Controls on the structural, stratigraphic and climatic development of the Central North Sea

Abstract

The North Sea is a marginal, epeirogenic sea lying in an intra-plate setting on the NW European continental shelf in the northern hemisphere at about 54 degrees north. It is a shallow, elongate, saucer-shaped depression that is more than 970 km long and 560 km wide; with an area of around 570,000 km2 and connected with the Atlantic Ocean both to the north through the Norwegian Sea, and to the south through the Dover Straits and English Channel. However, it has not always had this form nor existed in such a state, the rocks buried beneath the sea-floor indicate a long history of tectonic activity and markedly different environmental conditions from those present today. The North Sea is an important hydrocarbon province and it is essential to understand how it has evolved into its present form for successful exploration. Additionally, the large amounts of data gathered for use in hydrocarbon exploration provides a unique opportunity to investigate the structural and stratigraphic history of the area which may then provide analogues for understanding tectonic, stratigraphic, sedimentological and climatic responses through time in areas of the world where data is more limited. Climate is also recognized as playing a vital role in the stratigraphic development of the basin, influencing sedimentary settings and depositional facies. Extreme climate events such as hyperthermals and ice-ages are therefore important to study as these will have the most measurable effect on basin evolution. Additionally, studying hyperthermal events can provide information on the causes and consequences of global warming which is particularly relevant to the present day. The accepted understanding of the geology of the Central North Sea is that the current structural configuration arose from a period of rifting during the Jurassic. This extension formed a trilete extensional system consisting of three rift arms, the Moray Firth Basin, Viking Graben and Central Graben. The underlying structure of the Central North Sea is dominated by the influence of the Central Graben which itself is split into two arms, the Eastern and Western Troughs. This dominance highlights one of the central problems in interpreting regional geological histories as the most recent tectonic events tend to overprint and often obscure critical features of older geological events, leading to erroneous and confusing tectonic reconstructions. Additionally, the Jurassic rifting episode created many of the structural traps which today are exploited for hydrocarbons and has therefore been the subject of many of the previous geological studies undertaken within the Central North Sea.