Incised valley lengthens upstream by headward erosion with attendant flow piracy. Downstream the valley lengthens by forced regression. Gravity flows carry sands to deep basin. During the rapid fall, focussing of flow into incised valley leads to flow deepening with attendant increase in shear stress. As a result the deposition within the incised valley is better sorted and has enhanced porosity.
Growth faults develop along the prograding delta front.
They seem to initiate and continue during the rapid fall phase, but may have begun during the previous highstand systems tract. We suspect that this was due to the subsidence profile and the resulting distribution of relative base level. The erosion front migrated headward by nick point retreat, followed by a wave of deposition that migrated headward. Possibly deposition is forced by widening of flow path causing flow shallowing, coupled with relative base level rise in the basin center. Ultimately valley widens across the basin with penecontemporaneous sedimentation, producing a relatively widespread, albeit subtle, disconformity across the basin.