The Efficiency of Elemental Geochemistry and Weathering Indices as Tracers in Aeolian Sediment Provenance Fingerprinting

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.