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Era (geology)

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Title: Era (geology)  
Author: World Heritage Encyclopedia
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Subject: Cenozoic, Paleozoic, Ordovician, Cretaceous, Geology of the North Sea
Collection: Geochronology, Geologic Time Scale, Geological Eras, Units of Geologic Time by Rank
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Era (geology)

A geologic era is a subdivision of geologic time that divides an eon into smaller units of time. The Phanerozoic Eon is divided into three such time frames: the Paleozoic, Mesozoic, and Cenozoic represent the major stages in the macroscopic fossil record. These eras are separated by catastrophic extinction boundaries, the P-T boundary between the Paleozoic and the Mesozoic and the K-T boundary between the Mesozoic and the Cenozoic. There is evidence that catastrophic meteorite impacts played a role in demarcating the differences between the eras.

The Hadean, Archean and Proterozoic eons were as a whole formerly called the Precambrian. This covered the four billion years of Earth history prior to the appearance of hard-shelled animals. More recently, however, those eons have been subdivided into eras of their own.

Era Time frame (Ma = million years ago)
Cenozoic to present day
Mesozoic
Paleozoic
Neoproterozoic
Mesoproterozoic
Paleoproterozoic
Neoarchean
Mesoarchean
Paleoarchean
Eoarchean
Hadean Eon
not officially divided into eras
Formation of Earth to

See also


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