The Listafjorden–Drangedal Fault Complex of the Agder–Telemark Lineament Zone, southern Norway. A structural analysis based on remote sensing and potential field data

ABSTRACT The Listafjord–Drangedal Fault Complex is a central structure in the NE-SW-trending Agder–Telemark Lineament Zone that dominates the structural grain and topography of southernmost tip of Norway. The fault can be followed for a distance of more than 170 km from the shelf area off Listafjorden–Fedafjorden in Vest Agder county to Drangedal in Telemark county. It has been analyzed by the use of digital topographic, remote sensing and potential field data, supported by field investigations. At least seven separate left-stepping fault segments have been identified. These are characterized by numerous internal fault lenses, separate fault strands and fault splays, partly displaying contrasting fault attitude and style of deformation. The northeastern termination of the Listafjord–Drangedal Fault Complex consists of fanning fault branches (horse-tailing), whereas its southwestern termination is buried below sediments in the continental shelf and remains obscure. The fault rocks of the various fault segments include cataclasites and mylonites that in places are interlayered with zones of fault gouge. By tentative correlation to the Hunnedalen dyke system in Rogaland, the age of initiation for the Listafjord–Drangedal Fault Complex is suggested to be Late Proterozoic. Parts of the fault complex were affected by at least two stages of faulting including (dextral?) shear and top-to-the-SE extension. The latter stage is assumed to be of post-Caledonian age, and recent seismic activity suggests that this ancient structural grain is still seismically active.