RECONSTRUCTING WATER-SEDIMENT PALEO-FLUXES FROM RIVER DUNE DEPOSITS

Global models of water-sediment fluxes rely in part on functional relationships between water-sediment river discharge and drainage area for their prediction or reconstruction of environmental conditions. Consequently, the difficulty in documenting the prehistoric impact of changes in climate resides in estimating paleo-drainage area. It is important to search for independent sources of information about fluvial water-sediment paleo-fluxes, and the analysis of the sedimentary record can bring critical insights to this issue. In addition, most present flux models predict values at river mouths and the case of material and processes within river networks, i.e. where it matters the most to the population, still requires consideration.

Modern and ancient river deposits, which are commonly composed of dune cross-stratification, reflect the variation of flow conditions and the successive deposition/erosion events in time and space. This paper review the basics and recent applications of the quantitative interpretation of dune deposits in regard to climate change, and presents a new approach for linking these stratigraphic models to new fluvial morphodynamics models, hence making possible the estimation of flow conditions and sediment fluxes. Results come from the analysis of experimental and natural data on dunes and/or deposits from modern and Pleistocene Rivers. The present results are potentially important for helping us to understand and distinguish the variability of water-sediment fluxes due to climate and/or anthropogenic controls.