About 22 ka in the past, when the climate was cold, dry and windy. the gulfs were dry plus the peninsula was connected to Kangaroo Island. The sea level rose until about 7000 yrs back, producing the gulf and forming The present cliffs, shorelines, dunes and marshes with the coastline. https://erickplduj.bloggerchest.com/11513706/the-greatest-guide-to-arkaroola-ridge-top-tours