| Summary: | The Altevatn-Måskanvarri area of inner Troms provides a critical link between the more intensively studied areas in northernmost-Sweden and Finnmark to the north. It is composed of a stack of far-travelled Caledonian thrusts sheets overlying autochthonous sediments deposited on the Precambrian basement. The thrust sheets can be divided into those derived from the Baltoscandian margin and others representing outboard terranes. The lowermost thrust sheet in the area, the Målselv Nappe (Lower and Middle Allochthons) is composed of mylonitic metasediments and granitoids. These are overlain by schists and augen gneisses of the Seve Nappe Complex (Upper Allochthon), and a mafic dyke complex (Rohkunborri Nappe) which occupies the upper part of the Seve. There is a general thinning of the Seve Nappe Complex northwards and it wedges out in the northernmost part of the study area. The overlying Vaddas Nappe of the Køli Nappe Complex (Upper Allochthon) is dominated by pelitic and garphitic schists and subordinate amphibolites. Evidence of Neoproterozoic to Cambrian crustal extension, sedimentation in a rift-related basin and subsequent intrusion of mafic dyke swarms is preserved within the Rohkunborri Nappe. The latter is thought to represent the outermost rifted part of the Baltoscandian passive margin and miogeocline closes to the continent-ocean transition zone. 49117
|
|---|