摘要
本文通过断陷盆地第四纪地层层序与沉积间断、盆地早期地层下伏红色风化壳的层位、山地古夷平面的变形、金沙江阶地与洱海湖滨阶地发育的构造分析,提出新构造期的下限为330×104aBP左右、新构造运动的波动具有明显的递进性并呈现波动周期逐渐缩短、频率增大和晚第四纪断块差异性运动增强的基本趋势,探讨了新构造运动对地貌发育的控制作用。
Mt Yulongxue (5596 meters a.b.l.) and Mt. Cangshan (4122 meters a.b.l.) which are located in the southeast of Tibet Plateau and the central part of the Hengduan Mountain System are major peaks in the northwest part of Yunnan province. In this region, the geomorphic type belongs to paralled fold-fault high mountains and basins of the intense erosion and deep down-cutting; the stepped landforms are developed in the mountain land; the Quaternary sediments are 2000 meters in the basin and active faults are long. This is an intensive mobility region of the neotectonics. That is why the great turn of the Jingsha River and the Hutiao Canyon appear in this region.By the neotectonic analysis of the Quaternary superposition and hiatuses in the basins, the horizon of the residuum of laterite type under the lower stratum in the basins, the information of paleoplanation in mountain land and the terraces of rivers and lakes, the conclutions of this text as follows:The major basins in the region are graben ones during the neotectonic period. The Song-maopo Formation in the lower part of the basins is unconformity on the Precenozoic. The residuum of laterite type was developed along the unconformity. It is buried palaeoplanation surface. All these show that the landform in the region was developed with the differential block movement, namely neotectonic movement, on the extensive uplifting background. The regional unconformity represented by the residuum of laterite type under the Songmaopo Formation is the neotectonic limit mark. The lower boundary of neotectonic period is 3.3 million years BP. or so. In other areas of the Hengduan Mountain System, they are 3.16-3.4 million years BP. in Kunming,3.2 million years BP. in Yuanmou and 3.3 million years BP. in Panzhihua. The boundary is close to Gauss/Gilbert in the paleomagnetic chronogocal scale of Late Cenozoic.The facts that the five unconformities occurred in the Quaternary Column, which happened3.3 million years BP., or so, between the end of Early Pleistocene and the beginning of Middle Pleistocene, 34-30 thou. years BP. or so and 8-7 thou. years BP. or so, show that the neotectonic fluctuation has the progression and its trends are to shorten the cycle of fluctuation, to increase the frequency and to strenghthen the differential block movement in Late Quaternary.During the neotectonic period, the uplifting quantities has accumulated to 2200-4400 meters; the gradient of differential block movement has accumulated to 4000 meters; the average rate is 0.2-0.6 mm/a for the accumulation in the basins and the value for accumulation in the basin with the uplifting in the mountain land is 0.3-0.6/1.The landform forming process in this region has experienced three stages, namely penepla-nation stage (previously 3.3 million years BP.) and lake- basin stage in the mountain land (from 3.3 million years BP. to the end of Early Pleistocene) and river stage in high mountain (since Middle Pleistocene). The latter the two stages belong to the neotectonic period. The neotectonic movement has controlled the important transform of landform forming process, the pattern of regional landform and the forming of neotectonic landform. The great turn of the Jinsha River and the deep down-cutting of the Hutiao Canyon closely connected with the turn are a special phenomenon of neotectonic landform. Obviously, the neotectonics is the major factor for the land-form forming of the young orogenic zone.
出处
《地理学报》
EI
CSSCI
CSCD
北大核心
1992年第5期430-440,共11页
Acta Geographica Sinica
基金
国家自然科学基金资助项目。
关键词
第四纪
沉积
层状地貌
新构造
Neotectonic landform
Paloplanation surface
Neotectonic period
Jian-chuan laterite
Songmaopo formation
