Hamed Khani

Pre-Mesozoic structural configuration in the northern North Sea rift basin; as a result of Devonian orogenic collapse in the Scandinavian-Scottish Caledonides

The northern North Sea rift basin is a product of multiple rifting phases during the Mesozoic time, developed on the heterogeneous crust comprising preexisting structures inherited from the Caledonian Orogeny and the Devonian post orogenic collapse. Pre-Mesozoic structural configuration and the basement rock distribution in the northern North Sea area has been investigated by an integration of more than 200,000 km² two dimensional regional seismic reflection data and more than 75 basement wells. Four main seismic facies has been described below the top acoustic basement surface and has been utilized to consistently map the seismic reflection patterns in the study area. Thick (500-1000 ms) high amplitude dipping reflection packages interpreted as offshore extensional shear zones that has been linked to the northwest and west dipping (towards the hinterland) onshore shear zones in the southwestern Norway including the Nord-Sogn Detachment Zone (NSDZ), Bergen Arc, Hardangerfjord, Karmøy and Stavanger Shear Zones (BASZ, HSZ, KSZ and SSZ respectively). However, several east and west dipping structures has also been mapped in the Måløy Slope, East Shetland Basin, East Shetland Platform and around the Utsira High and Åsta Graben. These structures shows the development of both foreland and hinterland dipping shear zones in the northern North Sea area, while towards the margin of the orogenic belt in the SW Norway and NE offshore Scotland only hinterland dipping structures have been developed. These pre-rifting structures seem to exert a first order control on the geometry and the development of the northern North Sea rift basin.