During the Ordovician, most of the world's land was collected together in thesuper-continent Gondwana. Gondwana consisted of Southern Europe,Africa, South America, Antarctica, and Australia. Throughout the Ordovician,Gondwana moved towards the South Pole where it finally came to rest at theend of this period. In the Early Ordovician, North America roughly straddledthe equator and almost all of that continent lay underwater. However, by theMiddle Ordovician North America became land with a karst topography onexposed carbonate rocks that developed. Taconica, a tectonic highland,formed along the margin of eastern North America. Also at this time,Western and Central Europe were separated and located in the Southern Tropics;Europe shifted towards North America from higher to lower latitudes.
During the Middle Ordovician, uplifts took place in most of the areas thathad been under shallow shelf seas. These uplifts are seen as the precursor toglaciation. Also during the Middle Ordovician, latitudinal plate motions appearto have taken place, including the northward drift of the BaltoscandianPlate (northern Europe). Increased sea floor spreading and ridge activityaccompanied by volcanic activity occurred in the Llanvirnian. Ocean currentschanged as a result of lateral continental plate motions causing the opening ofthe Atlantic ocean. Sea levels underwent regression and transgression globally. Because of sea level transgression, flooding of the Gondwana craton occurredas well as regional drowning which caused carbonate sedimentation to stop.
During the Ashgillian (Late Ordovician), a major glaciation centered inAfrica occurred. Because of this global disturbance, oxygenation, ocean erosion,and a severe drop in sea level resulted. In addition, aggressive circulation,then shrinking, of tropical belts also resulted. This glaciation caused adramatic regression of ocean waters which drained nearly all craton platforms.More specifically, this glaciation contributed to ecological disruption andmass extinctions. Nearly all conodonts disappeared in the NorthAtlantic Realm while only certain lineages becameextinct in the Midcontinental Realm. Asaphoid larvae-bearing trilobites,echinoderms, brachiopods, bryozoans, graptolites, and chitinozoans alsobecame extinct. The Atlantic Ocean closed as Europe moved towards NorthAmerica. Climatic fluctuations were extreme as glaciation continued and becamemore extensive. Cold climates with floating marine ice developed asthe maximum glaciation was reached.
The Ordovician Period. The Ordovician Period lasted almost 45 million years, beginning 488.3 million years ago and ending 443.7 million years ago. During this period, the area north of the tropics was almost entirely ocean, and most of the world's land was collected into the southern supercontinent Gondwana.
- What does ordovician mean? Of, relating to, or being the period of geologic time from about 488 to 443 million years ago, the second period of the.
- A copy of Mac OS X 10.5 Leopard (or earlier): We can't tell you how to obtain this, but a simple Google search will. You will need an.ISO file that should be saved directly to your iPhone or iPad.
For additional maps of the Ordovician world, visit theOrdovicianpage at the Paleogeography Through Geologic Time site by Dr. Ron Blakey of Northern Arizona University.
Read about the Ordovician Mass Extinction at theHooper Virtual Paleontology Museum.
Find out more about the Ordovician paleontology and geology of North America at the Paleontology Portal.
Sources:Ordovician Mass Extinction Percent Of Life
C. Barnes & Z. Ji, 1993. A major conodont extinction event during the Early Ordovician within the Midcontinental realm. Paleogeography, Paleoclimatology, Paleoecology, pp. 37-47.
T. N. Koren, 1991. Evolutionary Crisis of the Ashgill Graptolites. Geological Survey of Canada, pp. 157-164
J. R. Laurie & B. D. Webby, 1992. Preliminary correlation of latest Cambrian toEarly Ordovician sea level events in Australia and Scandinavia. Global Perspectives on Ordovician Geology, pp. 381-394.
Ordovician Mac Os Download
Ordovician Mac Os Downloads
J. D. Marshall, P. J. Brenchley, P. Mason, G. A. Wolff, R. A. Astini, L. Hints,& T. Meidla, 1997. Global Carbon Isotopic Events Associated with Mass Extinction and Glaciation in the Late Ordovician. Paleogeography, Paleoclimatology, Paleoecology, pp. 195-210.
