Clastic sabkhas and diachroneity at the top of the Sherwood Sandstone Group: East Irish Sea Basin

The identification of early evaporite sulphate cements with a marine isotopic signature within the Ormskirk Sandstone Formation supports previous models of diachroneity at the contact of the Sherwood Sandstone Group and the Mercia Mudstone Group in the East Irish Sea Basin. Basin-wide correlations suggest that, at the onset of transgression, a range of sandflat and aeolian dune environments co-existed on the margins of the basin with marginal marine environments toward the basin centre. One of the major implications of this model is that the high quality aeolian sandstone reservoirs encountered near the top of the Ormskirk Sandstone in the southern parts of the East Irish Sea Basin have no reservoir correlatives in large areas of the basin but can be predicted on the margins.