Estimating bed form height from sorting preserved in sedimentary records of river dunes, deltas and bars (original) (raw)
2007, Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, Enschede, NL, 17-21 September 2007
We present a proof of principle for using a recent model for grain size-sorting over a bed form lee face to reconstruct the bed form height from a partially preserved dune or delta deposit. The lee face sorting model was developed to describe the grain size-selective deposition of particles over a bed form lee face for use in a new type of stochastic sediment continuity model for conditions with nonuniform sediment and river dunes. The lee face sorting model is applied to variable elevation ranges of the measured sorting in dunes and deltas of which the height is known but not used in the model predictions. We find that reliable estimates of the bed form height and the composition of the lee face deposit can be derived, under the conditions that more than 50% of the original bed form height has been preserved and sufficient samples of the bed composition over this range are taken. The estimate of the bed form height is a lower limit, as the method shows a systematic underestimation of the original bed form height due to the sorting being stronger over the lower part of a bed form than over its upper part. The sorting model can thus be applied to estimate bed form height and bed load sediment composition from vertical sorting profiles collected from individual cross-sets of partially preserved bed form deposits. Bed form height and sediment composition are robust indicators for palaeoflow conditions.
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