Age (geology)

Units in geochronology and stratigraphy[1]
Segments of rock (strata) in chronostratigraphyTime spans in geochronologyNotes to
geochronological units
EonothemEon4 total, half a billion years or more
ErathemEra10 defined, several hundred million years
SystemPeriod22 defined, tens to ~one hundred million years
SeriesEpoch34 defined, tens of millions of years
StageAge99 defined, millions of years
ChronozoneChronsubdivision of an age, not used by the ICS timescale

A geologic age is a subdivision of geologic time that divides an epoch into smaller parts. A succession of rock strata laid down in a single age on the geologic timescale is a stage.

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