3.2.4 Supergroup (Overgruppe)
3.2.4.1 A supergroup is a stratified body of rock or superficial deposits consisting of two or more groups, or of groups and formations. In addition to lithostratigraphical units, a supergroup can also include volcanic suites, volcanic complexes or intrusive-volcanic complexes.
3.2.4.2 Supergroup is a formal lithostratigraphical unit ranking next above group.
3.2.4.3 A supergroup has a regional distribution, its thickness and extent being determined by the groups and formations that are incorporated. A supergroup need not consist of the same groups and formations throughout its area of distribution.
3.2.4.4 A supergroup is mappable at the surface and traceable in the subsurface with the help of geological and geophysical methods. It is a suitable lithostratigraphical unit for portrayal on small-scale regional maps.
3.2.4.5 A supergroup can consist of (a) an assemblage of superposed groups, (b) an assemblage of groups and formations where the formations do not form part of a group, or (c) an assemblage of groups, individual formations and volcanic suites, volcanic complexes or intrusive-volcanic complexes. The lithostratigraphical and lithodemic units in a supergroup are closely related as regards geological evolution. They are likely to be formed in basins associated in time and space through a common geotectonic framework (e.g. basins within the same segment or terrane of an orogen).
3.2.4.6 A supergroup is only named formally, this being done in accordance with the "general rules for naming and defining geological units" (Chap. 2). The proper name (Section 2.2.2) of a supergroup which is exposed at the surface should be the name of a relatively large district, e.g. a county or a region of the country, where the supergroup occurs in a substantial portion of the area and constitutes an important part of the bedrock. An alternative name to a geographical name can be used as a proper name for a supergroup on the continental shelf (Section 2.2.4). The proper name is placed between the words "the ... Supergroup", without any lithic designation.
3.2.4.7 A supergroup should only be erected after thorough evaluation of whether it will have any practical value. Considerable mapping and scientific documentation of the geological composition and evolutionary history of the succession in question is required before it can be formally defined as a supergroup (see Section 2.4).
3.2.4.8 Examples: Few supergroups have been defined in Norwegian territory. The Precambrian sequence of sedimentary and volcanic origin found in Telemark was originally called "Telemarksuiten" (the Telemark Suite) (Dons 1960). It should now be called "the Telemark Supergroup". In Finnmark, Pharaoh et al. (1983) defined the lithostratigraphical Raipas unit as "the Raipas Supergroup".
3.2.4.9 Key references: ISSC (1976), NACSN (1983).