为获得不受粒度分选效应影响的黄土矿物学风化指标,对甘肃西峰和山西吉县黄土-古土壤典型样品分离成9个粒级后进行了X射线衍射测试,分析了不同粒级中钾长石/斜长石比值（K/P比值）的变化规律。研究结果表明,黄土-古土壤中K/P比值受粒度分选效应的影响,细粒级（〈1μm,1~2μm）的K/P比值显著高于粗粒级（〉2μm）;黄土在源区的沉积旋回过程中和沉积区的成壤过程中斜长石都经历了一定程度的化学风化作用,呈现出大陆风化早期阶段特征,并且这种风化作用主要发生在细粒级中,因此,黄土和古土壤（2 um K/P比值能够有效地排除粒度分选效应的影响,直接指示黄土沉积在源区和沉积区风化作用。
Loess deposits with varying thickness are widely distributed on the intermontane valleys and piedmont zones on the northern side of the central Shandong mountainous regions. However, the basal ages and material resources of the loess deposits are not clear. The paper studied the Qingzhou loess profile in Shandong with magnetostratigraphic and optical stimulated luminescence (OSL) methods and further investigated its main provenances with the mineralogical methods. The magnetostratigraphic results showed that the Brunhes/Matuyama (B/M) reversal boundary was not recognized, suggesting a basal age younger than 0.78 Ma. Extrapolations by sedimentation rates, based on the upper part depositional rate from the OSL age, the basal age of the Qingzhou loess is about 0.5 Ma. Until now, older loess deposits have not been reported on the northern side of the central Shandong mountainous regions. The results of the paper indicate that the loess deposits in this area might have strated from the Middle Pleistocene. The basal age of Qingzhou loess is approximately synchronous with the Xiashu loess in the middle-lower reaches of Yangtze River. Major components of clay minerals in the Qingzhou profile are dominated by illite. Other clay mineral compositions are mainly smectite, chlorite and kaolinite, which are similar with the Xifeng loess in the Loess Plateau. However, the contents of smectite and the ratios of illite and kaolinte in the Qingzhou loess samples are higher than those in the Xifeng loess samples of the Loess Plateau, indicating that the loess in the northern side of the central Shandong mountainous regions has different sources from that of the loess deposits in the Loess Plateau. The clay mineral analysis further reinforces the earlier conclu- sion that the marine strata exposed in the Laizhou Bay and the fluvial plain of the lower reaches of Yellow River during the glacier periods are the main material sources for the Qingzhou loess deposits, which is an indicator to the local aridification of the lower reaches o
