Controls on submarine canyon connection to the shoreline: a numerical modelling approach

Abstract

Submarine canyons with heads located close to shorelines, known as shore-connected canyons, provide a focussed pathway for basinward sediment transport. Placing greater constraints on the key parameters that control the formation of shore-connected canyons can help us predict the efficiency of sediment export to deep-water under different environmental conditions and through time. Using a numerical model incorporating geomorphic principles, we show that shore-connected canyons are most active when fluvial discharge is high, the continental shelf is steep and narrow, and the magnitude of relative sea-level change is high. The numerical model reproduces observed bathymetric distributions of shore-connected submarine canyons, indicating that the empirical relationships underlying these numerical models are accurate descriptions of shore-connected canyon formation in nature. Our study provides constraints on the key quantifiable parameters controlling shore-connected submarine canyon formation and maintenance, such as fluvial discharge and basin physiography, allowing for more accurate predictions of the efficiency and timing of sediment transfer to the deep sea under different conditions. The model results suggest that; 1) submarine canyons may form frequently on the slope due to submarine processes, but subaerial processes control which submarine canyons are most likely to connect to the shoreline, 2) margin physiography and sediment supply are more influential in driving submarine canyon incision across the shelf and sediment transfer than the exact nature of the gravity flow triggering mechanism, and 3) the stratigraphic records of shore-connected submarine canyons and fans are more influenced by onshore climate and tectonics than eustasy.