5 Paleoclimate I (Posters)

Thursday, 24 July 2003
1:30 PM - 4:30 PM

AEOLIANITE AND BARRIER DUNE CONSTRUCTION SPANNING THE LAST TWO GLACIAL-INTERGLACIAL CYCLES FROM THE SOUTHERN CAPE COAST, SOUTH AFRICA

Paper number: 5-28
Program: Technical Sessions
Time: 1:30 PM – 4:30 PM

Authors

Abstract

The southern Cape region of South Africa has extensive coastal aeolianites and barrier dunes which offer the potential to increase our understanding of palaeoenvironments in an area of considerable climatic and oceanic sensitivity as well as of archaeological importance. Whilst previously reported their lack of chronostratigraphy has precluded an understanding of their relationship with Late Quaternary climatic and sea-level fluctuations. Sedimentological and geomorphological studies combined with an optical luminescence dating programme for sites on both Cape Agulhas and the Wilderness cordon dunes reveal aeolianite and barrier dune construction spanning at least the last two glacial-interglacial cycles. Aeolianite deposition has occurred on the Southern Cape coast at c. 68-75, 89-95, 104-122, 176-189 and >210 ka before the present. Using this and other published data coupled with known Late Quaternary sea level fluctuations and palaeocoastline configurations it is concluded that these depositional phases appear to be controlled by interglacial and subsequent interstadial sea-level high stands. These marine transgressions and regressions allowed on-shore carbonate rich sediment movement and subsequent aeolian reworking to occur at similar points in the landscape on a number of occasions. The lack of carbonates in more recent dunes (Oxygen isotope stage 1/2 and 4/5) are attributed not to leaching but due to changes to carbonate production in the sediment source area caused by increased terrigenous material and/or changes in the balance between the nutrient rich cold Benguela and warm Agulhas ocean currents.