Editorial: Sculpting processes in shelf-incised canyons: implications for margin architecture, resource potential and environmental management

Résumé

The five contributions gathered in this Research Topic highlight how sculpting sedimentary processes influence shelf-edge morphology, sediment storage and sourceto-sink connectivity along continental margins from diverse geological settings. These contributions converge around three key themes that define the dynamics of shelfincised canyons: (1) Recent sedimentary processes and morphodynamics influencing sediment storage and release in two end-member situations of sediment sourcing: fluvial supply (Congo Canyon; Hasenhündl et al.) vs littoral drift (Mattole Canyon; Joerger et al.); (2) Sedimentary canyons as natural and anthropogenic archives according to degree of incision, from shelf-incised to shelf-margin canyons (López-Quirós et al.); (3) Canyon initiation and development under different controls: tectonics, gravity flows, bottom currents (Gamberi et al.; Verweirder et al.).Large river-fed systems highlight the role of sustained sediment supply in morphodynamic behaviour. The Congo Canyon-Channel system provides a morphometric perspective on channel-modifying processes thanks to repeated fullcoverage bathymetric surveys (Hasenhündl et al.). Through systematic identification of morphometric fingerprints, three morphodynamic reaches are distinguished, each characterized by different processes: landslide-induced damming and re-incision in the upper reach, meander sweep and avulsion dynamics in the middle reach, and knickpoint migration with multi-stage sediment transport in the distal sector. These observations reveal how canyon-channel systems exhibit a distinct zonation of sediment storage and release, with implications for sediment flux to the deep sea and for hazards to seabed infrastructure.Shelf-incised canyons may also be sustained by coastal processes even in the absence of large fluvial systems. Along the northern California margin, littoral convergence adjacent to the Mattole submarine canyon promotes sediment accumulation in the canyon head region (Joerger et al.). Numerical wave modelling and sedimentological analyses indicate that bathymetric sheltering and seasonal wave-direction variability drive convergence of sediments derived from coastal streams. This study highlights how canyon heads can function as dynamic buffers, storing sediment over decadal scales before episodic evacuation. Importantly, it shows that shelf-incised canyons operate along a continuum of connectivity states, with sediment supply modulated by coastal hydrodynamics rather than by major river systems.Environmental forcing, including anthropogenic influence, adds another layer of complexity to canyon dynamics. In the western Mediterranean, the Motril, Carchuna and Calahonda shelf-incised canyons exhibit contrasting sedimentary behaviours reflecting differences in fluvial input, longshore drift and degree of incision, even within a very narrow shelf. (López-Quirós et al.). Multi-proxy sedimentological and geochemical records reveal how Late Holocene climatic fluctuations and human activity have modulated sediment delivery. This study reinforces the notion that not all shelf-incised canyons function as transport pathways to the deep basin; some of them may act as sensitive environmental archives, recording the progressive imprint of hydroclimatic variability and anthropogenic disturbances. The Motril Canyon preserves a highresolution archive of environmental change over the last two millennia. In contrast, the Carchuna Canyon contains several sandy layers that document the periodic occurrence of gravity flows during the recent past.Canyon initiation pathways are strongly dependent on gravitationally-induced processes. On the tectonically active northern Sicilian margin, submarine landslides play a primary role in canyon nucleation and shelf-edge indentation (Gamberi et al.). Multibeam and seismic data reveal that different landslide styles generate distinct canyon morphologies that contribute to margin degradation and shelf indentation. Debris flows are shown to be the dominant mechanism driving slope excavation and canyon propagation. This contribution also underscores that canyon formation is part of a hierarchical process of margin adjustment to tectonic tilting and uplift.The land-detached Gollum Channel System in the Porcupine Seabight exemplifies a multigenerational canyon-channel complex whose origin predates Quaternary glaciations (Verweirder et al.). Seismic stratigraphy indicates initiation linked to early Pliocene margin tilting, with subsequent reuse by glacially derived gravity flows. Repeated incision along preferential pathways and interaction with along-slope bottom currents redistributed sediments towards drifts and cold-water coral mounds downstream. This case study emphasises that some canyon systems are structurally inherited and persist through multiple climatic regimes, serving as long-term conduits embedded within evolving margin frameworks.Understanding sculpting processes in shelf-incised canyons is not solely a matter of geomorphological interest. These canyons excavate, store and redistribute sediments, reactivate inherited pathways and encode environmental change within their fills. Recognizing these coupled dynamics moves the focus beyond canyon morphology and towards the broader question of how continental margins maintain and reorganize sediment-routing systems through time. Considering different tectonic forcings, conditions of sediment supply and degrees of canyon incision, the studies presented in this collection provide new insights into how shelf-incised canyons are initiated, maintained and reactivated, and offer a physical framework upon which future biological, geochemical and hazard-related investigations can build.

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