TL Dating of Loess in China

TL ages of 56 loess samples collected from Xinjiang and the middle reaches of the Yellow Riverwere determined by using fine-grained quartz and man-made light source bleaching techniques. Theresults indicate that: 1. The well-preserved loess sections in Xinjiang began depositing 400000 a ago. Theloess/paleosol series may be comparable with that observed in the middle reaches of the Yellow Riverbut the depositing time was probably delayed by 30000-50000 a. 2. The bottom boundary age of the Malan loess varies from one place to another. The TLdates can be divided into two groups: 70000-130000 a and 30000-50000 a. The TL data are con-sistent with the appearance of two warmer climate periods since the Pleistocene, indicating obviousregional differences in stratigraphic development of loess, i.e., paleosol occurred in the warm climateperiod in the same location, but loess was deposited in other locations. The initial age of loessdeposition tends to become older from west to east and from south to north. In contrast, the cold cli-matic belt showed an opposite trend. The TL ages of loess provide strong evidence for theQuaternary stratigraphy throughout geological times and the shift tendency of climatic belt. 3. The depositing rate of the Malan loess along the middle reaches of the Yellow River variesfrom place to place but the TL age shows a linear relationship with the depositing thickness. The de-positing rate of loess in the north is higher than that in the south, suggesting that loess materials arederived from desert areas of northern China.