Fades of subglacial channel sedimentation in late‐Pleistocene drumlins, Northern Ireland

Abstract

The sedimentology of three sand‐cored drumlins in central Ulster. Northern Ireland is described. The sand‐cores of the drumlins consist of complex sequences of cohesive sediment gravity forms, grain‐flow deposits, turbiditic sands and deltaic sands and gravels, showing complex fades relationships. The bulk of the sediments formed in water‐filled cavities associated with a major subglacial meltwater escape route excavated in bedrock. The sand‐cores are overlain by a streamlined carapace of basal melt‐out till. A model is presented to account for spatial variations in faeies arrangement within the sand‐cores. Three specific meltwater depositional subenvironments were recognised: (1) main channel axis, (2) main channel flank, and (3) minor tributary channel. The sand‐cores formed prior to the main phase of basal melt‐out till deposition and before drumlin streamlining.