Glaciomarine sediments of the Isle of Man as a key to late Pleistocene stratigraphic investigations in the Irish Sea Basin

The northern part of the Isle of Man in the central Irish Sea Basin is identified as a raised marine foreland containing the largest subaerial exposure of last glaciation marine and glaciomarine sediments yet recognized on the British continental shelf. A large push ridge that crosses the foreland identifies a major ice limit. The ridge divides the foreland stratigraphy into a coarsening-upward marine sequence of pelagic muds with dropstones, sand, and gravel to the south from offlapping stratified and massive sandy diamict assemblages overlying glaciotectonized marine sediments to the north. Coarse-grained diamicts are argued to form part of a push-ridge-subaqueous-outwash depositional system deposited when processes of suspension deposition, density underflow, ice rafting, highly variable traction-current activity, and sediment gravity flow were operative adjacent to a grounded marine ice margin. The identification of large offshore submarine banks aligned parallel to the Bride moraine suggests that construction of the push-ridge-subaqueous-outwash depositional system may have been repeated during ice recession. This and published descriptions of other “Irish Sea tills” indicate that analogous structures and sediments are present offshore and around the Irish Sea Basin.