Geology and structural evolution of pre-Caledonian rocks and the ?Devonian Sutorfjella conglomerate, northern Prins Karls Forland (Svalbard)

On northern Prins Karls Forland, Early Vendian metasediments (Glenbegdalen and Taylorfjellet units) were thrust over conglomerates, quartz-carbonate schists, quartzites and phyllites of the Macnairrabbane unit. Remnants of microfossils in dolomite clasts of the conglomerates indicate an Early Paleozoic age of the Macnairrabbane unit. The Glenbegdalen, Taylorfjellet and Macnairrabbane units were affected by two ductile phases of isoclinal folding (D1, D2), followed by a third ductile to brittle stage (D3) of NE-vergent folding. This polyphase deformation post-dated the deposition of the Early Paleozoic Macnairrabbane unit, indicating a Caledonian age of D1 to D3. The Sutorfjella conglomerate on the west-coast of Prins Karls Forland contains clasts which are characterized by two stages of ductile folding and foliation (D1, D2), whereas the matrix is unaffected by any ductile deformation. The Sutorfjella conglomerate unconformably overlies the vertical short limb of a F3-fold. These observations suggest that the Sutorfjella conglomerate represents a post-Caledonian sediment which could be related to the ?Late Silurian to Early Devonian molasse basins in NW Spitsbergen. The occurrences of some reddish beds and red-weathered clasts indicate an ?Early Devonian age. The youngest convergent deformation (D4) is characterized by thrust-faulting and nappe-stacking in the basement rocks and by the formation of a F4-fold in the Sutorfjella conglomerate. Compared with the structures on Brøggerhalvøya, this deformation could be assigned to the formation of the Tertiary West Spitsbergen Fold-and-Thrust Belt.