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37-489: The Ordovician was divided into three series and six global stages in 1995. Although at the time of 2005 GSSPs for the overlying Darriwilian and underlying " second stage " had already been ratified, definition of a GSSP for the first stage of the Middle Ordovician Series caused difficulties due to the deficiencies of the selected biohorizon and section. The Dapingian was the last Ordovician stage to be ratified, and

74-448: A coupling of seawater oxygenation with Ordovician biodiversity. Another alternative is that the breakup of an asteroid led to the Earth being consistently pummelled by meteorites, although the proposed Ordovician meteor event happened at 467.5±0.28 million years ago. Another effect of a collision between two asteroids, possibly beyond the orbit of Mars, is a reduction in sunlight reaching

111-503: A diversification, the event also marked an increase in the complexity of both organisms and food webs . The number of different life modes among hard-bodied organisms doubled. Taxa began to exhibit greater provincialism and have more localized ranges, with different faunas at different parts of the globe. Communities in reefs and deeper water began to take on a character of their own, becoming more clearly distinct from other marine ecosystems. Benthic environments drastically increase in

148-650: A harbinger of much colder climate in the next Darriwilian age. At the end of the Dapingian, continental ice was growing with small changes in volume caused by changes in the Earth's orbit. The Great Ordovician Biodiversification Event (GOBE) lasted in the Dapingian. Fan et al. (2020) define GOBE as a 20 Myr interval that began in the Tremadocian and ended in the late Dapingian, although other researchers have suggested different temporal limits. The extensive transgression associated with rapid tectonic subsidence, occurred at

185-530: A key trigger for GOBE. Furthermore, Ordovician biodiversification pulses were closely linked to terminations of positive carbon isotope excursions, which are characteristic of anoxia, suggesting that diversification occurred in concert with increasing oxygen content. After the Steptoean positive carbon isotope excursion about 500 million years ago, the extinction in the ocean would have opened up new niches for photosynthetic plankton, who would absorb CO 2 from

222-587: A large, nutrient-rich ecospace , favoring diversification. There seems to be an association between orogeny and the evolutionary radiation, with the Taconic orogeny in particular being singled out as a driver of the GOBE by enabling greater erosion of nutrients such as iron and phosphorus and their delivery to the oceans around Laurentia. In addition, the changing geography led to a more diverse landscape, with more different and isolated environments; this no doubt facilitated

259-652: A level in the Fennian stage of the Arenig . Great Ordovician Biodiversification Event The Great Ordovician Biodiversification Event ( GOBE ), was an evolutionary radiation of animal life throughout the Ordovician period, 40 million years after the Cambrian explosion , whereby the distinctive Cambrian fauna fizzled out to be replaced with a Paleozoic fauna rich in suspension feeder and pelagic animals. It followed

296-542: A new habitat. As with the Cambrian Explosion , it is likely that environmental changes drove the diversification of plankton , which permitted an increase in diversity and abundance of plankton-feeding lifeforms, including suspension feeders on the sea floor, and nektonic organisms in the water column . If the Cambrian Explosion is thought of as "producing" the modern phyla , the GOBE can be considered as

333-507: A proxy for B. triangularis , T. laevis , and graptolites, which were absent from the section. The Huanghuachang section of China hosted a more diverse fauna of index fossils, including Baltoniodus triangularis and biostratigraphically useful graptolites and chitinozoans . The Huanghuachang section was approved as the GSSP for the third stage in 2006, and was ratified by the ICS in 2007. The Dapingian

370-516: A series of Cambrian–Ordovician extinction events , and the resulting fauna went on to dominate the Palaeozoic relatively unchanged. Marine diversity increased to levels typical of the Palaeozoic, and morphological disparity was similar to today's. The diversity increase was neither global nor instantaneous; it happened at different times in different places. Consequently, there is unlikely to be

407-403: A simple or straightforward explanation for the event; the interplay of many geological and ecological factors likely produced the diversification. According to a comprehensive study of biodiversity throughout the Palaeozoic, GOBE began 497.05 Ma and ended 467.33 Ma, lasting for 29.72 Myr. GOBE did not constitute one single event, as different clades diversified during different time intervals of

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444-608: Is an outcrop of the Ningkuo Formation, consisting of mainly black shale. The lower boundary of the Darriwilian is defined as the first appearance datum of the graptolite species Undulograptus austrodentatus in that section. A secondary fossil marker is the graptolite Arienigraptus zhejiangensis . The base of the Darriwilian is also the base of the Undulograptus austrodentatus graptolite zone. This zone lies just above

481-569: Is confirmed by the discovery of fossils of cornutan stylophorans Phyllocystis in these regions. Planopora , the oldest сystoporate bryozoan to form erect, bifoliate colonies, is known from the Dapingian of the Baltic paleobasin, Leningrad Oblast , Russia. Darriwilian The Darriwilian is the upper stage of the Middle Ordovician . It is preceded by the Dapingian and succeeded by

518-528: Is derived from Darriwil, a parish in County of Grant , Victoria (Australia) . The name was proposed in 1899 by Thomas Sergeant Hall . The GSSP of the Darriwilian is the Huangnitang Section ( 28°51′14″N 118°29′23″E  /  28.8539°N 118.4897°E  / 28.8539; 118.4897 ) near the village Huangnitang, 3.5 km southwest of Changshan County Town ( Zhejiang , China ). It

555-608: Is named after Daping, a village that lies near the Dapingian GSSP at Huanghuachang. The Chenjiahe section, an outcrop with similar rocks, can be found 5 km to the north of the Huanghuachang section. The name of the Dapingian stage was introduced in June 2007 and approved alongside the stage's ratification, beating out earlier suggestions such as "Volkhovian" and "Huanghuachangian". The Global Boundary Stratotype Section and Point ( GSSP ) of

592-608: The Flat Landing Brook Formation in New Brunswick , Canada may have caused rapid climatic cooling and biodiversification. Thallium isotope shifts show an expansion of oxic waters throughout deep water and shallow shelf environments during the latest Cambrian and earliest Ordovician coeval with increasing burrowing depth and complexity observed among ichnofossils and increasing morphological complexity among body fossils. Thus, heightened oxygen availability may have been

629-801: The Floian -Dapingian boundary at 470 million years ago. The exact boundary lies 10.57 m above the base of Dawan Formation . The Dapingian overlaps with the upper part of the Arenig , a geologic stage used in England . It is also equivalent to the lower part of the North American Whiterockian stage, most of the Baltic/Russian Volkhov stage, and the Castlemainian and Yapeenian stages which have been used in Australia. In Baltoscandia, especially in

666-666: The Upper Ordovician Sandbian Stage. The lower boundary of the Darriwilian is defined as the first appearance of the graptolite species Undulograptus austrodentatus around 467.3 million years ago. It lasted for about 8.9 million years until the beginning of the Sandbian around 458.4 million years ago. This stage of the Ordovician was marked by the beginning of the Andean-Saharan glaciation . The name Darriwilian

703-581: The "filling out" of these phyla with the modern (and many extinct) classes and lower-level taxa. The GOBE is considered to be one of the most potent speciation events of the Phanerozoic era, increasing global diversity severalfold and leading to the establishment of the Palaeozoic evolutionary fauna . Notable taxonomic diversity explosions during this period include that of articulated brachiopods , gastropods , and bivalves . The acritarch record (the majority of acritarchs were probably marine algae) displays

740-519: The Dapingian is the Huanghuachang section ( 30°51′38″N 110°22′26″E  /  30.8605°N 110.3740°E  / 30.8605; 110.3740 ), in Huanghuachang , Yichang , China . It is an outcrop of the Dawan Formation . The lower boundary is defined as the first appearance of the conodont species Baltoniodus triangularis in the type section. Radiometric dating has constrained

777-531: The Earth's surface due to the vast dust clouds created. Evidence for this geological event comes from the relative abundance of the isotope helium-3 , found in ocean sediments laid down at the time of the biodiversification event. The most likely cause of the production of high levels of helium-3 is the bombardment of lithium by cosmic rays , something which could only have happened to material which travelled through space. However, rather than sparking evolutionary diversification, other lines of evidence point to

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814-620: The East Baltic, the global stage boundary corresponds to the bases of the Megistaspis polyphemus Trilobite Zone and probably Isograptus victoriae victoriae Graptolite Zone. At the beginning of the Dapingian, there was a drop in sea level of 70–80 m, which is reflected in the rocks as a well-developed hardground surface in Baltoscandia. Changes in sea level during Dapingian age appear to be associated with short pulses of cooling, which have become

851-536: The Floian may reflect the initiation of a cooling through organic carbon burial that has been proposed to have kickstarted GOBE. In the longer term as well, increasing carbon isotope ratios track biodiversity increase, further pointing to a link between cooling and GOBE. The cooling during the Middle and early Late Ordovician in particular is known for its associated burst of biodiversification. The volcanic activity that created

888-616: The Late Cambrian and Early and Middle Ordovician. During the Late Ordovician, diversification slowed down thanks to increased endemism and interbasinal dispersal, bringing an end to GOBE. Possible causes include an increase in marine oxygen content, changes in palaeogeography or tectonic activity , a modified nutrient supply, or global cooling. The dispersed positions of the continents, high level of tectonic/volcanic activity, warm climate, and high CO 2 levels would have created

925-622: The North Atlantic Microzarkodina parva conodont zone. The base also lies in the upper part of the North American Histiodella altifrons conodont zone. The Undulograptus austrodentatus graptolite zone is known from outcrops around the world, making the base of the Darriwilian easily correlatable. The Darriwilian overlaps with the upper Arenig and the Llanvirn . The base of the Darriwilian can be correlated with

962-574: The Ordovician meteor event instead postdating the Darriwilian biodiversity burst by about 600 kyr and the start of glaciation by 800 kyr. Instead of facilitating the radiation, the meteor event may have antagonistically acted to temporarily retard and halt biological diversification according to this thesis. The above triggers would have been amplified by ecological escalation, whereby any new species would co-evolve with others, creating new niches through niche partitioning, trophic layering, or by providing

999-427: The Ordovician radiation beautifully; both diversity and disparity peaked in the middle Ordovician. The warm waters and high sea level (which had been rising steadily since the early Cambrian) permitted large numbers of phytoplankton to prosper; the accompanying diversification of the phytoplankton may have caused an accompanying radiation of zooplankton and suspension feeders. Taxonomic diversity increased manifold;

1036-540: The amount and variety of bioturbation. The planktonic realm was invaded as never before, with several invertebrate lineages colonising the open waters and initiating new food chains at the end of the Cambrian into the early Ordovician. Among the newcomers colonising the planktonic realm were trilobites and cephalopods. Estuarine environments also experienced increased colonisation by living organisms. And as ecosystems became more diverse, with more species being squeezed into

1073-439: The atmosphere and release large amount of oxygen. More oxygen and a more diversified photosynthetic plankton as the bottom of the food chain, would have affected the diversity of higher marine organisms and their ecosystems. In the Middle to Late Ordovician, after GOBE, an expansion of anoxic waters occurred in sync with a ~50% decline in benthic invertebrates in various epicontinental seas, providing further indirect support for

1110-703: The base of the Whiterockian stage in western North America. T. laevis was also roughly correlated with the appearance of the graptolite Isograptus v. lunatus . The Whiterock Narrows section in the Ninemile Formation of Nevada was the initial suggestion for the GSSP of the third stage, but a 2001 review of the site revealed that its local conodont fauna was misaligned with wider graptolite zonation. In its place, two formal GSSP candidates were proposed. The Niquivil section of Argentina used another widespread species, Protoprioniodus (Cooperignathus) aranda , as

1147-480: The emergence of bioprovinciality, and speciation by isolation of populations. The widespread reef development on the Baltican shelf in particular is attributable to the landmass's northward drift into more oligotrophic waters, enabling diversification of its reef biota. Widespread volcanism and its delivery of biologically important trace metals has similarly been proposed as a GOBE trigger, albeit controversially. On

Dapingian - Misplaced Pages Continue

1184-633: The end of the Dapingian in the Southern Urals . The Komstad Regressive Event roughly corresponds to the Dapingian. Funeralaspis , the oldest named odontopleurine trilobite , was discovered in the Dapingian of the Antelope Valley Formation in Inyo County , California . Since the Dapingian, there has been a connection between the Afro-European part of Gondwana and Baltica , which

1221-609: The entire Early Palaeozoic. An analysis of the Paleobiology Database (PBDB) and Geobiodiversity Database (GBDB) found no statistical basis for separating the two radiations into discrete events. A proposed biodiversity gap known as the Furongian Gap is thought by some researchers to have existed between the Cambrian Explosion and GOBE existed during the Furongian epoch, the final epoch of the Cambrian. However, whether this gap

1258-478: The food web, a more complex tangle of ecological interactions resulted, promoting strategies such as ecological tiering. The global fauna that emerged during the GOBE went on to be remarkably stable until the catastrophic end-Permian extinction and the ensuing Mesozoic Marine Revolution . Recent work has suggested that the Cambrian Explosion and GOBE, rather than being two distinct events, represented one continual evolutionary radiation of marine life occurring over

1295-422: The other hand, global cooling has also been offered as a cause of the radiation, with long-term biodiversity trends showing a positive correlation between cooling and biodiversity during GOBE. An uptick in fossil diversity correlates with the increasing abundance of cool-water carbonates over the course of this time interval. A transient high magnitude shift towards more positive carbon isotope ratios during

1332-456: The total number of marine orders doubled, and families tripled. Marine biodiversity reached levels comparable to those of the present day. Beta diversity was the most important component of biodiversity increase from the Furongian to the Tremadocian . From the Floian onward, alpha diversity dethroned beta diversity as the greater contributor to regional diversity patterns. In addition to

1369-511: Was initially referred to as an informal and unnamed "third stage" corresponding to the early part of the Middle Ordovician. This third stage was meant to represent the appearance of several major index fossils . The conodont Baltoniodus triangularis , a species found in Baltica and China, defined the base of the regional Baltoscandian Volkhov stage. Another conodont, Tripodus laevis , defined

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