Large-scale glaciotectonic thrust structures in the eastern Danish North Sea

Abstract

AbstractThe distribution of shallow, detached thrust fault complexes in the eastern Danish North Sea has been mapped based on 6400 km of high-resolution multichannel seismic data. Individual thrust segments are 200–1000 m long and 100–250 m thick with up to 200 m of horizontal displacement. Thrusting mainly affected upper Middle Miocene to lower Pleistocene strata and predated an extensive system of now buried subglacial valleys. The thrust structures are located along a 200 km long NW-SE trend. The general thrust direction is towards the SW, parallel to inferred directions of ice movement during the Elsterian and Saalian glaciations. This direction is, however, also parallel to the dip of the underlying detachment surface. The detachment surface corresponds to the mid-Miocene unconformity in the SE and the base of the Quaternary to the northwest. Detachment is generally located at depths of 130–270 m below sea level.The structures are interpreted as glaciotectonic thrust structures of Elsterian and/or Saalian age. The driving mechanism is interpreted to be gravity spreading in front of glaciers advancing from the north, NE and east. Thrusting was facilitated by the presence of SW-dipping detachment surfaces.