CONICET | Buscador de Institutos y Recursos Humanos

Self-similar downstream grain-size fining trends in fluvial deposits are being increasingly used to simplify 18 equilibrium sediment transport dynamics in numerical models. Their ability to collapse time-averaged behavior of a 19 depositional system into a simple mass balance framework, makes them ideal for exploring the sensitivity of 20 sediment routing systems to their climatic and tectonic boundary conditions. This is important if we want to better 21 understand the sensitivity of landscapes to future environmental change. However, the extent to which self-22 similarity is detectable in the deposits of natural systems is unconstrained. In transport limited systems, such as 23 alluvial fans, sediment can be recycled and this behavior has been highlighted as a mechanism by which allogenic 24 grain-size fining trends are buffered. Here, we evaluate evidence of self-similarity in surface gravel-size 25 distributions on three geomorphically diverse alluvial fans in the Iglesia basin, south Central Argentine Andes. We 26 determine the statistical similarity between size distributions and demonstrate that a deviation from similarity occurs 27 when there is significant variability in the coarse tails of the distributions. Our analysis indicates a strong correlation 28 between the degree of sediment recycling and the significance of coarse clasts present on the bed surface. However, 29 these coarse clasts have little impact on the bulk of the size distribution and, by fitting a relative mobility transfer 30 function, we demonstrate that size-selectivity alone can explain the size distributions observed. This is evidence to 31 suggest the geomorphic dynamics of individual systems have only a minor influence on deposited grain size trends. 32

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