Abstract: Extension and Inversion in Rift Basins around the Complex Evolving North Sea Triple Junction

Faisal Jaffri, Michael P. Coward

Examination of seismic data over the Viking, Moray Firth, and Central grabens has allowed the timing, direction and amount of post-Triassic extension to be independently determined in each component of the North Sea triple junction. This has led to an understanding of the complex interaction of the three grabens during successive phases of structural evolution.

During the Late Jurassic (Oxfordian-Kimmeridgian) the South Viking Graben and Outer Moray Firth were extending in an approximately east-west direction. At the same time the Inner Moray Firth was extending in a northwest-southeast orientation, with the majority df dip-slip extension taken up along the Smith Bank Fault. In the Volgian the Outer Moray Firth was caught between the continued east-west opening of the South Viking Graben and the rapidly northeast-southwest extending Central Graben. The extension direction in the Outer Moray Firth switched to a northeast-southwest direction to accommodate the change in stress orientation. This caused block rotation and oblique-slip movement on the earlier northeast-southwest oriented faults. The Inner Moray Firth possibly accommodated this ch nge in extension by oblique-slip along the Great Glen Fault. The structural configuration in the triple junction area was further complicated at the end of the Jurassic and beginning of the Cretaceous by major inversion of the Volgian rift basins in the Central and South Viking Grabens.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994