THE PALAEOCLIMATIC EVOLUTION OF THE YELLOW RIVER SOURCE AREA SINCE 130ka B P

By a comprehensive analysis of the proxy indices of climate such as readily soluble salt and spore-pollen of borehole profiles in Dougeyong Basin,the palaeoclimatic evolution pattern of the Yellow River source area since 130 ka B P has been revealad:1.From 130 ka B P to 110 ka B P,it was cold and dry;2.From 110 to 82 ka B P,cold but more humid;3.From 82 to 10.4ka B P,cold and dry;4.From 10.4 ka B P to recent(i.e.,Holocene),there was an alternation of warm-humid and cold-dry climate.And the climate in Holocene can further be divided into three stages:1)10.4-7.6 ka B P it was Anathermal;2)7.5-3.5 ka B P Megathermal;3)3.5 ka B P present Katathermal.In general palaeoclimate the area has a longer and earlier cold period and a shorter and later warm period as compared to other regions of the world.The climate fluctuations since Holocene have occurred at a time scale of one thousand years.Since Late Holocene there has been a gradual decreasein temperature and humidity.