Tectonic evolution of the southern-Central Irish Sea Basin

Interpretation of 2D seismic reflection data combined with correlation of f ive wells in the southern part of the Central Irish Sea Basin show a NE-SW trending graben, whose bounding faults are considered to be reactivated lin eaments of Precambrian age. The basin-fill comprises mainly Carboniferous a nd Triassic successions, with localised and thin occurrences of lower Juras sic and Tertiary rocks, all of which are unconformably overlain by Quaterna ry sediments. Due to poor data quality, the structural evolution of the are a during the Late Palaeozoic is poorly understood. During the Triassic, the basin was subjected to thermal subsidence with a phase of minor uplift in the Anisian. The major phase of extension in the basin took place during th e ?Middle - Late Jurassic and had a NW-SE orientation. Subsequent Late Jura ssic sinistral shear along the NE-SW trending basin bounding fault is sugge sted to have taken place, giving rise to a series of north-south intra-basi nal faults. The present-day structure of the basin is a broad anticline, in herited from a Cretaceous - Early Tertiary compressional phase. During the Palaeocene the area was subjected to regional uplift, followed by minor ext ension along the NW boundary fault during the Eocene - Oligocene. A Late Te rtiary phase of transpression is postulated to have occurred, which inverte d north-south trending faults and folded the base-Tertiary unconformity.