The paleo-precipitation history recorded by the characteristics of grain-size of Lake Jingpo during Holocene

Grain-size composition of lacustrine sediment is a powerful indicator to water impetus change and humid variation in the history. Based on the analyses on the grain-size composition characteristics of JPH-1 core , from Lake Jingpo, northeastern of China, combined with C age sequence, the Holocene history of paleo-precipitation changes in this region can be concluded as below; ( 1 )9300 -8540 cal aBP was a relatively dry period accompanied with less precipitation. (2) 8540 -6350 cal aBP was a high lake level period, when the precipitation was relatively abundanto. (3) 6350 -4800 cal aBP, the climate became drought gradually. (4) 4800 -3120 cal aBP, the climate changed wet again. (5) 3120 - 1580 cal aBP was a relatively stable period maintained a high lake level with abundant precipitation. (6) 1580 cal aBP-present, it was an another climatically oscillation period in which the precipitation has been changing frequently. In recent centuries, the human activities, such as clearing the forest, destroying the original vegetation in lake watershed resulted in massive exposure of land surface, remarkable increase of erosion and more terrestrial materiel carried into lake. Therefore, the portion of coarser particles increased markedly.