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Single-grain post-infrared luminescence (SG-pIRIR) protocols allow dating of fluvial deposits that present large scatter in equivalent dose (De) distribution because of heterogeneous bleaching (zeroing) of the grains by sunlight exposure before deposition. In such settings though, luminescence signals measured in modern deposits tend to be better bleached downstream. It suggests that the study of alongstream luminescence signals may allow the quantification of fluvial transport processes and the transient storage of particles in floodplains [1, 4, 5, 6]. In this study, we aim to measure the alongstream distribution of SG-pIRIR signal from modern floodplain deposits of several braided and wandering rivers running in Chile along a latitudinal climatic gradient (Rio Tolten, Rio Allipen, Rio Ñuble, Rio Itata, Rio Choapa, Rio Huasco). Those rivers run from 1000km South of Santiago, where catchments receive up to 2000 mm of annual precipitations, to Huasco in the South of Atacama desert, with precipitations less than 100 mm per year. Measurements of Terrestrial Cosmogenic Nuclide (TCN) 10Be concentrations in modern fluvial sediments indicate a latitudinal gradient in catchment-wide erosion rates from 10² to 10-1 mm/kyr northward [2]. Our catchments of interest are therefore distributed over a distance of more than 2000km between latitudes of 40°S and 28°S, and take place under different climatic conditions, from an oceanic climate in the South to a desertic one in the North, which likely influences the fluvial style of rivers. In this study, we would like to take advantage of this climatic and erosional gradient to investigate further the differences that can occur alongstream in the luminescence signal, and see if we can document different transport parameters along those gradients. Finally, we will combine our luminescence data with state-of-the-art quantification of rates of surface processes by in-situ TCN measurements (10Be, 26Al, 14C and Kr isotopes [3]). [ABSTRACT FROM AUTHOR]

Understanding sediment movement over time and space requires quantitative tools. The trapped charge phenomenon or luminescence properties of sand grains are one of the potential techniques in sediment tracing [4]. Luminescence of sand grains builds up during burial in sedimentary deposits and resets at the Earth's surface when exposed to sunlight. This sensitivity to daylight exposure can be utilized to quantify Earth's surface processes such as sediment transport and or soil mixing. Thus, the variations in the magnitude of the luminescence signal, raise the possibility of quantifying rates of Earth surface processes via measurements of the luminescence signal. In this study, we aim to investigate the luminescence signature of hillslope denudation by measuring the percentage of bleached versus non-bleached (saturated) grains in associated modern fluvial deposits for a large variety of source catchments (in Chile and New Zealand) with contrasting morphometric properties. We will utilize feldspar single-grain pIRIR measurement protocols to measure the luminescence signature and perform the data analyses previously described in [5]. Our research will offer innovative constraints on weathering intensity and hillslope denudation and how they are related to the denudation rates of the selected catchments. We will thus use paired in situ 14C and 10Be terrestrial cosmogenic nuclides (TCN) measurements for some selected catchments in the Southern Alps of New Zealand and Chile (both with pronounced climatic gradients), to complement and compare our luminescence data. Numerous studies have already proven the dependency of denudation rates on landscape characteristics such as the mean slope of the catchments or mean hillslope gradients and to external forces such as tectonic uplift and climate [1,2,3]. [ABSTRACT FROM AUTHOR]