CoachA chronostratigraphic unit is the body of all the rocks formed during a given interval of geological time, and only during it; its boundaries are surfaces of equal age. The interval of time itself is a geochronologic unit. The ranks, from the smallest, are the stage (its time: an age), the series (an epoch), the system (a period), the erathem (an era) and the eonothem (an eon); each unit is made of several consecutive units of the rank below.
| chronostratigraphic unit (rock) | geochronologic unit (time) | example |
|---|---|---|
| eonothem | eon | Phanerozoic |
| erathem | era | Cenozoic |
| system | period | Paleogene |
| series | epoch | Paleocene |
| stage | age | Danian () |