4.2.6 Stage (Etasje)
4.2.6.1 Stage is the formal chronostratigraphical unit ranking next below series. It is usually valid over a more limited area than a series, and has so far been found most useful for regional classification and correlation. The aim should be to define stages in such a way that they have a potential for use in worldwide correlation. The division of time corresponding to a stage is age (alder).
4.2.6.2 Substage (underetasje) -- A stage may be subdivided, completely or partially, into substages. The corresponding division of time is a subage (underalder).
4.2.6.3 Names of stages -- Like series, stages are given formal names which consist of a geographical name from a type area combined with the words "the ... Stage" (written in one word in Norwegian -- "....etasjen"). When misunderstanding cannot arise, the geographical name can be used alone. In British and American English the geographical name is used with the adjectival ending "-ian" or "-an". These endings are not to be used in texts written in Norwegian. Examples of stages are the Sheinwood Stage or simply Sheinwoodian (sheinwoodetasjen or sheinwood) and the Homerian (homeretasjen), which are European divisions of the Wenlock in the Silurian System. The traditional alphanumerical "stages" in the Cambro-Silurian succession of the Oslo Region are informal stratigraphical terms of mixed litho- and biostratigraphical character.