Mass wasting along atlantic continental margins:A comparison between NW-Africa and the de la Plata River Region (Northern Argentina and Uruguay)

The passive continental margins of the Atlantic Ocean are characterized by thick sedimentary successions, which might become unstable resulting in landslides of various sizes. The type of mass-wasting differs between individual margin sections but the reasons for these differences are not well understood. The NW-African continental margin is characterized by several large-scale but infrequent landslides, while the continental margin in the de la Plata River region (northern Argentina and Uruguay) shows widespread small-scale mass transport deposits. These different styles of mass wasting can be explained by different oceanographic and sedimentary settings. The margin off Northwest Africa is characterized by high primary productivity caused by oceanic upwelling as well as locally focused aeolian input resulting in relatively high sedimentation rates. This setting leads to sediment instabilities arising primarily from underconsolidation of deposited sediments and widespread weak layers. In contrast, the modern ocean margin off Uruguay and northern Argentina is characterized by strong contour currents and a high amount of fluvial sediment resulting in widespread contouritic deposits. These contourites are potentially unstable leading to smaller but more frequent landslides.