Controls on global submarine canyon occurrence and formation processe s– Insights from Spatial Point Pattern Analysis –

Submarine canyons are the main conduits that transport material such as sediment, organic carbon, and litter from the continent to the deep sea. This transport of material is more efficient when the canyon heads incise into the shelf, as opposed to canyons that are confined to the continental slope. The specific controls on the distribution of these two canyon types along the world’s continental margins remain unquantified and we still lack knowledge about these seascape shaping processes.

Spatial statistics on a global scale help to reveal these processes.  In this study, we successfully predict the global patterns of submarine canyon occurrence along major continental margins based on terrestrial and marine environmental variables using point patterns on linear networks. We show that submarine canyon density of both types increases as a function of gradient of the continental slope which is the most important predictor. Subsequently, the locations of slope-confined canyons are best predicted by age of the adjacent ocean lithosphere with old ages corresponding to high canyon densities. Shelf-incised canyons are best predicted by the shelf gradient which correlates positively with shelf-incised canyon densities and, to a lesser extent, by high water discharge from the adjacent catchments.

Our results show that marine variables – primarily the continental slope gradient - are most crucial for spatially predicting submarine canyons while terrestrial variables are of lesser importance. The influence of terrestrial conditions and shelf morphology on slope-confined canyons is minimal. However, incision of canyons into the shelf is facilitated when shelves are steep and river discharge is high, highlighting the secondary role of canyon head erosion by terrestrially derived sediment. Our results underscore that the formation of submarine canyons worldwide is mainly governed by backward erosion along steep continental slopes by mass failure and/ or erosive sediment density currents.  Erosion by sediment flows carrying sediment directly from terrestrial sources is likely less important for the formation of submarine canyons.