580,000-year environmental reconstruction from aeolian deposits at the Mu Us Desert margin, China

A 76.7 Pn-thick section of aeolian sediment is exposed in the transition zone between the Mu Us Desert and the Loess Plateau of northern China. The aeolian sediments contain sand beds, loess layers, and palaeosols. The particle-size distribution data and the SEM examination of quartz grains suggest the sand beds are wind-blown origin. Palaeomagnetic measuring combined with thermoluminescence (TL) dating and pedostratigraphic correlation suggests the studied aeolian sequences were deposited within about 580 kyr. The sand layers appear to reflect the episodic extensions of Mu Us Desert during phases of active dune formation and intensified winter monsoon. Both the stratigraphy and the proxy climatic curves such as bulk magnetic susceptibility and grain size indicate that large amplitude second-order climatic oscillations occur during both glacial and interglacial periods. It is worth noting that nearly all the interglacial soils can be sub-divided by the intercalated sand or loess beds, this second-order climatic oscillations are on the order of 10,000 of years which may reflect the precession-scale variations of southeast summer monsoon driven by the orbital pacing of insolation in low latitudes. (C) 1999 Elsevier Science Ltd. All rights reserved.