The Strata And Environmental Of Salawusu During The Stage Of Middle And Late Pleistocene In Haojiayao In Hetao Basin

Based on methods of lithostratigraph, geomorphology and sedimentlogy as well as the field work, the paper deals with the lacustrine deposits from the Haojiayao section in Tuoketuo town, Inner Mongolia Autonomous Region.The depositional sequence of the Haojiayao section has been established as it could be divided into three depositional stages and the second stage includes three sub-stages.Haojiayao section is 47m thick in all.The upper part of the section is covered by loess from Chengchuan formation whose thickness is 3.5m,its deposition period is from 94.5 Ka BP to 19.3 Ka BP which belong to Late Pleistocene; Salawusu formation is 43.5m thick whose period is from 144.4 Ka BP to 99.3 Ka BP. It links Middle and Late Pleistocene and their deposition is disconnected.The median grain-size of Haojiayao section is 59.75μm, Grain-size frequency curves indicates the main composition of haojiayao section is sand sediment and silt fraction, the lower strata of Haojiayao section is composed of bad sortable grit fraction, the top is composed of good sortable silt fraction. Frequency curves of sediment are divided into three types, they are double kurtosis, triplicate kurtosis and fourfold kurtosis; Grain-size distribution is consist of different components and frequency curves.The LOI550 section of Haojiaoyao is positive correlated to mean grain-size value, thin clay and silt but it is negative correlated to grit fraction and fine sands. The correlation between LOI950 and different grain is bad.Higher vaules of LOI550 section and that of fine grains indicate a warm-humid climate; The lower values of LOI550 section and that of corase grains indicate a cold- dry climate;the relation between LOI950 and environment is complicated.The Salawusu formation recorded the characterisitic of environmental change when oxygen isotope is in 5b-6b, its environmental recordining is identical to that of GRIP. The great various recordings between Salawusu formation and stalagmite in Dongge cave indicate environment in Tuoketuo was mainly dominated by monsoon from eastern Asian and its recording is not fully coincident with that of GRIP which reflect a special environmental change in regional climate.