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Topic: Early Ordovician

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Late Ordovician

Ordovician

Paleozoic

Bryozoa

Geologic timescale

	The Ordovician Period of the Paleozoic Era
		The boundary between the Cambrian and the Ordovician is marked by the appearance of planktic dictyonemid graptolites.
		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.
		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 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)

	Ordovician
		Early in the Ordovician period, the climate was tropical and mildly warm, with an atmosphere containing an excess of moisture.
		In the beginning of the Ordovician period bushy graptolites formed a foundation for the rapidly evolving planktonic graptolites.
		Kentucky Bluegrass Region is composed of limestones and shale from the Ordovician Period.
	www.denison.edu /biology/bio380-2001/Ordovician.html (2100 words)

	Ordovician (Site not responding. Last check: 2007-10-26)
		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 - Wikipedia, the free encyclopedia
		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 transgressions 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.
	en.wikipedia.org /wiki/Ordovician (1185 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)

	Palaeos Paleozoic: Ordovician: Early Ordovician
		From the point of view of a hypothetical Late Ordovician oberver, the Early Ordovician was the "good old days." Things were simpler then.
		The Early Ordovician also saw the evolution of two new high-level taxa of blastoids -- but the entire clade was extinct by the end of the Ordovician.
		Since no land plants had yet evolved, and Ordovician climates were well stratified from north to south, this was a broad, lifeless barrier to dispersal, not the east-west faunal highway it would become in the Devonian and Late Paleozoic.
	www.palaeos.com /Paleozoic/Ordovician/EarlyOrd.html (780 words)

	Chapter 11 (The Later Ordovician)
		Starfish were also important predators in the Ordovician seas and used the suckers on their tube feet to pull apart the shells of brachiopods and clams in order to devour the soft tissue inside.
		Early Paleozoic jawless fish are collectively termed ostracoderms which means "shell skin" and refers to the bony exterior that was a distinctive trait of many of these fishes, although some were unarmored.
		Following deposition of dolomite across vast areas of the continent during the Early Ordovician, the sea retreated and the interior of the continent was again exposed to weathering and erosion.
	www.uh.edu /~geos6g/1376/ordovician11.html (3113 words)

	ORDOVICIAN (Site not responding. Last check: 2007-10-26)
		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)

	Canning Basin, Western Australia
		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.
		Ordovician sea level changes can be traced in the Canning Basin strata with the appearance of condensed marine fossil sections.
	www.ucmp.berkeley.edu /ordovician/canning.html (1056 words)

	Department of Geology, University at Buffalo
		Early diverse radiolarian assemblages are reported from the Middle Cambrian of Australia, the late Cambrian to early Ordovician of the Cow Head Group of western Newfoundland and from Hunan, China.
		Early Ordovician radiolarians from western Newfoundland and Spitsbergen.
		Radiolarians from the Llandovery (early Silurian) of Solberga, Dalarna, Sweden.
	www.geology.buffalo.edu /contrib/research/malradio.htm (782 words)

	barnes-pubs.htm
		The Sr isotopic composition of Ordovician and silurian brachiopods and conodonts: relationships to geological events and implications for coeval seawater.
		Ferretti, A. and Barnes, C.R. Upper Ordovician conodonts from the Kalkbank Limestone of Thuringia, Germany.
		Barnes, C.R. and Bergstrom, S.M. Conodont biostratigraphy of the uppermost Ordovician and lowermost Silurian.
	web.uvic.ca /seos/people/barnes-pubs.htm (2713 words)

	tectonicandes
		An extensive Ordovician basin formed to the west of the Arequipa Antofalla block and was filled with turbidites and to a lesser degree with volcanic rocks from the FEE (Figures 9, 10).
		Early Cretaceous is marked by a new marine transgression in the Aconcagua Platform, a decrease of plutonism in the Coastal Cordillera and extensive volcanism associated with an aborted marginal basin (Aberg et al, 1984).
		The extensional regime that characterizes this segment during the Jurassic and Early Cretaceous is the result of an elevated thermal gradient that causes crustal spreading and as is responsible for the thick pile of volcanic rocks with burial metamorphism.
	www.geo.arizona.edu /geo5xx/geo527/Andes/tectonicandes.html (3389 words)

	Paleobiology 3
		The Cambrian is bracketed by large scale glaciation at the close of the Proterozoic and by a similar occurrence early in the Ordovician.
		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.emc.maricopa.edu /faculty/farabee/BIOBK/BioBookPaleo3.html (4490 words)

	The Early Ordovician in the Sistema de Famatina
		In this area, the early Ordovician strata are represented by very different rocks, which were considered as members of Volcancito Formation (lower and upper members of Turner 1960, 1964 and Filo Azul and Peña Negra members of Esteban, 1999).
		Ordovician, is the presence of a genuine biofacies of cyclopygid trilobites in the Bordo Atravesado
		Astini, R. A.; Benedetto, J.L. and Vaccari, N.E. The early Paleozoic evolution of the Argentine Precordillera as a Laurentian rifted, drifted and collided terrane.
	www.unt.edu.ar /fcsnat/INSUGEO/geologia_16/04-Esteban.htm (6040 words)

	Geol Evol Virginia-Cross Section H
		In the early Ordovician eastern North America lies below the equator in the southern trade wind belt, and prevailing winds easily blow volcanic ash from the terrane in our direction where it settles across the shallow carbonate seas, long before the collision.
		The HFRV fault is not new; it was active in the Grenville (Stage A), and is reactivated by the Taconic collision.
		In the Ordovician, as the terrane approaches, the bulge is the first thing to hit North America, and it slightly lifts the continent into an arch, moving like a wave inland.
	csmres.jmu.edu /geollab/vageol/vahist/H-MidO.html (2256 words)

	EARLY EVIDENCE FOR LAND INHABITATION
		Evidence for early land plants is first encountered in fluvial sediments (Massanutten Sandstone) of the Early Silurian (Llandoverian) of Virginia.
		Polsterlands are believed to exist in the Late Ordovician of Nova Scotia and Pennsylvania (which also include abundant burrows, but no root traces).
		Brakelands are found as early as Late Silurian and continue into the Carboniferous.
	www.colby.edu /~ragastal/Paleobotany/earlyevidence.htm (781 words)

	chap 8
		Cratonic Sequences of Paleozoic A. Sauk Sequence: Late proterozoic to Early Ordovician B. Tippecanoe Sequence: Early Ordovician to Early Devonian C. Kaskaskia Sequence: Early Devonian to End of Mississippian D. Absaroka Sequence: Pennsylvanian to Early Jurassic IX.
		African history: Mid to late Ordovician A. Mid-Ordovician: Africa "upside down" relative to orientation today; located near S pole, moving S B. Late Ordovician: S polar ice cap covers 1000s km2 (is now Sahara desert region) C. Evidence of glaciation 1.
		Early Paleozoic Climates A. Transgressions = mild climates, windswept low terrain's B. Regressions and orogenic episodes = harsher more diverse climates; winds diverted by mountains C. Earth rotation was faster (days shorter, tidal effects greater) D. No land plants 1.
	www.umt.edu /geosciences/faculty/stanley/g106/g106_ch8.htm (1092 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.
		Note the expansion of life on land in the carboniferous, including early reptiles and in particular, extensive land plants in swamps.
	earth.usc.edu /~stott/Catalina/Ordovician.html (926 words)

	Trilobite Page
		The Ibex Fauna, named for the epoch during which it flourished, is characterized by Early Ordovician dominance followed by severe diversity reductions in the later Ordovician (conforming to a null hypothesis of cohort decay).
		The Ordovician trilobites were more successful at exploiting new environments, notably reefs, but they too suffered a crisis, during the mass extinction at the end of the Ordovician.
		Whiterock Fauna families, and in particular Silurian Fauna groups, can generally be traced only to the Early Ordovician, and in many cases they are entirely "cryptogenetic." These clades certainly had Cambrian forebears, but the fact that they have avoided detection is a strong indication that novel morphologies were being developed very rapidly.
	www.peripatus.gen.nz /Taxa/Arthropoda/Trilobita/Trilobite.html (3066 words)

	Fossil Record of the Bryozoa (Site not responding. Last check: 2007-10-26)
		The oldest known fossil bryozoans, including representatives of both major marine groups, the Stenolaemata (tubula r bryozoans) and Gymnolaemata (boxlike bryozoans), appear in the Early Ordovician.
		The stenolaemate bryozoans quickly radiated in the early Paleozoic and are very characteristic fossils of Paleozoic rocks, sometimes making substantial contributions to the formation of reefs, calcareous shales, and limestones.
		Uncalcified gymnolaemates are known as fossils from the Late Ordovician on, almost exclusively as distinctive borings in carbonate substrates such as shells.
	www.ucmp.berkeley.edu /bryozoa/bryozoafr.html (336 words)

	Mineral & Petroleum Resources - Bedrock Mapping
		The Caledonia Zone is generally considered to represent a crustal fragment rifted from the margin of Gondwana during opening of the Early Paleozoic Iapetus Ocean.
		The St. Croix Zone is characterized by Late Cambrian to Early Ordovician volcanic rocks and Early to Middle Ordovician shales and wackes.
		The arc and back-arc terranes represented by the St. Croix, Miramichi, and Elmtree zones were accreted to the Gondwanan continental margin during contraction of the Iapetus Ocean in the Late Ordovician to Silurian.
	www.gnb.ca /0078/minerals/Geological_Zonation_NB-e.asp (354 words)

	ORDOVICIAN (Site not responding. Last check: 2007-10-26)
		Chapters on the Cambrian, Ordovician and Silurian for a forthcoming book revising the Geological Timescale (F. Gradstein editor, C.U.P.) have been submitted, jointly with Mike Melchin, John Shergold and Pete Sadler, and use the new CONOP-based timescale for the Ordovician and Silurian (Sadler and Cooper in prep.).
		Two papers dealing with Ordovician trilobites from the Condroz Ridge, Belgium, being studied from a palaeogeographic point of view are in preparation (one in collaboration with Bob Owens and Thomas Servais, and the other jointly with Jean-Louis Henry).
		The ichnologic record of the Ordovician radiation is the subject of a manuscript (coauthored with Mary Droser) to be published in the coming book of the IGCP 410 Project “The Great Ordovician Biodiversification Event” A review on the depositional evolution of the Famatina Basin is also in progress.
	seis.natsci.csulb.edu /ISOS/OrdovicianNews2002/14-CurrentReportsM.htm (5152 words)

	Newfoundland
		The Early Ordovician included the early evolutionary radiation of the Class Gastropoda, but few recent studies have been made of the Class from this interval.
		This basic research of identifying the taxa and accurately documenting their stratigraphic occurrence is important for studies of diversity patterns and the early evolutionary trends within the Gastropoda.
		Gastropods are relatively common and diverse in the Lower Ordovician of western Newfoundland, but relatively few studies have been made of them since the 19th century.
	www.sulross.edu /pages/3856.asp (270 words)

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