Seepage-induced erosion of submarine carbonate escarpments: a numerical simulation

A three-dimensional, numerical model has been constructed to examine the seepage-induced erosional process of the Florida carbonate escarpment. The erosion takes place either by the mechanical failure associated with the seepage force or the corrosion due to the fluid chemistry. The numerical model assumes homogeneous Darcian fluid flow and uses the strongly implicit finite different scheme. The erosion is reflected in the model as removal of the finite difference cells whose pore pressure gradient exceeds a prescribed critical value for failure. Seafloor is the surface boundary of zero-excess pore pressure. The fluid is assumed to enter from the landward side of the formation. The model results show that the topographic variation of the surface boundary causes refraction of the fluid flow field and that the flow focuses at the base of the escarpment. The seepage-induced erosion takes place bottom-up, steepens the lower escarpment slope, and hence, further intensifies the flow at the base. Because of this positive feed-back mechanism between the hydrogeological regime and the geomorphogy, the escarpment wall keeps retreating landward. This mechanism can also be responsible for the formation and growth of the theater-headed submarine canyons on the Florida Escarpment. Spacing and shape of these canyons are strongly influenced by the geometrical and hydrological parameters of the carbonate escarpment.