Permo-Triassic architecture of the Northern North Sea

R.A. Hodgkinson1, J.R. Underhill1, M. Tomasso2, N. Banbury1, R. Cooper.3

1 Geology & Geophysics, University of Edinburgh, West Mains Rd, Edinburgh

2 Department of Geology, University College Dublin, Belfield, Dublin 4, Ireland

3 TotalFinaElf UK PLC, Crawpeel Road, Altens Industrial Estate, Aberdeen,

Richard.Hodgkinson@glg.ed.ac.uk

The northern North Sea basin is ~200km wide, fault bounded basin composite of Permo-Triassic and Jurassic extensional events. The region is characterised by first order NW to NE striking normal faults that define Late Jurassic tilted fault blocks 10km+ in width. The large faults that exerted significant control on extension, subsidence, basin geometry and sedimentation patterns are generally assumed to be established during the Permo-Triassic, with reactivation during the Jurassic.

A comprehensive well-calibrated 3D seismic data set, complemented by a number of 2D seismic traverses provide a nearly complete coverage of the Northern North Sea region, is loaded at the University of Edinburgh. This extensive data set affords an unparalleled view of the early Permo-Triassic rift history of the Northern North Sea, allowing the recognition of Permo-Triassic faults and also enabling the study of the individual sub-basins and the region as a whole.

Restoration of the Northern North Sea for the effects of Late Jurassic rifting shows that in the UKCS the Triassic basins are delimited by westward dipping first-order normal faults that can be related to two episodes of rifting during the Triassic. These faults have a spacing of ~30km and exerted significant control on sedimentation patterns. During the Jurassic rift event the Triassic faults were cross-cut, giving an arête-like appearance within the seismic data locally.

On the Horda Platform of the Norwegian Shelf, the Triassic faults, particularly those associated with the Øygarden Fault Zone and the eastern margin of the Brage Horst, underwent a simple reactivation during the Jurassic. Elsewhere on the platform there appears to be a ‘soft-link’ between the two rift episodes that cannot be readily resolved without invoking an intra-Triassic decollement.

The poster provides a series of regional E-W seismic traverses across the Northern North Sea, identifying key structures and their importance in the Permo-Triassic evolution of the region.

This study, undertaken at the University of Edinburgh, wholly funded by TotalFinaElf UK PLC, as part of a proprietary study to investigate the Triassic evolution of the Northern North Sea.