Geochemical Responses to PALAEOCLIMATE:EVIDENCE from the Early-Mid Holocene Lake Deposits at Dishaogouwan Section in the Salawusu Catchment of Inner Mongolia

Sediment grain size,organic carbon content(TOC),carbonate content and stable carbon and oxygen isotopes of carbonates in the Dishaogouwan section on the south edge of the Mu Us desert in Inner Mongolia were sludied in this paper.Age data were used to establish an age model for this section.All the sedimentary and geochemical paleoenvironmental proxies were used to reconstruct the palaeoenvironmental changes since 11 000 aBP,to 4 380 aBP,early to mid Holocene in this area.During the period from 11 000 aBP to 9 950 aBP,the study area was cool and dry.Precipitation in the south north part of Shanxi Loess Plateau and the water from melted Dishaogouwan frozen stratum were the main replenishment water for the Salawusu cathment.During the period of 9 950~9 100 aBP of early Holocene,temperature and precipitation increased with a high effective humidity,and the Dishaogouwan lake came into being.From 9 100 aBP to 5 850 aBP,temperature and precipitation continued to increase but effective humidity was a little lower,while the lake developed to its maximum and lasted for a long time.From 5 850 aBP to 5 100 aBP,temperature and precipitation started decreasing and the lake shrank at the same time.From 5 100 aBP to 4 700 aBP,palaeodune formed in this area under dry climate.There was a short period of temperature and rainfall rising during 4 500~4 380 aBP,and a small lake formed over a carbonate impermeable layer.Desertification has prevailed under the dry condition since 4 380 aBP up to present.