关键词: 晚新生代, 泥石流活动, 构造运动, 季风演化

Abstract:

According to a large amount of field measurements and indoor annual measuring data and research on the distribution characteristics of debris flow movement deposits in different stages since the late Cenozoic Era,we believe that the large scale debris flow movement in the east border of the Tibetan Plateau and its surrounding regions since the late Cenozoic Era started from the late Pliocene.Debris flow in the early Pleistocene was fully developed in the east border of the Tibetan Plateau and the debris flow movement was relatively weak in the east piedmont of Taihang Mountains and Beijing in North China.Debris flow movement was most active in the middle Pleistocene.There was still certain debris flow movement around Xiaojiang Valley in the east border of the Tibetan Plateau in the late Pleistocene, while the movement became weaker both in Bailongjiang Valley, south Gansu,and the north piedmont of Qinling,and stronger in Beijing area and the east piedmont of Taihang Mountains.Debris flow movement took on a characteristic of periodicity which had corresponding relationship with the periodic uplifting of the Tibetan Plateau and the establishment of Asian monsoon.Great changes in the strength and influential areas of the Southeast monsoon and the Southwest monsoon which affected China since the late Cenozoic Era had also taken place.As a product of monsoon,debris flow movement history was the same as loess and paleosol and recorded the forming and developing processes of the two monsoons since the late Cenozoic Era.Under the influence of the Tibetan Plateau movement during 3.6～1.7MaBP, typical modern monsoon was formed gradually, and precipitation in the form of torrential rain and a large scale of debris flow movement initiated in the east border of the Tibetan Plateau.The Kun(lun) and Yellow (River) movement during 1.1～0.6MaBP enlarged the rise and fall of terrain and uplifting of the Plateau got to a new critical value, meanwhile the motive power and heating power effect of the Plateau reached a new balance point. Debris flow movement was unusually active in the east border of the Tibetan Plateau. Debris character had also changed from the early Pleistocene when diluted and sub-viscous debris flow movement predominated to the period when viscous debris flow movement predominated. North China then started to enter a debris flow movement stage. Under the influence of Gonghe movement at 0.15MaBP, the influenced area by the Southwest monsoon rapidly decreased, and most parts of eastern China were mainly affected by the Southeast monsoon, and advance and retreat changes of the Southeast monsoon had an absolutely controlling impact on environmental evolution. Debris flow movement weakened in the east border of the Tibetan Plateau.During the last interglacial period, debris flow movement ceased to develop in the inland regions far away from Indian Ocean and Pacific Ocean.

Key words: late Cenozoic Era, debris flow movement, tectonic movements, Asian monsoon