西峰剖面午城黄土游离铁与全铁比值数据集（1200-2600kaB.P.）

基于西峰剖面午城黄土的FeD和FeT测试，建立该剖面早第四纪的古风化强度序列。2.6~1.6Ma期间，古土壤整体较低的风化强度指示了第四纪初期较弱的夏季风环境效应。从1.6Ma开始，黄土和古土壤的风化强度都呈增加趋势，指示了夏季风环流的加强。早更新世古土壤的风化强度与后期相比总体较低，而黄土层的风化强度总体偏高，反映了较小的冰期-间冰期旋回反差。古风化强度在冰期-间冰期尺度的波动及其显著的约40ka周期，体现了全球冰量变化对我国北方季风环境的较强控制作用。但是，1.6Ma开始的夏季风效应的加强、约100ka周期的出现及风化强度更为突出的约20ka周期等特征均难以用全球冰量变化解释。我们认为，低纬热带过程对季风环流的控制是导致这些现象的主要原因。

Based on the measurements of FeD and FeT in the Wucheng Loess at the Xifeng Section, a paleoweathering intensity sequence for the Early Quaternary of this section was established. During 2.6–1.6 Ma, the generally low paleoweathering intensity of the paleosols indicates a weak environmental effect of the summer monsoon in the early Quaternary. Starting from 1.6 Ma, the paleoweathering intensities of both loess and paleosols show an increasing trend, indicating the intensification of the summer monsoon circulation. The paleoweathering intensities of Early Pleistocene paleosols are generally lower than those of later periods, while those of loess layers are generally higher, reflecting a smaller contrast between glacial and interglacial cycles. The fluctuations of paleoweathering intensity at the glacial-interglacial scale and its significant ~40 kyr cycle reflect the strong control of global ice volume changes on the monsoonal environment in northern China. However, features such as the intensification of the summer monsoon effect starting from 1.6 Ma, the emergence of the ~100 kyr cycle, and the more prominent ~20 kyr cycle of paleoweathering intensity cannot be readily explained by global ice volume changes. We propose that the control of monsoon circulation by low-latitude tropical processes is the main cause of these phenomena.