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An epoch is in geology a division of the geologic timescale. Epochs are subdivisions of periods and are themselves subdivided into ages.^[1]

All periods of the Phanerozoic have 2, 3 or 4 epochs. Earlier periods had (as of 2009) not yet been subdivided into epochs. The time span of an epoch can differ, but is usually between 50 and 5 million years. The youngest epochs of the geologic timescale are even shorter: the Pliocene and Pleistocene epochs lasted less than 3 million years, the Holocene epoch lasts only 10.000 years.

Rock layers deposited during an epoch are called a series. Series are subdivisions of the stratigraphic column just like epochs are subdivisions of the geologic timescale.

References

1. ^ Gradstein et al. (2004)

• Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press