Reply to discussion on ‘Reactivation of landsliding following partial cliff stabilization at Barton-on-Sea, Hampshire’ by M. E. Barton & P. Garvey Quarterly Journal of Engineering Geology and Hydrogeology , 44, 233–248

Abstract

We thank the discussers for their contribution and the interesting questions they raise regarding our paper (Barton & Garvey 2011). We will divide their comments and questions into four sets and answer each of these in turn. A well-developed bedding plane shear surface is developed at 0.2 m above the ferruginous concretionary layer marking the top of Zone F1 in the cliffs fronting the Naish Farm estate. It forms a very prominent and unmistakable feature in a scarp face in this area, which is well seen to the west of the area being considered in the paper. We note that the discussers have been to see this but they make no comment on the problems encountered when trying to trace this surface eastwards towards the Cliff House Landslide and Barton-on-Sea. The scarp becomes a much less discernible feature, being dissected by a number of mudslides, and the area is extensively covered with talus and scrub vegetation. Exposures become very rare, which is not what one expects when a bedding plane shear surface is controlling the morphology of the undercliffs. By dint of struggling through the mud and scrub, we managed to find an exposure [NGR 423038 093065], which is about 50 m west of ‘Tom’s Garden’ (see fig. 1 of the paper), in the correct part of the stratigraphy but were unable to find either polishing or slickensiding along bedding planes above the concretionary layer. We presume, therefore, that shearing along the F2 surface is not continuous from east to west along this portion of the outcrop. We have commented upon this is our paper (on p. 235) and noted that it is a curious feature and an interesting subject for future research. Movement along the F2 surface is resumed further east and was clearly involved in …