488.3–443.7 million years ago
Mean atmospheric O2 content over period duration ca. 13.5 Vol %
(68 % of modern level)
Mean atmospheric CO2 content over period duration ca. 4200 ppm
(15 times pre-industrial level)
Mean surface temperature over period duration ca. 16 °C
(2 °C above modern level)
Sea level (above present day) 180m; rising to 220m in Caradoc and falling sharply to 140m in end-Ordovician glaciations
The Ordovician (pronounced /ɔrdəˈvɪʃən/) is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago (ICS, 2004, chart). It follows the Cambrian Period and is followed by the Silurian Period. The Ordovician, named after the Celtic 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. Lapworth, recognizing that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods, realized that they should be placed in a period of their own.
While recognition of the distinct Ordovician Period was slow in the United Kingdom, other areas of the world accepted it quickly. It received international sanction in 1906, when it was adopted as an official period of the Paleozoic Era by the International Geological Congress.
Life continued to flourish during the Ordovician as it did in the Cambrian, although the end of the period was marked by a significant mass extinction. Invertebrates, namely mollusks and arthropods, dominated the oceans. Fish, the world's first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life had yet to diversify on land.
The Ordovician Period started at a major extinction event called the Cambrian–Ordovician extinction events some time about 488.3 ± 1.7 Mya (million years ago), and lasted for about 44.6 million years. It ended with the Ordovician–Silurian extinction event, about 443.7 ± 1.5 Mya (ICS, 2004) that wiped out 60% of marine genera.
The dates given are recent radiometric dates and vary slightly from those used in other sources. This second period of the Paleozoic era created abundant fossils and in some regions, major petroleum and gas reservoirs.
The boundary chosen for the beginning both of the Ordovician Period and the Tremadocian stage is highly useful. Since it correlates well with the occurrence of widespread graptolite, conodont, and trilobite species, the base of the Tremadocian allows scientists not only to relate these species to each other, but to species that occur with them in other areas as well. This makes it easier to place many more species in time relative to the beginning of the Ordovician Period.
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ordovician — ORDOVICIÁN, Ă, ordovicieni, e, s.n., adj. 1. s.n. A doua perioadă a paleozoicului. 2. adj. Care se referă la ordovician (1) sau la formaţiile din această perioadă. [pr.: ci an] – Din fr. ordovicien. Trimis de ionel bufu, 09.05.2004. Sursa: DEX 98 … Dicționar Român
Ordovician — [ôr΄də vish′ən] adj. [< L Ordovices, ancient Celtic tribe in Wales] [sometimes o ] designating or of the second geologic period of the Paleozoic Era, characterized by the development of abundant marine invertebrates and the first vertebrates… … English World dictionary
Ordovician — Or do*vi cian, a. [From L. Ordovices, a Celtic people in Wales.] (Geol.) Of or pertaining to a division of the Silurian formation, corresponding in general to the Lower Silurian of most authors, exclusive of the Cambrian. n. The Ordovician… … The Collaborative International Dictionary of English
Ordovician — (adj.) geological period following the Cambrian and preceding the Silurian, 1879, coined by English geologist Charles Lapworth (1842 1920) from L. Ordovices, name of an ancient British tribe in North Wales. The period so called because rocks from … Etymology dictionary
Ordovician — ► ADJECTIVE Geology ▪ relating to the second period of the Palaeozoic era (between the Cambrian and Silurian periods), about 510 to 439 million years ago, a time when the first vertebrates appeared. ORIGIN from Ordovices, the Latin name of an… … English terms dictionary
Ordovician — adjective Etymology: Latin Ordovices, ancient people in northern Wales Date: 1879 of, relating to, or being the period between the Cambrian and the Silurian or the corresponding system of rocks see geologic time table • Ordovician noun … New Collegiate Dictionary
Ordovician — /awr deuh vish euhn/, Geol. adj. 1. noting or pertaining to a geologic period of the Paleozoic Era, from 500 million to 425 million years ago, notable for the advent of fish. See table at GEOLOGIC TIME. n. 2. the Ordovician Period or System.… … Universalium
Ordovician — 1. adjective Of a geologic period within the Paleozoic era; comprises lower, middle and upper epochs from about 488 to 443 million years ago. 2. noun The Ordovician period … Wiktionary
Ordovician — Or•do•vi•cian [[t]ˌɔr dəˈvɪʃ ən[/t]] adj. 1) gel noting or pertaining to a geologic period of the Paleozoic Era, from 500 million to 425 million years ago, notable for the advent of fish 2) gel the Ordovician Period or System • Etymology: 1879;… … From formal English to slang
Ordovician — ordovikas statusas T sritis ekologija ir aplinkotyra apibrėžtis Žemės geologinės istorijos paleozojaus eros antrasis periodas, buvęs po kambro, prieš silūrą; per tą laikotarpį susidariusių uolienų sistema. Prasidėjo Ordovician500 mln. m., truko… … Ekologijos terminų aiškinamasis žodynas