Late Quaternary wetter epochs in the southeastern Badain Jaran Desert,Inner Mongolia,China

【摘要】：正Scientific investigations of the deserts of northwestern China are still quite limited in number,so that opinions on the formation and evolution of the drylands of China are sometimes speculative.In order to contribute to better understanding of the palaeoenvironmental history of this region,this paper presents proxy data inferred from study of five sediment profiles from the eastern and southeastern margins of the Badain Jaran Desert,Inner Mongolia,China.The research methods include field observation and laboratory analyses of the sediment and water samples.The chronology is based on thermoluminiscence and radiocarbon dating.The strongly cemented,reddish(laterite-coloured) dunes on the eastern margin of the Badain Jaran were dated to ca 57-51 ka and the strongly cemented,reddish(laterite-coloured) aeolian sand on the southeastern margin was dated to ca 121 ka.The presence of this type of dune sand in these areas indicates that the extent of the sand seas was larger than at present at these times in the past.Loess sedimentation between ca 25 and 18 ka on the southeastern margin is interpreted here as consistent with a less arid climate.High lake levels on the southeastern margin of the Badain Jaran and in the dune fields were dated mainly to ca 89 ka and the Early Holocene,respectively. The humid conditions during the Early Holocene in the Badain Jaran are consistent with climatic trends found in other deserts.It is argued that the sand seas in northwestern China were more extensive sometimes during globally warmer periods recorded in the marine isotopic stages.In addition to the westerlies,the mobile polar highs presumably brought moisture from Arctic regions to the deserts of northwestern China during glacials.