Late Plio-Pleistocene humidity fluctuations in the western Qaidam Basin (NE Tibetan Plateau) revealed by an integrated magnetic-palynological record from lacustrine sediments

Deciphering the climatic evolution of the Tibetan Plateau region during the Plio-Pleistocene is hampered by the lack of continuous archives and proxy datasets indicative of moisture availability. Here we assess the suitability of magnetic susceptibility (chi) measured on lacustrine sediments as a paleohydrological proxy based on material from drill core SG-1 (2.69-0.08 Ma) from the western Qaidam Basin. Our assessment is based on directly comparing chi with the Artemisia/Chenopodiaceae (A/C) pollen ratio, which represents a sensitive, well-established proxy for moisture changes in arid environments. We find that higher and lower chi values represent drier and less dry conditions, respectively, for the Late Plio-Pleistocene. Less dry phases were likely caused by transiently increased influence of the westerlies and/or decreased influence of the Asian winter monsoon on glacial-interglacial time scales. An exception from this relationship is the interval between similar to 1.9 and 1.3 Ma, when the SG-1 chi record exhibits a 54 ka cyclicity, which may indicate summer monsoon influence on the Qaidam Basin during that time. After similar to 1.3 Ma, the summer monsoon influence may have ceased due to global cooling, with the consequence that the Asian winter monsoon and the westerlies exerted a stronger control on the hydrology of the Qaidam Basin. (C) 2015 University of Washington. Published by Elsevier Inc. All rights reserved.