Research Of Sedimentary Record In Terraces And Climate Vary In The Upper Reaches Of Minjiang River,China

The intensive uplift of Qinghai-Tibet on the Cenozoic era has great effect on landform and the water system evolution of the marginal area. Depositional records in the sedimentary basin and river terrace not only mark the hydrodynamic force condition and the origin of deposit, but also record the local tectonic activity and the climate changes. The Minjiang River is situated in the eastern margin of the Qinghai-Tibet, where exists multilevel river terraces in the upper reaches, especially terraces III distributing widely and developing largely. This thesis pick up the terraces III of Diexi and Maoxian to make researches in sedimentary. It discusses about the tectonic activities and climate changes of the eastern margin of the Qinghai-Tibet, on the base of genesis analyses and regional contrast."Depositional system" is 3-D lithofacies unit of depositional environment and sedimentary body, which are originally related. Analyzing of depositional system needs more 2-D or 3-D survey.The method of depositional systematical analyzing is applicable to sedimentary unit dividing and genesis analying, so it is widely accepted and extensively applied by numerous workers. Lithofacies, the most important concept in the depositional system, was put forward by Miall (1978) when he studied the potamoclastic deposit. It is the basic type of lithofacies which was divided according to lithology and its sedimentary structures. Lithofacies discernment and division is a simple, convenient and comparatively objective method in the field description of depositional system.Based on field investigation of lithofacies, this paper discuss the sedimentary history and tectonic and climatic history in the two research areas of Diexi and Maoxian in the upper reaches of Minjiang River by using the method of depositional system analyzing. The results are giving just as following:a) Diexi study district which should be located in the end of barrier lake, mainly developed fluvial depositional system, lake depositional system, alluvial fan...