Cenozoic

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The Cenozoic Era (also Cænozoic or Cainozoic, pronounced /ˌsɛnəˈzoʊ.ɨk/ or /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 mya 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

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 mya; 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.

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