Stratigraphical relationships and a revised lithostratigraphical nomenclature for the Carboniferous, Permian and Triassic rocks of the offshore East Irish Sea Basin

Abstract

Abstract The Lower Permian and Triassic successions of the offshore East Irish Sea Basin are probably the thickest of the United Kingdom Continental Shelf or UK mainland, but currently, no hierarchical lithostratigraphy exists for this offshore area. A summary is presented of the first comprehensive hierarchical lithostratigraphical nomenclature scheme to be established for the Carboniferous, Permian and Triassic rock successions of the offshore East Irish Sea Basin. This scheme, which has been sponsored by interested exploration companies, identifies 25 formal lithostratigraphical divisions following the methodology already established in BGS-UKOOA (British Geological Survey-United Kingdom Offshore Operators’ Association) revisions of North Sea lithostratigraphy. Sixteen new lithostratigraphical names are introduced (nine in the Mercia Mudstone Group, one in the Sherwood Sandstone Group, three each within the Permian and Carboniferous successions). The lithology, wireline log characteristics and nature of the lower boundary are discussed briefly for each lithostratigraphical unit, together with correlations to the adjacent onshore successions where appropriate. Formal definitions of lithostratigraphic units, including type and reference sections are fully documented elsewhere. The aims of this study are to rationalize the existing terminology and to provide a practical scheme that will have the widest acceptance within the oil industry.