4.2.5 Series (Serie)
4.2.5.1 Series is the formal chronostratigraphical unit ranking next below the system. Series always form the major divisions of a system. A series is the most important chronostratigraphical correlation unit within a geological province, between provinces and between continents. Series are being defined and used to an increasing extent for worldwide correlations, but well-defined provincial series can still be used. The division of time corresponding to a series is an epoch (epoke).
4.2.5.2 Names of series -- A series is given a formal name which may be a geographical name from the type area, combined with the words "the ... Series", written in separate words in English but in one word ("....serien") in Norwegian. When misunderstanding cannot arise, the geographical name can be used alone. The Silurian System, for example, is divided into the following series, the Llandovery (llandovery), Wenlock (wenlock), Ludlow (ludlow) and Pridoli (pridoli) Series. Formal names of series may also consist of the system name preceded by Lower (undre), Middle (midtre), and Upper (øvre).
In British English it has now become standard to use geographical names for series without the endings "-ian" or "-an" (Holland et al. 1978). In American English, however, these adjectival endings are also recommended to be used in series names (NACSN 1983).
4.2.5.3 Misuse and informal use of the term "Series" -- The term "Series" has previously been employed formally as a lithostratigraphical designation (e.g. "Ringeriksserien" -- the Ringerike Series), as a designation for groups of magmatic rocks, or with an approximate biostratigraphical meaning (e.g. "Pentamerusserien" -- the Pentamerus Series). "Series" must not be used in such connections. Such terms must be changed to a suitable lithostratigraphical, lithodemic or biostratigraphical term carrying formal rank, or be abandoned.
"Series" can only be used formally in a chronostratigraphical sense. It may be used for clearly informal designations in other categories of geological units, except biostratigraphical units and those defined on the basis of time or age (e.g. nappe series, ice-marginal series, schist series).