关键词: 拒马河, 边滩, 二元结构, 串沟沉积, 侧积体, 半干旱环境

Abstract: In this paper, the author describes the sedimentary features of point bar in piedmont inclined plain deposited under the regime of semiarid-sernihumid climate. Some new concepts are deduced as follows-.1) The profile shape of the Rong Cheng point bar is controlled by the semiarid climate, namely, the terrace-shaped relief of the point bar is the result of the floods of different stages and different extent.2) Inclined erosion plane, the indicator to distinguish the point bar and to divide lateral deposit is the intrinsic attribute of the erosion of the point bar.3) One point bar may consist of several lateral deposits, which are the important foundation to restore the forming history of the point bar.4 The effect of the transverse cross-circulating current of the meander section in semiarid climate region is less. The decreasing of the energy resulted in the receding of the flood is the key cause of the positive rhythm formation from coarse to fine of the point bar deposit. In this case there is more large scale trough cross-bedding and parallel bedding, but fewer turbulent cross-bedding at the bottom of the point bar.5) Semiarid climate is the favourable condition for the formatiozi of the point bar and chute deposits. Its existence makes the whole point bar complicated.6) The point bar binary structure consists mainly of the products produced by leading current when the current returns to the channel after a flood receding.

Key words: Juma Kiver, Point bar, Binary structure, Chute deposit, Lateral depositional unit, Semi-arid environment