Structural modelling of the south Porcupine Basin, offshore Ireland: implications for the timing, magnitude and style of crustal extension

Abstract

AbstractRegional structural synthesis together with 2D forward and reverse flexural isostatic basin modelling techniques have been used to investigate the extensional and subsidence history of the southern part of the Porcupine Basin. Two structural interpretations of seismic line GSP97-19 have been considered: (1) a Mid-Late Jurassic rift basin based upon seismic interpretation of well-defined tilted fault blocks, with subsidence modelling of the thick overlying sediment section predicting high lithosphere stretching factors of up to β = 6; (2) a Mid-Jurassic-Early Cretaceous rift responsible for a thick Barremian-Aptian synrift sequence within the basin centre resulting in reduced maximum lithospheric stretching factors of β = 2.3. The variance in published estimates of crustal thickness beneath the basin cannot distinguish between these scenarios. A comparison between stretching factors and the amount of observable upper-crustal faulting suggests that depth-dependent lithospheric stretching may be a feature of the basin, as in other sedimentary basins along the Atlantic margin, and is directly associated with the onset of Cretaceous plate break-up in the Atlantic.