Series (stratigraphy)

Series are subdivisions of rock layers based on the age of the rock and formally defined by international conventions of the geological timescale. A series is therefore a sequence of strata defining a chronostratigraphic unit. Series are subdivisions of systems and are themselves divided into stages.

Series is a term defining a unit of rock layers formed during a certain interval of time (a chronostratigraphic unit); it is equivalent (but not synonymous) to the term geological epoch (see epoch criteria) which defines the interval of time itself, although the two words are sometimes confused in informal literature.