Cliff-top storm deposits (55-63m amsl) from Morgan Bay, South Africa

Abstract

Smith, A.M, Green, A.N, Cooper, J.A.G. et al., 2014. Cliff-top storm deposits (55-63m amsl) from Morgan Bay, South Africa. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 349–353, ISSN 0749-0208.Cliff-top storm deposits (CTSDs) occur south of Morgan Bay, South Africa at elevations varying from ±55- to 63m. These occur as a ±10m-wide horizontal fringe of shell breccia mixed into a very thin (>15cm) sandy soil on the cliff top platform. Visually it is evident that the shell breccia is of various ages. Comparisons with proven wave breccia from this area indicate the same source. We suggest that this breccia was deposited as fall-out from wave and wind-borne plumes produced by wave bores striking the cliff base. These bores would likely have been produced by waves at least ~40m in height. Alternative interpretations, such as a perched marine desposit or tsunamiite are rejected in favour of CTSDs produced by multiple large wave events.