Depth of extensional faulting on the Mid-Norway Atlantic passive margin.

Abstract

Two crustal-scale cross-sections of the Mid-Norwegian Atlantic passive margin are discussed. Large W- and E-dipping normal faults relate to extension of the continental crust following the Caledonian orogeny and the subsequent opening of the Atlantic ocean. The passive margin extends from the ocean-continental boundary west of the Vøring Marginal High to the innermost extensional normal faults 90 km west of the Caledonian thrust front. Based on earthquake data and published results of geophysical modelling and seismic interpretation, the average depth to which the normal faults extend in the offshore domain is estimated to 20+.5 km. The depth corresponds to the brittle-ductile transition in the crust of the stretched Mid-Norwegian continental margin. Above this transition the crust extended by brittle faulting (titled blocks), below this limit the crust extended in a ductile manner.