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Toarcian
The Toarcian is, in the International Commission on Stratigraphy, ICS' geologic timescale, an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic. It spans the time between 184.2 Megaannum, Ma (million years ago) and 174.7 ±0.8 Ma. It follows the Pliensbachian and is followed by the Aalenian. The Toarcian Age began with the Toarcian Oceanic Anoxic Event, a major anoxic event associated with marine extinctions and increased global temperatures that sets its fossil faunas apart from the previous Pliensbachian age. It is believed to have ended with a global cooling event known as the Comptum Cooling Event, although whether it represented a worldwide event is controversial. Stratigraphic definitions The Toarcian takes its name from the city of Thouars, just south of Saumur in the Loire Valley of France. The stage was introduced by French palaeontologist Alcide d'Orbigny in 1842, after examining stratum, rock strata of this age in a quar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toarcian Oceanic Anoxic Event
The Toarcian extinction event, also called the Pliensbachian-Toarcian extinction event, the Early Toarcian mass extinction, the Early Toarcian palaeoenvironmental crisis, or the Jenkyns Event, was an extinction event that occurred during the early part of the Toarcian age, approximately 183 million years ago, during the Early Jurassic. The extinction event had two main pulses, the first being the Pliensbachian-Toarcian boundary event (PTo-E). The second, larger pulse, the Toarcian Oceanic Anoxic Event (TOAE), was a global oceanic anoxic event, representing possibly the most extreme case of widespread ocean deoxygenation in the entire Phanerozoic eon. In addition to the PTo-E and TOAE, there were multiple other, smaller extinction pulses within this span of time. Occurring during the supergreenhouse climate of the Early Toarcian Thermal Maximum (ETTM), the Early Toarcian extinction was associated with large igneous province volcanism, which elevated global temperatures, acidified t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anoxic Event
An anoxic event describes a period wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O2), creating toxic, euxinic ( anoxic and sulfidic) waters. Although anoxic events have not happened for millions of years, the geologic record shows that they happened many times in the past. Anoxic events coincided with several mass extinctions and may have contributed to them. These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating. On the other hand, there are widespread, various black-shale beds from the mid-Cretaceous which indicate anoxic events but are not associated with mass extinctions. Many geologists believe oceanic anoxic events are strongly linked to the slowing of ocean circulation, climatic warming, and elevated levels of greenhouse gases. Researchers have proposed enhanced volcanism (the release of CO2) as the "central external trigger for euxinia." Human activities in the Holocene epoch, such as t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Global Boundary Stratotype Sections And Points
This is a list of Global Boundary Stratotype Sections and Points. Since 1977, Global Boundary Stratotype Sections and Points (abbreviated GSSPs) are internationally agreed upon reference points on stratigraphic sections of rock which define the lower boundaries of stages on the geologic time scale. They are selected by the International Commission on Stratigraphy based on multiple factors, but their accessibility and the degree to which they are representative of the same boundary on sections worldwide are among the most important. Since GSSPs require well-preserved sections of rock without interruptions in sedimentation, and since most are defined by different stages of animal life, defining them becomes progressively more difficult as one goes farther back in time. Organization of this list This list is divided first into the geologic eras of the Phanerozoic (the Cenozoic, the Mesozoic, and the Paleozoic) and then into the geologic periods of each era. Each period is marke ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic–Jurassic extinction event, 201.3 Ma (million years ago), and ends at the start of the Middle Jurassic 174.7 ±0.8 Ma. Certain rocks of marine origin of this age in Europe are called "Lias Group, Lias" and that name was used for the period, as well, in 19th-century geology. In southern Germany rocks of this age are called Black Jurassic. Origin of the name Lias There are two possible origins for the name Lias: the first reason is it was taken by a geologist from an England, English quarryman's dialect pronunciation of the word "layers"; secondly, sloops from north Cornwall, Cornish ports such as Bude would sail across the Bristol Channel to the Vale of Glamorgan to load up with rock from coastal limestone quarries (lias and Carbonif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dactylioceras
''Dactylioceras'' was a widespread genus of ammonites from the Lower Jurassic period, approximately 180 million years ago ( mya).Like many other ammonites, the genus ''Dactylioceras'' is extremely important in biostratigraphy, being a key index fossil for identifying their region of the Jurassic. It had a nearly cosmopolitan distribution during the time it existed. Etymology The name ''Dactylioceras'' comes from the Greek ''dactyl'', meaning “finger”, and ''keras'', meaning "horn" and refers to the shell's branching ribs. Description ''Dactylioceras'' are generally small, averaging in diameter. They have a strong, ribbed shell. The ribs are slightly inclined forward, running over the outer edge, and either simple or forking at outer end. Though they eventually died out 180 mya, their style of ribbing was copied by numerous subsequent ammonite genera until the whole group became extinct 66 million years ago with the dinosaurs. Ecology ''Dactylioceras'' probably lived by sca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pliensbachian
The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 192.9 ±0.3 Ma and 184.2 ±0.3 Ma (million years ago). The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian. The Pliensbachian ended with the extinction event called the Toarcian turnover. During the Pliensbachian, the middle part of the Lias was deposited in Europe. The Pliensbachian is roughly coeval with the Charmouthian regional stage of North America. Stratigraphic definitions The Pliensbachian takes its name from the hamlet of Pliensbach in the community of Zell unter Aichelberg in the Swabian Alb, some 30 km east of Stuttgart in Germany. The name was introduced into scientific literature by German palaeontologist Albert Oppel in 1858. The base of the Pliensbachian is at the first appearances of the ammonite species '' Bifericeras donovani'' and genera '' Apo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thouars
Thouars () is a commune in the Deux-Sèvres department in western France. On 1 January 2019, the former communes Mauzé-Thouarsais, Missé and Sainte-Radegonde were merged into Thouars. It is on the River Thouet. Its inhabitants are known as ''Thouarsais''. The Toarcian stage of the Jurassic takes its name from the town. History Although there is evidence of human habitation here 5,000 years ago, it is only in the seventh century that the town appears in the historical record. In the 760s, Thouars found itself in Aquitaine, the most robust fortress in the entire region according to contemporary chroniclers. This was a violent decade as Duke Waïfre, struggling to preserve the independence of Aquitaine, fought against the expansionist ambitions of the French King, Pepin the Short. In 762, accompanied by his son, the future Charlemagne, appeared outside Thouars. He destroyed the Gallo-Roman town and torched the castle. In the ninth century the first of a line of viscou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aalenian
The Aalenian () is a subdivision of the Middle Jurassic Epoch/Series of the geologic timescale that extends from about 174.7 ±0.8 Ma to about 170.9 ±0.8 Ma (million years ago). It was preceded by the Toarcian and succeeded by the Bajocian. Stratigraphic definitions The Aalenian takes its name from the town of Aalen, some 70 km east of Stuttgart in Germany. The town lies at the northeastern end of the Swabian Jura. The name Aalenian was introduced in scientific literature by Swiss geologist Karl Mayer-Eymar in 1864. The base of the Aalenian is defined as the place in the stratigraphic column where the ammonite genus '' Leioceras'' first appears. The global reference profile (GSSP) is located 500 meters north of the village of Fuentelsaz in the Spanish province of Guadalajara.Cresta ''et al.'' (2001) The top of the Aalenian (the base of the Bajocian) is at the first appearance of ammonite genus '' Hyperlioceras''. In the Tethys domain, the Aalenian contains four ammonit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geologic Timescale
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardised international units of geological time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precise ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peniche, Portugal
Peniche (), officially the City of Peniche (), is a seaside municipality and a city in the Oeste region, in the historical province of Estremadura, and in the Leiria District. It has 26,431 inhabitants, in an area of 77.55 km2. The city itself has a population of about 15,600 inhabitants. The present mayor is Henrique Bertino, elected by the independent coalition GCEPP (''Grupo de Cidadãos Eleitores por Peniche''; Electors for Peniche Group of Citizens). The idiomatic expression '' Friend from Peniche'', used to describe someone who wants to receive things at the expense of other without giving anything in return, comes from here. History and landmarks The city was built on a rocky peninsula which is considered by geologists a unique example of the Toarcian turnover during the worldwide Early Jurassic extinction. Peniche is known for its long beaches, which are popular for recreational activities and sports such as surfing, windsurfing, bodyboarding and kite surfing. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lias Group
The Lias Group or Lias is a lithostratigraphic unit (a sequence of rock strata) found in a large area of western Europe, including the British Isles, the North Sea, the Low Countries and the north of Germany. It consists of marine limestones, shales, marls and clays. ''Lias'' is a Middle English term for hard limestone, used in this specific sense by geologists since 1833. In the past, geologists used ''Lias'' not only for the sequence of rock layers, but also for the timespan during which they were formed. It was thus an alternative name for the Early Jurassic epoch of the geologic timescale. It is now more specifically known that the Lias is Rhaetian to Toarcian in age (over a period of 20 million years between ) and thus also includes a part of the Triassic. The use of the name "Lias" for a unit of time is therefore slowly disappearing. Subdivisions In southern England, the Lias Group is often divided into Lower, Middle and Upper subgroups. In Southern England the Lias i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
