Geotechnical properties and sedimentological processes of the Rhône continental margin

Abstract

Water content, bulk density, undrained cohesion and Atterberg limits have been measured in 71 cores sampled in the Rhône delta system, from shore to rise. The mean values of these properties vary from one physiographical zone to another; the inner part of the continental shelf shows mean maximum values of bulk density and cohesion higher than the outer part, whereas it is the reverse for water content and Atterberg limits. On the continental slope, the mean maximum values are generally lower than on the continental shelf, except for bulk density, and quite similar to those found on the continental rise. In each physiographical zone the variation of these properties with burial depth is related to the stratigraphy (e.g., superposition of Holocene and Pleistocene muds on the shelf and slope, alternation of pelagic and turbiditic facies on the rise) and to the major sedimentological and hydrodynamical conditions (such as, among others, flocculation on the inner shelf, turbidites or suspended deposits on the rise). Comparison between the plasticity chart of the Rhône cone system and of the entire Mediterranean Sea sediments reveals two major determinative factors for the Atterberg limits: sedimentation mechanisms and mineralogy of the clay fraction.