单词 | ordovician |
释义 | Ordovicianadj.n. Geology. A. adj. Of, relating to, or designating the second period of the Palaeozoic era, which occurred between about 510 million and 439 million years ago, following the Cambrian and preceding the Silurian. Cf. Silurian adj. and n.1 2.The Ordovician period was marked by the diversification of many invertebrate groups, notably graptolites, and the appearance of the first vertebrates (jawless fish). ΘΚΠ the world > the earth > structure of the earth > age or period > [adjective] > primary or Palaeozoic > Ordovician Ordovician1879 Cincinnatian1899 Caradocian1910 the world > the earth > structure of the earth > age or period > stratigraphic units > [adjective] > primary or Palaeozoic > Ordovician Ordovician1879 1879 C. Lapworth in Geol. Mag. 2nd Decade 6 14 The whole of the great Bala district where Sedgwick first worked out the physical succession among the rocks of the intermediates or so-called Upper Cambrian or Lower Silurian system..lay within the territory of the Ordovices; a tribe as undaunted in its resistance to the Romans as the Silures... Here, then, we have the hint for the appropriate title for the central system of the Lower Palæozoics. It should be called the Ordovician System. 1888 Daily News 24 Sept. 6/2 Strata representing ordovician, silurian, and carboniferous times. 1915 Bot. Gaz. 59 420 The area is within the basin of the Trent River and comprises some 1,345,000 acres..with a very thin soil over the recently glaciated granitic rocks of Archaean and Ordovician age. 1955 Times 4 June 8/5 It is a site of great geological interest for its variety of Ordovician volcanic lavas, with intrusive igneous rocks interbedded with fossiliferous mudstones and slates. 1991 A. Milne Fate of Dinosaurs (BNC) 52 As time passed there was a possible lowering of local temperatures in the succeeding Ordovician period. B. n. With the. The Ordovician period; the system of rocks dating from this time. ΘΚΠ the world > the earth > structure of the earth > age or period > [noun] > primary or Palaeozoic > Ordovician Ordovician1884 1884 Amer. Naturalist 18 409 For the Upper Cambrian or Bala group holding the second fauna, wrongly claimed by some as a lower member of the Silurian, and by others called Cambro-Silurian, he prefers the term Ordovician, now accepted by many British and continental geologists. 1902 A. J. Jukes-Browne Student's Handbk. Stratigr. Geol. viii. 118 In Ayrshire..the Ordovician has the ordinary facies of a formation accumulated at no great distance from a continental coast-line. 1967 D. H. Rayner Stratigr. Brit. Isles iv. 80 In the British Isles the first fragmental remains of vertebrates are known from the Silurian beds, although bony plates have been found in the Ordovician of the United States. 2000 C. Tudge Variety of Life ii. xxiii. 561 The first land plants were presumably algae, resembling coleochactaleans, which ventured on to land in the late Ordovician, about 450 million years ago. This entry has been updated (OED Third Edition, September 2004; most recently modified version published online March 2022). < |
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