USGS Divisions of Geologic Time—Updated in 2018

Divisions of Geologic TimeMajor Chronostratigraphic and Geochronologic Units
by USGS/AASG, 2018

Excerpted from USGS link below: “Advances in stratigraphy and geochronology require that any time scale be periodically updated. Therefore, the Divisions of Geologic Time is dynamic and is modified as needed to include accepted changes of unit names and boundary age estimates. This fact sheet updates the Divisions of Geologic Time released in two previous USGS fact sheets (U.S. Geological Survey Geologic Names Committee, 2007, 2010).”

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