Impact of storms on mixed carbonate and siliciclastic shelves: insights from combined diffusive and fluid-flow transport stratigraphic forward model

摘要

A quantitative stratigraphic model of mixed carbonate/siliciclastic continental shelves is presented to investigate the relationships between depositional processes and stratigraphic responses at long-term, large spatial scales. A diffusion model is combined with a fluid-flow approach to simulate both long-term factors, i.e. the processes controlling large-scale architecture, and short-term processes, i.e. sediment redistribution by storms. Any net sediment accumulation is the result of the succession of a storm and a fair-weather period. Sediments are mobilized by waves and advected by low-frequency currents during storm events. Sediments are then reworked and redistributed downslope by diffusive processes during fair-weather period. The results are successful in capturing several major characteristics of both modern and ancient depositional systems (geometry; differential preservation, net accumulation rates). The study highlights the importance of waves and unidirectional currents. Depositional geometry and shelf morphology depend on the balance between available sediment supply (generated in situ or detrital) and the transport energy, which is related to the style of sediment transport (diffusive or advective), and to the magnitude and frequency of storms.