ABSTRACT
ABSTRACT: Groundwaters of known age contained in major aquifer systems in theAfrican sedimentary basins are of specific value in determining low resolution (±1000 a) characteristics of past climates, specifically palaeotemperature, air mass origins, humid/arid transitions and rainfall intensity. Results from both northern and southern Africa indicate the predominance of a westerly Atlantic air flow during the Late Pleistocene. Greater aridity during the Last Glacial Maximun (LGM) over most of northern Africa is recorded by the absence of dated groundwaters. An intensification of the African monsoon during the Early Holocene is apparent from isotopically light groundwaters found especially in Sudan. Maximum cooling around the LGM of 5-7◦C is recorded in the noble gas recharge temperatures from Africa. Modern recharge can be readily identified from the chemical and isotopic signatures (Cl, δ18O and 3H) in the unsaturated zone and in shallow groundwaters. The results indicate the non-renewability of many groundwater sources now being exploited across the arid and semi-arid regions of Africa.
