An Upper Proterozoic unconformity in northern Wedel Jarlsberg Land, southwest Spitsbergen: lithostratigraphy and tectonic implications

Abstract

Recent field studies of Upper Proterozoic rocks in northern Wedel Jarlsberg Land, southwest Spitsbergen, have shed new light on the pre-Caledonian evolution of the region. A regional angular unconformity divides the greenschist-facies metasedimentary rocks into two distinct tectono-siratigraphic sequenees. The sub-unconformity (Nordbukta) sequence, exposed in the southwestern part of the study area, consists mainly of quartzites, phyllites and dolomites, and may be correlative with Proterozoic rocks exposed east of Recherchebreen (Magnethøgda sequence) and south of Torellbreen (Dcilegga sequence). The Nordbukta sequence was affected by large-scale recumbent folding during late (?) Proterozoic tectonism. Strata above the unconformity (Dunderbukta-Recherchefjorden sequence) include conglomerates, dolomites, green and black phyllites, meta-basalts and Vendian (?) diamictites, with laterally complex depositional relationships. The continuation of this sequence south of Torellbreen is the Sofiebogen Group in the Hornsund area. The apparent continuity of both sub- and supra-unconformity Proterozoic rocks across Recherchebreen and Torellbreen is not compatible with the hypothesis that a major late Devonian strike-slip terranc boundary lies beneath these glaciers.