Rocky reaches of the southeast African coastline are characterized mainly by log-spiral and headland-bound bays. Extensive fieldwork was carried out to investigate both documented and new exposures of Cretaceous beds on the southern KwaZulu-Natal and upper Eastern Cape (Transkei) coasts. Our results suggest that geological inheritance plays an important role in the contemporary rocky coast geomorphology. We offer evidence that post-Gondwana break-up mass flow channels play an important role in the present southeast African coastline morphology. Mass flow channels contain fills of incompetent Cretaceous rocks which are being preferentially eroded by prevailing marine and fluvial processes to form headland-bound embayment landforms. This study has identified an important geomorphic process for the development of the current southeast African coastline.