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TERTIARY

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Originally appearing in Volume V26, Page 661 of the 1911 Encyclopedia Britannica.
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TERTIARY , in See also:

geology, the See also:time-See also:division which includes the See also:Eocene, Oligocene, See also:Miocene and See also:Pliocene periods, in other words, it is the earlier portion of the See also:Cainozoic era. By some authorities the See also:term Tertiary is made to embrace in addition to the foregoing periods those of the See also:Quaternary (See also:Pleistocene and See also:Holocene), i.e. " Tertiary " is made the See also:equivalent of Cainozoic. On logical grounds there is much in favour of this See also:interpretation; but having in view the See also:state of See also:geological literature, it is certainly better to restrict the use of the term in the manner indicated above. Tertiary rocks were among the latest to receive the careful See also:attention of geologists, and the name was introduced by G. See also:Cuvier and H. See also:Brongniart in 18io (Essai sur la geographic mineralogique See also:des environs de See also:Paris, 18ro-11, 1st ed.). See also:Deshayes (183o) worked out the percentages of See also:recent fossils found at several horizons in those strata, and upon this See also:Sir C. See also:Lyell (1852) founded the See also:main periods, viz. the Eocene with 31 per cent. of recent forms, Miocene 17 per cent., Pliocene 35 to 50 per cent. Subsequent investigations naturally modified the numerical values upon which this nomenclature was based, but without altering the See also:order of the periods. Later, E. See also:Beyrich introduced the Oligocene See also:period, and some geologists recognize a Palaeocene or See also:early Eocene period.

See also:

European geologists very generally use the grouping adopted by R. Horns : Younger Tertiary = Neogene (Miocene, Pliocene). Older Tertiary = Palaeogene (Palaeocene, Eocene, Oligocene). The See also:great number and variety of mammalian remains has made it possible for the Tertiary rocks to be classified by their means: see A. Gaundry, See also:Les enchainements du monde See also:animal—mammiftres Tertiaires (1878) ; W. B. See also:Dawkins, Q. J. Geol. See also:Soc. Lond. (188o) ; Forsyth See also:Major, Geol.

Mag. (See also:

London, 1899); and H. F. See also:Osborn, J. L. \Vortman, G. F. See also:Matthew, for western See also:North See also:America, See also:Bull. Am. See also:Mus. Nat. Wish, xii.

(1899). During the Tertiary era the See also:

geographical configuration of the globe was steadily approaching that of the See also:present See also:day; but in the earlier See also:part of the time there still existed the great See also:equatorial ocean " Tethys," and there is See also:evidence that See also:East See also:India and See also:Africa, See also:Australia and See also:Asia, north See also:Europe and North America were probably severally See also:united by See also:land connexions. As the period advanced, along the very See also:line that had been occupied by the nummulitic See also:sea (Tethys) the crust began to be folded up, giving rise to the See also:Alps, Carpathians, See also:Caucasus, Himalayas and other mountains, some of the early Tertiary marine formations being now found raised more than 16,000 ft. above the present level of the sea. Associated with these crustal movements were enormous outpourings of volcanic materials. The faunal aspect of the Tertiary periods differs strikingly from that of preceding Secondary or Mesozoic; in See also:place of the great saurian See also:reptiles we find the rapid development and finally the maximum expansion of mammals. See also:Snakes and true birds advanced rapidly towards their See also:modern position. In the seas, bony See also:fish and crab-like decapods increased in See also:numbers and variety, while pelecypods and gasteropods took the prominent place previously occupied by See also:ammonites and belemnites, and, leaving behind such forms as Rudistes, Inoceramus, &c., they gradually See also:developed in the direction of the modern regional See also:groups. In the plant See also:world, the dicotyledonous See also:angiosperms gradually assumed the leading role which they occupy to-day. The See also:climate in See also:northern latitudes seems to have passed from temperate to sub-tropical, with See also:minor fluctuations, until at the See also:close a rapid lowering of temperature ushered in the glacial period. (J. A.

End of Article: TERTIARY

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TERTULLIAN (c. 155-c. 222)

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