| Silurian period 443. 7 - 416 million years ago ↓
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Key events of the Silurian
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Key events of the Silurian period. The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The Devonian is a geologic period and system of the Paleozoic era spanning from to million years ago. The Lau event was the last of three relatively minor Mass extinctions during the Silurian period having a major effect on the Conodont fauna (but barely The Ireviken event was a minor extinction event at the Llandovery/Wenlock boundary (mid Silurian) The Paleozoic or Palaeozoic Era (from the Greek palaio (παλαιο "old" and zoe (ζωη "life" meaning "ancient life"
Axis scale: millions of years ago. |
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The Silurian is a geologic period and system that extends from the end of the Ordovician period, about 443. The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 7 ± 1. 5 Ma (million years ago), to the beginning of the Devonian period, about 416. Annum is one form of the Latin noun meaning Year, not a form normally used for derivatives in modern languages the accusative singular The Devonian is a geologic period and system of the Paleozoic era spanning from to million years ago. 0 ± 2. 8 Ma (ICS, 2004)[6]. The International Commission on Stratigraphy (ICS, sometimes referred to by the unofficial " International Stratigraphic Commission " is a daughter or major Subcommittee 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. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere The base of the Silurian is set at a major extinction event when 60% of marine species were wiped out. An extinction event (also known as mass extinction; extinction-level event, ELE is a sharp decrease in the number of Species in a relatively short period See Ordovician-Silurian extinction events.
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Historiography
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. Sir Roderick Impey Murchison 1st Baronet KCB FRS ( 19 February, 1792 &ndash 22 October, 1871) was an influential In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes Events and trends Electromagnetic induction discovered by Michael Faraday. He named the sequences for a Celtic tribe of Wales, the Silures, extending the convention his friend Adam Sedgwick had established for the Cambrian. Celts (ˈkɛlts or /ˈsɛlts/, see Names of the Celts The Silures were a powerful and warlike Tribe of ancient Britain, occupying approximately the counties of Monmouthshire, Breconshire and Adam Sedgwick ( 22 March 1785 &ndash 27 January 1873) was one of the founders of modern Geology. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with 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. Year 1835 ( MDCCCXXXV) was a Common year starting on Thursday (link will display the full calendar of the Gregorian Calendar (or a Common The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other 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 resolved the conflict by defining a new Ordovician system including the contended beds. Charles Lapworth ( September 20, 1842 &ndash 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. Joachim Barrande ( August 11, 1799 - October 5, 1883) was a French Geologist and Palaeontologist. He divided the Silurian rocks of Bohemia into eight stages. Bohemia (Čechy; Bohemia Czechy is a historical region in central Europe, occupying the western two-thirds of the traditional Czech Lands, currently the 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. Edward Forbes ( February 12, 1815 – November 18, 1854) was a British naturalist. The Devonian is a geologic period and system of the Paleozoic era spanning from to million years ago. 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.
Silurian subdivisions
The Silurian Period of time is usually broken into early (Llandovery and Wenlock) and late (Ludlow and Pridoli) subdivisions (epochs). The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other 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. Index fossils (also known as guide 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 Lower Carboniferous ( Mississippian 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:
- Pridoli Epoch - no stages defined (late Silurian)
- Ludlow Epoch divided into
- Ludfordian (Late Silurian: late Ludlow)
- Gorstian (Late Silurian: early Ludlow)
- Wenlock Epoch divided into
- Homerian (early or middle Silurian: late Wenlock)
- Sheinwoodian (early or middle Silurian: early Wenlock)
- Llandovery Epoch divided into
- Telychian (Early Silurian: late Llandovery)
- Aeronian (Early Silurian: mid Llandovery)
- Rhuddanian (Early Silurian: early Llandovery)
In North America a different suite of regional stages is used:
- Cayugan (Late Silurian - Ludlow)
- Lockportian (middle Silurian: late Wenlock)
- Tonawandan (middle Silurian: early Wenlock)
- Ontarian (Early Silurian: late Llandovery)
- Alexandrian (earliest Silurian: early Llandovery)
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. Gondwana (ɡɒnˈdwɑːnə originally Gondwanaland) was a southern Supercontinent that existed about 500 to 200 Ma ago The southern continents remained united during this period. 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. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. An unconformity is a buried Erosion surface separating two rock masses or strata of different ages indicating that Sediment deposition was not Other cratons and continent fragments drifted together near the equator, starting the formation of a second supercontinent known as Euramerica. A craton ( Greek kratos / κρἀτος ( neut. "strength" is an old and stable part of the Continental crust that has survived Continental drift is the movement of the Earth 's Continents relative to each other The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the In Geology, a supercontinent is a Landmass comprising more than one Continental core or Craton. Euramerica (also known as Laurussia or Old Red Continent) was a minor Supercontinent created in the Devonian as the result of a collision between
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. The Caledonian orogeny is a mountain building event recorded in the Mountains and Hills of northern Scotland, Ireland, England, 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. Evaporites (iˈvæpəraɪt are water-soluble Mineral sediments that result from the Evaporation of bodies of surficial Water. 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 Teays River (teɪz taze was an important preglacial 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. Panthalassa ( Greek, meaning 'all seas' also known as the Panthalassic Ocean, was the vast global Ocean that surrounded the Supercontinent Other minor oceans include two phases of the Tethys— the Proto-Tethys and Paleo-Tethys— the Rheic Ocean, a seaway of the Iapetus Ocean (now in between Avalonia and Laurentia), and the newly formed Ural Ocean. The Proto-Tethys Ocean was an ancient Ocean that existed from the latest Ediacaran to the Carboniferous (550-330 Ma) The Paleo-Tethys Ocean was an ancient Paleozoic Ocean. It was located between the Paleocontinent Gondwana and the so called Hunic terranes The Rheic Ocean was an Ocean in the Paleozoic Era that existed between to the north the Continent of Baltica (northern The Iapetus Ocean was an Ocean that existed in the Southern Hemisphere between Laurentia ( Scotland and North America) and Baltica Avalonia was an ancient Microcontinent or Terrane whose history formed much of the older rocks of Western Europe, Atlantic Canada and parts of the Laurentia (also known as the North American craton) like all Craton land was created as continents moved about the surface of the Earth 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. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 A greenhouse (also called a glasshouse or hothouse) is a building where plants are cultivated Early in the Silurian, glaciers retreated back into the South Pole until they almost disappeared in the middle of Silurian. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the southernmost point on the surface of the Earth. 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. For the variety of clam see Donax. Coquina ( Spanish, "cockle" koʊˈkiːnə is an incompletely consolidated Later in the Silurian, the climate cooled slightly, but in the Silurian-Devonian boundary, the climate became warmer.
Silurian aquatic biota
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. Petroleum ( L petroleum, from Greek πετρέλαιον, lit Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, Extensive beds of Silurian hematite -- an iron ore -- in eastern North America were important to the early American colonial economy. Hematite, also spelt hæmatite, is the Mineral form of Iron(III oxide (Fe2O3 one of several Iron oxides Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 An ore is a volume of rock containing components or Minerals in a mode of occurrence that renders it valuable for mining
Coral reefs made their first appearance during this time, built by extinct tabulate and rugose corals. Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water The tabulate corals, forming the order Tabulata, are an Extinct form of Coral. The Rugosa Rose is also sometimes just called "Rugosa" The Rugosa, also called the Tetracoralla, are an extinct order 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. Osteichthyes (ˌɒstiːˈɪkθiːz also called bony fish, are a taxonomic Class of Fish that includes the ray-finned fish ( Actinopterygii Acanthodii (sometimes called spiny sharks) is a class of extinct Fishes having features of both bony fish ( Osteichthyes) and cartilaginous fish ( The jaw is either of the two opposable structures forming or near the entrance to the Mouth. A gill is an anatomical structure found in many aquatic organisms A diverse fauna of Eurypterids (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. The eurypterids (sea scorpions include the largest known Arthropod that ever lived (with the possible exception of Arthropleuridae) FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. New York ( is a state in the Mid-Atlantic and Northeastern regions of the United States and is the nation's third most populous Leeches also made their appearance during the Silurian Period. Leeches are Annelids comprising the Subclass Hirudinea. There are freshwater terrestrial and marine leeches Brachiopods, bryozoa, molluscs, and trilobites were abundant and diverse. Brachiopods (from Latin brachium, arm + New Latin -poda, foot are a small phylum of Benthic Invertebrates Also Bryozoans are tiny colonial Animals that generally build stony Skeletons of Calcium carbonate, superficially similar to Coral (although some Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 Trilobites ("three-lobes" are extinct Arthropods that form the class Trilobita.
First terrestrial biota
The Silurian was the first period to see macrofossils of extensive terrestrial biota, in the form of moss forests along lakes and streams. Mosses are small soft Plants that are typically 1–10 cm (0
The first fossil records of vascular plants, that is, land plants with tissues that carry food, appeared in the second half of the Silurian period. Vascular plants (also known as tracheophytes or higher plants) are those Plants that have lignified tissues for conducting The earliest known representatives of this group are the Cooksonia (mostly from the northern hemisphere) and Baragwanathia (from Australia). Cooksonia is an extinct grouping of primitive Land plants The earliest Cooksonia date from the Late Wenlock (middle Silurian) about Baragwanathia is a genus of extinct plants of the division Lycopodiophyta of Late Silurian to Early Devonian age fossils of which have 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. In Vascular plants xylem is one of the two types of transport tissue Phloem being the other In Vascular plants phloem is the living tissue that carries organic Nutrients (known as photosynthate particularly Sucrose, a sugar to The Psylophyta form a Stem group to the Kingdom Plantae, comprising the land plants In Biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions In Botany, a stoma (also stomate; plural stomata) is a tiny opening or pore found mostly on the underside of a Plant Leaf Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Rhyniophyta and primitive lycopods were other land plants that first appear during this period. Rhyniophyta is a division of early Vascular plants including the class Rhyniopsida. The Division Lycopodiophyta (sometimes called Lycophyta) is a tracheophyte subdivision of the Kingdom Plantae It is the oldest extant (living
End Silurian extinction
At the end of Silurian, a series of minor extinction events, including the Lau event, occurred. An extinction event (also known as mass extinction; extinction-level event, ELE is a sharp decrease in the number of Species in a relatively short period The Lau event was the last of three relatively minor Mass extinctions during the Silurian period having a major effect on the Conodont fauna (but barely They were probably caused by climate change or impact events. Climate change is any long-term significant change in the “average weather” that a given region experiences See also Impact crater An impact event is the Collision of a large Meteoroid, Asteroid or Comet (generically
References
- Emiliani, Cesare, 1993. Cesare Emiliani ( 8 December 1922 - 20 July 1995) was an Italian-American scientist considered one of the greatest Geologists and 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. Events 313 - Roman emperor Licinius unifies the entire Eastern Roman Empire under his rule Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar.
External links
- Paleos: Silurian
- UCMP Berkeley: The Silurian
- Paleoportal: Silurian strata in U.S., state by state
- USGS:Silurian and Devonian Rocks (U.S.)
- International Commission on Stratigraphy (ICS). Geologic Time Scale 2004. Retrieved on September 19, 2005.
- Examples of Silurian Fossils
| Silurian period | |||
|---|---|---|---|
| Llandovery | Wenlock | Ludlow | Pridoli |
| Rhuddanian | Aeronian Telychian |
Sheinwoodian | Homerian | Gorstian | Ludfordian | |
| Paleozoic era | |||||
|---|---|---|---|---|---|
| Cambrian | Ordovician | Silurian | Devonian | Carboniferous | Permian |
Dictionary
Silurian
-adjective
- (geology) Of a geologic period within the Paleozoic era; comprises the Llandovery, Wenlock, Ludlow and Pridoli epochs from about 439 to 409 million years ago.
-proper noun
- (geology) The Silurian period.
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