Fades of subglacial channel sedimentation in late-Pleistocene drumlins, Northern Ireland |
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Authors: | GEORGE F. DARDIS A. MARSHALL McCABE |
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Affiliation: | School of Environmental Sciences, Ulster Polytechnic. Shore Road, Newtownahhev, Co. Antrim, BT37 OQB, Northern Ireland |
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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. |
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