Abstract
Confirmation of cost-effective and reliable tracers for aeolian sediment (sand dune) source fingerprinting warrants further research. Accordingly, the main objective of the work reported in this paper was to investigate the efficiency of weathering indices in aeolian sediment fingerprinting using a case study of a fragile arid region in Qom Province, Iran. Eight geochemical elements (Al, Ca, Fe, K, Na, Mg, Si, Ti) and 17 associated weathering indices were measured in 34 aeolian source samples and 10 sand dune target sediment samples in three absolute particulate size fractions. For each fraction, three final composite fingerprints (i.e., geochemical elements only, weathering indices only and a combination of the two) for discerning and ascribing the aeolian sediment sources were selected. The Modified MixSIR Bayesian un-mixing model was used to apportion aeolian source contributions using the final composite fingerprints. Regardless of the composite fingerprint used, all results across the different size fractions suggested that the south-eastern alluvial fan is the dominant (average contribution 50.6%, SD 19.0%) source of the sand dune samples, with the western alluvial fan being the second most important (average contribution 38.4%, SD 20.4%) source. Comparisons of the posterior distributions for the predicted source proportions generated using the nine composite fingerprints (three kinds of composite fingerprints*three particle size fractions) showed that the composite fingerprints combining the geochemical elements and weathering indices generated the most powerful source material discrimination. Our results demonstrate the use of weathering indices alongside more conventional elemental geochemistry tracers for investigations into sand dune sediment provenance.
Highlights
Wind erosion has three stages comprising abrasion, deflation, and accumulation 1
Our results demonstrate the use of weathering indices alongside more conventional elemental geochemistry tracers for investigations into sand dune sediment provenance
Using the < 125 μm fraction, the geochemical elements and weathering indices only composite signatures suggested that the south-eastern alluvial fan is the main source of the sand dunes, whereas the signature combining geochemical elements and weathering indices suggested that the western alluvial fan is the main source (52.9%) of the sampled sand dune sediment
Summary
Wind erosion has three stages comprising abrasion, deflation, and accumulation 1. The principal controlling factors for sand dune formation include wind direction and velocity, the available supply of sand in source areas subject to wind erosion, source area surface roughness, aggregate stability, presence of crusting, soil texture and moisture, vegetation cover and the presence of residues [2,3,4]. Effective wind erosion mobilises erodible soil particles, which can be deposited subsequently on agricultural land, roads and railways, and in settlements. Given these on-site and off-site consequences of wind erosion [5,6], there is a need to determine the key sources of aeolian sediment in order to target and select robust strategies for stabilising the source areas. The alternative approach to management is to focus on identifying the key sources of aeolian sediment to target interventions for decreasing the supply of sand generating off-site aeolian sediment deposits (i.e., sand dunes)
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