The Neoproterozoic Visingsö Group of southern Sweden : lithology, sequence stratigraphy and provenance of the Middle Formation

Sammanfattning: The depositional setting of the Neoproterozoic Visingsö Group has long been a subject of discussion. This study aims to provide additional insights into the lithological composition and provenance of the sediments and to provide a sequence stratigraphic framework in order to define the depositional setting. It focuses on rocks belonging to the Middle Formation of the Visingsö Group located at the Näs locality, Visingsö, Sweden. The meth-ods employed included descriptions of lithology, stratigraphic variations and identification of sedimentary patterns through detailed facies logs. Furthermore LA-ICP-MS analyses of U/Pb ages on detrital zircons were performed to determine their provenance. The sediments are characterized by an immature composition, short transport distance and wave-dominated deposition. The sedimentary cycles are composed of coarsening-upwards intervals terminated by short transgressive episodes. Identified detrital ages of zircons are largely composed of ages that can be found in the region. The sequence stratigraphic framework is in accord with existing rift-basin models and showed that dep-osition was controlled by tectonic activity that created the space necessary for the deposition of sediments. This newly created space was filled in large parts by locally derived material with a smaller, more far-travelled, compo-nent.