Fault distribution and timing in the Central Irish Sea Basin

Abstract

AbstractWell data analysis and the interpretation of 2D and 3D seismic reflection data provide valuable insights into the distribution and timing of fault activity within the Central Irish Sea Basin (CISB). Structural and stratigraphic relationships have been used to constrain the timing of fault movements and to interpret the mapped fault patterns in terms of the tectonic evolution of the area. Four main fault trends are identified at the Top Lower Triassic Sherwood Sandstone Group level: I, a NE-SW fault trend that parallels the basin-bounding faults and is believed to be of Mesozoic age; II, a pervasive system of northsouth-trending faults that cross-cut the earlier NE-SW-trending faults, which manifests evidence of later Mesozoic extension followed by post-Oligocene transpressional fault reactivation; III, a NNE-SSW-trending, steeply dipping, fault set; IV, a WNW-ESE-trending conjugate extensional set that formed perpendicular to the NNE-SSW-trending transpressional faults during Late Tertiary dextral shearing. Early Tertiary axial centred basin inversion and regional exhumation have resulted in the elevation of the Sherwood Sandstone reservoir to shallow structural levels within the basin. Continued fault reactivation into Late Tertiary time has resulted in the compartmentalization of mapped structural closures and suggests that trap integrity is a major exploration risk factor in the CISB.