oa Annals of the Natal Museum - Pleistocene shorelines in the southern and south-eastern Cape Province (Part 2)

Volume 21, Issue 2
  • ISSN : 0304-0798



Shorelines at 18, 9, 6, 3½ and 1½ m S.L. are traceable along the whole southern Cape coast as far as Cape Town. The first three form Krige's Major and Minor Emergences. Krige probably considered his Major Emergence to be the earliest pleistocene shoreline because higher beach-exposures are rare in the area in which he mainly worked, being largely masked by massive dune-rock. I have discussed the higher beaches as far as Cape Agulhas in part 1; between Cape Agulhas and False Bay very few exposures are known, but they seem to correspond in altitude with those near Riversdale. In the Cape Peninsula no certain shorelines are known even as low as 30 m, so it seems that tectonic movement and erosion have disorganized all the older deposits. The 18-metre shoreline presents few problems. Discussion is centred on whether there were two separate transgressions to 9 m and 6 m, on evidence from morphology, artefacts, fauna and isotopic dates. The evidence from artefacts is fairly conclusive; it seems that rolled Late Acheulian and Sangoan appear in the 6-metre gravels, unrolled in the 9-metre; but many artefacts have been removed from critical sites and cannot now be traced. No fauna can be proved to be associated with the 6-metre terrace. Isotopic dates, to be used with caution, suggest that the 6-metre shoreline belongs to a Würm-interstadial; they will be discussed again for the Atlantic coast of the Cape, whence more have been obtained. The 9-metre shoreline almost certainly dates to the Eem interglacial. In estuarine beds assignable to the 9-metre sea occurs the typical Swartkops-fauna, with a few warm-water and extinct species in addition to many still living in the southern Cape. Nearly all open beaches of the same stage lack the typical species of this fauna. Some of these species have been found in beds belonging probably to the 18-metre transgression; but fauna from this level is scanty and cannot be properly evaluated. Practically nothing has been found in the 30-metre beaches. It may be significant for an interpretation of global climatic trends that warm-water fauna occurs at the same time at both ends of Africa at about the same latitude. The holocene transgressions, to 3½ and 1½ m, are distinguishable at many points along the whole southern Cape. A few isotopic dates indicate that the latter is after 2000 B.P.; the former, which has been recorded elsewhere in Africa, dates to about 5000 B.P. These dates confirm Fairbridge's curves of holocene rise of sea-level for steep coasts.

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