QUANTITATIVE ESTIMATES OF PALAEOPRECIPITATION AT XIFENG, IN THE LOESSPLATEAU OF CHINA

Using Be-10, recent studies (Heller et al., 1993; Beer et al., 1993) h ave tried to reconstruct palaeoclimatic records by separating the seco ndary (pedogenic) and primary (aeolian; detrital) contributions to the magnetic susceptibility of Chinese loess. Here we use a technique, wh ich monitors the temperature dependence of magnetic remanence, to esti mate the magnetisation and relative contribution of the superparamagne tic (SP), single-domain (SD) and multidomain (MD) ferrimagnetic compon ents in the Xifeng loess section. On the assumption that the SP ferrim agnetic component is dominantly of pedogenic origin, the magnetisation of this component has also been determined for samples taken from the topmost palaeosol (SO), at six sites over the Loess Plateau, and dire ctly correlated with present day precipitation at these sites. This co rrelation is then used to estimate quantitatively palaeoprecipitation for the topmost 16 m of the Xifeng section, which covers about the las t 140,000 years. The data indicate a considerably reduced precipitatio n during the glacial, loess-forming periods and a significantly higher level of precipitation than today during the last interglacial period .