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Encyclopedia > Silurian

The Silurian is a major division of the geologic timescale that extends from the end of the Ordovician period, about 443.7 ± 1.5 Ma (million years ago), to the beginning of the Devonian period, about 416.0 ± 2.8 Ma (ICS 2004). As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by 5-10 million years. The base of the Silurian is set at a major extinction event when 60% of marine species were wiped out. See Ordovician-Silurian extinction events. Silurian: The Silurian is a major division of the geologic timescale that extends from the end of the Ordovician period, c. ... The geologic time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of the Earth. ... Artist impression of the Ordovician Sea. ... Annum is a Latin noun meaning year. ... For the Celtic language, see Southwestern Brythonic language; for the residents of the English county, see Devon. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... Rock redirects here. ... An extinction event (also known as: mass extinction; extinction-level event, ELE) occurs when there is a sharp decrease in the number of species in a relatively short period of time. ... The Ordovician-Silurian extinction event, labeled End O here. ...

Contents

Historiography

Silurian reef complex on Gotland, Sweden.
Silurian reef complex on Gotland, Sweden.

The Silurian system was first identified by Sir Roderick Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, extending the convention his friend Adam Sedgwick had established for the Cambrian. In 1835 the two men presented a joint paper, under the title On the Silurian and Cambrian Systems, Exhibiting the Order in which the Older Sedimentary Strata Succeed each other in England and Wales, which was the germ of the modern geological time scale. As it was first identified, the "Silurian" series when traced farther afield quickly came to overlap Sedgwick's "Cambrian" sequence, however, provoking furious disagreements that ended the friendship. Charles Lapworth eventually resolved the conflict by defining a new Ordovician system including the contended beds. Image File history File links Metadata Size of this preview: 800 × 287 pixelsFull resolution‎ (4,700 × 1,687 pixels, file size: 1. ... Image File history File links Metadata Size of this preview: 800 × 287 pixelsFull resolution‎ (4,700 × 1,687 pixels, file size: 1. ... For other uses, see Reef (disambiguation). ...   is a county, province and municipality of Sweden and the second largest island in the Baltic Sea after Zealand. ... Sir Roderick Murchison Sir Roderick Impey Murchison (February 19, 1792 – October 22, 1871), was an influential Scottish geologist who first described and investigated the Silurian era. ... For other uses, see strata (novel) and strata title. ... This article is about the country. ... // Electromagnetic induction discovered by Michael Faraday Evolutionary theorist Charles Darwins expedition on the HMS Beagle. ... Celts, normally pronounced // (see article on pronunciation), is widely used to refer to the members of any of the peoples in Europe using the Celtic languages or descended from those who did. ... The Silures were a powerful and warlike tribe of ancient Britain, occupying approximately the counties of Monmouth, Brecon and Glamorgan. ... Adam Sedgwick (March 22nd, 1785–January 27, 1873) was one of the founders of modern geology. ... For other uses, see Cambrian (disambiguation). ... | Come and take it, slogan of the Texas Revolution 1835 was a common year starting on Thursday (see link for calendar). ... The table and timeline of geologic periods presented here is in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy. ... Charles Lapworth (September 20, 1842 – March 13, 1920) was an English geologist. ...


The French geologist Joachim Barrande, building on Murchison's work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages. His interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the original groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the oldest fossils. Joachim Barrande (August 11, 1799 - October 5, 1883) was a French geologist and palaeontologist. ... Flag of Bohemia Bohemia (Czech: ; German: ) is a historical region in central Europe, occupying the western and middle thirds of the Czech Republic. ... Edward Forbes (February 12, 1815 - November 18, 1854), British naturalist, was born at Douglas, in the Isle of Man. ... For the Celtic language, see Southwestern Brythonic language; for the residents of the English county, see Devon. ...


Silurian subdivisions

The Silurian Period of time is usually broken into early (Llandovery and Wenlock) and late (Ludlow and Pridoli) subdivisions (epochs). Nevertheless, some schemes use an early (Llandovery), middle (Wenlock) and late (Ludlow and Pridoli) breakdown. These faunal stages are characterized by their index fossils, new species of colonial marine Graptolites that appeared in each. Epochs of time correspond to series of rocks (as periods of time correspond to systems of rocks), which are referred to as belonging to the lower, middle, or upper part of the rock column, analogous to early, middle, or late Silurian time. The epochs and stages from youngest to oldest are: In the geological timescale, the Llandovery epoch (from 443. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... In the geological timescale, the Ludlow epoch (from 422. ... In the geological timescale, the Pridoli epoch (from 418. ... A division of geologic time less than a period and greater than an age. ... Faunal stages are a subdivision of geologic time used primarily by paleontologists who study fossils rather than by geologists who study rock formations. ... Index fossils (or zone fossils) are fossils used to define and identify geologic periods (or faunal stages). ... Graptolites (Graptolithina) are fossil colonial animals known chiefly from the Upper Cambrian through the Mississippian (Lower Carboniferous). ...

  • Přídolí Epoch - no stages defined (late Silurian)
  • Ludlow Epoch divided into
    • Ludfordian (late Ludlow - late Silurian)
    • Gorstian (early Ludlow - late Silurian)
  • Wenlock Epoch divided into
    • Homerian (late Wenlock - early or middle Silurian)
    • Sheinwoodian (early Wenlock - early or middle Silurian)
  • Llandovery Epoch divided into
    • Telychian (late Llandovery - early Silurian)
    • Aeronian (mid Llandovery - early Silurian)
    • Rhuddanian (early Llandovery - early Silurian)

In North America a different suite of regional stages is used: In the geological timescale, the Přídolí epoch (from 418. ... In geology, the Ludlovian or Ludlow Group is the name of the uppermost subdivision of the Silurian rocks in Great Britain. ... In the geologic timescale, the Ludfordian is the age of the Ludlow epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that is comprehended between 421. ... In the geologic timescale, the Gorstian is the age of the Ludlow epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that is comprehended between 422. ... In the geologic timescale, the Homerian is the second age of the Wenlock epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that is comprehended between 426. ... In the geologic timescale, the Sheinwoodian is the age of the Wenlock epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that is comprehended between 428. ... In the geologic timescale, the Telychian is the age of the Llandovery epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that is comprehended between 436. ... In the geologic timescale, the Aeronian is the age of the Llandovery epoch of the Silurian period of the Paleozoic era of the Fanerozoic eon that is comprehended between 439 million and 436 million years ago, approximatedly. ... In the geologic timescale, the Rhuddanian is the age of the Llandovery epoch of the Silurian period of the Paleozoic era of the Phanerozoic eon that is comprehended between 443. ...

  • Cayugan (Late Silurian - Ludlow)
  • Lockportian (Middle Silurian - Wenlock)
  • Tonawandan (Middle Silurian - Wenlock)
  • Ontarian (Early Silurian - Llandovery)
  • Alexandrian (Early Silurian - Llandovery)

Motto: Ut Incepit Fidelis Sic Permanet (Loyal she began, loyal she remains) Other Canadian provinces and territories Capital Toronto Largest city Toronto Lieutenant Governor James K. Bartleman Premier Dalton McGuinty (Liberal) Area 1,076,395 km² (4th)  - Land 917,741 km²  - Water 158,654 km² (14. ... Alexandrian is either: Alexandria Alexandrian text-type This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

Silurian paleogeography

During the Silurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late Ordovician glaciation. The melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. Other cratons and continent fragments drifted together near the equator, starting the formation of a second supercontinent known as Euramerica. For other uses of Gondwana and Gondwanaland, see Gondwana (disambiguation). ... This article is about the geological formation. ... There is a billion year gap in the geologic record where this 500 million year old dolomite unconformably overlays 1. ... World geologic provinces. ... Plates in the crust of the earth, according to the plate tectonics theory Continental drift refers to the movement of the Earths continents relative to each other. ... World map showing the equator in red In tourist areas, the equator is often marked on the sides of roads The equator marked as it crosses Ilhéu das Rolas, in São Tomé and Príncipe. ... In geology, a supercontinent is a land mass comprising more than one continental core, or craton. ... Euramerica (also known as Laurussia) was a minor supercontinent created in the Devonian by the collision of Laurentia and Baltica (Scandian Orogeny). ...



When the proto-Europe collided with North America, the collision folded coastal sediments that had been accumulating since the Cambrian off the east coast of North America and the west coast of Europe. This event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway. At the end of the Silurian, sea levels dropped again, leaving telltale basins of evaporites in a basin extending from Michigan to West Virginia, and the new mountain ranges were rapidly eroded. The Teays River, flowing into the shallow mid-continental sea, eroded Ordovician strata, leaving traces in the Silurian strata of northern Ohio and Indiana. The Caledonian orogeny is a hypothetical series of events in geologic history explaining a group of highland formations that are very similar in composition, stratigraphy and fossils: the mountains and hills of northern England, Wales, Scotland, Ireland and west Norway. ... A sample of evaporite material Evaporites (IPA: ) are water-soluble, mineral sediments that result from the evaporation of bodies of surficial water. ... The Teays River was an important pre-glacial river that drained much of the area now drained by the Ohio River, and more. ...


The vast ocean of Panthalassa covered most of the northern hemisphere. Other minor oceans include, Proto-Tethys, Paleo-Tethys, Rheic Ocean, a seaway of Iapetus Ocean (now in between Avalonia and Laurentia), and newly formed Ural Ocean. Panthalassa (Greek for all seas) was the vast ocean that surrounded the supercontinent Pangaea during the late Paleozoic era and the early Mesozoic era. ... Proto-Tethys Ocean was an ancient ocean that existed from the latest Ediacaran to the Carboniferous. ... The Paleo-Tethys Ocean was an ancient Paleozoic ocean. ... The Rheic Ocean was an ocean in the Paleozoic Era that existed between the continent of Baltica (northern Europe) and number of terranes broken up from Gondwana, including the future southern Europe. ... The Iapetus Ocean was an Ocean that existed in the Southern Hemisphere between Scotland, England and Scandinavia between 400 and 600 million years ago. ... Avalonia was a paleomicrocontinent also known as a Terrane. ... This article or section does not adequately cite its references or sources. ... Ural Ocean was a small, ancient ocean that was situated between Siberia and Baltica. ...


Climate

During this period, the Earth entered a long warm greenhouse phase, and warm shallow seas covered much of the equatorial land masses. Early in the Silurian, glaciers retreated back into the South Pole until they almost disappeared in the middle of Silurian. The period witnessed a relative stabilization of the Earth's general climate, ending the previous pattern of erratic climatic fluctuations. Layers of broken shells (called coquina) provide strong evidence of a climate dominated by violent storms generated then as now by warm sea surfaces. Later in the Silurian, the climate cooled slightly, but in the Silurian-Devonian boundary, the climate became warmer. This article is about Earth as a planet. ... The Royal Greenhouses of Laeken. ... This article is about the geological formation. ... For other uses, see South Pole (disambiguation). ... Categories: Stub ...


Silurian biota

Artist's impression of Silurian fishes.

Silurian high sea levels and warm shallow continental seas provided a hospitable environment for marine life of all kinds. Silurian beds are oil and gas producers in some areas. Extensive beds of Silurian hematite -- an iron ore -- in eastern North America were important to the early American colonial economy. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Pumpjack pumping an oil well near Lubbock, Texas Ignacy Łukasiewicz - creator of the process of refining of kerosene from crude oil. ... This article is about the fossil fuel. ... Hematite, also spelled haematite, is the mineral form of Iron(III) oxide, (Fe2O3), one of several iron oxides. ... For other uses, see Iron (disambiguation). ... For other uses, see Ore (disambiguation). ... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ...


Coral reefs made their first appearance during this time, built by extinct tabulate and rugose corals. The first bony fish, the Osteichthyes appeared, represented by the Acanthodians covered with bony scales; fishes reached considerable diversity and developed movable jaws, adapted from the supports of the front two or three gill arches. A diverse fauna of Eurypterus (Sea Scorpions) -- some of them several meters in length -- prowled the shallow Silurian seas of North America; many of their fossils have been found in New York State. leeches also made their appearance during the Silurian Period. Brachiopods, bryozoa, molluscs, and trilobites were abundant and diverse. Some of the biodiversity of a coral reef, in this case the Great Barrier Reef, Australia. ... Tabulate Corals lived entirely during the Paleozoic. ... Suborders Columnariina† Cystiphyllina† Streptelasmatina† The Rugosa, also called the Tetracoralla, are an extinct order of coral that were abundant in Middle Ordovician to Late Permian seas. ... Classes Actinopterygii Sarcopterygii Osteichthyes are a taxonomic superclass of fish, also called bony fish that includes the ray-finned fish (Actinopterygii) and lobe finned fish (Sarcopterygii). ... Orders Climatiiformes Ischnacanthiformes Acanthodiformes Acanthodii (sometimes called spiny sharks) is a class of extinct fishes, having features of both bony fish (Osteichthyes) and cartilaginous fish (Chondrichthyes). ... Human jaw front view Human jaw left view Human jaw top view The jaw is either of the two opposable structures forming, or near the entrance to, the mouth. ... In aquatic organisms, gills are a respiratory organ for the extraction of oxygen from water and for the excretion of carbon dioxide. ... Orders many, all extinct The eurypterids were the largest known arthropods that ever lived. ... For other uses, see Fossil (disambiguation). ... State nickname: Empire State Other U.S. States Capital Albany Largest city New York Governor George Pataki Official languages None Area 141,205 km² (27th)  - Land 122,409 km²  - Water 18,795 km² (13. ... Orders Arhynchobdellida Rhynchobdellida *There is some dispute as to whether Hirudinea should be a class itself, or a subclass of the Clitellata. ... Classes Lingulata Paterinata (extinct) Craniforma Chileata (extinct) Obolellata (extinct) Kutorginata (extinct) Strophomenata (extinct) Rhynchonellata Brachiopods (from Latin bracchium, arm + New Latin -poda, foot) make up one of the major animal phyla, Brachiopoda. ... Classes Stenolaemata Gymnolaemata Phylactolaemata Bryozoans are tiny colonial animals that generally build stony skeletons of calcium carbonate, superficially similar to coral. ... Classes Caudofoveata Aplacophora Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda † Rostroconchia † Helcionelloida † ?Bellerophontida The molluscs (British spelling) or mollusks (American spelling) are members of the very large and diverse phylum Mollusca. ... For the robot vacuum cleaner, see Electrolux Trilobite. ...


Myriapods became the first proper terrestrial animals. The terrestrial ecosystems included the first multicellular terrestrial animals that have been identified, relatives of modern spiders and millipedes whose fossils were discovered in the 1990s. Classes [1] Chilopoda Diplopoda Pauropoda Symphyla Myriapoda is a subphylum of arthropods containing millipedes, centipedes and others. ... A coral reef near the Hawaiian islands is an example of a complex marine ecosystem. ... Diversity 111 families, 40,000 species Suborders Mesothelae Mygalomorphae Araneomorphae  See table of families Wikispecies has information related to: Spiders Spiders are predatory invertebrate animals that have two body segments, eight legs, no chewing mouth parts and no wings. ... For other uses, see Millipede (disambiguation). ...


Silurian flora

The first fossil records of vascular plants, that is, land plants with tissues that carry food, appeared in the Silurian period. The earliest known representatives of this group are the Cooksonia (mostly from the northern hemisphere) and Baragwanathia (from Australia). A primitive Silurian land plant with xylem and phloem but no differentiation in root, stem or leaf, was much-branched Psilophyton, reproducing by spores and breathing through stomata on every surface, and probably photosynthesizing in every tissue exposed to light. Rhyniophyta and primitive lycopods were other land plants that first appear during this period. Divisions Non-seed-bearing plants †Rhyniophyta †Zosterophyllophyta Lycopodiophyta †Trimerophytophyta Pteridophyta Ophioglossophyta Superdivision Spermatophyta †Pteridospermatophyta Pinophyta Cycadophyta Ginkgophyta Gnetophyta Magnoliophyta The vascular plants, tracheophytes or higher plants are plants in the kingdom Plantae that have specialized tissues for conducting water, minerals, and photosynthetic products through the plant. ... Artists impression of Cooksonia Cooksonia are an extinct genus of primitive land plants. ... Baragwanathia longifolia is an ancient and extict species of vascular plant. ... In vascular plants, xylem is one of the two types of transport tissue in plants, phloem being the other one. ... In vascular plants, phloem is the living tissue that carries organic nutrients, particularly sucrose, a sugar, to all parts of the plant where needed. ... Psilophyta is a division of the Kingdom Plantae. ... This article or section is in need of attention from an expert on the subject. ... This is not about surgically created bowel openings; see stoma (medicine) In botany, a stoma (also stomate; plural stomata) is a tiny opening or pore, found mostly on the undersurface of a plant leaf, and used for gas exchange. ... The leaf is the primary site of photosynthesis in plants. ... Rhyniophyta were among the first modern-style land plants, which seem to have been fully vacular (they used tubes to carry nutrients through their stems), and may have been direct descendants of cooksonia, the very first land plants thought to start to develop a vascular system. ... Classes Lycopodiopsida - clubmosses Selaginellopsida - spikemosses Isoetopsida - quillworts The Division Lycopodiophyta (sometimes called Lycophyta) is a tracheophyte subdivision of the Kingdom Plantae. ...


End Silurian extinction

End Silurian extinction.

At the end of Silurian, a series of minor extinction events, including the Lau event, occurred. They were probably caused by climate change or impact events.[citation needed] Image File history File links Description Total Phanerozoic biodiversity during the same interval. ... Image File history File links Description Total Phanerozoic biodiversity during the same interval. ... An extinction event (also known as: mass extinction; extinction-level event, ELE) occurs when there is a sharp decrease in the number of species in a relatively short period of time. ... The Lau event was the last of three relatively minor mass extinctions during the Silurian period, and is marked by an excursion in geochemical isotopes and a change in depositional regime. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 450,000 years For current global climate change, see Global warming. ... Artists impression of a major impact event. ...


References

  • Emiliani, Cesare, 1993. Planet Earth : Cosmology, Geology and the Evolution of Life and Environment.
  • Mikulic, DG, DEG Briggs, and J Kluessendorf. 1985. A new exceptionally preserved biota from the Lower Silurian of Wisconsin, USA. Philosophical Transactions of the Royal Society of London, 311B:75-86.
  • Moore, RA, DEG Briggs, SJ Braddy, LI Anderson, DG Mikulic, and J Kluessendorf. 2005. A new synziphosurine (Chelicerata: Xiphosura) from the Late Llandovery (Silurian) Waukesha Lagerstatte, Wisconsin, USA. Journal of Paleontology:79(2), pp. 242-250.
  • Ogg, Jim; June, 2004, Overview of Global Boundary Stratotype Sections and Points (GSSP's) http://www.stratigraphy.org/gssp.htm Accessed April 30, 2006.

Cesare Emiliani in the early 1950s when he was doing his pioneering research at the University of Chicago (Photo from the Archives of the Rosenstiel School of Marine and Atmospheric Science, University of Miami) Cesare Emiliani (8 December 1922, Bologna, Italy - 20 July 1995, Palm Beach Gardens, Florida, USA) is... is the 120th day of the year (121st in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

External links

Wikimedia Commons has media related to:
Silurian
Silurian period
Llandovery Wenlock Ludlow Přídolí
Rhuddanian | Aeronian
Telychian
Sheinwoodian | Homerian Gorstian | Ludfordian
Paleozoic era
Cambrian Ordovician Silurian Devonian Carboniferous Permian

  Results from FactBites:
 
Silurian - LoveToKnow 1911 (1438 words)
The Silurian rocks may occur in close continuity with the upper Ordovician, as in S. Europe; or, as in the typical region, the Llandovery beds may rest unconformably upon older rocks; in N. America also there is a marked unconformity on this horizon.
In a general sense the Silurian period was one of comparative quiescence as regards crustal disturbances, and a relative sinking of the land was followed by a relative elevation affecting wide areas in the N. hemisphere.
Volcanic activity was quite subordinate in Silurian times; flows of diabase occurred at the commencement of the period in Bohemia, and evidence of minor basaltic flows and tuffs is found at Tortworth in Gloucestershire and at a few localities in N. America.
Palaeos Paleozoic : Silurian : The Silurian Period (1861 words)
A Silurian sea floor, showing numerous tabulate corals of the genus Favosites large Stromatoporoids, the "sunflower coral" (possibly a green alga) Ischadites, and rugose corals of the genera Entelophyllum, Kodonophyllum, Streptelasma and Craterophyllum.
However, evidence from the eurypterid fauna of the Upper Silurian Bertie Waterlime Formation, New York, suggests that two distinct transitional assemblages existed, perhaps caused by a difference in the environmental preferences of juvenile and adult eurypterids (‘ontogenetic segregation’) (Manning 1993).
The eurypterids from the Upper Silurian of the Welsh Borderland may represent a previously undescribed, ontogenetically mixed, eurypterid assemblage, influenced by a series of facies changes; this is supported by sedimentological evidence (Manning, 1993).
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