Paleo-monsoon activities of Mu Us Desert, China since 150 ka BP - a study of the stratigraphic sequences of the Milanggouwan Section, Salawusu River area

The interbeddings of the aeolian sand dune facies and the fluvio-lacustrine and paleosol facies in the Milanggouwan stratigraphic section have been ex amined by a series of geological methods: including grain size, magnetic su sceptibility, spore-pollen and fossil analyses along with various dating me thods. The results showed a basic difference in depositional environments b etween the sand dune facies and the fluvio-lacustrine and paleosol facies. At least 27 cycles of alternate depositions of the aeolian dune sands and t he fluvio-lacustrine facies and/or paleosols from 150 ka B.P. have been dis covered in the Mu Us Desert. These cycles reflect the climatic variations t hat were induced by the growth and decline and confrontation between the wi nter monsoon and the summer monsoon of East Asia in the past 150 ka. The sp ore-pollen and magnetic susceptibility analyses suggest a great increase of rainfall (+40-120%) and temperature (2-6 degrees C) during the prevailing summer monsoon periods. This is the only sedimentary profile that represent s the climatic variations of millennial scale in the desert areas of north China for the late Quaternary. The high-resolution results on paleo-monsoon variations from the section may indicate sensitive reactions of the margin desert to climatic changes. (C) 2000 Elsevier Science B.V. All rights rese rved.