A RECENT SEDIMENTARY STUDY ON SAND BAR IN XIASHAN LAKE

Based on recent sedimentary study, and combined with particle size analysis, this paper discussed the depositional features of sand bars in Xiashan Lake in detail. The study shows that as a sedimentary microface in lake, bar can be divided into three sedimentary units:bar front,bar main body and back bar. Bar front suffers waves obviously, whose sediment is mainly beach ridge and sheet sand made up of wave sand and swash sand. Bar main body is made by thicker fine to medium sand that was built or rebuilt by wave and wind, and can be subdivided into bar-beach and bar-dune complexes. However, back bar belongs to limited bay during high water level periods and swamp during low water level periods. As the result of coastline, geomorphology and other factors, bar is formed in the lake shore and shallow lake environment, and is controlled by lake wave and lake current, and also by wind when bar exposes to the air during low water level periods. Long shore currents which derive from wave play a key role in the evolution of bar sand body. Bar body is deposited by hydrodynamics of lake during high water level seasons, and rebuilt by wind during dry seasons.