A model for the headward erosion of submarine canyons induced by downslope-eroding sediment flows
A simple, physically based computer model of continental slope evolution is used to investigate the sequence of submarine canyon formation. The model simulates submarine canyons as evolving under the influence of sedimentation, slope failure, sediment flow erosion, and topography. Interactions between these factors are modeled as being governed by local sea-floor slope, which in the model determines the extent of sea-floor failures, directs the downslope path of sediment flows triggered by the failures, and scales the amount of sea-floor erosion caused by the sediment flows. Based on these interactions, the model simulates a three-stage sequence for submarine canyon formation: (1) the erosion of pre-canyon rills by sediment flows initiated at sites on the upper slope oversteepened by sedimentation; (2) localized slope failure of the walls and/or floor of the rills at one or more mid- to lower-slope sites destabilized by sediment flow erosion; and (3) evolution of the failure into a headward-eroding canyon that advances upslope along the rills by sediment-flow-driven retrogressive failure. Through this sequence, the model simulates canyon and intercanyon morphology that successfully reproduces crosscutting relations observed between Lindenkohl Canyon and adjacent erosional slope rills on the passive-margin New Jersey continental slope, and between slope failures and long, narrow dendritic tributaries that enter into the Aoga Shima Canyon on the convergent-margin Izu-Bonin fore arc. These results suggest that the model may be applicable in explaining submarine canyon formation along a variety of continental margins. More significantly, in illustrating how sediment flows might repeatedly trigger retrogressive failures, the model presents a new explanation for submarine canyon formation that reconciles morphologic evidence for headward canyon erosion by mass wasting with the stratigraphic evidence for canyon inception by downslope-eroding sediment flows.