Characteristics And Distribution Of The Distributive Fluvial System Around The Sugan Lake Basin

Distributive Fluvial System(DFS)is a new concept of sedimentology put forward in 2010 on the basis of statistics of modern sedimentary systems developed in more than 700 continental sedimentary basins around the world.Branch river system is widely distributed in continental sedimentary basins in Northwest China.In recent years,DFS academic views have been published in many authoritative foreign journals,and foreign scholars have established a quantitative database of DFS source sink system.However,there is relatively little attention about DFS in China,and there is no relevant case report.Therefore,the study of the DFS in this paper is of great significance: DFS integrates the earlier study of alluvial fan,fluvial fan and great fan into the same term,which promotes the systematization of the classification and description of the sedimentary system;the study of the DFS can provide a new way to determine the distribution pattern of sedimentary systems.The Sugan Lake basin located in the northwest of Qinghai Province,is a sub of Qaidam Basin.The basin is mainly formed by the continuous uplift of the Saishiteng mountain.The geomorphic unit types in the basin are rich and have large numbers of DFS developed.This paper takes the DFS developed in the Sugan Lake basin as the research object,through the method of combining Google Earth satellite image with Radar Digital Elevation data,supplemented by field investigation and UAV etc.used to study the DFS geometric form characteristics in different regions of the Sugan Lake basin;the fluvial pattern and sedimentary characteristics of DFS development in different regions are summarized;the correlation of various geometric form parameters of DFS is quantitatively analyzed;The differences of DFS geometry and channel pattern in different regions are discussed.According to the study on the geometric characteristics of DFS in each block,DFS generally starts from the top of valley and radiates downward;DFS is convex on the cross section,concave in the radial direction,and the proximal slope is larger than the middle slope,the distal slope is the smallest.There are great differences in DFS radius,slope and area in different regions;the rivers in the two DFS meet are relatively developed,and there are also great differences in DFS fluvial types in different locations of the basin.The study on the fluvial pattern of DFS development in the Sugan Lake basin shows that the river pattern in this area is mainly braided river,and the width of the river decreases from the top to the end of DFS.Different regions are affected by relative discharge,slope and sediment supply,and the developed channel patterns are quite different.There are three types of channel patterns: braided channel,single braided channel and braided channel turning into meandering channel.The results of the investigation on the Contemporary sedimentation of the great and small Halteng Rivers show that the sedimentary characteristics are as follows: from the top to the end,the river burst becomes more and more serious,the hydrodynamic condition of the fluvial weakens,the width of the fluvial becomes narrower,and the ratio of the flood plain area to the river area increases gradually from the top to the end.By studying the mechanism of the change of the DFS river course,the interpretation of the sedimentary process can be refined.According to the sedimentary characteristics of different zones of DFS,the Great Halteng River is divided into four zones,and the Small Halteng River is divided into three zones.Through the analysis of the modern sedimentary style,it can provide reference for the study of DFS sedimentary model and promote the diversification of the study of sedimentary model.The correlation analysis of the geometry of the Sugan Lake basin shows that the DFS area increases with the radius,showing a strong positive correlation;the relationship between the slope and the DFS area shows that the slope decreases with the increase of the radius;the relationship between the DFS area and the source area shows that the DFS area increases with the source area.The correlation analysis of DFS geometry parameters can provide a reference for the quantification of source sink system.The analysis of the controlling factors of DFS geometry and channel pattern shows that,the intensity of tectonic activity is positively correlated with the size of DFS source area and the shape of fan.The stronger the tectonic activity is,the larger the change of fan geometry will be.The influence of parent rock properties on DFS mainly lies in the supply of material source.In the area of parent rock with poor resistance to erosion and weathering,the sediment supply of DFS is sufficient,the DFS radius extends far,and the fan area is large.Hydrological conditions control different areas the development of DFS is influenced by the size of regional hydrodynamics,and the development scale of DFS is larger in the region with stronger hydrodynamics.By analyzing the differences of tectonic,geology and hydrology in different regions,we can grasp the distribution law of DFS as a whole.