|关键词: 鄱阳湖 湿地 现代沉积 粒度 动力作用
|Granulometric characteristics and their dynamic interpretation on present deposits of typical wetland in Poyang Lake
Hu Chunhua, Zhu Haihong
Nanjing Institute of Geography and.Limnology, Chinese Academy of Sciences, Nanjing 210008
|Based on granulometric analysis on the present deposits of the typical wetland in Poyang Lake, the components of these present deposits are exposed to range mainly from fine silt with mud to very fine muddy silt, showing low-energy depositional environment of the delta front. The grain-size distributions are mainly controlled by the gravitative lake current and partly reworked by wind wave actions. During flood periods, the lake gravitative current is dominative since it controls not only grain-size regional distributions, but also the rule which granulometric characteristics gradually change from the top of meadow bottomlands to muddy bottom lands. During low water periods, the wave and wind actions are active. In transitional bottomland at the wind-faced bank at the sedimentary section profile, the wave action reworks sediments much coarser, and results in granulometric features accordant change and, especially, abrupt change at the topographic gradient break of larger depression. The wind erodes "Sand Hill" and moves eroded materials to the wetland nearby, which makes sediment coarser and richer in sand in part of the wetland. These dynamic actions also control the wetland evolution and result in the following eco-environment aggravation, i. e., the wetland, the meadow bottomland, the transitional bottomland and the muddy bottomland expansed, and water area gradually replaced by the meadow bottomland during low water periods. However, the above-mentioned problem can be solved by building sluice-dams.
|Key words: Poyang Lake wetland present deposits granulometry dynamical action