Tracing the movement of sediment in fluvial systems using multiple elevated temperature infrared stimulated luminescence

The transport of sediment across the Earth shapes both the human and physical world. Sediment transport is both a driver of and responder to landscape evolution over geological time scales, inextricably linked to climate processes and tectonic activity. It is a regulator of biogeochemical cycling, water quality and supply, soil quality and ecosystem health. A quantitative understanding of sediment transport processes is a key to sustainable development, yet current methods for doing so are highly inefficient and often lack the spatial-temporal resolution to account for localised effects. This thesis develops single grain feldspar multiple elevated temperature infrared stimulated luminescence (MET-IRSL) as a tool to address some of these challenges to quantifying the movement of sediment in river systems. It is demonstrated that single grain MET-IRSL is both highly efficient and able to determine localised variability of sediment transport rates and pathways.

This thesis first investigates the process of luminescence signal reduction, known as bleaching, to determine an ideal function with which to model bleaching for grains in a fluvial sediment transport scenario. Optimal methods for measuring MET-IRSL signal and analysing output are developed and tailored to extract transport information. These techniques are applied to three fluvial systems including the Solimões River, the name given to the main strand of the Amazon system. A burialbleach model is constructed to apply to downstream datasets of MET-IRSL combined signals. Using this model, it is demonstrated that the application of single grain MET-IRSL can produce credible storage times and transport rates for sediments in fluvial systems. Furthermore, this model is adapted to reconstruct the histories of individual grains using parameters derived directly from MET-IRSL measurement. It is shown that single grains can independently contribute bleaching and storage histories to a transport rate that is coherent with the information provided by the combined MET-IRSL signals.