ORBITAL FORCING OF CLIMATE OVER SOUTH-AFRICA - A 200,000-YEAR RAINFALL RECORD FROM THE PRETORIA SALTPAN

Late Pleistocene variations in rainfall in subtropical southern Africa n are estimated from sediments preserved in the Pretoria Saltpan, a 20 0000 year-old closed-basin crater lake on the interior plateau of Sout h Africa. We show that South African summer rainfall covaried with cha nges in southern hemisphere summer insolation resulting from orbital p recession. As predicted by orbital precession geometry (Berger, 1978), this South African record is out of phase with North African palaeomo nsoon indices (Street and Grove, 1979; Rossignol-Strick, 1983; McIntyr e el al., 1989); the amplitude of the rainfall response to insolation forcing agrees with climate model estimates (Prell and Kutzbach, 1987) . These results document the importance of direct orbital insolation f orcing on both subtropical North and South African climate as well as the predicted antiphase sensitivity to precessional insolation forcing . (C) 1998 Elsevier Science Ltd. All rights reserved.