Geologic age

A geologic age is the lowest rank unit of time for the geologic time scale (Figure 1). Geologic ages are also referred to as "stages" (the chronostratigraphic name) or simply "ages". Ages are usually between two and ten millions years in length. Ages are subsections of longer epochs. Age names typically end in the suffix "-ian" or "-an". [1]

Figure 1. The ICS Chronostratigraphic Chart[2]

For Further Reading


  1. International Commission on Stratigraphy."Chapter 9. Chronostratigraphic units" Accessed Nov.12, 2018 [Online]. Available:
  2. International Commission on Stratigraphy."International Chronostratigraphic Chart v2018" Accessed Nov.8, 2018 [Online]. Available: