Bedding-controlled coastal landslides in Southeast Britain between Axmouth and the Thames Estuary

Abstract

The coastline of Southeast Britain is formed in sedimentary rocks of Jurassic, Cretaceous and Tertiary age, the majority of these deposits containing thick strata of mudrocks, which have very low angles of dip. Where these strata are appropriately exposed, particularly at the foot of a coastal slope, they give rise to landslides where all or part of the sliding surface follows a single bed of mudrock. Where the dip of the bedding is steep, such landslides are referred to as dip-slope failures. However, landslides where the basal sliding surface is controlled by the location and orientation of a single argillaceous bed in the sequence are better termed ‘bedding-controlled’ landslides. In addition, where coastal slopes contain several layers of mudrocks, geometrically similar landslides may occur with perched slide surfaces breaking out at a higher level within the slopes. Landslides with strong bedding-controlled basal shear surfaces are the predominant form of instability along the southeast coastline of Britain. Many of the individual landslide cases used in this paper have been studied separately over many years. The general similarity of the different records is discussed, drawing important inferences on a number of aspects of these landslides with a variety of basal sliding surface geometries.