Regional structural evolution of the North Sea: oblique slip and the reactivation of basement lineaments

Abstract

Basement lineaments pre-dating the dominant Mesozoic basin formation of the North Sea are fundamental controlling features within the polyphase tectonic evolution of NW Europe. These inherent zones of weakness were repeatedly reactivated during the evolution of the North Sea rift system. The regional and geometrical constraints imposed by the presence of these pre-existing tectonic grains during the Mesozoic extensional deformation suggest that oblique-slip movement must have occurred along many of the basin-bounding faults in a non-preferential orientation for dip-slip reactivation.While the North Sea can be considered in broad terms as a series of linked, elongated grabens developed in response to dominantly E-W extensional intra-plate stresses, the orientation, distribution and character of pre-existing shear zones ultimately controlled the geometry of many Mesozoic basins and their faulted margins.Four types of inherent basement features are recognized as having influenced subsequent basin development: (a) wide, diffuse zones of NW-SE and NE-SW basement shear, e.'g. in the Central Graben; (b) narrow shear zones oblique to primary Mesozoic extensional faults, e.g. in the East Shetland Basin; (c) E-W-trending discrete fault systems, e.g. on the Western Platform; and (d) massive palaeohighs, e.g. the Halibut Horst.The distribution of these distinct structural features throughout the North Sea was controlled by Early Paleozoic plate tectonic evolution. Repeated Mesozoic and Cenozoic reactivation along fundamental zones of weakness, including oblique-slip displacements and basinal inversion, has led to areas of highly complex structuration. Hence, there is the potential for numerous structural and stratigraphic hydrocarbon trapping mechanisms associated with these underlying basement lineaments.Although the total amount of horizontal crustal movement may be limited, understanding of the role of oblique-slip along pre-existing zones of weakness and the effect of long-lived palaeohighs within the basin is crucial to place Mesozoic and Tertiary hydrocarbon accumulations within a realistic North Sea tectonostratigraphic framework.

Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

“…Bartholomew et al, 1993;Erratt et al, 1999;Whipp et al, 2014) and passive margin rift systems are dissected by cross cutting faults, in a similar geometry observed in Malawi (Paton et al, 2008, Tsikalas et al, 2008Antobreh et al, 2009;Heine et al, 2013). Often these structures are not well defined as a consequence of poor quality data, wide spacing of available 2D lines, or a sub-salt setting.…”

Influence of fault reactivation during multiphase rifting: the Oseberg area, Northern North Sea rift

“…1A) (e.g. Bartholomew et al, 1993;Glennie, 1987;Smethurst, 2000;Stewart et al, 1992;Ziegler, 1990). The Permian-Early Triassic rifting lasted for 25-37 m.y.…”

“…of relative tectonic quiescence and post-rift thermal subsidence (e.g. Bartholomew et al, 1993;Glennie, 1987;Lepercq and Gaulier, 1996;Roberts et al, 1995;Ziegler, 1990). The Middle Jurassic -Early Cretaceous rift phase (e.g.…”

Lough Neagh: the site of a Cenozoic pull-apart basin

“…The nature and mode of formation of pull-apart basins have been the subject of study by many workers, and examples have been described worldwide (for example, Aydin & Nur 1982;Mann et al 1983;Sylvester 1988;Bartholomew et al 1993;Oudmayer & de Jager 1993;Dooley et al 1999;Reijs & McClay 2003). Pull-aparts are generally defined as zones of extension produced at bends or step-overs in a strike-slip fault system.…”