• 责任者：Ma Hongjie (Faculty of Land Resource Engineering ; Kunming University of Science and Technology ; Kunming 650093 ; China) ; Zhang Shitao
• 刊名：Quaternary Sciences
• 出版年：2013
• 卷期：33(3)
• 关键词：更新世 ; Pleistocene ; 断陷盆地 ; fault-downwarping basins ; 古环境 ; paleoenvironment ; 云南 ; Yunnan Province
• 页码：p.471-478
• 图表：illus., 1 table, 20 refs.
• 分类号：1400
• issnNo：ISSN1001-7410
• isbnNo：CN11-2708/P

Midu basin was studied by thermoluminescence dating, sedimentary facies and pollen analysis, to understand the characteristics of rift and environmental Change during Middle and Late Pleistocene in the western Yunnan. According to the field investigation,there are at least five terrace levels presenting in the west side of Midu basin, which correspond to five intermittent rifts. We mainly investigated four terraces in the west side of the Midu basin, namely level I -terrace of Qijiaying, level Ill-terrace of Longhuashi, level IV-terrace of Ping＇ anzhuang, level V-terrace of Dashuping,and the TL dating values of level I terrace,level m terrace,level IV terrace,level V terrace are 239.06± 26.30ka, 239.06± 26.30ka, 320. 85± 35.29ka, and 332.07± 36.59ka, respectively. The chronology analysis indicated that,the landscape of basin and range in the Midu basin western Yunnan was formed by intermittent rift during the last 33ka,and the trend was characterized by a fast rift and then a slow rift. Analysis of sedimentary characteristics showed that the early period the lake basin rift rate was relatively fast because the sedimentary characteristics was presented by the semi-deep lake sediment. Besides, the late sedimentary characteristics,mainly appearing the shore of the shallow lake,showed that lake basin rift rate was relatively slow. It could be explained that the activity of the south section of Chenghai fault zone was weak in that period. The sedimentary facies and pollen analysis showed that, river or lake in the basin among mountains exsited during the middle Late Pleistocene. Moreover, the climate history was from cool and humid, to warm and humid, then to cool and humid again. There are many alluvial fans in the west and north margin of the Midu basin,which are in a linear arrangement. The east margin of the Midu basin appears more than a single fan alluvial body. It meant that the rift rate of the lake basin was relatively fast in the west and north side of the Midu basin. From north to south,the scale of the alluvial fans becomes smaller, and the deposits is from coarse to fine and the fan slope is from big to small in the west side of the basin. We concluded that the rift activity in the northern side of the Midu basin was strong and the trend of northward tilting in the basin has occurred yet.