Cenozoic

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Cenozoic era 65.5 - 0 million years ago

Events of the Cenozoic view • discuss • edit -65 — – -60 — – -55 — – -50 — – -45 — – -40 — – -35 — – -30 — – -25 — – -20 — – -15 — – -10 — – -5 — – 0 — Neogene Miocene       Cretaceous Paleocene Eocene Oligocene Pliocene Pleistocene       ← PETM ← N. Amer. prairie expands[1] ← First Antarctic glaciers[2] ← K-T mass extinction ← Messinian salinity crisis[3] ← Holocene begins 11.5 ka ago P a l æ o g e n e N e o g e n e  Cenozoic  Mesozoic An approximate timescale of key Cenozoic events. Axis scale: Ma before present.

The Cenozoic (also Cænozoic or Cainozoic) Era (pronounced /ˌsiːnɵˈzoʊɪk/, /ˌsɛnəˈzoʊɪk/) (meaning "new life" (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.

Contents 1 Subdivision 2 Tectonics 3 Climate 4 Life 5 See also 6 References 7 Bibliography

[edit] Subdivision

The Cenozoic Era is divided into two periods, the Paleogene and Neogene, and they are in turn divided into epochs. The Paleogene consists of the Paleocene, Eocene, and Oligocene epochs, and the Neogene consists of the Miocene, Pliocene, Pleistocene, and Holocene epochs, the last of which is ongoing. Historically, the Cenozoic has been divided into periods (or sub-eras) named the Tertiary (Paleocene through Pliocene) and Quaternary (Pleistocene and Holocene). It is known as the age of mammals.

[edit] Tectonics

Geologically, the Cenozoic is the era when the continents moved into their current positions.^{[clarification needed]} 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.^[4]

[edit] 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 [1], eventually leading to the glaciations of the Pleistocene ice age, the current interglacial of which is the Holocene period.

This section requires expansion.

[edit] 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, or the age of birds. Grass also played a very important role in this epoch, 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 snakes evolved into a huge amount of forms, especially colubrids, following the evolution of their current 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, oreodonts, whales, primates, entelodonts, saber-toothed cats, mastodons and mammoths, three-toed horses, giant rhinoceross like Indricotherium, and brontotheres.

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[edit] 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

[edit] References

[edit] Bibliography

• British Caenozoic Fossils, 1975, The Natural History Museum, London.
• Geologic Time, by Henry Roberts.