Geological period

The Paleogene (alternatively Palaeogene) is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic era. [Formerly the period covered by the Paleogene was called the first part of the Tertiary, which usage is no longer official. [ "Whatever happened to the Tertiary and Quaternary?"] ] Lasting 42 million years, the Paleogene is most notable as being the time in which it is theorized that mammals evolved from relatively small, simple forms into a plethora of diverse animals in the wake of the mass extinction that ended the preceding Cretaceous Period. Some of these mammals would evolve into large forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial and even airborne environments. Birds also evolved considerably during this period changing into roughly-modern forms. Most other branches of life on earth remained relatively unchanged in comparison to birds and mammals during this period. Some continental motion took place. Climates cooled somewhat over the duration of the Paleogene and inland seas retreated from North America early in the Period.

This period consists of the Paleocene, Eocene, and Oligocene Epochs. The end of the Paleocene (55.5/54.8 Ma) was marked by one of the most significant periods of global change during the Cenozoic, a sudden global change, the Paleocene-Eocene Thermal Maximum, which upset oceanic and atmospheric circulation and led to the extinction of numerous deep-sea benthic foraminifera and on land, a major turnover in mammals.The Paleogene follows the Cretaceous Period and is followed by the Miocene Epoch of the Neogene Period. The terms 'Paleogene System' (formal) and 'lower Tertiary System' (informal) are applied to the rocks deposited during the 'Paleogene Period'. The somewhat confusing terminology seems to be due to attempts to deal with the comparatively fine subdivisions of time possible in the relatively recent geologic past, when more information is preserved. By dividing the Tertiary Period into two periods instead of five epochs, the periods are more closely comparable to the duration of 'periods' in the Mesozoic and Paleozoic Eras.


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  • Paleogene — Paléogène ère Cénozoïque Néogène Holocène Pléistocène Pliocène Miocène …   Wikipédia en Français

  • paléogène — [ paleɔʒɛn ] n. m. • 1902; de paléo et gène ♦ Sc. Première partie de l ère tertiaire (⇒ nummulitique). ● paléogène nom masculin Première période de l ère cénozoïque (40 millions d années, environ), subdivisée en paléocène, éocène et oligocène. ●… …   Encyclopédie Universelle

  • Paleogene — [pā′lē ə jēn΄] adj. [sometimes p ] designating or of the first geologic subdivision of the Tertiary Period, subdivided into the Paleocene, Eocene, and Oligocene epochs designating or of the first geologic subdivision of the Tertiary Period,… …   English World dictionary

  • Paléogène — ère Cénozoïque Néogène Holocène Pléistocène Pliocène Miocène …   Wikipédia en Français

  • Paleogene — adjective Etymology: German Paläogen, from palä pale + gen (from Greek genēs born) more at gen Date: 1882 of, relating to, or being the earlier part of the Tertiary including the Paleocene, Eocene, and Oligocene or the corresponding series of… …   New Collegiate Dictionary

  • Paleogene — /pay lee euh jeen /; esp. Brit. /pal ee /, Geol. adj. 1. noting or pertaining to the earlier part of the Cenozoic Era, in the system adopted by some geologists, occurring from 65 to 25 million years ago and including the Oligocene, Eocene, and… …   Universalium

  • Paleogene — 1. adjective Of a geologic period within the Cenozoic era; comprises the Paleocene, Eocene and Oligocene epochs from about 65 to 23 million years ago. 2. noun The Paleogene period …   Wiktionary

  • paleogene — paleogenas statusas T sritis ekologija ir aplinkotyra apibrėžtis Žemės geologinės istorijos kainozojaus eros pirmasis periodas, prasidėjęs prieš paleogene70 mln. m. po kreidos periodo ir pasibaigęs prieš neogeną (truko paleogene41 mln. m.); per… …   Ekologijos terminų aiškinamasis žodynas

  • Paléogène —    Le paléogène est une période géologique de l ère cénozoïque, elle s étend de 65,5 à 23,03 millions d années …   L'Abécédaire du Vin

  • paleogene — I. ˈpālēəˌjēn, ˈpal noun Usage: usually capitalized Etymology: German paläogen, from palä pale + gen (from root of Greek genesthai to be born) more at kin : the earlier part of the Tertiary including the Paleocene, Eoce …   Useful english dictionary

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