Quaternary Drainage Evolution Of The Songhua River:Indications From Heavy Minerals And Sedimentology

The study on the evolution of the songhua river system is of great significance to the understanding of the tectonic,climatic and geomorphic evolution in this region,but the study is very weak.River sediment is the product of river geological process,and it is an important geological archive for studying water system evolution.In this paper,based on the experiment,the core sediments of the Huang Shan in Harbin were selected as the research object,and the paleomagnetism,susceptibility and heavy minerals were analyzed.The results are as follows:(1)Harbin HuangShan are a total of 29 heavy mineral core sediments,respectively,zircon,apatite,rutile,anatase,titanium white stone,sphene,monazite,tremolite,hornblende,tourmaline,garnet,epidote,pyroxene,ilmenite,limonite,titanium magnetic iron ore,magnetic limonite,magnetite,magnetic hematite,limonite,glauconite,niobium tantalite,kyanite,chalcopyrite and pyrite,moissanite,spinel,chromium spinel,galena,anthophyllite.(2)the magnetic susceptibility characteristics of the upper and lower strata at the core depth of 62.3m are significantly different.The magnetic susceptibility of the strata below 62.3m is extremely low(even 0),while the magnetic susceptibility of the strata above 62.3m suddenly increases and presents periodic high and low changes.(3)62.3 m upper and lower strata there exist obvious differences in characteristics of heavy mineral,62.3 m above the cores,ilmenite + red limonite,sphene(73-125 microns)and sphene + red limonite,titanium white stone(125-250 microns)as the main characteristics,the core of 62.3 m the following paragraphs to sphene + ilmenite,zircon(73-125 microns)and sphene + ilmenite + red limonite(125-250 microns)as the main features.(4)the characteristics of heavy mineral assemblages in the strata above 62.3m are similar to those of modern rivers in the direction of songyuan;The characteristics of the heavy mineral assemblages in the strata below 62.3m are similar to those of the river heavy mineral assemblages in the direction of yilan-jiamusi.(5)water flow has a certain sorting effect on heavy minerals,and the distribution of heavy minerals in the two grain sizes is significantly different.(6)The change of sediment source reflected by the difference of magnetic susceptibility and heavy minerals indicates the change of water system in the middle anupper reaches of the Quaternary Songhua River.In the early early Pleistocene,the flow of water in the Ilan section of the source of the Songhua River poured westward from the direction of Ilan into the Songnen Lake Basin;in the late Early Pleistocene,the Kaifen Water Ridge continued to rise and the Sanjiang Plain and the Songnen Plain continued to descend,resulting in increased river traceability erosion on both sides of the watershed;at 0.94 Ma.B.P.The water flow of the Songhua River is reversed and flows westward through the valley into the Sanjiang Plain.