Fingerprinting upland sediment sources: particle size‐specific magnetic linkages between soils, lake sediments and suspended sediments

Abstract

Accelerated erosion of fine-grained sediment is an environmental problem of international dimensions. Erosion control strategies and targeting of mitigation measures require robust and quantitative identification of sediment sources. Here, we use magnetic 'fingerprinting' to characterize soils, and examine their affinity with and contribution to suspended sediments transported within two subcatchments feeding Bassenthwaite Lake, northwest England. A high-resolution soil magnetic susceptibility survey was made using a field susceptometer (ZH Instruments, SM400 probe). Combining the spatial and vertical (down-profile) soil magnetic data, a subset of soil profiles was selected for detailed, laboratory-based magnetic remanence analyses. The magnetic properties of the catchment soils are highly particle size-dependent. Magnetic analyses were performed on the 31-63 μm fraction, for particle size-specific comparison both with the suspended sediments and lake sediments. Fuzzy cluster analysis groups the soil magnetic data into six clusters, apparently reflecting variations in parent material and horizon type, with three magnetically hard soils as unclassified outliers. Examination of the cluster affinity of the soils, suspended sediments and lake sediments indicates that topsoils of the upper Newlands Valley and subsoils around Keskadale Beck are a major source of the Newlands Beck suspended load, and the recent (post-nineteenth century) sediments in the deep lake basin. Older lake sediments show strong affinity with a small number of the Derwent suspended sediments and one of the Glenderamackin soils. A large number of Derwent suspended sediments show no affinity with any of the soils or lake sediments, instead forming a coherent, discrete and statistically unclassified group, possibly resulting from mixing between the magnetically hard subsoils of the medium to high-altitude Glenderamackin and Troutbeck areas and softer, lower altitude Glenderamackin soils. The lack of any affinity of these suspended sediments with the lake sediments may indicate deposition along the Derwent flood plain and/or in the shallow delta of Lake Bassenthwaite. Particle size-specific magnetic fingerprinting is thus shown to be both highly discriminatory and quantitatively robust even within the homogeneous geological units of this catchment area. Such a methodological approach has important implications for small-large scale catchment management where sources of sediment arising from areas with uniform geology have been difficult to determine using other approaches, such as geochemical or radionuclide analyses.

Assessing damaged road verges as a suspended sediment source in the Hampshire Avon catchment, southern United Kingdom

“…The fingerprinting approach relies upon the link between the properties or fingerprints of suspended sediment and those of its principal sources (Foster and Lees, 2000;Walling, 2004, Walling, 2005). A range of properties has been successfully deployed as sediment source fingerprints including mineral-magnetism, mineralogy, radiometric and isotopic properties or geochemistry (Walling and Woodward, 1992;Caitcheon, 1993Caitcheon, , 1998Lees, 1999;Hillier, 2001;Douglas et al, 2003;Walling and Collins, 2005;Collins et al, 2009; Hatfield and Maher, 2009;Stutter et al, 2009;Wilkinson et al, 2009). In situations where several potential sources are being investigated, it is essential to assemble so-called composite fingerprints comprising individual properties responding to contrasting environmental controls (Collins and Walling, 2002).…”

“…A number of studies have used time-integrating traps to collect representative samples of suspended sediment flux for source apportionment purposes (e.g. Collins and Walling, 2006;Walling et al, 2006;Hatfield and Maher, 2009). In order to examine the relative importance of damaged road verges during higher magnitude floods resulting in overbank inundation and deposition, 12 samples of sediment from the floodplain surface (up to 2-cm depth) were collected at the outlet of the River Sem sub-catchment.…”

Conservatism of mineral magnetic signatures in farm dam sediments in the South African Karoo: the potential effects of particle size and post-depositional diagenesis

“…To date we do not know the rate at which such in-growth occurs and whether significant changes occur over relatively short periods of time. Particle size specific source tracing was also explored by Hatfield and Maher (2009) who demonstrated the ability of specific particle size fractions to achieve good discrimination between sediment sources even in homogeneous catchments.…”

Assessing the sources of sediment transported in gully systems using a fingerprinting approach: An example from South-east China

“…These signatures used a combination of the Kruskal-Wallis H-test and multivariate Discriminate Function Analysis (DFA), as proposed by Collins et al (Collins et al, 1997b;Collins and Walling, 2002). A number of other studies have used this method in sediment tracing (Chong et al, 2009;Collins et al, 2010b;Hatfield and Maher, 2009;Walling et al, 2006;Walling et al, 2008;Mukundan et al, 2010;Samani et al, 2011). There were two steps for discriminated sediment sources, and a number of sediment source tracing studies have employed this method (Collins et al, 1997b;Collins and Walling, 2007;Mukundan et al, 2010;Samani et al, 2011).…”