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Template:Geological period 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.^[1] Lasting 42 million years, the Paleogene is most notable as being the time in which mammals evolved from relatively small, simple forms into a large group 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 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 Mya) was marked by one of the most significant periods of global change during the Cenozoic, 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.

Paleogene in geology

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.^[2]

Lower Tertiary explorations to date include (partial list) :

Notes

^ 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?"
^ "Lower Tertiary". Halliburton. Retrieved 2011-07-13.

External links

Paleogene Microfossils: 180+ images of Foraminifera

Preceded by the Proterozoic Eon	Phanerozoic Eon
	Paleozoic Era						Mesozoic Era			Cenozoic Era
	Cambrian	Ordovician	Silurian	Devonian	Carboniferous	Permian	Triassic	Jurassic	Cretaceous	Paleogene	Neogene	4ry

[1] 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?"

[2] "Lower Tertiary". Halliburton. Retrieved 2011-07-13.

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-The '''Paleogene''' (alternatively '''Palæogene''', informally '''Lower Tertiary''') is a [[geologic period|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]].<ref>Formerly the period covered by the Paleogene was called the first part of the [[Tertiary]], which usage is no longer official. [http://www.stratigraphy.org/bak/geowhen/TQ.html "Whatever happened to the Tertiary and Quaternary?"]</ref> Lasting 42 million years, the Paleogene is most notable as being the time in which [[mammal]]s [[evolution|evolved]] from relatively small, simple forms into a large group of diverse [[animal]]s 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 [[ocean|marine]], specialized terrestrial and even airborne environments.  [[Bird]]s 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 [[plate tectonics|continental motion]] took place.  [[Climate]]s cooled somewhat over the duration of the Paleogene and inland seas retreated from [[North America]] early in the period.
+The '''Paleogene''' (alternatively '''Palæogene''', informally '''Lower Tertiary''') is a [[geologic period|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]].<ref>Formerly the period covered by the Paleogene was called the first part of the [[Tertiary]], which usage is no longer official. [http://www.stratigraphy.org/bak/geowhen/TQ.html "Whatever happened to the Tertiary and Quaternary?"]</ref> Lasting 42 million years, the Paleogene is most notable as being the time in which [[mammal]]s [[evolution|evolved]] from relatively small, simple forms into a large group of diverse [[animal]]s 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 [[ocean|marine]], specialized terrestrial, and airborne environments.  [[Bird]]s 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 [[plate tectonics|continental motion]] took place.  [[Climate]]s 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]] [[Epoch (geology)|Epochs]]. The end of the Paleocene (55.5/54.8&nbsp;Mya) was marked by one of the most significant periods of global change during the Cenozoic, 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.