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Events of the Cenozoic
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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.
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The Cenozoic is divided into two periods, the Tertiary (also sometimes referred to in terms of a Neogene Period or the Paleogene Period) and the Quaternary .[4] The Quaternary was officially recognized by the International Commission on Stratigraphy in June 2009.[5]
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 .[6]
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.
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 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 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.
| 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 | |
CAINOZOIC (from the Gr. Katv6s, recent, cod life), also written Cenozoic (American), Kainozoisch, Cinozoisch (German), Cenozoaire (Renevier), in geology, the name given to the youngest of the three great eras of geological time, the other two being the Mesozoic and Palaeozoic eras. Some authors have employed the term "Neozoic" (Neozoisch) with the same significance, others have restricted its application to the Tertiary epoch (Neozoique, De Lapparent). The "Neogene" of Homes (1853) included the Miocene and Pliocene periods; Renevier subsequently modified its form to Neogenique. The remaining Tertiary periods were classed as Paleogaen by Naumaun in 1866. The word "Neocene" has been used in place of Neozoic, but its employment is open to objection.
Some confusion has been introduced by the use of the term Cainozoic to include, on the one hand, the Tertiary period alone, and on the other hand, to make it include both the Tertiary and the post-Tertiary or Quaternary epochs; and in order that it may bear a relationship to the concepts of time and faunal development similar to those indicated by the terms Mesozoic and Palaeozoic it is advisable to restrict its use to the latter alternative. Thus the Cainozoic era would embrace all the geological periods from Eocene to Recent. (See TERTIARY and PLEISTOCENE.) (J. A. H.)
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[[File:|thumb|250px|The K/T boundary. The intermediate claystone layer contains 1000 times more iridium than the upper and lower layers. It is the boundary between Cretaceous and Tertiary Periods. The rock is from Wyoming, USA.]]
The Cainozoic (Cenozoic) is the present geological era. The word is derived from Greek kainos = "new", and zoe = "life". The era covers the period from 65.5 million years ago to the present. It started after the Cretaceous–Tertiary extinction event, which saw the demise of the last non-avian dinosaurs and the end of the Mesozoic Era. The Cainozoic era is ongoing, and is divided into two periods, the Tertiary and the Quaternary, and they are divided into epochs.
During the Cainozoic the continents moved into their present positions. The climate started warm, but global cooling continued steadily, and finally ice ages occurred. On land, the Cainozoic is the era of mammals, and of birds and flowering plants. Grassland became a major habitat, and aquatic mammals took over the roles of predatory reptiles like the mosasaurs and plesiosaurs. As a result, the ecological landscape of the Cainozoic has become quite different from the Mesozoic.[1]
The Cainozoic is spilt down as follows:
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