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

Abstract

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. Highresolution 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.

Distribution, characteristics and condition of Arctic charr (Salvelinus alpinus) spawning grounds in a differentially eutrophicated twin‐basin lake

“…Hydroacoustic survey of the lake bottom A multibeam bathymetry of the lake bottom was produced in September 2010 using a SIMRAD Kongsberg EM3002D dual head system operating at 300 kHz on the British Geological Survey vessel R/ V White Ribbon, providing 100% coverage of both the north and south basins in areas where water depth exceeded 5 m (Miller et al 2013). Coverage of shallower areas was limited by technical constraints.…”

“…Sixty-nine sediment samples from the lake bed (33 in the north basin and 36 in the south basin) were collected in June 2011 using a 2 L Van Veen F42A grab as described in detail in Miller et al (2013). Visual descriptions and grain size analysis were used to identify a number of distinct lake bed facies, that is, gyttja (composed of fine to very coarse organicrich, olive-green silt), finely laminated mud, fine sand and gravel.…”

Glacial and paraglacial history of the Troutbeck Valley, Cumbria, UK: integrating airborne LiDAR, multibeam bathymetry, and geological field mapping

“…More recent studies have identified recessional moraines in Windermere (Pinson et al, 2013), upper Eskdale (Wilson, 2004) and to the south of Windermere (Clark et al, 2004) which are correlated with late stage residual BIIS retreat. In Windermere, the moraines are visible in the multibeam bathymetry as major ridges which cross-cut the basin creating a stepped topography (Miller et al, 2013). These glaciogenic landforms are thought to have formed by still-stands and/or small readvances indicating active ice during glacial retreat rather than in situ stagnation and downwasting.…”

“…The swath bathymetry survey in Windermere was undertaken in September 2010 on the British Geological Survey (BGS) vessel R/V White Ribbon using a SIMRAD Kongsberg EM3002D dual head system providing 100% coverage of both the North and South Basin to 5m water depth, as detailed in Miller et al (2013). Post processing was completed using CARIS HIPS/SIPS and filtered data was gridded at 1m resolution, corrected to Ordnance Datum Newlyn using lake level data from an electronic gauge taken at continuous 15 minute intervals to an accuracy of ±2mm.…”

Modern Pollution Signals in Sediments from Windermere, NW England, Determined by Micro-XRF and Lead Isotope Analysis

“…The lake occupies a radial pre-glacial river valley and is orientated NNW to SSW, measuring c. 17 km in length with a maximum width of c. 1.5 km and depth of 62 m in the north. The sedimentology of the lake bed is dominated by gyttja (fine to very coarse organic rich silt) and the geomorphology is characterised by several steps and ridges, interpreted as the surface expression of recessional moraines formed during ice retreat (Miller et al, 2013;Pinson et al, 2013). The bedrock of the catchment is predominantly comprised of the Borrowdale Volcanic Group (BVG) in the north, and the Silurian (Windermere Supergroup) in the south (Mitchell, 1956;Millward et al, 2000) (Fig.…”