Preservation and Completeness of Fluvial Meandering Deposits Influenced by Channel Motions and Overbank Sedimentation

Abstract

AbstractAssessing the contribution of geomorphic processes to the (non‐)preservation of sedimentary deposits is necessary to account for potential bias in measured accumulation rates in the stratigraphic record. In this study, a series of numerical simulations of fluvial meandering successions is performed using FLUMY, a model of channel motions and sedimentary facies deposition. We develop tools to measure non‐deposition (stasis S) and reworking (R) of previously deposited sediment between iterations, which are both generators of hiatuses in the sedimentary record. We then compare S and R with measurements of accumulation rates and completeness (C). Results show that combining measurements of both topographic and facies changes allows for a better record of surface evolution than measuring topographies only. Accumulation rate dependence on measurement time span allows distinguishing between two regimes. The first one (anti‐persistent) is characteristic of channel avulsion and compensational stacking until the whole domain is visited by overbank deposition, corresponding to the visitation timescale Tv. In the second regime (persistent), reworking by channel migration is the remaining active process until the whole system has aggraded one channel depth, corresponding to the compensation timescale Tc. Based on these results, we propose a new simple formulation based on stasis and reworking to estimate average completeness.