ABSTRACT

The MGS1 segment of the Milanggouwan stratigraphic section, which is located on the southeastern margin of the Mu Us Desert in China, recorded 11 sedimentary cycles consisting of aeolian dune sands overlapping with fluvio-lacustrine facies or paleosols in the Holocene. Through the analysis of trace elements, gastropods, and sporopollen fossils in some layers of the MGS1, this study presents the monsoon climate fluctuations on the millennial-scale in the Mu Us Desert during the Holocene. The results show that the contents of trace elements (P, Pb, Rb, Nb, Zr, V, Sr, Cu, Ni, As, Ba, and Co) have similar distribution characteristic, their contents are low in the dune sands but are relatively high in the overlying fluvio-lacustrine facies or paleosols showing 11 cycles in alternation of valleys and peaks. The trace elements in the paleo-mobile dune sands of MGS1 are quite consistent with those of modern mobile dune sands in Salawusu River Valley; therefore, paleo-mobile dune sands can be assumed to be a result of the main periods of the prevalence of East Asian winter monsoon. The increased element contents in the overlying fluvio-lacustrine facies or paleosols are mainly due to the prevailing East Asian summer monsoon. In addition, the 11 elements’ cycles represent the climate changes on the millennial-scale in the alternation of East Asian winter and summer monsoons in the Holocene. The paleoecology indicated by gastropods and sporopollen fossils reflects the warm and humid sparse forest grassland environment prevailing in the East Asian summer monsoon when the fluvio-lacustrine facies were deposited; the sporopollen is missing in the dune sands, presumably, it might be dry and windy sandy desert then. The dominant periods of the winter monsoon in these cycles, in terms of time and nature of the climate, could correspond to the cold events in the North Atlantic and lakes, loess, peat and stalagmites in China. It probably indicates that the millennial-scale environmental changes in China’s desert regions may be caused by the changes of solar radiation and the increase in ice volume in the Northern Hemisphere during the Holocene.