"Series are subdivisions of rock layers made based on the age of the rock and coresponding to the dating system unit called an epoch, both being formally defined international conventions of the geological timescale. A series is therefore a sequence of rock depositions defining a chronostratigraphic unit. Series are subdivisions of systems and are themselves divided into stages. Series is a term defining a unit of rocklayers formed in a certain interval in time; it is equivalent to the term geological epoch epoch criteria defining the interval of time itself, although the two words are sometimes confused in informal literature."@en . "Series are subdivisions of rock layers made based on the age of the rock and coresponding to the dating system unit called an epoch, both being formally defined international conventions of the geological timescale. A series is therefore a sequence of rock depositions defining a chronostratigraphic unit. Series are subdivisions of systems and are themselves divided into stages."@en . "Series (stratigraphy)"@en . . . . .