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Fault Growth and Linkage as Controls from Depocentre Development: The Coffee-Soil Fault Zone, Danish North Sea

Duffy, Oliver 1; Gawthorpe, Rob 1; Docherty, Matthew 2; Brocklehurst, Simon H.1
1 SEAES, University of Manchester, Manchester, United Kingdom.
2 Exploration and New Business, Mærsk Olie og Gas AS, Copenhagen, Denmark.

This study focuses on the eastern margin of the Danish Central Graben around the Poul Plateau, a complex segment boundary along the basin-bounding NNW-SSE-trending Coffee-Soil fault system. The present day Coffee-Soil fault system is a westerly-dipping, hard-linked, basin-bounding fault system, with a significant sinistral jog in the fault trace around the Poul Plateau. Strain localisation processes and an earlier stage of soft-linkage between northern and southern fault components are inferred by the presence of a zone of distributed deformation at the Poul Plateau. The Coffee-Soil fault system developed due to episodic phases of regional rifting, ranging from Permian to the Early Cretaceous ages.

We present an interpretation of the Late Triassic to Early Cretaceous kinematic evolution of the Coffee-Soil fault system, using evidence preserved within the syn-rift stratigraphy. Detail has been elucidated through seismic stratigraphic analysis from near the base syn-rift (Late Triassic) through to the Early Cretaceous. Analysis of the 3D morphology of TWTT structure maps has been integrated with analysis of syn-rift stratal thickness variations and present-day fault geometry in plan and cross-section. These techniques have identified major depocentre shifts, sequential filling and coalescence of hanging wall sub-basins, all of which may be used in the interpretation of fault system evolution. We suggest that the ca.25 km-long southern segment of the Coffee-Soil fault evolved through the hierarchical coalescence of a minimum of three shorter (4-8 km long) palaeo-segments with linkage dated at between Top Oxfordian and Late Kimmeridgian. Timing of linkage across the main Poul Plateau segment boundary is poorly-constrained, although it is inferred to post-date palaeo-segment linkage within the southern segment. Post-linkage strain localisation and acceleration in subsidence and accommodation rates is likely to have controlled a subsequent major landward shift in facies.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009