Bedforms on the northwest irish shelf: indication of modern active sediment transport and over printing of paleo-glacial sedimentary deposits

Abstract

Recent mapping programmes in Irish territorial waters, such as the Irish National Seabed Survey and the Integrated Mapping for the Sustainable Development of Ireland's Marine Resource programme, have generated high resolution multibeam bathymetry, backscatter and sediment sample datasets at an unprecedented resolution and coverage. Building upon previous mapping of glacial landforms on the northwest Irish continental shelf, a 1:225,000 scale map identifying contemporary bedforms has been produced between 54 degrees 40 ' N/56 degrees 10 ' N and 10 degrees 2 ' W/6 degrees 45 ' W. The analysis of bathymetric derivatives and backscatter interpretation has enabled the classification of several types of depositional feature including six sediment wave assemblages. Erosional features have also been identified across the shelf in the form of surface sediment lineations, as well as more spatially confined formations such as furrows. Based on wave asymmetry, sedimentary composition and orientation, in agreement with published modelled hydrodynamic conditions, these bedforms are assumed to be contemporary features. Data interpretation, particularly of backscatter imagery reveals that these sediments mask the acoustic signatures of an underlying glacial architecture and may alter their apparent morphology due to burying.