Nappe units along the Caledonian margin in central Scandinavia (Grong-Olden to Nasafjallet): definition, distinction criteria and tectonic evolution
Number of Authors: 32018 (English)In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 140, no 1, p. 66-89Article in journal (Refereed) Published
Abstract [en]
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 Jamtlandian 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 Akerberget Nappe represents the level between the Stalon Nappe and the Ammarnas Complex. Their hangingwall is the Sadenaive Nappe and the overlying Seve Nappe Complex. The Danabergen, Akerberget, Sadenaive 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 Akerberget Nappe. The Danabergen Nappe contains small garnet porphyroblasts. The Ammarnas Complex and the Sadenaive 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.
Place, publisher, year, edition, pages
2018. Vol. 140, no 1, p. 66-89
Keywords [en]
Scandinavian Caledonides, Danabergen Nappe, angstrom kerberget Nappe, Sadenaive Nappe, Slussfors Nappe, fabrics, metamorphism, microstructure, tectonic evolution
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-157765DOI: 10.1080/11035897.2018.1453864ISI: 000432160200007OAI: oai:DiVA.org:su-157765DiVA, id: diva2:1223364
2018-06-252018-06-252025-02-07Bibliographically approved