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Šilalė Event
The Šilalė Event was an extinction event affecting conodonts during the Přídolí, the final stage of the Silurian period. Timing The Šilalė Event, first identified in the Milaičiai-103 core in southwestern Lithuania, is marked by a negative carbon isotope excursion in carbonate rocks known as the Šilalė Negative Carbon Isotope Event. This isotopic excursion is also known from the Jočionys-299 borehole in eastern Lithuania, as well as in coeval deposits in the Appalachian Basin of North America and has also been termed the Šilalė Low. The amplitudes of the ~405 Ka long eccentricity cycle were at their lowest point of the entire Přídolí during the Šilalė Event. The end of the Šilalė Event corresponds to the beginning of the ''Delotaxis detorta'' conodont biozone, a conodont biozone once erroneously thought to have corresponded to the latest Přídolí. Effects The Šilalė Event resulted in a decline in conodont diversity and a corresponding increase not just in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extinction Event
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. 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 disagreement as to what constitutes a "major" extinction event, and the data chosen to measure past diversity. The "Big Five" mass extinctions In a landmark paper published in 1982, Jack Sepkoski and David M. Raup identified five particular geological intervals with excessive diversity loss. They were originally identified as outliers on a general trend of decreasing extinction rates during the Phanerozoic, but as more stringent statistical tests have been applied t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brachiopoda
Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major categories are traditionally recognized, articulate and inarticulate brachiopods. The word "articulate" is used to describe the tooth-and-groove structures of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic skeletal feature, by which the two main groups can be readily distinguished as fossils. Articulate brachiopods have toothed hinges and simple, vertically oriented opening and closing muscles. Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hangenberg Event
The Hangenberg event, also known as the Hangenberg crisis or end-Devonian extinction, is a mass extinction that occurred at the end of the Famennian stage, the last Stage (stratigraphy), stage in the Devonian Period (roughly 358.9 ± 0.4 million years ago). It is usually considered the second-largest extinction in the Devonian Period, having occurred approximately 13 million years after the Late Devonian mass extinction (Kellwasser event) at the Frasnian-Famennian boundary. The event is named after the Hangenberg Shale, which is part of a sequence that straddles the Devonian-Carboniferous boundary in the Rhenish Massif of Germany. Geological evidence The Hangenberg Event can be recognized by its unique multi-phase sequence of sedimentary layers, representing a relatively short interval of time with extreme fluctuations in the climate, sea level, and diversity of life. The entire event had an estimated duration of 100,000 to several hundred thousand years, occupying the upper thir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dasberg Event
The Dasberg Event was a minor extinction event that occurred during the Famennian, the final stage of the Devonian period. It is often considered to be one of the events contributing to the Late Devonian extinction, which is believed by many palaeontologists to have been a protracted event that took place over millions of years. Timing The Dasberg Event occurred during the late Famennian in the ''Palmatolepis gracilis expansa'' conodont biozone, near the boundary between the lower and middle parts of the ''expansa'' biozone. Causes Anoxia has been implicated as the main cause of the Dasberg Event. In the deep-shelf Kowala site in the Holy Cross Mountains of Poland, possible evidence of either intermittent anoxia throughout the water column or of prevalent anoxia in surficial waters concurrent with oxygenated bottom water in the lower Dasberg shale comes from low ratios of uranium to thorium, the dominance of small framboids combined with the presence of large framboids, and the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frasnian-Famennian Extinction
The Late Devonian mass extinction, also known as the Kellwasser event, was a mass extinction event which occurred around 372 million years ago, at the boundary between the Frasnian and Famennian ages of the Late Devonian period.Racki, 2005McGhee, George R. Jr, 1996. The Late Devonian Mass Extinction: the Frasnian/Famennian Crisis (Columbia University Press) It is placed as one of the "Big Five" most severe mass extinction events in Earth's history, with likely around 40% of marine species going extinct, though the degree of severity is contested. A second mass extinction called the Hangenberg event, also known as the end-Devonian extinction, occurred 13 million years later around 359 million years ago, bringing an end to the Famennian and Devonian, as the world transitioned into the Carboniferous Period. The effects of the two extinction events have historically been conflated, and both events collectively profoundly reshaped marine ecosystems. Although it is well established tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lau Event
The Lau event was the last of three relatively minor mass extinctions (the Ireviken, Mulde, and Lau events) during the Silurian period. It had a major effect on the conodont fauna, but barely scathed the graptolites, though they suffered an extinction very shortly thereafter termed the Kozlowskii event that some authors have suggested was coeval with the Lau event and only appears asynchronous due to taphonomic reasons. It coincided with a global low point in sea level caused by glacioeustasy and is closely followed by an excursion in geochemical isotopes in the ensuing late Ludfordian faunal stage and a change in depositional regime. Biological impact The Lau event started at the beginning of the late Ludfordian, a subdivision of the Ludlow stage, about . Its strata are best exposed in Gotland, Sweden, taking its name from the parish of Lau. Its base is set at the first extinction datum, in the Eke beds, and despite a scarcity of data, it is apparent that most major groups su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mulde Event
The Mulde event was an anoxic event, and marked the second of three relatively minor mass extinctions (the Ireviken, Mulde, and Lau events) during the Silurian period. It coincided with a global drop in sea level, and is closely followed by an excursion in geochemical isotopes. Its onset is synchronous with the deposition of the Fröjel Formation in Gotland. Perceived extinction in the conodont Conodonts, are an extinct group of marine jawless vertebrates belonging to the class Conodonta (from Ancient Greek κῶνος (''kōnos''), meaning " cone", and ὀδούς (''odoús''), meaning "tooth"). They are primarily known from their hard ... fauna, however, likely represent a change in the depositional environment of sedimentary sequences rather than a genuine biological extinction. Higher resolution δ13C isotope analysis identifies differences in the organic and carbonate carbon isotope curves (Δ13C), allowing the inference of a sustained drop in CO2 levels coincident wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lundgreni Event
The Lundgreni Event, also known as the Mid-Homerian Biotic Crisis, was an extinction event during the middle Homerian age of the Silurian period. Evidence for the event has been observed in Silurian marine deposits in the Iberian Peninsula, Bohemia, and Poland. Timing In the Kosov quarry in Bohemia, the extinction is observed during the latest ''lundgreni'' biozone and over the course of the ''flemingii'' biozone interval. The following ''parvus'' biozone, corresponding to the ''nassa'', the ''parvus-nassa'', or ''dubious-nassa'' biozones in other localities, represents a post-extinction interval, which is in turn followed by the ''frequens'', ''praedeubeli-deubeli'', and ''ludensis-gerhardi'' biozones that mark the period of recovery from the extinction. Causes Eutrophication and anoxic event, anoxia coeval with abrupt ecological changes have been implicated as extinction mechanisms bringing about the Lundgreni Event. Immediately after the extinction event, geological record ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ireviken Event
The Ireviken event was the first of three relatively minor extinction events (the Ireviken, Mulde, and Lau events) during the Silurian period. It occurred at the Llandovery/ Wenlock boundary (mid Silurian, ). The event is best recorded at Ireviken, Gotland, where over 50% of trilobite species became extinct; 80% of the global conodont species also became extinct in this interval. Anatomy of the event The event lasted around 200,000 years, spanning the base of the Wenlock epoch. It is associated with a period of global cooling. It comprises eight extinction "datum points"—the first four being regularly spaced, every 30,797 years, and linked to the Milankovic obliquity cycle. The fifth and sixth probably reflect maxima in the precessional cycles, with periods of around 16.5 and 19 ka. The final two data are much further spaced, so harder to link with Milankovic changes. Casualties The mechanism responsible for the event originated in the deep oceans, and made its way into the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gondwana Research
''Gondwana Research'' is a peer-reviewed scientific journal with an "all earth science" scope and an emphasis on the origin and evolution of continents. It is part of the Elsevier Elsevier ( ) is a Dutch academic publishing company specializing in scientific, technical, and medical content. Its products include journals such as ''The Lancet'', ''Cell (journal), Cell'', the ScienceDirect collection of electronic journals, ... group, published by Journal Center, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China. References External links * Geology journals Elsevier academic journals English-language journals {{Geology-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GFF (journal)
GFF may refer to: Entertainment * Girlfriends Films, an American pornographic studio * Glasgow Film Festival, in Scotland * Gothenburg Film Festival, in Sweden Sports * Gabonese Football Federation * Gambia Football Federation * Georgian Football Federation * Göteborgs FF, Swedish football club * Gothenburg Football Association * Guinean Football Federation * Guyana Football Federation Other uses * ''GFF'' (journal), a geology journal * General feature format, a file format used for describing genes * Gesellschaft für Freiheitsrechte (Society for Civil Rights), a Berlin-based non-profit organization * Göteborgs FyrverkeriFabrik, a Swedish fireworks company * Griffith Airport, in New South Wales, Australia * Griffith railway station Griffith railway station is located on the Yanco–Griffith line in New South Wales, Australia. It serves the city of Griffith. History Griffith station opened on 3 July 1916 when the Temora-Roto line was extended from Barellan. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
