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Robertson Group, Petroleum Division, Llandudno, Gwynedd, LL30 1SA, UK
The scale on which flexural subsidence has taken place in the North Sea region from the Late Palaeocene is very much greater than the scale on which fault-controlled subsidence and flexural subsidence occurred during the Mesozoic. In addition, uplift of the Scottish Highlands occurred during the Cenozoic on a scale comparable with that of the subsidence in the North Sea region during this time.
The Moray Firth, Mesozoic to Tertiary basin is divided into two distinct areas as a consequence of its Tertiary subsidence history, the Inner Moray Firth being uplifted and eroded and the Outer Moray Firth undergoing apparently continuous subsidence. The geometries of the pre-erosional sequences in the Moray Firth area indicate a Cenozoic history of both subsidence and uplift, providing a link between the subsiding North Sea region and the uplifted Scottish Highlands. Using seismic mapping and cross sections constructed therefrom, across the Moray Firth and North Central Graben areas, the relative subsidence and uplift is displayed as part of a unified process of crustal flexuring.
It is suggested that the flexural subsidence and uplift in the North Sea region and Scottish Highlands during the Cenozoic is associated with the onset of sea-floor spreading of the North Atlantic to the west. Furthermore it is proposed that the magnitude of Cenozoic subsidence in the North Sea region does not relate to the magnitude of Mesozoic extension which preceded it, the two processes being driven by different mechanisms.
