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Paleogene period
65.5 - 23.03 million years ago
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Paleogene-EoceneGlobal.jpg
Mean atmospheric O2 content over period duration ca. 26 Vol %[1]
(130 % of modern level)
Mean atmospheric CO2 content over period duration ca. 500 ppm[2]
(2 times pre-industrial level)
Mean surface temperature over period duration ca. 18 °C [3]
(4 °C above modern level)
Events of the Cenozoic
view • discuss •  edit
-65 —
-60 —
-55 —
-50 —
-45 —
-40 —
-35 —
-30 —
-25 —
-20 —
-15 —
-10 —
-5 —
0 —
N. Amer. prairie expands[4]
First Antarctic permanent ice-sheets[5]
Holocene begins 11.5 ka ago
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An approximate timescale of key Cenozoic events.
Axis scale: Ma before present.

The Paleogene (alternatively Palæogene, informally Lower Tertiary) 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.[7] Lasting 42 million years, the Paleogene is most notable as being the time in which mammals evolved from relatively small, simple forms into a plethora of diverse animals in the wake of the Cretaceous–Tertiary extinction event 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.

Contents

Paleogene in geology

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General

Oil industry relevance

The Paleogene is notable in the context of offshore oil drilling, and especially in Gulf of Mexico oil exploration, where it is usually referred to as the "Lower Tertiary". These rock formations represent the current cutting edge of deep-water oil discovery.

Lower Tertiary rock formations encountered in the Gulf of Mexico oil industry tend to be comparatively high temperature and high pressure reservoirs, often with high sand content (70%+) or under very thick salt sediment layers.[8]

Lower Tertiary explorations to date include (partial list) :

Notes

  1. ^ Image:Sauerstoffgehalt-1000mj.svg
  2. ^ Image:Phanerozoic Carbon Dioxide.png
  3. ^ Image:All palaeotemps.png
  4. ^ Retallack, G.J. (1997). "Neogene Expansion of the North American Prairie". PALAIOS 12 (4): 380-390. http://links.jstor.org/sici?sici=0883-1351(199708)12%3A4%3C380%3ANEOTNA%3E2.0.CO%3B2-Q. Retrieved 2008-02-11.  
  5. ^ Zachos, J.C.; Kump, L.R. (2005). "Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene". Global and Planetary Change 47 (1): 51-66. doi:10.1016/j.gloplacha.2005.01.001. Bibcode2005GPC....47...51Z.  
  6. ^ Krijgsman, W.; Garcés, M.; Langereis, C.G.; Daams, R.; Van Dam, J.; Van Der Meulen, A.J.; Agustí, J.; Cabrera, L. (1996). "A new chronology for the middle to late Miocene continental record in Spain". Earth and Planetary Science Letters 142 (3-4): 367-380. doi:10.1016/0012-821X(96)00109-4.  
  7. ^ 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?"
  8. ^ "Lower Tertiary". Halliburton. http://www.halliburton.com/ps/default.aspx?navid=1375&pageid=3339. Retrieved 2009-09-05.  
Preceded by Proterozoic eon 542 Ma - Phanerozoic eon - Present
542 Ma - Paleozoic era - 251 Ma 251 Ma - Mesozoic era - 65 Ma 65 Ma - Cenozoic era - Present
Cambrian Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Paleogene Neogene Quaternary

Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

Contents

English

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Wikipedia

Adjective

Paleogene (comparative more Paleogene, superlative most Paleogene)

Positive
Paleogene

Comparative
more Paleogene

Superlative
most Paleogene

  1. (geology) Of a geologic period within the Cenozoic era; comprises the Paleocene, Eocene and Oligocene epochs from about 65 to 23 million years ago.

Proper noun

Singular
Paleogene

Plural
-

Paleogene

  1. (geology) The Paleogene period.

See also


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