Lake bed geomorphology and sedimentary processes in glacial lake Windermere, UK

A 1:10,000 map of the geomorphological features and sedimentary processes shaping the landscape is presented for Windermere, the largest lake in the English Lake District. High-resolution multibeam bathymetry and backscatter data, lake bed photography and sediment samples reveal a complex landform record, and have been used to identify nine sub-basins separated by steps, ridges and isolated topographic highs probably related to the retreat of the British and Irish Ice Sheet. Debris flows and anthropogenic features are superimposed on the general bathymetric framework formed since the Last Glacial Maximum. Five distinct lake bed facies are identified through ground-truthing, and are used to describe the sedimentology of the lake revealing a dominance of gyttja. Coarser sediments are found in lake-marginal shallow waters, where the morphology is shaped by dredging scars and circular dredging deposits. Post-glacial slope failure and modern sedimentary processes such as debris flows have further shaped the lake bed and removed the surface drape of gyttja, exposing an underlying facies of Pre-Holocene finely laminated mud.