Abstract

The large amount of data now available on the North Sea stratigraphy, and on the history of the positive structures which form the sites of the oilfields, provides a basis for a review of basin development.

The area was initially occupied by two inter-cratonic basins: the Northern Basin had a Devonian ancestor; the Southern Basin dates back at least to the Carboniferous. During the Permian and Trias broad intercratonic subsidence continued in the south, but rifting developed across the separating Mid North Sea High and in the Northern Basin. Rifting (taphrogenic) control of subsidence became widely dominant through the Jurassic and lower Cretaceous, dying away in the upper Cretaceous, with major subsidence in the Viking Graben in the Northern Basin and in a series of narrow troughs in the south. No opening of the crust was associated with the central rifting: deep penetrations have encountered Devonian or Precambdan in the rift floor. For the most part the upper Cretaceous sagged into the earlier depressions with minor faulting only, but in the south inversion of the troughs took place in late Cretaceous and early Tertiary times; this may have had a compressional (orogenic) cause.

The Tertiary basin developed as a single, relatively simple synclinal subsidence of the whole North Sea area, centred on the main rift system but showing an absence of fault-control.

Interruptions in deposition on the individual structural high areas show wide correspondence in the North Sea. Except for a major late Triassic movement limited to the Netherlands and adjoining areas they show also close relation to those in Britain. The most notable are early middle Jurassic, early upper Jurassic and end Jurassic/lower Cretaceous. These produced erosional phases even in the deeper parts of the basin. They were entirely of epeirogenic type.

Halokinetic movements of Permian salt produced many local complications (especially in the Southern North Sea Basin) with consequent structural and stratigraphical anomalies from the middle Trias onwards.

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