Onshore Provenance of Clasts from Offshore Glacial Deposits, Nw Irish Continental Shelf

We present the first provenance study of glacial clasts from the offshore northwest Irish continental shelf to support regional, Devensian, ice flow paths from Ireland, Northern Ireland and Scotland. Seven clasts retrieved from seabed cores have been examined using a range of analytical methods to determine their bedrock provenance. Hand specimen description, thin section petrography, biostratigraphy and geochemistry have all proven valuable in making reliable identifications. The identification of a clast of arkosic, bioclastic conglomerate, from the mid-shelf core CE08-12, containing archaediscid foraminifera and the calcareous algae Koninckopora tenuiramosa, suggest this rock was sourced from the Carboniferous Lower Viséan Ballyshannon Limestone Formation; however, because this bedrock type is widespread onshore, and probably offshore, it provides little additional constraint on ice flow paths interpreted from geomorphological studies. A clast of syenitic orthogneiss from the outer shelf Malin Sea core CE08-28, is consistent with derivation from the Proterozoic Rhinns Complex exposed on the island of Inishtrahull. This clast identification supports movement of material from east to west, most likely related to Northern Irish and/or Scottish ice-flows and agrees with terrestrial and marine geomorphological evidence.