Crescent-shaped morphotectonic features in the Gulf of Cadiz (offshore SW Iberia)

Multibeam swath bathymetry data from the Northwestern part of the Gulf of Cadiz revealed the existence of several intriguing kilometric crescentic depressions lying between −4300m and −4700m, never before reported to occur at such great depths. Morphological parameterization of these features, coupled with a detailed analysis of multi-channel and middle resolution seismic profiles, showed that these crescent-shaped features were formed due to the existence of specific time-recurrent interaction between: a) regional active thrusts, which portray the overall tectonic scenario in the area, and on top of which most crescentic depressions are carved; and b) tectonically induced scouring comprising localized erosion and simultaneous progradational sedimentation, produced by downslope currents of probable turbiditic origin. The obtained results also suggest a possible contribution of fluid migration and extrusion processes, such as mud volcanism and associated pockmark formation, besides gravity driven landslides and slumping, in the development of the studied crescentic depressions.