Cenozoic
| Cenozoic Era 65.5 - 0 million years ago |
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Events of the Cenozoic
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An approximate timescale of key Cenozoic events.
Axis scale: Ma before present. |
The Cenozoic Era (also Cænozoic or Cainozoic, pronounced /ˌsɛnəˈzoʊ.ɨk, ˌsiːnəˈzoʊ.ɨk/; meaning "new life", from Greek καινός kainos "new", and ζωή zoe "life") is the most recent of the three classic geological eras and covers the period from 65.5 million years ago to the present. It is marked by the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and the end of the Mesozoic Era. The Cenozoic era is ongoing.
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Subdivision
The Cenozoic is divided into two periods, the Tertiary (also sometimes divided into the Neogene and Paleogene periods) and the Quaternary.[4] The Quaternary was officially recognized by the International Commission on Stratigraphy in June 2009.[5]
Tectonics
Geologically, the Cenozoic is the era when the continents moved into their current positions. Australia-New Guinea, having split from Gondwana during the early Cretaceous, drifted north and, eventually, collided with South-east Asia; Antarctica moved into its current position over the South Pole; the Atlantic Ocean widened and, later in the era, South America became attached to North America.
India collided with Asia between 55 and 45 million years ago; Arabia collided with Eurasia, closing the Tethys ocean, around 35 million years ago.[6]
Climate
The Cenozoic Era has been a period of long-term cooling. After the tectonic creation of Drake Passage, when South America fully detached from Antarctica during the Oligocene, the climate cooled significantly due to the advent of the Antarctic Circumpolar Current which brought cool deep Antarctic water to the surface. The cooling trend continued in the Miocene, with relatively short warmer periods. When South America became attached to North America creating the Isthmus of Panama, the Arctic region cooled due to the strengthening of the Humboldt and Gulf Stream currents,[7] eventually leading to the glaciations of the Pleistocene ice age, the current interglacial of which is the Holocene epoch.
Life
The cenozoic Era is the age of new life. During the Cenozoic, mammals diverged from a few small, simple, generalized forms into a diverse collection of terrestrial, marine, and flying animals, giving this period its other name, the Age of Mammals, despite the fact that birds still outnumbered mammals two to one. The Cenozoic is just as much the age of savannas, the age of co-dependent flowering plants and insects, and the age of birds. Grass also played a very important role in this era, shaping the evolution of the birds and mammals that fed on it. One group that diversified significantly in the Cenozoic as well were the snakes. Evolving in the Cenozic, the variety of snakes increased tremendously, resulting in many colubrids, following the evolution of their current primary prey source, the rodents.
In the earlier part of the Cenozoic, the world was dominated by the gastornid birds, terrestrial crocodiles like Pristichampsus, and a handful of primitive large mammal groups like uintatheres, mesonychids, and pantodonts. But as the forests began to recede and the climate began to cool, other mammals took over. The cenozoic is full of mammals both strange and familiar, including chalicotheres, creodonts, whales, primates, entelodonts, saber-toothed cats, mastodons and mammoths, three-toed horses, giant rhinoceros like Indricotherium, and brontotheres.
See also
- Geologic Time Scale
- K-T Boundary
| 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 | |
References
- ↑ 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.
- ↑ 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. Bibcode: 2005GPC....47...51Z.
- ↑ 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.
- ↑ International Commission on Stratigraphy (August). "International Stratigraphic Chart". http://www.stratigraphy.org/upload/ISChart2009.pdf. Retrieved 6 January 2010.
- ↑ doi:10.1002/jqs.1338
This citation will be automatically completed in the next few minutes. You can jump the queue or expand by hand - ↑ doi:10.1016/j.palaeo.2008.04.021
This citation will be automatically completed in the next few minutes. You can jump the queue or expand by hand - ↑ http://www.whoi.edu/oceanus/viewArticle.do?id=2508
Bibliography
- British Caenozoic Fossils, 1975, The Natural History Museum, London.
- Geologic Time, by Henry Roberts.