2.4.9 Age
Knowledge about their age plays no direct role in definition and erection of formal geological units, other than time units. The age of a geological unit will nonetheless be of considerable interest and should be mentioned.
In the case of a metamorphic lithodeme, the metamorphic age should be kept distinct from the age of formation of the primary rock (protolith). The basis for age assignments is to be given. The relative age of movement and deformation forms the basis for distinguishing between complexes and systems in the structural and tectonostratigraphical categories (see Section 1.2).