Resources
Geologic Timescale

GSA Geologic Time Scale

Version 6.0
Updated October 2022

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The Geological Society of America Geologic Time Scale shows color-coded time divisions based on the rock record of Earth. Cenozoic, Mesozoic, Paleozoic, and Precambrian eons are subdivided into Periods, which are then subdivided into Epochs and Ages.

Earlier versions:

2018 (v. 5.0)

2012 (v. 4.0)

2009 (v. 3.0)

1999 (v. 2.0)

1983 (v. 1.0)

Read about the changes to v. 4.0 (2012):

Commentary

GSA Bulletin Article (Walker, et al. 2013)
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