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Topic: Ordovician Period

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	Ordovician - Wikipedia, the free encyclopedia
		The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era.
		The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879, to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in northern Wales into the Cambrian and Silurian periods respectively.
		The Ordovician came to a close in a series of extinction events that, taken together, comprise the second largest of the five major extinction events in Earth's history in terms of percentage of genera that went extinct.
	en.wikipedia.org /wiki/Ordovician (1015 words)

	Ordovician Period
		The Green Point GSSP for the base of the Ordovician System, as well as the base of the Lower Ordovician Series and the lowest stage, was approved by the International Commission on Stratigraphy in December 1999 and ratified by the IUGS in January 2000.
		The Ordovician was an age of evolutionary experimentation, in which new organisms evolve to replace those that died out at the end of the Cambrian.
		Gagnier, Pierre-Yves 1995: Ordovician Vertebrates and Agnathan Phylogeny.
	www.peripatus.gen.nz /paleontology/Ordovician.html (2874 words)

	The Ordovician Period of the Paleozoic Era (Site not responding. Last check: 2007-10-29)
		The Ordovician period began approximately 505 million years ago, with the end of the Cambrian, and ended around 438 million years ago, with the beginning of the Silurian.
		The boundary between the Cambrian and the Ordovician is marked by the appearance of planktic dictyonemid graptolites.
		Ordovician strata are characterized by numerous and diverse trilobites and conodonts (phosphatic fossils with a toothlike appearance) found in sequences of shale, limestone, dolostone, and sandstone.
	www.science501.com /PTOrdovician.html (1229 words)

	AllRefer.com - Ordovician period (Geology And Oceanography) - Encyclopedia
		Ordovician period[Orduvish´un] Pronunciation Key [from the Ordovices, ancient tribe of N Wales], second period of the Paleozoic era of geologic time (see Geologic Timescale, table) from 505 to 438 million years ago.
		It was similar to the preceding Cambrian period, with shallow seas spread for most of the time over the British Isles, Scandinavia, the Baltic region, the Mediterranean region, a large part of Siberia, and much of North America.
		Among the economic resources of the Ordovician strata are oil, natural gas, the lead and zinc of Wisconsin, Iowa, and Illinois, the "Portland cement rock" of Pennsylvania and New Jersey, Vermont marble, and the calcium phosphate of the Tennessee limestone.
	reference.allrefer.com /encyclopedia/O/Ordovici.html (533 words)

	Silurian - Wikipedia, the free encyclopedia
		The Silurian is a major division of the geologic timescale that extends from the end of the Ordovician period, about 443.7 Ma (million years ago), to the beginning of the Devonian period, about 416.0 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.
		During this period, the Earth entered a long warm greenhouse phase, and warm shallow seas covered much of the equatorial land masses.
	en.wikipedia.org /wiki/Silurian (930 words)

	Ordovician
		Early in the Ordovician period, the climate was tropical and mildly warm, with an atmosphere containing an excess of moisture.
		At the end of the Cambrian period, after the mass extinction of trilobites and nautiloids, there was a period of adaptive radiation of numerous faunal and phyla groups.
		Kentucky Bluegrass Region is composed of limestones and shale from the Ordovician Period.
	www.denison.edu /biology/bio380-2001/Ordovician.html (2100 words)

	Environment of the Ordovician Period
		During the Ordovician Period, the surface of the earth was dramatically different than it is today.
		Ordovician life was characterized by a dramatic increase of the shelly fauna, corals, and bryozoans.
		In order to understand how the environment of the Ordovician Period differed from today (the Quaternary Period), it is necessary to realize that continental drift has dramatically changed the face of the earth since the Ordovician Period.
	members.wri.com /jeffb/Fossils/drift.shtml (493 words)

	[No title]
		~Devonian The Devonian is the fourth period of the Paleozoic Era.
		~Ordovician The Ordovician* is the second period of the Paleozoic Era.
		~Silurian In the Silurian Period the rugose and tabulate corals and the bryozoans began to be the primary structural reef formers.
	www.usd.edu /exam/backup/exam3.txt (2824 words)

	Prehistoric Life - Ordovician Period in Victoria. (Site not responding. Last check: 2007-10-29)
		Most of the Ordovician rocks in Victoria were deposited in deep water, and most of the fossils they contain are forms that floated in the surface waters, such as graptolites.
		Rhabdinopora scitulum from the Lower Ordovician of the Romsey district, Victoria.
		Climacograptus bicornis, from the Upper Ordovician of the Wellington River, Victoria.
	www.museum.vic.gov.au /prehistoric/fossils/ordovician.html (157 words)

	The Ordovician Period: The Rise of The Cephalopods
		Ordovician rocks were first found in Wales, so its name comes from a tribe of people who once lived in the area where the rocks were found.
		During the Ordovician Period, Gondwana gradually moved toward the South Pole until it covered the pole at the end of the period.
		During the first parts of the Ordovician Period the climate was fairly warm.
	www.fossils-facts-and-finds.com /ordovician_period.html (595 words)

	Ordovician (Site not responding. Last check: 2007-10-29)
		Early in the Ordovician period, a huge mobile belt, the Appalachian craton, was encroached by the Sauk Sea.
		Carbonate deposition dominated the land on the craton as the Sauk Sea transgressed during this early Ordovician period.
		During the early Ordovician Period, gentle uplift and erosion removed a large amount of the Peerless Formation in this area.
	www.caveofthewinds.com /ordovician.html (214 words)

	Ordovician Period, Kentucky Geological Survey
		The oldest rocks exposed at the surface in Kentucky are Ordovician in age and are exposed in the Blue Grass Region.
		Ordovician fossil stromatoporoids can be seen along roadcuts in the Blue Grass Region, especially near Lexington, where the white mounds contrast against the gray limestones.
		A variety of stemmed crinoids are shown in the background of the Ordovician scene.
	www.uky.edu /KGS/fossils/ordov.htm (498 words)

	The Palaeozoic Era.
		It is the longest period of the Palaeozoic era.
		The Carboniferous period is the time during which most of the world's coal deposits were laid down, the coal being formed from compressed layers of rotting vegetation.
		It is the earliest period of the Palaeozoic era.
	www.bobainsworth.com /fossil/palaeozoic.htm (870 words)

	ordovician period - infos
		Ordovician period[Orduvish'un] Pronunciation Key [from the Ordovices, ancient tribe of N Wales...
		An intro to the Ordovician Period, includes a review of each of the geological sub-divisions and the various forms of life that lived during this time...
		The Ordovician: 490 to 443 Million Years Ago The Ordovician: 490 to 443 Million Years Ago This site describes the Ordovician period, which is best known for its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and...
	www.angelfire.com /alt2/ang7/18/ordovician-period.html (275 words)

	Canning Basin, Western Australia (Site not responding. Last check: 2007-10-29)
		The Ordovician period of the Paleozoic Era is an interval exhibiting increased animal diversity and an abundance of marine life.
		During the early Ordovician period, the Australian continent was located at the equator.
		Although the environment today is desert, evidence suggests that the basin was a deep water marine environment of high faunal diversity during the Ordovician period.
	www.ucmp.berkeley.edu /ordovician/canning.html (1056 words)

	ENGLISH NATURE - Special Sites
		At the beginning of the Ordovician, the part of the continental plate that is now England lay about 600 S and formed part of the supercontinent of Gondwana.
		Climate was cool at the beginning of the Ordovician and gradually became warmer as Avalonia drifted northwards.
		There is evidence of a widespread and major phase of glaciation at the end of the Ordovician which caused a major fall in sea-level and the extinction of marine organisms.
	www.english-nature.org.uk /Special/geological/sites/stratiperiod11.asp (282 words)

	BBC Evolution Weekend: Extinction Files - Mass Extinctions (Site not responding. Last check: 2007-10-29)
		the Ordovician was a period of relative stability in the Earth's history, which may have been an important factor in the substantial growth of biological diversity which took place.
		However, as the period drew to a close, 440 million years ago, there was a huge extinction event- with some animal groups losing more than half their species.
		there seem to have been two peak periods of extinction - one at the beginning of the glaciation, and another at the end of the extinction, between 500 thousand and 1 million years later, when sea levels rose rapidly.
	www.bbc.co.uk /education/darwin/exfiles/ordovician.htm (183 words)

	458 million years ago - Ordovician Period
		During the early part of the Ordovician, global sea level dropped, exposing many previously flooded areas to erosion.
		Repeated sequences of sea level rise with continental flooding, then sea level falls with continental erosion are the norm during most of the Paleozoic Era.
		As we saw in the Cambrian, thick deposits limestone formed from the remains of countless shelled marine animals that died and accumulated on the sea bottom.
	www2.nature.nps.gov /geology/usgsnps/pltec/sc458ma.html (402 words)

	The Ordovician Mass Extinction (Site not responding. Last check: 2007-10-29)
		The Ordovician period was an era of extensive diversification and expansion of numerous marine clades.
		Although organisms also present in the Cambrian were numerous in the Ordovician, a variety of new types including cephalopods, corals (including rugose and tabulate forms), bryozoans, crinoids, graptolites, gastropods, and bivalves flourished.
		However, as in the Cambrian, life in the Ordovician continued to be restricted to the seas.
	hannover.park.org /Canada/Museum/extinction/ordmass.html (174 words)

	Ordovician Period (Site not responding. Last check: 2007-10-29)
		The term Ordovician was first used in the 1870s to describe a sequence of rocks in Wales.
		The name Ordovician was derived from the name of an ancient British tribe.
		These Ordovician rocks were defined based on a particular type of fossil assemblage contained within them.
	www.watersheds.org /earth/gtime02b.htm (83 words)

	Ordovician HSU NHM
		The Ordovician lasted nearly 70 million years and saw the transition from very primitive to relatively modern life-forms in the seas.
		All of the common invertebrate fossil groups and a few vertebrates were present by the end of this period.
		Starfish (Auluroidea sp) and crinoids (Iocrinus subcrassus) are represented in the collection, as is an extinct form of echinoderm, the edrioasteroid (Isorophus cincinnatiensis).
	www.humboldt.edu /~natmus/lifeThroughTime/Ordovician.web/index.html (383 words)

	Ordovician period
		Especially noteworthy was the appearance of a few primitive, fishlike vertebrates (jawless fishes) and tiny land plants resembling liverworts.
		Table of Geological Periods - It is generally assumed that planets are formed by the accretion of gas and dust in a cosmic cloud,...
		Silurian period - Silurian period [from the Silures, ancient tribe of S Wales, where the period was first studied;...
	www.factmonster.com /ce6/sci/A0836806.html (498 words)

	Ordovician Period - Search Results - MSN Encarta (Site not responding. Last check: 2007-10-29)
		Ordovician Period - Search Results - MSN Encarta
		Ordovician Period, in geology, second division of the Palaeozoic Era of the geological timescale, spanning a period from 500 million years ago to...
		Marine life continued to proliferate in younger geological periods, and to leave a copious fossil record.
	uk.encarta.msn.com /Ordovician_Period.html (114 words)

	Ordovician
		Despite the tremendous expansion of life during the Ordovician Period there was a devastating mass extinction of organisms at the end of the Ordovician.
		Glacial deposits of late Ordovician age were discovered there in the 1970s in Saharan Desert region.
		Repeated glaciations and de-glaciations raised and lowered sea level causing expansion declines of swamps throughout the Carboniferous Period.
	earth.usc.edu /~stott/Catalina/Ordovician.html (926 words)

	Ordovician Period (Site not responding. Last check: 2007-10-29)
		In the Early Ordovician, this landmass was far south of the equator.
		At the beginning of Ordovician time, volcanoes were active in the Avalon Zone, spreading their debris over the land and shallow seas of Cape Breton Island and the Antigonish Highlands.
		At the close of the Ordovician Period, the White Rock Formation was deposited on top of the Halifax Formation.
	museum.gov.ns.ca /fossils/geol/ordo.htm (355 words)

	Nearctica - Paleontology - Periods - Ordovician to Devonian
		Learn about the Ordovician Period in the Utica, New York region, one of the more famous fossil localities in North America.
		A wonderful introduction to the Devonian with information on the plants and animals of the period, the stratigraphy and subdivisions within the period, the plate tectonics, and localities around the world where Devonian deposits are located.
		An introduction to the Devonian with a dictionary of terms and special emphasis on the fish of the period and their role in the rise of terrestrial animals.
	www.nearctica.com /paleo/periods/devon.htm (420 words)

	The Ordovician (Site not responding. Last check: 2007-10-29)
		The Ordovician period began approximately 510 million years ago, with the end of the Cambrian, and ended around 445 million years ago, with the beginning of the Silurian.
		More recently, there has been found evidence of tetrahedral spores that are similar to those of primitive land plants, suggesting that plants invaded the land at this time.
		The Ordovician Period is part of the Paleozoic Era.
	www.ucmp.berkeley.edu /ordovician/ordovician.html (318 words)

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