Deep weathering, neotectonics and strandflat formation in Nordland, northern Norway

We have carried out chemical and geophysical studies of the weathering and measured the tectonic strain using the GPS method. A parallel and shallow zone of increased seismicity along the coast largely reflecting extensional stress has previously been mapped. New GPS data and previous datasets such as DInSAR, repeated levelling and focal plane solutions indicate that the outer Ranafjorden area is under E-W extension and subsidence. An irregular relative subsidence pattern on the order of 1 mm yr super(-1) has previously been recorded on InSAR-PS data. Deeply weathered bedrock occurs around Vestfjorden and southwards to Ranafjorden. Electrical resistivity profiling reveals weathered bedrock extending to 20-100 m depth over large areas. Calculations of weathering indices and mass balance from XRF analysis show leaching of the major elements. We argue that the weathering is partly of Early Mesozoic age, since the Late Jurassic to Early Cretaceous faults in the Lofoten-Vesteralen area are little affected by the alteration.