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

AbstractThis 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 f...