurs, most therapsids, and most of the amphibians were eliminated. Non-dinosaurian archosaurs continued to dominate aquatic environments, while non-archosaurian diapsids continued to dominate marine environments, the Temnospondyl lineage of large amphibians also survived until the Cretaceous in Australia. Permian–Triassic extinction event,252 Ma at the Permian-Triassic transition, Earths largest extinction killed 57% of all families, 83% of all genera and 90% to 96% of all species
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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
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Plesiosauria
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The Plesiosauria or plesiosaurs are an order or clade of Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period, possibly in the Rhaetian stage and they had a worldwide oceanic distribution. Plesiosaurs were among the first fossil reptiles discovered, in the beginning of the nineteenth century, scientists realised how distinctive their build was and they were named as a separate order in 1835. The first plesiosaurian genus, the eponymous Plesiosaurus, was named in 1821, since then, more than a hundred valid species have been described. In the early twenty-first century, the number of discoveries has increased, leading to an understanding of their anatomy, relationships. Plesiosaurs had a flat body and a short tail. Their limbs had evolved into four long flippers, which were powered by muscles attached to wide bony plates formed by the shoulder girdle. The flippers made a movement through the water. Plesiosaurs breathed air, and bore live young, there are indications that they were warm-blooded, plesiosaurs showed two main morphological types. Some species, with the build, had long necks and small heads. Other species, some of them reaching a length of up to seventeen metres, had the pliosauromorph build with a neck and a large head. The two types are related to the strict division of the Plesiosauria into two suborders, the long-necked Plesiosauroidea and the short-neck Pliosauroidea. Modern research, however, indicates that several long-necked groups might have had some short-necked members or vice versa, therefore, the purely descriptive terms plesiosauromorph and pliosauromorph have been introduced, which do not imply a direct relationship. Plesiosauroidea and Pliosauroidea today have a limited meaning. The term plesiosaur is properly used to refer to the Plesiosauria as a whole, but informally it is meant to indicate only the long-necked forms. Skeletal elements of plesiosaurs are among the first fossils of extinct reptiles recognised as such, the Welshman Edward Lhuyd in his Lithophylacii Brittannici Ichnographia from 1699 also included depictions of plesiosaur vertebrae that again were considered fish vertebrae or Ichthyospondyli. In 1719, William Stukeley described a skeleton of a plesiosaur. The stone plate came from a quarry at Fulbeck and had used, with the fossil at its underside
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Mosasaur
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Mosasaurs are an extinct group of large marine reptiles. Their first fossil remains were discovered in a quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from a group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of the Cretaceous period, with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators and they became extinct as a result of the K-T event at the end of the Cretaceous period, about 66 million years ago. Mosasaurs breathed air, were powerful swimmers, and were well-adapted to living in the warm, mosasaurs were so well adapted to this environment that they gave birth to live young, rather than returning to the shore to lay eggs as sea turtles do. The smallest-known mosasaur was Dallasaurus turneri, which was less than 1 m long, larger mosasaurs were more typical, with many species growing longer than 4 m. Mosasaurus hoffmannii, the largest known species may have reached up to 17 m in length, currently, the largest publicly exhibited mosasaur skeleton in the world is on display at the Canadian Fossil Discovery Centre in Morden, Manitoba. The specimen, nicknamed Bruce, is just over 13 m long, mosasaurs had a body shape similar to those of modern-day monitor lizards, but were more elongated and streamlined for swimming. Their limb bones were reduced in length and their paddles were formed by webbing between their long finger and toe bones and their tails were broad, and supplied their locomotive power. Until recently, mosasaurs were assumed to have swum in a similar to the one used today by conger eels and sea snakes. However, new evidence suggests that many advanced mosasaurs had large, crescent-shaped flukes on the ends of their tails, similar to those of sharks, rather than use snake-like undulations, their bodies probably remained stiff to reduce drag through the water, while their tails provided strong propulsion. These animals may have lurked and pounced rapidly and powerfully on passing prey, Early reconstructions showed mosasaurs with dorsal crests running the length of their bodies, which were based on misidentified remains of tracheal cartilage. By the time this error was discovered, depicting mosasaurs with such crests in artwork had already become a trend, mosasaurs had double-hinged jaws and flexible skulls, which enabled them to gulp down their prey almost whole. A skeleton of Tylosaurus proriger from South Dakota included remains of the diving seabird Hesperornis, a bony fish, a possible shark. Mosasaur bones have also found with shark teeth embedded in them. One of the items of mosasaurs were ammonites, molluscs with shells similar to those of Nautilus. Holes have been found in fossil shells of ammonites, mainly Pachydiscus. Whether this behaviour was common across all classes of mosasaurs is not clear
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Chicxulub impactor
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It impacted a few miles from the present-day town of Chicxulub in Mexico, after which the impactor and its crater are named. The impactors crater is more than 180 km in diameter, making it the third largest known crater on Earth. In September 2007, William F. Bottke, David Vokrouhlický and this argued that a collision in the asteroid belt 160 million years ago resulted in the Baptistina family of asteroids, the largest surviving member of which is 298 Baptistina. According to Bottke, the Chicxulub impactor was a fragment of a larger parent body about 170 km across. In 2010, another theory implicated the newly discovered asteroid P/2010 A2, alvarez hypothesis Timeline of Cretaceous-Paleogene extinction event research
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Rendzina
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Rendzina is a soil type recognized in various soil classification systems, including those of Britain and Germany as well as some obsolete systems. They are humus-rich shallow soils that are formed from carbonate- or occasionally sulfate-rich parent material. Rendzina soils are found in karst and mountainous regions. The term Rendzina originated from an old Polish word rzędzić, which means to chatter, soils of this type contain a significant amount of gravel and stones, which, during plowing, produce various sound effects, i. e. talk to the ploughman. In the World Reference Base for Soil Resources, Rendzina soils would be classified as Leptosols, Chernozems, Kastanozems, or Phaeozems, Rendzina soils typically develop from solid or unconsolidated rocky material that is carbonate- or sulfate-rich. Limestone is by far the most common, but others include dolomite, gypsum, marble, chalk, alongside physical weathering, which breaks down the structure of rocky material, chemical weathering, in particular the dissolution of carbonate, contributes to Rendzina development. When water with dissolved carbon dioxide comes into contact with carbonate minerals, the overall reaction is as follows, CaCO3 + H2O + CO2 →2 HCO3− + Ca2+ Loss of soluble minerals leaves the upper part of the soil enriched in insoluble materials, particularly clay minerals. At the same time, biological activity leads to an accumulation of humus in the surface soil, the upper soil horizon of a Rendzina therefore contains contains considerable amounts of humus. It can also be relatively carbonate- or gypsum-rich, although at much lower than in the rocky parent material. Progressive breakdown of the parent material and loss of carbonate or gypsum will ultimately convert a Rendzina into another soil type, since these processes occur relatively fast in comparison to weathering of most carbonate- and gypsum-free materials, Rendzinas represent a transitory stage in soil development. However, they can persist over the term if soil loss by erosion counteracts the soil development process. Typical areas for Rendzina soils are in karst and mountain landscapes and they are common in scarpland, wherever limestone is exposed. The rendzinas in Wales, UK, for example constitute a simple A-C profile, the combined effects of clay and humus content produce dark colors and crumb structure. Typical pH for Rendzina soils is between 5 and 8, and base saturation is high, calcium and magnesium are abundant, but potassium content is often low, so nutrient imbalances are common. Rendzina soils are poorly suited to agricultural use. Mechanical tillage is hindered by their shallowness, and the soil volume limits their capacity to store. Additionally, these often occur on slopes, where the risk of erosion is high. As a result, there is much semi-natural vegetation to be found in these areas,1938 USDA soil taxonomy Downland FAO soil classification
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Belgium
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Belgium, officially the Kingdom of Belgium, is a sovereign state in Western Europe bordered by France, the Netherlands, Germany, Luxembourg, and the North Sea. It is a small, densely populated country which covers an area of 30,528 square kilometres and has a population of about 11 million people. Additionally, there is a group of German-speakers who live in the East Cantons located around the High Fens area. Historically, Belgium, the Netherlands and Luxembourg were known as the Low Countries, the region was called Belgica in Latin, after the Roman province of Gallia Belgica. From the end of the Middle Ages until the 17th century, today, Belgium is a federal constitutional monarchy with a parliamentary system of governance. It is divided into three regions and three communities, that exist next to each other and its two largest regions are the Dutch-speaking region of Flanders in the north and the French-speaking southern region of Wallonia. The Brussels-Capital Region is a bilingual enclave within the Flemish Region. A German-speaking Community exists in eastern Wallonia, Belgiums linguistic diversity and related political conflicts are reflected in its political history and complex system of governance, made up of six different governments. Upon its independence, declared in 1830, Belgium participated in the Industrial Revolution and, during the course of the 20th century, possessed a number of colonies in Africa. This continuing antagonism has led to several far-reaching reforms, resulting in a transition from a unitary to a federal arrangement during the period from 1970 to 1993. Belgium is also a member of the Eurozone, NATO, OECD and WTO. Its capital, Brussels, hosts several of the EUs official seats as well as the headquarters of major international organizations such as NATO. Belgium is also a part of the Schengen Area, Belgium is a developed country, with an advanced high-income economy and is categorized as very high in the Human Development Index. A gradual immigration by Germanic Frankish tribes during the 5th century brought the area under the rule of the Merovingian kings, a gradual shift of power during the 8th century led the kingdom of the Franks to evolve into the Carolingian Empire. Many of these fiefdoms were united in the Burgundian Netherlands of the 14th and 15th centuries, the Eighty Years War divided the Low Countries into the northern United Provinces and the Southern Netherlands. The latter were ruled successively by the Spanish and the Austrian Habsburgs and this was the theatre of most Franco-Spanish and Franco-Austrian wars during the 17th and 18th centuries. The reunification of the Low Countries as the United Kingdom of the Netherlands occurred at the dissolution of the First French Empire in 1815, although the franchise was initially restricted, universal suffrage for men was introduced after the general strike of 1893 and for women in 1949. The main political parties of the 19th century were the Catholic Party, French was originally the single official language adopted by the nobility and the bourgeoisie
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Stratum
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In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers. The stratum is the unit in a stratigraphic column and forms the basis of the study of stratigraphy. Each layer is one of a number of parallel layers that lie one upon another. They may extend over hundreds of thousands of kilometers of the Earths surface. Strata are typically seen as bands of different colored or differently structured material exposed in cliffs, road cuts, quarries, individual bands may vary in thickness from a few millimeters to a kilometer or more. Each band represents a mode of deposition, river silt, beach sand, coal swamp, sand dune, lava bed. Geologists study rock strata and categorize them by the material of beds, each distinct layer is typically assigned to the name of sheet, usually based on a town, river, mountain, or region where the formation is exposed and available for study. For example, the Burgess Shale is an exposure of dark, occasionally fossiliferous. Slight distinctions in material in a formation may be described as members, formations are collected into groups while groups may be collected into supergroups. Archaeological horizon Geologic formation Geologic map Geologic unit Law of superposition Bed GeoWhen Database
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Chalk Group
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The Chalk Group is the lithostratigraphic unit which contains the late Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur across the wider northwest European chalk province and it is characterised by thick deposits of chalk, a soft porous white limestone, deposited in a marine environment. Chalk is a limestone that consists of coccolith biomicrite, a biomicrite is a limestone composed of fossil debris and calcium carbonate mud. Most of the debris in chalk consists of the microscopic plates. In addition to the coccoliths, the fossil debris includes a variable, the coccolithophores lived in the upper part of the water column. The Chalk Group usually shows few signs of bedding, other lines of flint nodules which become common in the upper part. Nodules of the mineral pyrite also occur and are oxidized to brown iron oxide on exposed surfaces. The Chalk Group is now divided into a White Chalk Subgroup and these modern divisions replace numerous earlier divisions, references to which occur widely on geological maps and in other geological literature. Previously no subgroups were defined but three formations were identified, the Upper Chalk, Middle Chalk and Lower Chalk, different formations are defined within the northern and southern provinces, from Norfolk northwards and south of the Thames valley respectively. A transitional province between the two and covering much of East Anglia and the Chiltern Hills is also recognised, a different approach again is taken as regards the succession beneath the North Sea. The Grey Chalk Subgroup is usually soft and greyish in colour. It is also the most fossiliferous, the strata of this subgroup usually begins with the Glauconitic Marl Member, named after the grains of the green minerals glauconite and chlorite which it contains. The remainder of the subgroup is argillaceous in its lower part (the West Melbury Marly Chalk Formation, in the central Chilterns the two parts are separated by the hard Totternhoe Stone, which forms a prominent scarp in some places. There are few, if any, flint nodules present and these two formations are not recognised within the northern province i. e. the outcrop north from East Anglia to Yorkshire, where the entire sequence is now referred to as the Ferriby Chalk Formation. The thickness of the Grey Chalk Subgroup strata varies, averaging around 200 feet and they often contains fossils such as the ammonites Schloenbachia, Scaphites, and Mantelliceras, the belemnite Actinocamax, and the bivalves Inoceramus and Ostrea. The White Chalk Subgroup includes what were designated the Middle Chalk and Upper Chalk Formations. The sparse fossils found in this include the brachiopod Terebratulina. It may contain ammonite and gastropod fossils in some nodular layers, the thickness of this sequence varies greatly, often averaging around 300 feet
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Netherlands
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The Netherlands, also informally known as Holland is the main constituent country of the Kingdom of the Netherlands. It is a densely populated country located in Western Europe with three territories in the Caribbean. The European part of the Netherlands borders Germany to the east, Belgium to the south, and the North Sea to the northwest, sharing borders with Belgium, the United Kingdom. The three largest cities in the Netherlands are Amsterdam, Rotterdam and The Hague, Amsterdam is the countrys capital, while The Hague holds the Dutch seat of parliament and government. The port of Rotterdam is the worlds largest port outside East-Asia, the name Holland is used informally to refer to the whole of the country of the Netherlands. Netherlands literally means lower countries, influenced by its low land and flat geography, most of the areas below sea level are artificial. Since the late 16th century, large areas have been reclaimed from the sea and lakes, with a population density of 412 people per km2 –507 if water is excluded – the Netherlands is classified as a very densely populated country. Only Bangladesh, South Korea, and Taiwan have both a population and higher population density. Nevertheless, the Netherlands is the worlds second-largest exporter of food and agricultural products and this is partly due to the fertility of the soil and the mild climate. In 2001, it became the worlds first country to legalise same-sex marriage, the Netherlands is a founding member of the EU, Eurozone, G-10, NATO, OECD and WTO, as well as being a part of the Schengen Area and the trilateral Benelux Union. The first four are situated in The Hague, as is the EUs criminal intelligence agency Europol and this has led to the city being dubbed the worlds legal capital. The country also ranks second highest in the worlds 2016 Press Freedom Index, the Netherlands has a market-based mixed economy, ranking 17th of 177 countries according to the Index of Economic Freedom. It had the thirteenth-highest per capita income in the world in 2013 according to the International Monetary Fund, in 2013, the United Nations World Happiness Report ranked the Netherlands as the seventh-happiest country in the world, reflecting its high quality of life. The Netherlands also ranks joint second highest in the Inequality-adjusted Human Development Index, the region called Low Countries and the country of the Netherlands have the same toponymy. Place names with Neder, Nieder, Nether and Nedre and Bas or Inferior are in use in all over Europe. They are sometimes used in a relation to a higher ground that consecutively is indicated as Upper, Boven, Oben. In the case of the Low Countries / the Netherlands the geographical location of the region has been more or less downstream. The geographical location of the region, however, changed over time tremendously
