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).