Diversity of modern turbidity currents in a land-detached submarine canyon

Turbidity currents in land-detached submarine canyons have long been considered largely inactive; however, recent observations offshore western Europe show that they can occur annually, challenging the highstand paradigm. Direct observations of turbidity currents in land-detached canyons remain rare, which has led to simplified assumptions about their behavior. Here, we combined autonomous underwater vehicle (AUV) surveys, mooring observations, and a box-core transect to examine the recent activity of turbidity currents in the land-detached Shortland Canyon, eastern Canada. Box cores comprise a turbidite with evidence of a dense basal layer, likely associated with rare large external triggers. AUV bathymetry does not support frequent turbidity currents with dense basal layers, as crescentic bed forms are poorly developed in the thalweg. AUV surveys and box cores indicate that most upper canyon turbidites are reworked by bottom currents, whereas deeper-water turbidites are more frequent and thin-bedded resulting from dilute turbidity currents. Mooring data reveal two slow-moving and dilute turbidity currents in 2024−2025 at 1050 m water depth that were not detected at shallower canyon-head sites, indicating that they were triggered at depth. Our results show that land-detached canyons do not follow a single behavioral pattern compared to shore-connected canyons, which typically show evidence of frequent shelf-edge turbidity currents. Some land-detached canyons experience annual large-scale turbidity currents, some are dormant, and others fall in between (this study). These findings underscore the conclusion that turbidity currents in land-detached submarine canyons are highly variable and cannot be generalized under a one-size-fits-all model.