Origin, developl11ent and evolution of structural styles

Structural inheritence has proved to be an important consideration in the development and evolution of structural styles in many hydrocarbon provinces. The prospective sedimentary basins ofthe North Sea and adjacent areas are no different and a knowledge of earlier tectonic events and structural trends helps in understanding subsequent structural effects more completely. Review of the main structures and knowledge of their regional plate-tectonic setting enables the tectonic development of the North Sea and surrounding areas to be considered under four main headings: Precambrian events, the Caledonian (Iapetus) plate cycle, the Variscan (Rheic) plate cycle and PostPermian tectonic events related either to Atlantic Ocean opening or to structural events in an intraplate setting. Comparisons made between Precambrian and Palaeozoic structural lineaments and those tectonic elements that most notably influenced Late Palaeozoic, Mesozoic and Cenozoic basin development indicate that much of the younger history of the North Sea area, which was so crucial for the hydrocarbon habitat in the basin, was controlled by the distribution of older, rigid, cratonic blocks and their intervening lines of weakness. Throughout the period that the North Sea has lain in an intraplate setting, the orientation of deeper structure relative to the prevailing stress orientation seems to have been fundamental in determining the nature and extent of deformation at any time, with nonorthogonal stress leading to a greater or lesser degree of oblique- or strike-slip movement on basement faults particularly in the Southern North Sea.