Detailed seafloor imagery of turbidity current bedforms reveals new insight into fine‐scale near‐bed processes

Alexandre Normandeau (1) , Patrick Lajeunesse (2) , Jean‐françois Ghienne (3) , Pierre Dietrich (4)

1 GSC Atlantic - Geological Survey of Canada [Dartmouth]
2 ULaval - Université Laval [Québec]
3 IPGS - Institut de physique du globe de Strasbourg
4 GR - Géosciences Rennes

High-resolution imagery of the morphological character of modern active turbidite systems are critical for understanding the complexity of turbidity current processes occurring on the seafloor. Here, we describe a 30 cm-resolution autonomous underwater vehicle (AUV) repeat bathymetric dataset that allows to significantly increase the geomorphological detail of crescentic bedforms in turbidite systems. This repeat imagery shows the erosion produced by dense basal layers at the base of turbidity currents, the inception of plunge pools, and the controls that hydraulic jump troughs have on subsequent flow path of weaker turbidity currents. Transverse small-scale scours located in cyclic step troughs suggest that weak flows follow local relief, therefore explaining the wide variability of turbidity current flow indicators observed in outcrops. This imagery demonstrates that turbidite systems are formed by the superimposition of erosion surfaces and depositional patterns recording contrasted flow behavior and provides new views on turbidity current behaviour in natural environments.

Keywords: Turbidity currents; AUV; cyclic steps; crescentic bedforms; Pointe-des-Monts

Domains: Hydrology; Geomorphology

Alexandre Normandeau, Patrick Lajeunesse, Jean‐françois Ghienne, Pierre Dietrich. Detailed seafloor imagery of turbidity current bedforms reveals new insight into fine‐scale near‐bed processes. Geophysical Research Letters, 2022, 49 (11), pp.e2021GL097389. ⟨10.1029/2021gl097389⟩. ⟨insu-03681046v2⟩