During the investigation of the Weishui River valley, the authors found many palaeoflood slack-water deposits sandwiched in Holocene loess-soil profiles. On the basis of field survey, the authors collected samples in the Yangling district and analyzed their grain size distribution, magnetic susceptibility, loss on combustion, and content of calcium carbonate. The evidence shows that sedimentary characteristics of slackwater deposits are different from loess and soil in the Holocene. The authors conclude that the corresponding palaeofloods occurred in 4 500~4 100 a B.P., on the basis of stratigraphic correlation, cultural layers in the above and below slack-water deposits and the age correlation of palaefloods that were main stream of Weishui River. The age is equivalent to late stage of Longshan Culture Age, and the palaeofloods correspond to floods before the Xia Dynasty. This study is important to reconstruct water level and peak discharge of Weishui River palaeofloods.
