Geochemical Characteristics and Sedimentary Environment of the Salawusu Section

The chemical compositions of and the contents of CaCO;,flee Fe;O;and REE in the sedimentsof the Salawusu section have been analyzed to investigate the geochemical features of differentsedimentary facies and explore their sedimentary environments during the Late Pleistocene.The con-tents of CaCO;,free Fe2O;and ∑ZREE in lacustrine deposits of the middle part of the section arehigher than those in the other parts,except SiO;which shows an opposite trend.According to thedistribution characteristics of the components mentioned above,the section may be divided into fourparts which are equivalent to those divided in terms of lithologic characters and sedimentary facies.More remarkable characteristics were observed with respect to the distribution of CaCO;,free Fe;O;,∑REE and SIO;/A12O;and FeO/Fe;O;ratios,which can be adopted as the geochemical indices forpaleoclimate division.From the above,four paleoclimate stages have been distinguished for thedeposition process.The first stage,dated at 0.20-0.15 Ma,is characterized by a dry and coldclimate;the second stage,ranging from 0.15 to 0.07 Ma,by a warm and slightly dry climate;thethird stage,about 0.07-0.01Ma,by a cold and humid climate;and prevailing in the last tenthousand years is the fourth stage,with the climate changing gradually from warm-humid towarm-dry.