Sediment dynamics in an upland temperate catchment: changing sediment sources,rates and deposition |
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| Authors: | Robert G Hatfield Barbara A Maher Jacqueline M Pates Philip A Barker |
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| Institution: | (1) Centre for Environmental Magnetism and Palaeomagnetism, Lancaster Environment Centre, Department of Geography, University of Lancaster, LA1 4YQ Lancaster, UK;(2) Lancaster Environment Centre, Environmental Science Department, University of Lancaster, LA1 4YQ Lancaster, UK;(3) Lancaster Environment Centre, Department of Geography, University of Lancaster, LA1 4YQ Lancaster, UK |
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| Abstract: | We examine sediment dynamics in an upland, temperate lake system, Lake Bassenthwaite (NW England), in the context of changing
climate and land use, using magnetic and physical core properties. Dating and analysis of the sedimentary records of nine
recovered cores identify spatially variable sedimentation rates across the deep lake basin. Mineral magnetic techniques, supported
by independent geochemical analyses, identify significant variations both in sediment source and flux over the last ∼2100 years.
Between ∼100 years BC and ∼1700 AD, sediment fluxes to the lake were low and dominated by material sourced from within the
River Derwent sub-catchment (providing 80% of the hydraulic load at the present day). Post-1700 AD, the lake sediments became
dominantly sourced from Newlands Beck (presently providing ∼10% of the lake’s hydraulic load). Three successive, major pulses
of erosion and increased sediment flux appear linked to specific activities within the catchment, specifically: mining activities
and associated deforestation in the mid-late nineteenth century; agricultural intensification in the mid-twentieth century
and, within the last decade, the additional possible impact of climate change. These results are important for all upland
areas as modifications in climate become progressively superimposed upon the effects of previous and/or ongoing anthropogenic
catchment disturbance. |
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| Keywords: | Environmental magnetism Magnetic susceptibility Sediment tracing Lake sediments Land use change Climate change |
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