126 / 2022-02-24 10:21:21

湖泊沉积对黑河分支河流体系的影响

Heihe DFS,lakes,stability,uniqueness

Abstract: Distributive Fluvial systems (DFS) refers to the fact that detrital particles carried by rivers can be carried far away after the rivers emerge from mountains to form radially extended and gently sloping depositional systems. DFS has good reservoir in the fan root and middle fan, and it is easy to form high-quality reservoirs with strong stability and large-scale oil and gas enrichment in the distributary area. The evolution process of DFS contains a large amount of palaeogeomorphology and paleoenvironment information, which can provide a basis for restoring the ancient landform and reconstructing environmental changes in the historical period. Heihe River is the second largest inland river in China. A huge distributive fluvial system (Heihe DFS ) is formed at the end of its main stream. The geomorphological characteristics and evolution o are related to the lake deposition in the DFS to a certain extent. Satellite remote sensing images and geomorphology, climate, soil and other data are used to analyze the stability and uniqueness of geomorphic characteristics and environmental changes of Heihe DFS, as well as the impact of lake deposition in DFS. The research shows that the DFS of Heihe River was formed in the Quaternary, and the main sedimentary driving forces are rivers, floods, winds and lakes. It has been stable in terms of boundary, geomorphic type and river distribution in recent decades. Climate and runoff are the main factors influencing the evolution of DFS. There is almost no lacustrine deposits in the fan root, and the proportion of lacustrine deposits in the edge fan is higher than that in the middle fan, and the lake deposits in the fan and the lake deposits in the edge fan are transformed by wind. The lakes in the middle fan have dried up, while the lakes in the edge fan have been shrinking since 1.6kaBP. Juyanze was divided into a few lakes . The East Juyanhai and the West Juanyanhai once dried up and the water volume has recovered in the last 20 years. Small deltas are developed where rivers enter lakes in the edge fan. The shrinkage of lakes is conducive to the expansion of aeolian sediment area. And it is accompanied by the withering of hygrophytes. Lake deposition of DFS is the main reason for the uniqueness of DFS in terms of cross section morphology, soil water content and sediment grain size characteristics. The ancient lakes in the fan made the DFS profile not convex. The lakes on the edge fan made the sediment particles became coarser. The shrinkage of lakes on the edge fan shows that DFS has not expanded significantly in recent 1000 years. The increase of lake area in the last 20 years narrowed the difference between the soil water content at the edge fan and the root fan.

Key words: Heihe DFS; lakes; stability; uniqueness