The widely distributed thick gravel deposits along the rim of the Tibetan Plateau have been long thought to be the product of rapid tectonic uplift of the plateau. However, this has been challenged by recent works that suggest these thick gravels may be the result of climate change. In this paper we carried out a detailed field measurement of gravel grain sizes from the Jiuquan and Gobi Gravel Beds in the top of the Laojunmiao section in the Jiuxi Basin in the northern margin of Qilian Mts. (northern Tibetan Plateau). The results suggest that the grain sizes of the Jiuquan and Gobi Gravel Beds over the last 0.8 Ma are characterized by nine coarse-fine cycles having strong 100-ka and 41-ka periodicities that correlate well with the loess-paleosol monsoon record and isotopic global climatic record from deep sea sediments as well as by a long trend of coarsening in gravel grain size. The coarse gravel layers were formed during the warm-humid interglaciations while the fine layers correspond to the cold-dry glaciations. Because the paleoclimate in NW China began to get dramatically drier after the mid-Pleistocene, we think the persistent coarsening of gravel grain size was most probably caused by the rapid uplift of the northern Tibetan Plateau, and that the orbital scale cyclic variations in gravel grain size were driven by orbital forcing factors that were superimposed on the tectonically-forced long-term coarsening trend in gravel size. These findings also shed new light on the interaction results of climate and tectonics in relation to the uplift of the Tibetan Plateau.
云南点苍山是大理冰期的命名地,通过文献查询明确了大理冰期这一概念提出的过程.基于多次的实地考察,对云南点苍山冰川地貌进行了系统研究,建立了该地区第四纪以来冰川活动可靠的年代序列,明确了冰川发育的规模.研究结果表明,点苍山最早的冰川活动发生于30～40 ka BP,之后经历了末次冰期晚阶段、晚冰期、新冰期等各次冰川前进,直至1.2～1.5 cal ka BP前后冰川最后消失.空间上,该地区的冰川活动仅局限于海拔3600m以上的主体部分,低海拔及其周边山体上没有冰川发育.
