Large scale structural control on regional coastline orientations: example from South-eastern France

Abstract : The morphology of rocky coastlines is the expression of the interaction between external forcings and the intrinsic rock mass properties, leading to a specific erosional response. Among these rock mass properties the contribution of structural discontinuities is still poorly understood. Nevertheless, recent studies suggest that geological structures may have a first order influence in controlling the coast morphology. Understanding how the structural pattern interacts with erosion processes is fundamental to assess the evolution of these environments. We propose a regional comparison between the orientation of rocky shorelines and faults segments in six different litho-structural units in the Provence and Cote d'Azur area (southern France). Our analysis reveals that in many of these sectors the dominant fault trend (E-W) is also present in the distribution of coastlines orientations. In some particular areas, a complex geological inheritance (Maures) blurs this apparent relationship between faults and coastal morphology. We conclude that, in our study area, the level of complexity of the structural setting seems to significantly control the nature and shape of the coastline.