Onshore-offshore correlation in the Andfjorden area and the structural controls on the opening and evolution of the Mesozoic sedimentary basins on Andøya and Andfjorden, northern Norway

Abstract

Onshore-offshore correlation of brittle faults has been undertaken in the Andfjorden area defining the boundary between the passive Lofoten-Vesterålen margin and the transform SW Barents Sea margin. This study has focused its efforts on onshore mapping of faults and fractures, the mapping of offshore faults and associated basin-ridge systems from seismic interpretation and the link between fault complexes onshore and offshore by integrating bathymetry data, DEM and magnetic anomaly data. This study demonstrates that both the onshore and offshore part of the Andfjorden area are characterized by NNE-SSW to NE-SW and E-W to ENE-WSW striking faults/fractures, creating a rhombic regional fault/fracture pattern. Kinematic indicators such as fibrous slickensides and geometric relationships (e.g. rotation of older fractures into younger), indicate dominantly normal-slip with components of dextral/sinistral strike-slip movements on all fracture sets. Pre-existing fabrics in the Precambrian basement rocks such as gneiss foliation and lithological boundaries appear, at least locally, to have influenced brittle faulting. Based on the onshore-offshore structural analysis, this study also investigates the structural development of the Mesozoic Andfjorden basin.