|
Black Jura
The Black Jurassic or Black Jura (german: Schwarzer Jura) in earth history refers to the lowest of the three lithostratigraphic units of the South German Jurassic, the latter being understood not as a geographical, but a geological term in the sense of a lithostratigraphic super group. Formerly and even occasionally today in the popular scientific literature, this term is equated to the chronostratigraphic series of the Lower Jurassic. This is however not quite correct, because the Black Jura does not exactly coincide with the chronostratigraphic boundaries of the Lower Jurassic. In addition, the term ''lias'', which was formerly frequently used (and sometimes is today) as a synonym, should no longer be used in connexion with the South German Jurassic. Instead, the term ''lias'', or ''North German Lias'', should be reserved for the roughly equivalent lithostratigraphic unit in the North German Jurassic. The deposition of the Black Jurassic took place about 199 to 175 million years ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithostratigraphic
Lithostratigraphy is a sub-discipline of stratigraphy, the geology, geological science associated with the study of stratum, strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are primarily igneous or sedimentary relating to how the rock was formed. Sedimentary rock, Sedimentary layers are laid down by Deposition (sediment), deposition of sediment associated with weathering processes, decaying organic matter (biogenic) or through chemical precipitation. These layers are often distinguishable as having many fossils and are important for the study of biostratigraphy. Igneous layers occur as stacks of lava flows, layers of lava fragments (called tephra) both erupted onto the Earth's surface by volcanoes, and in layered intrusions formed deep underground. Igneous layers are generally devoid of fossils and represent Magmatism, magmatic or volcanic activity that occurred during the geologic history of an area. There are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group (geology)
In geology, a group is a lithostratigraphic unit consisting of a series of related formations that have been classified together to form a group. Formations are the fundamental unit of stratigraphy. Groups may sometimes be combined into supergroups. Groups are useful for showing relationships between formations, and they are also useful for small-scale mapping or for studying the stratigraphy of large regions. Geologists exploring a new area have sometimes defined groups when they believe the strata within the groups can be divided into formations during subsequent investigations of the area. It is possible for only some of the strata making up a group to be divided into formations. An example of a group is the Glen Canyon Group, which includes (in ascending order) the Wingate Sandstone, the Moenave Formation, the Kayenta Formation, and the Navajo Sandstone. Each of the formations can be distinguished from its neighbor by its lithology, but all were deposited in the same vast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South German Jurassic
The term South German Jurassic (german: Süddeutscher Jura) in earth history is used to refer to a lithostratigraphy, lithostratigraphic rock unit at the hierarchical level of a group (geology), super group. The Sedimentary rock, rocks of the South German Jurassic were mainly deposited during the Jurassic period (199 to 146 million years ago). The boundaries of the South German Jurassic and those of the chronostratigraphy, chronostratigraphic or international Jurassic are not, however, exactly coincident. The depositions began rather later than the date of the international Triassic/Jurassic boundary and end as a result of erosion of the uppermost strata at various times during the Upper Jurassic, i.e. well before the international Jurassic/Cretaceous boundary. The rock unit of the South German Jurassic is underlain by Keuper; in between is a small stratigraphic hiatus. Above the South German Jurassic the beds follow discordantly and with a large stratigraphic gap; in addition, Rege ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chronostratigraphy
Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geological region, and eventually, the entire geologic record of the Earth. The standard stratigraphic nomenclature is a chronostratigraphic system based on palaeontological intervals of time defined by recognised fossil assemblages (biostratigraphy). The aim of chronostratigraphy is to give a meaningful age date to these fossil assemblage intervals and interfaces. Methodology Chronostratigraphy relies heavily upon isotope geology and geochronology to derive hard dating of known and well defined rock units which contain the specific fossil assemblages defined by the stratigraphic system. In practice, as it is very difficult to isotopically date most fossils and sedimentary rocks directly, inferences must be made in order to arrive at an age d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Series (geology)
Series are subdivisions of rock layers based on the age of the rock and formally defined by international conventions of the geological timescale. A series is therefore a sequence of strata defining a chronostratigraphic unit. Series are subdivisions of systems and are themselves divided into stages. Series is a term defining a unit of rock layers formed during a certain interval of time (a chronostratigraphic unit); it is equivalent (but not synonymous) to the term ''geological epoch'' (see epoch criteria) which defines the interval of time itself, although the two words are sometimes confused in informal literature. Series in the geological timescale The geological timescale has all systems in the Phanerozoic eonothem subdivided into series. Some of these have their own names, in other cases a system is simply divided into a Lower, Middle and Upper series. The Cretaceous system is for example divided into the Upper Cretaceous and Lower Cretaceous series; while the Carbonifer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lower Jurassic
The Early Jurassic Epoch (in chronostratigraphy corresponding to the Lower Jurassic 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 174.1 Ma. Certain rocks of marine origin of this age in Europe are called "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 English quarryman's dialect pronunciation of the word "layers"; secondly, sloops from north 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 limestone from South Wales was used throughout North Devon/North Cornwall as it con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synonym
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all synonyms of one another: they are ''synonymous''. The standard test for synonymy is substitution: one form can be replaced by another in a sentence without changing its meaning. Words are considered synonymous in only one particular sense: for example, ''long'' and ''extended'' in the context ''long time'' or ''extended time'' are synonymous, but ''long'' cannot be used in the phrase ''extended family''. Synonyms with exactly the same meaning share a seme or denotational sememe, whereas those with inexactly similar meanings share a broader denotational or connotational sememe and thus overlap within a semantic field. The former are sometimes called cognitive synonyms and the latter, near-synonyms, plesionyms or poecilonyms. Lexicograph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keuper
The Keuper is a lithostratigraphic unit (a sequence of rock strata) in the subsurface of large parts of west and central Europe. The Keuper consists of dolomite, shales or claystones and evaporites that were deposited during the Middle and Late Triassic epochs (about ). The Keuper lies on top of the Muschelkalk and under the predominantly Lower Jurassic Lias or other Early Jurassic strata. The Keuper together with the Muschelkalk and the Buntsandstein form the Germanic Trias Group, a characteristic sequence of rock strata that gave the Triassic its name. "Muschelkalk (geology)", Britannica Online Encyclopedia, October 2010, webpage: EB-39 Exposure The Upper Triassic is well exposed in Swabia, Franconia, Alsace and Lorraine and Luxembourg; it extends from Basel on the east side of the Rhine into Hanover, and through England into Scotland and north-east Ireland; it appears flanking the central plateau of France and in the Pyrenees and Sardinia. The Keuper sequence is li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brown Jurassic
The Brown Jurassic or Brown Jura (german: Brauner Jura or ''Braunjura'') in earth history refers to the middle of the three lithostratigraphic units of the South German Jurassic, the latter being understood not as a geographical, but a geological term in the sense of a lithostratigraphic super group. Formerly and even occasionally today in the popular scientific literature, this term is equated to the chronostratigraphic series of the Middle Jurassic. This is however not quite correct, because the Brown Jura does not exactly coincide with the chronostratigraphic boundaries of the Middle Jurassic. In addition, the term ''Dogger'', which was formerly frequently used (and sometimes is today) as a synonym should no longer be used in connexion with the South German Jurassic. Instead the term "Dogger" should be reserved for the roughly equivalent lithostratigraphic unit in the North German Jurassic. The Brown Jurassic was deposited about 175-161 million years ago. The Brown Jurassic foll ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jurassic System Of Europe
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified. The start of the Jurassic was marked by the major Triassic–Jurassic extinction event, associated with the eruption of the Central Atlantic Magmatic Province. The beginning of the Toarcian Stage started around 183 million years ago and is marked by an extinction event associated with widespread oceanic anoxia, ocean acidification, and elevated temperatures likely caused by the eruption of the Karoo-Ferrar large igneous provinces. The end of the Jurassic, however, has no clear boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined. By the beginning of the Jurassic, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
