Terrane analysis, regional nomenclature and crustal evolution in the Southwest Scandinavian Domain of the Fennoscandian Shield

Tectonostratigraphic terrane analysis of an orogenic belt involves the use of a well-defined nomenclature which is related to the internal structure and relative displacement of blocks in the orogenic "puzzle". The tectonostratigraphic terrane is the central concept in terrane analysis, and the term should be restricted to units fulfilling the definition, i.e. to fault-bounded crustal blocks which have distinct lithologic and stratigraphic successions and which have geologic histories different from neighbouring terranes. Application of terrane analysis to a complex, poly-orogenic region such as the Southwest Scandinavian Domain of the Fennoscandian Shield (SSD) must include information on the entire crustal evolution history of potential terranes, including petrological, geochemical and other non-geochronological information. At the present state of knowledge, no crustal block within the SSD fulfil the criteria as a Gothian or Sveconorwegian tectonostratigraphic terrane. Until basic evidence of terrane status is established for a given block of crust, the use of a descriptive regional nomenclature is therefore preferred. A revised, non-genetic nomenclature is proposed, which does not assign terrane status to any of its units, and which will hopefully help eliminating confusing differences in usage, and be helpful in future analysis of Gothian and Sveconorwegian tectonics and crustal evolution in the region, To reach a stage where terrane analysis of the Gothian and Sveconorwegian evolution of the SSD becomes meaningful, it is necessary to carry out both structural studies and isotopic dating of the ductile deformation zones which are potential terrane boundaries.