Nappe units along the Caledonian margin in central Scandinavia (Grong–Olden to Nasafjället): definition, distinction criteria and tectonic evolution. (2nd January 2018)

• Record Type: Journal Article
• Authors: Greiling, Reinhard O.; Kathol, Benno; Kumpulainen, Risto A.
• Is Part Of: GFF. Volume 140:Number 1(2018)
• Page Start: 66
• Page End: 89
• Publication Date: 2018-01-02
• Subjects: Scandinavian Caledonides -- Danabergen Nappe -- Åkerberget Nappe -- Sadenåive Nappe -- Slussfors Nappe -- fabrics -- metamorphism -- microstructure -- tectonic evolution; Geology -- Scandinavia -- Periodicals; Geology -- Periodicals; 554.8
• DOI: 10.1080/11035897.2018.1453864
• Languages: English
• ISSNs: 1103-5897

Abstract

Abstract: This study reviews lithological and stratigraphic data, new geological mapping results and microscopic work from the lower and middle Caledonian nappes in central Scandinavia, and suggests a model of their tectonic evolution. The Jämtlandian and Blaik Nappes represent the lower nappes, and are overlain, successively, by the Stalon, Danabergen and Slussfors Nappes. The latter occupies the level immediately beneath the Seve Nappe Complex. Farther north, around Lake Gautojaure, the Åkerberget Nappe represents the level between the Stalon Nappe and the Ammarnäs Complex. Their hangingwall is the Sadenåive Nappe and the overlying Seve Nappe Complex. The Danabergen, Åkerberget, Sadenåive and Slussfors Nappes are formally defined here. In the Blaik Nappe, brittle deformation gave rise to composite thrust systems. The overlying nappes show a more ductile deformation. The arkose sequence of the Stalon Nappe shows fine-grained recrystallization of muscovite. In contrast, finely recrystallized mica minerals form a phyllitic foliation in the Åkerberget Nappe. The Danabergen Nappe contains small garnet porphyroblasts. The Ammarnäs Complex and the Sadenåive Nappes show garnet with a straight internal foliation ( S i ), while the external foliation is refolded. This fabric suggests a time interval after early foliation development, in which garnet grew but no deformation occurred, and subsequent deformation. This may represent an episode of arrest of deformational activity and thrust movement. Spiral-shaped S i in garnets of the Slussfors Nappe indicate a contrasting and more complex metamorphic and structural evolution, perhaps similar to that of the Seve Nappe Complex, with a well-known, polyphase tectonic evolution.