Influence of Sediment Cohesion on Basin-Filling Sedimentation Patterns

Li, Qi; Straub, Kyle M.

Recent experimental and numerical modeling studies show that cohesive sediment promotes channelization on delta-tops and reduces channel mobility. Cohesion in field scale sediment transport systems is associated with the transport and deposition of fine grained sediment and vegetation. Further, we hypothesize that cohesion in transport systems is correlated with enhanced deposition in floodplains, as these are large reservoirs of fine-grained sediment. In this study, we use a cellular model of river avulsion proposed by Jerolmack and Paola (2007) to explore how avulsion thresholds and floodplain deposition affect basin-filling sedimentation patterns and stratigraphic architecture. We conduct numerical experiments that explore the influence of floodplain depositional rate and avulsion threshold, parameterized through a superelevation criteria, on basin-filling, both of which are correlated with system cohesion. Specifically, we explore how the compensation index, which describes the tendency for transport systems to preferentially fill topographic lows, is influenced by sediment cohesion in alluvial basins. The modeling results suggest: (1) increasing floodplain deposition rate and/or avulsion threshold increases the temporal persistence of depositional patterns. These result in systematic shifts from compensation dominated to clustering dominated stratigraphy as floodplain deposition rate and/or avulsion thresholds increase. (2) From proximal to distal basin locations a systematic decrease in the compensation index is observed. Finally, we compare numerical results with properties of a physical experiment that uses cohesive sediment. This study advances our understanding of sediment cohesion in sediment transport systems with implications for the filling of alluvial basins and our ability to predict reservoir scale stratigraphic architecture.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013