The Hettangian is the earliest age and lowest stage of the Jurassic period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma. The Hettangian is followed by the Sinemurian. In European stratigraphy the Hettangian is a part of the time span. An example is the British Blue Lias. Another example is the lower Lias from the Northern Limestone Alps where well-preserved but rare ammonites, including Alsatites, have been found; the Hettangian was introduced in the literature by Swiss palaeontologist, Eugène Renevier, in 1864. The stage takes its name from Hettange-Grande, a town in north-eastern France, just south of the border with Luxembourg on the main road from Luxembourg City to Metz; the base of the Hettangian stage is defined as the place in the stratigraphic column where fossils of the ammonite genus Psiloceras first appear. A global reference profile for the base was defined 2010 at the Kuhjoch in the Karwendel in western Austria; the top of the Hettangian stage is at the first appearances of ammonite genera Vermiceras and Metophioceras.
The Hettangian contains three ammonite biozones in the Tethys domain: zone of Schlotheimia angulata zone of Alsatites liasicus zone of Psiloceras planorbis At the end of the Triassic period, the ammonites died out entirely. During the Hettangian, the "Neoammonites" developed quickly, so that in the middle Hettangian a large number of genera and species existed. Triassic-Jurassic extinction event Komlosaurus carbonis Gradstein, F. M.. G. & Smith, A. G.. Renevier, E.: Notices géologiques et paléontologiques sur les Alpes Vaudoises, et les régions environnantes. I. Infralias et Zone à Avicula contorta des Alpes Vaudoises Bulletin de la Société Vaudoise des Sciences Naturelles 8, p. 39-97. GeoWhen Database - Hettangian Lower Jurassic timescale, at the website of the subcommission for stratigraphic information of the ICS Stratigraphic chart of the Lower Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy
In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from 168.3 Ma to around 166.1 Ma. The Bathonian age precedes the Callovian age; the Bathonian stage takes its name from Bath, a spa town in England built on Jurassic limestone. The name was introduced in scientific literature by Belgian geologist d'Omalius d'Halloy in 1843; the original type locality was located near Bath. The French palaeontologist Alcide d'Orbigny was in 1852 the first to define the exact length of the stage; the base of the Bathonian is at the first appearance of ammonite species Parkinsonia convergens in the stratigraphic column. The global reference profile for the base of the Bathonian was ratified as Ravin du Bès, Bas-Auran area, Alpes de Haute Provence, France in 2009; the top of the Bathonian is at the first appearance of ammonite genus Kepplerites. In the Tethys domain, the Bathonian contains eight ammonite biozones: zone of Clydoniceras discus zone of Hecticoceras retrocostatum zone of Cadomites bremeri zone of Morrisiceras morrisi zone of Tulites subcontractus zone of Procerites progracilis zone of Procerites aurigerus zone of Zigzagiceras zigzagRocks of Bathonian age are well developed in Europe: in the northwest and southwest oolite limestones are characteristically associated with coral-bearing and other varieties, with certain beds of clay.
In the north and northeast, etc. clays and ferruginous oolites prevail, some of the last being exploited for iron. They occur in the extreme north of North America and in the Arctic regions, Franz Josef Land, etc.. The well-known Caen stone of Normandy and "Hauptrogenstein" of Swabia, as well as the "Eisenkalk" of northwest Germany, "Klaus-Schichten" of the Austrian Alps, are of Bathonian age. Gradstein, F. M.. G. & Smith, A. G.. D'Omalius d'Halloy, J. B. J.. GeoWhen Database - Bathonian Jurassic-Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS Stratigraphic chart of the Upper Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy
Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with powerful limbs, they are known to have first appeared in the early Jurassic Period, persisted until the end of the Cretaceous Period. They have been found on every continent; the first dinosaur discovered in Antarctica was the ankylosaurian Antarctopelta, fossils of which were recovered from Ross Island in 1986. Ankylosauria was first named by Henry Fairfield Osborn in 1923. In the Linnaean classification system, the group is considered either a suborder or an infraorder, it is contained within the group Thyreophora, which includes the stegosaurs, armored dinosaurs known for their combination of plates and spikes. They sported a small brain size in proportion to their body, second only to the Saurischian sauropods, they were rather slow moving because of the shortness of the limbs combined with being incapable of running.
Their top speed was less than 10 km/hour. All ankylosaurians had armor over much of their bodies scutes and nodules, with large spines in some cases; the scutes, or plates, are rectangular to oval objects organized in transverse rows with keels on the upper surface. Smaller nodules and plates filled in the open spaces between large plates. In all three groups, the first two rows of plates tend to form a sort of half-ring around the neck; the skull has armor plastered on to it, including a distinctive piece on the outside-rear of the lower jaw. Ankylosaurs were built low to the ground one foot off the ground surface, they had triangular teeth that were loosely packed, similar to stegosaurs. The large hyoid bones left in skeletons indicates that they had flexible tongues, they had a large, side secondary palate. This means that they could breathe unlike crocodiles, their expanded gut region suggests the use of fermentation to digest their food, using symbiotic bacteria and gut flora. Their diet consisted of ferns and angiosperms.
Mallon et al. examined herbivore coexistence on the island continent of Laramidia during the Late Cretaceous. It was concluded that ankylosaurs were restricted to feeding on vegetation at, or below, the height of 1 meter. Possible neonate-sized ankylosaur fossils have been documented in the scientific literature. Ankylosauria is split into two families: Nodosauridae and Ankylosauridae. A third family, the Polacanthidae, is sometimes used, but is more found to be a sub-group of one of the primary families; the first formal definition of Ankylosauria as a clade, a group containing all species of a certain evolutionary branch, was given in 1997 by Carpenter. He defined the group as all dinosaurs closer to Ankylosaurus than to Stegosaurus; this definition is followed by most paleontologists today. This "stem-based" definition means that the primitive armored dinosaur Scelidosaurus, closer to ankylosaurids than to stegosaurids, is technically a member of Ankylosauria. Upon the discovery of Bienosaurus, Dong Zhiming erected the family Scelidosauridae for both of these primitive ankylosaurs.
In 2001, Carpenter proposed a new group uniting Scelidosaurus, Ankylosauridae and Polacanthidae, with Minmi, to the exclusion of Stegosaurus. However, many taxonomists find; this group traditionally includes Nodosaurus and Sauropelta. The nodosauridae had longer snouts than their ankylosaurid cousins, they did not sport the archetypal'clubs' at the ends of their tails. Nodosaurids had muscular shoulders and a specialized knob of bone on each shoulder blade called the acromial process, it served as an attachment site for the muscles. These spines would be used for self-defense against predators, they had wide, flaring hips and thick limbs. They had smaller, narrow beaks than the ankylosaurids, which allowed them to be selective over what plant matter they grazed on. Most nodosaurid finds are from North America. Major differences distinguishing the ankylosaurids from the nodosaurids is that the ankylosaurids had bony clubs at the end of their tails, domed snouts in front of the eyes, large squamosal plates projecting from the top and bottom of each side of the skull, all of which nodosaurids lacked.
The traditional ankylosaurids are from in the Cretaceous. They had much wider bodies and have been discovered with bony eyelids; the large clubs at the end of their tails may have been used in sexual selection. This family included Ankylosaurus and Pinacosaurus; the clubs were made of several plates of bone that were permeated by soft tissue, allowing them to absorb thousands of pounds of force. Their beaks were larger and broader than the nodosaurids, indicating that these ankylosaurs were generalists in their diet; the family Polacanthidae was named by George Reber Wieland in 1911 to refer to a group of ankylosaurs that seemed to him to be intermediate between the ankylosaurids and nodosaurids. This grouping was ignored by most researchers until the late 1990s, when it was used as a subfamily by Kirkland for a natural group recovered by his 1998 analysi
In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma. The Kimmeridgian precedes the Tithonian; the Kimmeridgian stage takes its name from the village of Kimmeridge on England. The name was introduced in literature by Swiss geologist Jules Thurmann in 1832; the Kimmeridge Clay Formation has its name from the same type location. It is the source for about 95% of the petroleum in the North Sea; the term Kimmeridgian has been used in two different ways. The base of the interval is the same but the top was defined by British stratigraphers as the base of the Portlandian whereas in France the top was defined as the base of the Tithonian; the differences have not yet been resolved. The base of the Kimmeridgian is at the first appearance of ammonite species Pictonia baylei in the stratigraphic column. A global reference profile for the base had in 2009 not yet been assigned; the top of the Kimmeridgian is at the first appearance of ammonite species Hybonoticeras hybonotum.
It coincides with the top of magnetic anomaly M22An. The Kimmeridgian is sometimes subdivided into Lower substages. In the Tethys domain, the Kimmeridgian contains seven ammonite biozones: zone of Hybonoticeras beckeri zone of Aulacostephanus eudoxus zone of Aspidoceras acanthicum zone of Crussoliceras divisum zone of Ataxioceras hypselocyclum zone of Sutneria platynota zone of Idoceras planula Guimarota Gradstein, F. M.. G. & Smith, A. G.. Thurmann, J.. GeoWhen Database - Kimmeridgian Jurassic-Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS Stratigraphic chart of the Upper Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy
Europe is a continent located in the Northern Hemisphere and in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west and the Mediterranean Sea to the south, it comprises the westernmost part of Eurasia. Since around 1850, Europe is most considered to be separated from Asia by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas and the waterways of the Turkish Straits. Although the term "continent" implies physical geography, the land border is somewhat arbitrary and has been redefined several times since its first conception in classical antiquity; the division of Eurasia into two continents reflects East-West cultural and ethnic differences which vary on a spectrum rather than with a sharp dividing line. The geographic border does not follow political boundaries, with Turkey and Kazakhstan being transcontinental countries. A strict application of the Caucasus Mountains boundary places two comparatively small countries and Georgia, in both continents.
Europe covers 2 % of the Earth's surface. Politically, Europe is divided into about fifty sovereign states of which the Russian Federation is the largest and most populous, spanning 39% of the continent and comprising 15% of its population. Europe had a total population of about 741 million as of 2016; the European climate is affected by warm Atlantic currents that temper winters and summers on much of the continent at latitudes along which the climate in Asia and North America is severe. Further from the sea, seasonal differences are more noticeable than close to the coast. Europe, in particular ancient Greece, was the birthplace of Western civilization; the fall of the Western Roman Empire in 476 AD and the subsequent Migration Period marked the end of ancient history and the beginning of the Middle Ages. Renaissance humanism, exploration and science led to the modern era. Since the Age of Discovery started by Portugal and Spain, Europe played a predominant role in global affairs. Between the 16th and 20th centuries, European powers controlled at various times the Americas all of Africa and Oceania and the majority of Asia.
The Age of Enlightenment, the subsequent French Revolution and the Napoleonic Wars shaped the continent culturally and economically from the end of the 17th century until the first half of the 19th century. The Industrial Revolution, which began in Great Britain at the end of the 18th century, gave rise to radical economic and social change in Western Europe and the wider world. Both world wars took place for the most part in Europe, contributing to a decline in Western European dominance in world affairs by the mid-20th century as the Soviet Union and the United States took prominence. During the Cold War, Europe was divided along the Iron Curtain between NATO in the West and the Warsaw Pact in the East, until the revolutions of 1989 and fall of the Berlin Wall. In 1949 the Council of Europe was founded, following a speech by Sir Winston Churchill, with the idea of unifying Europe to achieve common goals, it includes all European states except for Belarus and Vatican City. Further European integration by some states led to the formation of the European Union, a separate political entity that lies between a confederation and a federation.
The EU originated in Western Europe but has been expanding eastward since the fall of the Soviet Union in 1991. The currency of most countries of the European Union, the euro, is the most used among Europeans. In classical Greek mythology, Europa was a Phoenician princess; the word Europe is derived from her name. The name contains the elements εὐρύς, "wide, broad" and ὤψ "eye, countenance", hence their composite Eurṓpē would mean "wide-gazing" or "broad of aspect". Broad has been an epithet of Earth herself in the reconstructed Proto-Indo-European religion and the poetry devoted to it. There have been attempts to connect Eurṓpē to a Semitic term for "west", this being either Akkadian erebu meaning "to go down, set" or Phoenician'ereb "evening, west", at the origin of Arabic Maghreb and Hebrew ma'arav. Michael A. Barry, professor in Princeton University's Near Eastern Studies Department, finds the mention of the word Ereb on an Assyrian stele with the meaning of "night, sunset", in opposition to Asu " sunrise", i.e. Asia.
The same naming motive according to "cartographic convention" appears in Greek Ἀνατολή. Martin Litchfield West stated that "phonologically, the match between Europa's name and any form of the Semitic word is poor." Next to these hypotheses there is a Proto-Indo-European root *h1regʷos, meaning "darkness", which produced Greek Erebus. Most major world languages use words derived from Europa to refer to the continent. Chinese, for example, uses the word Ōuzhōu. In some Turkic languages the Persian name Frangistan is used casually in referring to much of Europe, besides official names such as Avrupa or Evropa; the prevalent definition of Europe as a geographical term has been in use since the mid-19th century. Europe is taken to be bounded by large bodies of water
In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from 170.3 Ma to around 168.3 Ma. The Bajocian age precedes the Bathonian age; the Bajocian stage takes its name from the Latin name of the town of Bayeux, in the region of Normandy in France. The stage was named and introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1842; the base of the Bajocian stage is defined as the place in the stratigraphic column where fossils of the ammonite genus Hyperlioceras first appear. A global reference profile for the base is located at Murtinheira, close to Cabo Mondego in Portugal; the top of the Bajocian is at the first appearance of ammonite species Parkinsonia convergens. The Bajocian is divided into Lower/Early and Upper/Late subages or substages. In the Tethys domain, the Bajocian contains seven ammonite biozones: zone of Parkinsonia parkinsoni zone of Garantiana garantiana zone of Strenoceras niortense zone of Stephanoceras humphriesianum zone of Sonninia propinquans zone of Witchellia laeviuscula zone of Hyperlioceras discites Gradstein, F.
M.. G. & Smith, A. G.. Alcide d´Orbigny. 1. Terrains oolitiques ou jurassiques, 642 pp. Bertrand, Paris. Pavia, G. & Enay, R.. Sepkoski, J.. Rodríguez-de la Rosa, Rubén A.. "Middle Jurassic ankylosaur tracks from Mexico". Boletín de la Sociedad Geológica Mexicana. 70: 379–395. GeoWhen Database - Bajocian Jurassic-Cretaceous and Lower Jurassic timescales, at the website of the subcommission for stratigraphic information of the ICS Stratigraphic chart of the Upper Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy
A continental shelf is a portion of a continent, submerged under an area of shallow water known as a shelf sea. Much of the shelves were exposed during interglacial periods; the shelf surrounding an island is known as an insular shelf. The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope followed by the flatter continental rise. Sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope, called the continental rise. Extending as far as 500 km from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope; the continental rise's gradient is intermediate between the shelf. Under the United Nations Convention on the Law of the Sea, the name continental shelf was given a legal definition as the stretch of the seabed adjacent to the shores of a particular country to which it belongs. Width of the continental shelf varies – it is not uncommon for an area to have no shelf at all where the forward edge of an advancing oceanic plate dives beneath continental crust in an offshore subduction zone such as off the coast of Chile or the west coast of Sumatra.
The largest shelf – the Siberian Shelf in the Arctic Ocean – stretches to 1,500 kilometers in width. The South China Sea lies over another extensive area of continental shelf, the Sunda Shelf, which joins Borneo and Java to the Asian mainland. Other familiar bodies of water that overlie continental shelves are the North Sea and the Persian Gulf; the average width of continental shelves is about 80 km. The depth of the shelf varies, but is limited to water shallower than 100 m; the slope of the shelf is quite low, on the order of 0.5°. Though the continental shelf is treated as a physiographic province of the ocean, it is not part of the deep ocean basin proper, but the flooded margins of the continent. Passive continental margins such as most of the Atlantic coasts have wide and shallow shelves, made of thick sedimentary wedges derived from long erosion of a neighboring continent. Active continental margins have narrow steep shelves, due to frequent earthquakes that move sediment to the deep sea.
The shelf ends at a point of increasing slope. The sea floor below the break is the continental slope. Below the slope is the continental rise, which merges into the deep ocean floor, the abyssal plain; the continental shelf and the slope are part of the continental margin. The shelf area is subdivided into the inner continental shelf, mid continental shelf, outer continental shelf, each with their specific geomorphology and marine biology; the character of the shelf changes at the shelf break, where the continental slope begins. With a few exceptions, the shelf break is located at a remarkably uniform depth of 140 m; the continental slope is much steeper than the shelf. The slope is cut with submarine canyons; the physical mechanisms involved in forming these canyons were not well understood until the 1960s. The continental shelves are covered by terrigenous sediments. However, little of the sediment is from current rivers. Sediments become fine with distance from the coast; these accumulate 15–40 cm every millennium, much faster than deep-sea pelagic sediments.
Continental shelves teem with life because of the sunlight available in shallow waters, in contrast to the biotic desert of the oceans' abyssal plain. The pelagic environment of the continental shelf constitutes the neritic zone, the benthic province of the shelf is the sublittoral zone. Though the shelves are fertile, if anoxic conditions prevail during sedimentation, the deposits may over geologic time become sources for fossil fuels; the accessible continental shelf is the best understood part of the ocean floor. Most commercial exploitation from the sea, such as metallic-ore, non-metallic ore, hydrocarbon extraction, takes place on the continental shelf. Sovereign rights over their continental shelves up to a depth of 100 m or to a distance where the depth of waters admitted of resource exploitation were claimed by the marine nations that signed the Convention on the Continental Shelf drawn up by the UN's International Law Commission in 1958; this was superseded by the 1982 United Nations Convention on the Law of the Sea.
Which created the 200 nautical miles exclusive economic zone, plus continental shelf rights for states with physical continental shelves that extend beyond that distance. The legal definition of a continental shelf differs from the geological definition. UNCLOS states that the shelf extends to the limit of the continental margin, but no less than 200 nmi and no more than 350 nmi from the baseline, thus inhabited volcanic islands such as the Canaries, which have no actual continental shelf, nonetheless have a legal continental shelf, whereas uninhabitable islands have no shelf. Baseline Continental Island Continental shelf pump Continental shelf of Russia Exclusive ec