Subglacial bedforms of the last British Ice sheet

Abstract

Subglacial bedforms are a characteristic feature of formerly glaciated landscapes. Formed parallel (e.g. drumlins) or transverse (ribbed moraine) to ice flow their preserved distribution is a valuable record of ice sheet configuration. To date these landforms have been underused in Britain such that we have only a simple static view of the flow patterns of the last British Ice Sheet, with glimpses of complexity recorded in just a few locations. Arguably, this is because of the lack of a suitable, ice-sheet scale, map of subglacial bedform distribution. We present the first consistent and countrywide map of subglacial bedforms for Britain produced from systematic mapping. Individual landforms were mapped from relief-shaded renditions of high-resolution elevation data and Landsat TM imagery. The outline or crest-line of each bedform was manually captured by onscreen digitisation directly into a Geographic Information System (GIS) database. Over 39,000 landforms were identified revealing new lineation patterns, multiple instances of cross-cutting/superimposition, and adding additional detail to the known distribution established by local field surveys. A near complete representation of the British subglacial bedform population, the map is a major step towards a detailed model of British Ice Sheet configuration by providing a suitable basis for reconstructing the flow evolution at the ice sheet scale, and a geomorphological framework for the interpretation of sedimentological and stratigraphical data. The map is presented at a scale of 1:525,000.