Geologic controls on the morphology of La Aguja submarine canyon

The seascape of the continental shelf and slope offshore Santa Marta is sculpted by the submarine Aguja Canyon, a deep seafloor incision that extends from the inner shelf to the continental rise along some 115 km. No major modern rivers flow into this canyon, thus ruling out principal fluvial control on the present geometry of this feature. Recently acquired multibeam sonar bathymetry data have provided insight into the three-dimensional geometry of this outstanding feature that disrupts the seafloor relief. In addition, seismic reflection data provide images of the internal structure of the canyon’s subsurface. In this study, we describe the morphology of the Aguja Canyon along a series of transects, interpret the structure under the canyon, and discuss possible geologic processes that played a role during its formation and modification. Seismic data indicate that incision of the canyon’s inner reach is the result of recent motion along the western termination of the active Oca strike–slip fault. Relief in the middle reach may be predominantly controlled by sedimentary processes (erosion, infilling and lateral thalweg migration). In the past, however, the middle reach may have been tectonically controlled. The outer reach appears to be the combined result of tectonics, sedimentary process and mud-diapiric intrusions. We conclude that the Aguja Canyon is predominantly a tectonic feature that accommodates shallow transpressive stresses as dislocation of the seafloor.