Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . oastal plains (berg winds:Shannon & Anderson 1982; Shannon 1985; Chapman & Shannon 1985). Thereare no quantitative data on the volumes of sediment transported during—nor onthe frequency of—these berg winds, but Shannon & Anderson (1982) havesuggested that one large katabatic event operating between 18° and 28°S mayinvolve as much particulate material as the annual sediment input from theOrange River. South of 23°S there are three zones in which large south-westerlytrending plumes have been consistently identified: the
Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . oastal plains (berg winds:Shannon & Anderson 1982; Shannon 1985; Chapman & Shannon 1985). Thereare no quantitative data on the volumes of sediment transported during—nor onthe frequency of—these berg winds, but Shannon & Anderson (1982) havesuggested that one large katabatic event operating between 18° and 28°S mayinvolve as much particulate material as the annual sediment input from theOrange River. South of 23°S there are three zones in which large south-westerlytrending plumes have been consistently identified: the largest is centred on theOrange River valley; the second between 10 and 20 km north of Luderitz; and thethird in the vicinity of Walvis Bay. These zones are thought to coincide withtopographic depressions that focus the winds (Shannon & Anderson 1982).Deposition appears to be confined to the continental shelf and, in comparisonwith fluvial input, is well dispersed, fine grained, and unlikely to be lost to the ANNALS OF THE SOUTH AFRICAN MUSEUM V/aW. — — — — Fracture zone 3km 3km isobath . Extent of drainage area Area of major aerosols Fig. 4. Drainage areas and fluvial sediment yields in southern = between Kunene and Orange rivers—no significant runoff; 2 = west coast: Orange, Olifantsand Berg rivers; 3 = southern Cape; 4 = east coast, including Tugela and Limpopo rivers. Runoff yield is in x 106 m3/yr. Abbreviations: = Cenozoic sediment accumulation rate/area within the 0,5 km isopachyte in m3/km2/yr; AFFZ = Agulhas-Falkland Fracture Zone; MFR = marginal fracture ridge. Rivers—K = Kunene, OR = Orange, OL = Olifants, B = Berg, T = Tugela, L = Limpopo. SOUTHERN AFRICAN DEEP-SEA SEDIMENTARY ENVIRONMENTS 7 marine environment by transport back onshore (although entry into food andchemical cycles will reduce the flux to the sea-floor). Depending on the frequencyof these winds (and the veracity of Shannon & Andersons 1982 suggestion), thetotal annu
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