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Implications of high frequency variations in sediment supply for stratigraphic architecture - a numerical approach

By J.B. Wassmer

Abstract

The stratigraphy of a depositional system is determined by the complex interaction between a great number of processes influencing the rate of sedimentation and the rate of accommodation space creation or destruction. Interpretation of this stratigraphy requires an extensive knowledge of all individual forcing parameters, their stratigraphic responses and correlations, but it also requires a good comprehension of the sediment transport processes. In the last few decades much research has been focused on the controlling factors of accommodation space and especially on the role of changes in global- and regional eustacy. The influence of the processes affecting sedimentation rate are often underrated, although in particular the change in rate of sediment supply can profoundly affect stratigraphy. Sediment supply is known to vary on many timescales. The influence of these variations in sediment supply on the architecture of a depositional basin is poorly understood. Research has previously been conducted on low frequency cyclic variations, but it remains to be seen how the system responds to higher frequency variations. These occur from Milankovitch cycle-scale to a yearly seasonal scale, but are most often time-averaged in numerical simulations. Therefore, in this study, a numerical model simulating linear and non-linear diffusive sediment transport to an alluvial basin was used to look at the effects of high frequency cyclic variations in sediment supply. It was found that cyclic variations in sediment supply profoundly affect basin stratigraphy. The response to a cyclic variation in sediment supply is similar for linear and non-linear systems, with the difference that non-linear systems can build-up towards higher slope-angles. Furthermore it was found that a time-averaging of high-frequency variations in sediment supply can be justified, depending on the scale and purpose of the numerical simulation. When considering the overall geometry of a basin, a timeaveraged sediment supply can be justified. The resulting geometry of a system with a time-averaged sediment supply is highly comparable to the geometry of a system with a sediment supply with high frequency variations. However, when considering individual stratigraphic sequences, high-frequency variations in sediment supply need to be taken into account. The time-averaged sediment supply does not result in the stratigraphy and internal sequences that result from high frequency variations in sediment supply

Topics: Geowetenschappen, sediment supply, high-frequency variation, alluvial basin, numerical model, diffusion,
Year: 2009
OAI identifier: oai:dspace.library.uu.nl:1874/37361
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