Shelf regulation: is marine shelf width partly determined by autogenic processes?

Shelf width, specifically the width of the marine portion of the topset of prograding continental margin clinoforms, is significant as an important control on sediment and carbon routing from delta mouth to deep-water. Previous studies suggest shelf width is controlled by initial bathymetry, sediment supply, and accommodation. In this study, multiple numerical stratigraphic forward models with various formulation assumptions are used to investigate how shelf width may also be determined by delta auto retreat processes. Model results suggest that growth of wide shelves is most likely under conditions of shallow initial bathymetry, low subsidence rates, high sediment supply rates, and low marine sediment diffusion rates. However, results also suggest more complex dynamics generating an equilibrium topset width when autoretreat processes limit clinoform progradation and “lock-in” an aggradational shelf margin trend. Through time this aggradational shelf margin becomes increasingly difficult for the system to prograde beyond without substantial increases in sediment supply relative to the initial progradational clinoforms supply. Similar results from multiple model formations suggest this self-regulating mechanism could produce a shelf-edge lock-in effect that is a significant autogenic control on maximum shelf width.