The Relationship Between Pregnancy Of Large Ancient Landslides And Erosion Of River At Shimian-luding In The Dadu River Valley

The Dadu River is located in the east edge of the Qinghai Tibet Plateau，regionalgeological constructed complex，Since the Quaternary period glacier movement withthe global climate and sea level changes become valleys formed evolution largearea geological environment evolution. since the late Pleistocene strong river erosiondeposition environment form dense development distribution of lcgm in the rivervalley slope，Massive sliding body formation and the sedimentary environment ofValley erosion formation transformation effect further, the two have relations morefar-reaching generation.The article selects the Dadu River ancient landslide intensive development anddistribution in the upper reaches of the Luding to asbestos section as the research area,The basic characteristics of erosion deposition investigation section Valley, Selectedfour typical ancient landslide formation in the evolution process and erosion of rivervalley of the gestation and birth of ancient landslide, the landslide formed mainly thecharacteristics of large scale damming lake, Selection lake facies sedimentarycharacteristics preserved relatively complete and systematic analysis of landslidedammed lake, lake, reveal the relationship between formation of evolution processand the erosion of river valley birth, then get the ancient river blocking landslide ofthe formation and erosion of river valley between birth relationship. The followingunderstanding and main achievements obtained in the research process: This paperselects the Dadu River ancient landslide intensive development and distribution in theupper reaches of the Luding to asbestos section as the research area, the basiccharacteristics of erosion deposition investigation section Valley, selected four typicalancient landslide formation in the evolution process and erosion of river valley of thegestation and birth of ancient landslide, the landslide formed mainly thecharacteristics of large scale damming lake, selection lake facies sedimentarycharacteristics preserved relatively complete and systematic analysis of landslide dammed lake, lake, reveal the relationship between formation of evolution processand the erosion of river valley birth, then get the ancient river blocking landslide ofthe formation and erosion of river valley between birth relationship. The followingunderstanding and main achievements obtained in the research process:（1）To summarize and analyze the research section of Dadu River Valley erodedsedimentary basic characteristics, including: The Dadu River in Luding-asbestossection selects23representative position analysis section of Valley longitudinal slopechange, get the slope shows the "slow-steep-slow" feature; The Dadu River Valleymainly developed three planation surfaces and VI terrace, summarize thelevels ofplanation surfaces and spatial and temporal distribution characteristics;Analysis of thebasic characteristics of the deep alluvium, summed up the five lithologic faciesdepositional system, initially established in deep cover, further analysis of its tectonicaccretion, the Quaternary glaciers and climate accretion, accretion of landslideformation mechanism.（2）According to the Dadu River Valley landform characteristics and researchsection of tectonic history, summed up the valley development experienced planationperiod, gully type planation period, deep canyon period of three stages, by using theprinciple of sequence stratigraphyanalysis of erosion characteristics changes ofsedimentary baselevel change based on the valley.（3）Statistics of Dadu River large ancient landslides distribution, found that10000years ago,19000years,22000years for the three landslide occurred morefrequently in time, and asbestos to Luding development and distribution of the mostintensive.（4）Comprehensive analysis get The whole process of formation and evolutionof the ancient river blocking Landslide with the common characteristics: The primarysliding form the river blocking landslide——the forming of Dammed lakes——The landslide dam breach of multi period——Landslide overall creep deformation——Front edge local multilevel sliding——The trailing edge of secondaryslip.Preliminary discussion the pregnancy relationship between the formation andevolution of the ancient landslide and erosion of river valley.（5）Jiajun dammed lake main effect zone from Jiajun to the upstream lengqi,about13.5km long, the averagewidth of about575m, area near8km2, the landslidedistributed between Dasonglin and Shangkuiwu, nearly2.8~3.0km long, the damheight is above120m, the channel release flood waters are formed on one side oflandslides, typical deposit distribution revealed the lake experienced two stages ofhigh lake level stable lacustrine sediments during the period, with two times thebuckling, happened many times in different degree in the overall collapse lake, savetime in more than200years.（6）Select ten typical lacustrine sediments of Jiajun landslide which revealed 17lithologic facies,constitute the eight major sedimentary facies, fluvial facies,limnetic facies and flooding facies multi characteristics of depositional system isfound in sedimentary layers. Last summarized Get the lake lithologic facies, andlake lake sedimentary sequence mode.（7）Expose the lake evolution, is a compound sedimentary system of lake facies,explore the ancient dammed lakes in the valley erosion pregnancy, mainly reflected in:Valley longitudinal slope of local changes, river valley terrace transformation, valleydeep overburden layer causes the entire valley erosion deposition process. Analysis ofthe barrier lake level changes have differences and lake level curve mutation,sensitivity, solitary, open lake determine basis and lake transgression.