Looking through drumlins: Testing the application of ground-penetrating radar

Abstract

Ground-penetrating radar (GPR) is becoming a commonly applied technique in geomorphology. However, its use in the study of subglacial bedforms has yet to be fully explored and exploited. This paper presents the results of a GPR feasibility study conducted on a drumlinized terrain in Cumbria, UK, where five drumlins were investigated using multiple radar antenna frequencies. The site was selected for the presence of nearby bedrock outcrops, suggesting a shallow drumlinized diamict-bedrock contact and a permeable lithology. Despite the clayey sediment and unfavourable weather conditions, a considerable penetration depth of ∼12m was achieved when using a 50MHz antenna, with a separation of 1 m, trace spacing of 1m and 128-fold vertical stack. Results indicate that the drumlinized diamict is in direct erosional contact with the bedrock. While the internal drumlin geometry is generally chaotic on the stoss side, evidence of layering dipping downflow at an angle greater than the drumlin surface profile was found on the lee side. The inter-drumlin areas comprise ∼4m of infill sediment that masks part of the original drumlin profile. Overall, this study indicates that GPR can be deployed successfully in the study of glacial bedform sedimentary architecture.