Morphodynamics in sediment-starved inner-shelf submarine canyons (Lower St. Lawrence Estuary, Eastern Canada)

Morphological expression of bedforms formed by supercritical sediment density flows on four fjord‐lake deltas of the south‐eastern Canadian Shield (Eastern Canada)

“…In order to support the interpretation herein that the bedforms observed on the four fjord‐lake deltas are formed by supercritical density flows, they are compared with cyclic steps and undulations observed elsewhere in marine and lacustrine settings. Figure A compares typical profiles from the four fjord‐lake deltas to bedforms observed in the Santa Monica (California; Tubau et al ., ), Monterey (California; Smith et al ., ), Pointe‐des‐Monts (Québec; Normandeau et al ., ) and Cape Breton (France; Mazières et al ., ) canyons. These profiles show that the bedforms have similar slopes, wavelengths, heights and stoss and lee slopes.…”

“…The crescentic bedforms observed in this study are often similar to bedforms observed in many submarine canyon and channel environments (Fig. ) (Smith et al ., , ; Paull et al ., ; Hill, ; Babonneau et al ., ; Hughes Clarke et al ., ; Mazières et al ., ; Normandeau et al ., , ; Tubau et al ., ). The origin of these bedforms in submarine canyons has been debated (Paull et al ., ) but many studies now suggest that they are formed by supercritical density flows (Froude number >1) and that they are cyclic steps (Lamb et al ., ; Cartigny et al ., ; Kostic, ; Fildani et al ., ; Tubau et al ., ; Turmel et al ., ): bedforms produced in the upper flow regime that migrate in an upslope direction.…”

“…(A) Typical profiles collected over different bedforms and their comparison with bedforms observed in the Santa Monica (Tubau et al ., ), Monterey (Smith et al ., ), Pointe‐des‐Monts (Normandeau et al ., ) and Cape Breton (Mazières et al ., ) canyons. (B) Aspect ratios of the bedforms observed in the fjord‐lakes compared with those from undulations in the Mediterranean deltas (Cattaneo et al ., ; Urgeles et al ., ), the review of bedforms done by Symons et al .…”

“…(B) Aspect ratios of the bedforms observed in the fjord‐lakes compared with those from undulations in the Mediterranean deltas (Cattaneo et al ., ; Urgeles et al ., ), the review of bedforms done by Symons et al . (), the Pointe‐des‐Monts canyons (Normandeau et al ., ) and the Wabush Lake bedforms (Turmel et al ., ). (C) Correlation between aspect ratio and local slope for a wide range of bedforms reviewed by Dietrich et al .…”

“…Additional evidence for a cyclic step origin is provided by the morphology of the bedforms. The crescentic bedforms are nearly identical to others observed in marine settings (Figs and A) (Babonneau et al ., ; Mazières et al ., ; Normandeau et al ., ). The step‐like bedforms consisting of steep lee slopes and flat to low‐angle stoss sides are also typical of cyclic steps (Zhong et al ., ).…”