A methodology for the investigation of land form-sediment relationships in British glaciated valleys.

Abstract

Recent progress in the understanding of the processes and products of glacial deposition in valleys, based mainly on work in actively glaciated environments, has led to the development of a general model of glacial valley landform-sediment relationships by Eyles (1983). Models which predict sediments from landforms can be of considerable use to engineers planning construction development in relict glaciated valleys, where the planning and execution of a ground investigation survey must yield the maximum geological Information. This study forms a critical review of the theory and practice involved in the characterisation of, and the inter-relationships between such landforms and sediments, and proposes a new conceptual model for their analysis, based on the case study of 7 sites In 4 British valleys glaciated during the Dimlington Stadial. Landforms have been characterised by mapping the surface morphology of a series of study areas using air photos and field survey. A feature-based morphological subdivision of the terrain was used to delineate landform associations used for further analysis. The sediment data from the available borehole log descriptions was initially stored in the geotechnical database GEOSHARE and was characterised in order to determine the main sediment facies present in the study area. The identification of facies groups making up the local stratigraphy was carried out by multivariate hypothesis testing. The plotting of the facies identified in the form of cross-sections and the contouring of the unit surfaces has yielded information on the distribution of sediment facies to compare with the distribution of landforms in the study areas in S Wales and the central Highlands of Scotland. By a process of investigation of the landform-sediment relationships of these glaciated valleys the first steps have been taken towards the identification of some aspects of glaciated valley sedimentary architecture, and means by which glacial terrains might be investigated using the information stored in the landforms. In particular it is noted how the appropriate model for landform-sediment relationships in a modern setting should be based on an analysis of postglacially 'evolved' sedimentary sequences in the appropriate local topographic framework. The active glacial settings used by Eyles (1983) are inappropriate as they reflect process environments which are subsequently heavily modified by deglacial events