青藏高原东缘和邻区晚新生代泥石流活动规律及其成因

本文根据大量野外考察资料和室内测年数据 ,通过对晚新生代以来不同时段泥石流沉积物的分布特征研究 ,总结了青藏高原东部及华北地区第四纪泥石流活动的规律。认为晚新生代大规模的泥石流活动始于晚第三纪 ,晚上新世～早更新世泥石流活动主要中心集中在青藏高原东部边缘地区 ;中更新世是泥石流活动最活跃的时段 ;晚更新世位于大陆内部的秦岭北坡及陇南山地泥石流活动减弱 ,华北北京山区及太行山东麓泥石流活动加强。第四纪泥石流活动的规律性变化与青藏高原的阶段性隆起及亚洲季风的建立有关

The study of debris flow's movement regulation and reasons in late Cenozoic Era in the eastern fringe of Tibetan Plateau and the nearby regions

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.