North Sea and NW approaches

The Carboniferous strata of the Central and Northern North Sea occupy a depositional basin that is laterally contiguous with, and located to the east of, the Midland Valley of Scotland (Chapter 14). The Carboniferous strata of the Southern North Sea occupy a depositional basin located between the Mid North Sea High to the north and the Wales- Brabant High to the south (Fig. 15.1). It is laterally contiguous with the Pennine Basin complex. An isolated area of Carboniferous strata has also been proved in the Clair Basin of the Northwest Approaches, west of the Shetland Isles. The Tournaisian and oldest Visean strata have been proved beneath Permian and younger cover in the Central and Northern North Sea, within the Outer Moray Firth, Western Platform and Central Graben, eastwards from the coast of Southeast Scotland along the crest and southern flanks of the Mid North Sea High and in the Clair Basin, west of Shetland (Fig. 15.1). The strata are dominated by red, fluvial and playa-lake deposits (Upper Old Red Group). Younger Visean strata include the grey, fluviolacustrine deposits within the Forth Approaches Basin and Outer Moray Firth Basin of the Central and Northern North Sea (Firth Coal Formation). Visean to lower Namurian lacustrine, marine, fluvial and fluvio-deltaic sediments are proved in the Southern North Sea eastwards from the Northumberland coast along the western crest and southern flanks of the Mid North Sea High (Farne Group). The Zeeland Formation, an offshore equivalent of the platform carbonate rocks of the Peak Limestone Group, is known to be present along the northern flank of the Wales-Brabant High in the Southern North Sea and could also occur on isolated horst blocks within the main basinal area. A late Visean and Namurian succession of hemipelagic mudstone and fluvio-deltaic cycles (Whitehurst Group) is present across the Southern North Sea, and is overlain by Westphalian strata dominated by grey fluvio-lacustrine (Coal Measures facies) and red alluvial deposits (Conybeare Group)