Controls on Fluvial Incision of Continental Shelves

Fagherazzi, Sergio¹, Alan Howard², W. Niedorodac³, Patricia Wiberg² (1) Florida State University, Tallahassee, FL (2) University of Virginia, Charlottesville, VA (3) URS Corp, Tallahassee, FL

During sea level low stands continental shelves were dissected by a network of channels somewhat resembling today's coastal plain streams. The network was subsequently buried or erased by marine processes during sea-level transgression, so that only some tracts are conserved in the geological record. Herein we use a numerical model to study the processes responsible for total channel incision during sea level regression. We find that four factors control the total incision on the shelf: i) the presence of convex deposits; ii) the evolution of the rivers towards equilibrium (graded) conditions; iii) geometrical differences between coastal plain and shelf; and iv) the exposure of the continental slope. The model is then applied to the Adriatic Sea, Italy. Simulations show that incisions in the Adriatic shelf develop in high-stand fluvial deposits in the early stages of sea level fall. At lower sea level, fluvial incision occurs in the mid-Adriatic due to the regrading of the Po River after the capture of the Apennine streams in its drainage system.