Tectonostratigraphy and structure of the Staloluokta area, Padjelanta, southern Norrbotten Caledonides, Sweden

Abstract

A new window (the Staloluokta Window) has been recognized, in the area to the southeast of Lake Virihaure, in the Padjelanta National Park, southern Norrbotten Caledonides, Sweden. The window exposes rocks of the Middle Allochthon below the Seve-Köli Nappe Complex of the Upper Allochthon. An easterly-overturned, complex antiform controls the form of the window and folds all the tectonic contacts in the area. A granitoid-bearing conglomerate (Virihaure Conglomerate) and a garnetiferous pelitic phyllite, belonging to the Middle Allochthon comprise the core of the window. These units are overthrust by anorthosite, quartzite, garnet-amphibolite, graphitic dolomite and eclogite-bearing calcareous schist of the Seve Nappes and metasediments and metavolcanites of the Lower Köli Nappes, all belonging to the Upper Allochthon. Rock units of the Upper Allochthon show evidence of extreme attenuation both on a regional scale in the Sarek-Padjelanta area and on a local scale within the Staloluokta area. The 3 km thick Seve packet in the southern part of the Sarek mountains is thinned down to 400 m in the eastern part of the Staloluokta area (86% thinning) and to only a few metres in the western part (99% thinning). Although the Seve Nappes in the Staloluokta area are extremely attenuated, certain key levels from each of the Seve mega-lenses in southern Norrbotten (Vaimok, Sarek and Tsäkkok Lenses) as well as the basal anorthosite unit are preserved at least locally; thus the internal Seve tectonostratigraphy is recognizable from the thrust front, at least 70 km westwards towards the hinterland.

Key Words:

• Tectonostratigraphy
• window
• antiform
• tectonic thinning
• eclogite
• conglomerate
• Middle Allochthon
• Upper Allochthon
• Seve Nappes
• Lower Köli Nappes
• Staloluokta area
• southern Norrbotten Caledonides
• Sweden