Sediment supply controls on sequence stratigraphy

Abstract

A three-dimensional numerical model of deltaic deposition is used to study the influence of sediment supply changes on delta development. Sediment supply will have a cyclic variation under conditions of constant linear sea level rise and a combined cyclic sediment supply at cyclic relative sea-level. Results illustrate the differences in 3D form of delta, cross-section stratal geometry, and delta evolution during cycles of sediment supply change. During initial increase in sediment supply, stratal geometry is dominated by the prograditional to aggraditional with progressively steepening of the break point trajectory. During decrease of sediment supply, stratal geometry is controlled by amount of sediment volume supplied. Low sediment supply lead to a stratal geometry change from prograditional to aggraditional to aggraditional at a much earlier stage than deltas with high sediment supply. As a result, there is a delay on onset of aggradation is associate with an increase in sediment supply volume. The delta evolution during combine sediment supply under condition of a sinusoidal sea-level cycle form incised channels with varying head ward lobes during sea level fall. At sea level rise, sediment supply fills the relict topography around the lobes, forming an apron. The delta morphology and internal geometry are strongly controlled by changes in sea-level, but variation in sediment affect strike variation, shoreline shifts and basinward expansion.