Paleoclimatic and paleoenvironmental evolution recorded by the aeolian sand-paleosol sequence in the Zoigê basin

The aeolian sand-paleosol sequence in the Zoigê basin is a sensitive record of paleoclimate change and paleoenvironmental evolution for the northeastern region in the Tibet Plateau. A typical aeolian sand-paleosol section, called Xiaman, was tested for its AMS C age, grain size, magnetic susceptibility and sporo-pollen. Then the paleoclimate and paleoenvironment evolution since the last deglacial period in this area was discussed. The results show that the land desertification in the Zoigê basin occurred at least in the last deglacial period of more than 16 ka years ago. Variations of the formation structure, grain size and magnetic susceptibility indicate that the paleoclimate has undergone many alternations of cold and warm, and the sandy land has also experienced many processes of fixation and activation. The climate tended to be relatively warm and wet during 16130~6460 aB.P., around 3445 aB.P. and 700 aB.P.. There was a very warm period during 8170~6460 aB.P.. Since 11.3 kaB.P., the sporo-pollen contents of warm-fitted trees in paleosol have decreased considerably, while that of herbaceous plants, especially swampy plants, such as Myriophyllum and Syperaceae, have increased obviously, indicating that the paleoenvironment has significantly changed and the swampy peats have begun to develop.