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Topic: Ordovician

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	The Ordovician
		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.
		The Ordovician is best known for the presence of its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts (early vertebrates).
		From the Early to Middle Ordovician, the earth experienced a milder climate in which the weather was warm and the atmosphere contained a lot of moisture.
	www.ucmp.berkeley.edu /ordovician/ordovician.html (318 words)

	The Ordovician Period of the Paleozoic Era
		The boundary between the Cambrian and the Ordovician is marked by the appearance of planktic dictyonemid graptolites.
		Ordovician rocks are typified by considerable thickness of lime and other carbonate rocks that accumulated in shallow subtidal and intertidal environments.
		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)

	Ordovician System - LoveToKnow 1911
		The line of demarcation between the Ordovician and the Cambrian is not sharply defined, and beds on the Tremadoc horizon of the Cambrian are placed by many writers at the base of the Ordovician, with good palaeontological reasons.
		While the Ordovician rocks in Scania, the Baltic provinces and north-central Russia are undisturbed and level-bedded, those on the western side of the Scandinavian axis and in the Urals have suffered movement and are metamorphosed into schists, phyllites, quartzite, marble, andc.; and, especially in Scandinavia, have been extensively thrust.
		In the polar regions Ordovician rocks are represented by the Trenton limestone in Boothia and King William's Land; by limestones with Caryocystis granetum in east Greenland;.and in the Barrow Straits by beds with Asaphus and Maclurea.
	www.1911encyclopedia.org /Ordovician_System (2048 words)

	Graptolites (Graptolithina) + pterobranchs (Pterobranchia) = hemichordate class Graptolithoidea.
		Kozlowskitubus Mierzejewski, 1978 from the Ordovician and Silurian of Poland
		Dictyonema flabelliforne polonicum Tomczyk, 1962 from the Ordovician of Poland
		Micrograptus Eisenack, 1974 from the Ordovician erratic boulders of Baltoscandia
	www.graptolite.net (581 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)

	Stratigraphy of the Ordovician
		Graptolites, extinct planktonic organisms, are most often used to correlate Ordovician strata.
		The boundary between the Cambrian and the Ordovician is marked by the appearance of planktic dictyonemid graptolites.
		Rocks formed from sediments deposited on the margins of Ordovician shelves are commonly dark, organic-rich mudstones which bear the remains of graptolites and may have thin seams of iron sulfide.
	www.ucmp.berkeley.edu /ordovician/ordostrat.html (320 words)

	Palaeos Paleozoic : Ordovician : The Ordovician Period
		Ordovician trilobites were for the most part quite different from their Cambrian predecessors.
		During the Ordovician the Crinoids, rare during the Cambrian, suddenly appear and diversify in large numbers.
		Their cousins the conodont animals, worm-like or eel-like organisms known mostly from numerous isolated denticles (which were used to support some kind of grasping or breathing structure in the mouth or throat) represent a major component, quite possibly predators and certainly nektonic/pelagic, in the marine food-chain.
	www.palaeos.com /Paleozoic/Ordovician/Ordovician.htm (2035 words)

	Ordovician Period
		During the early Ordovician period the first vertebrate fish have been found.
		Visit our Online Yahoo Dinosaur Store to see our museum quality dinosaurs and prehistoric animals !
		Webmasters interested in Josef Moravec's paleo-art are welcome to create a link to Prehistoric World Images site.
	www.prehistory.com /timeline/ordovician.htm (152 words)

	Ordovician Period (Site not responding. Last check: )
		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)

	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.
		In the Middle Ordovician the sea spread over North America to a greater extent than in any other period and laid down the Trenton limestone, which in its eastern section is overlaid or intercalated with the Utica mud shale.
		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)

	The Geology of Ohio--The Ordovician
		During the Ordovician, Ohio was in southern tropical latitudes and dominated by warm, shallow seas.
		Ordovician rocks are particularly well exposed in the southern tier of Ohio counties where the surface is mantled only by thin glacial drift of Illinoian age.
		The base of the Ordovician System in Ohio is nowhere exposed in the state and was long interpreted to be at the Knox unconformity, the boundary between the Knox Dolomite and the overlying Wells Creek Formation.
	www.ohiodnr.com /geosurvey/oh_geol/97_fall/ordovici.htm (3721 words)

	Ordovician Summary
		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.
		Sea levels were high during the Ordovician; in fact during the Tremadocian, marine transgressionss worldwide were the greatest for which evidence is preserved in the rocks.
		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.
	www.bookrags.com /Ordovician (1860 words)

	ORDOVICIAN (Site not responding. Last check: )
		The most important Ordovician and mid-Palaeozoic successions with associated biotas were examined in a number of sections in the Gobi region of southern Mongolia (Mushgai and Shine Jinst areas), and in the Tsagaan del area, west of Bayankhongor (central Mongolia).
		The most diverse and well preserved Ordovician biotas (brachiopods, corals, bryozoans, conodonts and a few stromatoporoids) were found in the Tsagaan del hill area of central Mongolia, though stratigraphically the succession is limited, mainly Ashgillian in age.
		Three of the most-talented, younger scientists (all leading Ordovician specialists) from Argentina were also supported, with near 40% of the total, because the costs of travel from Argentina to attend meetings in California and Mongolia remains very expensive, and local Argentinian support for the younger scientists is almost non-existent.
	seis.natsci.csulb.edu /ISOS/OrdovicianNews2002/10-ProjectsI.htm (7594 words)

	Ordovician
		The Ordovician could appear to be an expansion of the Cambrian since the sea was still filled with invertebrates.
		Early in the Ordovician period, the climate was tropical and mildly warm, with an atmosphere containing an excess of moisture.
		Kentucky Bluegrass Region is composed of limestones and shale from the Ordovician Period.
	www.denison.edu /biology/bio380-2001/Ordovician.html (2100 words)

	Highbeam Encyclopedia - Search Results for Ordovician
		Ordovician The second of six periods that constitute the Palaeozoic Era, named after an ancient Celtic tribe, the Ordovices.
		The Cambrian, Ordovician, and Silurian Periods together form the Lower Palaeozoic Sub-Era; the Devonian, Carboniferous, and Permian the Upper Palaeozoic Sub-Era.
		Stratigraphy and geochemistry of Ordovician volcanic rocks of the Eel River area, west-central New Brunswick.
	www.encyclopedia.com /SearchResults.aspx?Q=Ordovician (794 words)

	Ordovician Pogonophora from Poland
		List of pogonophores known from the Ordovician of Poland:
		Mierzejewski, P. Ultrastructure, taxonomy and affinities of some Ordovician and Silurian organic microfossils.
		Toothed bristles of Pogonophora were not hitherto described in the fossil state and this may represent an example of
	www.countofcalmont.com /pogonophora.html (232 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)

	The Early Paleozoic
		The Ordovician is noteworthy because of the moves some green algae made toward the shoreline, and possibly onto land, becoming the first plants.
		Nemagraptus gracilis, a graptolite from the Athens Shale (Ordovician) of Alabama.
		The late Ordovician also saw the spread of major glaciers in Gondwana, and the environmental conseqwuences that accompany that spread: sea-level falling, changes in oceanic circulation, cooling of the climate and restriction of the tropical belts.
	www.cartage.org.lb /en/themes/Sciences/Paleontology/Paleozoology/EarlyPaleozoic/EarlyPaleozoic.htm (3988 words)

	Ordovician - Glasgledius (Site not responding. Last check: )
		The Ordovician Period is the second of the six (seven in North America) periods of the Paleozoic Era.
		The Ordovician follows the Cambrian Period and is followed by the Silurian Period.
		The Ordovician -- named for a Welsh tribe -- was defined by Charles Lapworth in 1879 to resolve a situation where followers of Adam Sedgwick and Murchison were placing the same rock beds in the Cambrian and Silurian Periods respectively.
	www.glasglow.com /E2/or/Ordovician.html (333 words)

	Ordovician - Search Results - MSN Encarta
		Ordovician Period, second division of the Paleozoic Era of the geologic time scale, spanning a period from about 488 million to 444 million years...
		Most of the early complex life forms of the Cambrian explosion lived in the sea.
		The most characteristic animals of the Ordovician period (500 million to 435 million years ago) were the graptolites, which were small, colonial...
	encarta.msn.com /Ordovician.html (130 words)

	Ordovician Fossils In The Toquima Range, Central Nevada
		The Vinini is an incredibly widespread unit throughout central Nevada, a dominantly siliceous assemblage of shales, siltstones, cherts and quartzites that bear sporadic occurrences of abundant graptolites.
		At Ikes Canyon the Middle Ordovician Antelope Valley Limestone is roughly 950 feet thick, yielding prodigious numbers of fossilized shelly creatures.
		The prominent outcrops of the Middle Ordovician Antelope Valley Limestone immediately north of the mouth of Ikes Canyon, Nye County, Nevada, yield common to abundant silicified invertebrate fossils, including brachiopods (arguably the most common fossil type encountered), echinoderm debris, trilobites, sponges, ostracodes, conodonts, bryozoans, pelecypods, cephalopods and gastropods.
	members.aol.com /Waucoba7/tr/toquima.html (2545 words)

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