甘肃文县天池地质成因及环境效应分析

碳酸盐岩地区永久型堰塞湖地质成因鲜有研究,在少雨区域这类堰塞湖的环境效应也缺乏系统分析,其地质成因机制具有理论与现实意义,但目前其成因机理并不十分清楚。通过野外详细调查和C14测年,对文县天池的形成原因和环境效应进行较深入研究,得出如下结论:天池是(6 450±73)年前,强震触发下天池沟右、左岸同时发生相向高位高速远程滑坡堵塞天池沟形成的,滑坡堆积体的"反粒序堆积结构特征"使堰塞坝物质粒径结构具有"下部小上部大"和"中间小两边大"的特征,致使天池能够长期稳定存在,成为天然的水库,形成独特的小气候,进而塑造丰富、多样和异质的景观类型。天池的长期存在,加快了堰塞坝下游的侵蚀下切速率,使湖区内的下切受到控制,对湖区上游的沟谷下切速率影响较小。地貌上形成鲜明的对比。

Analysis of the formation mechanism and environmental effects of Tianchi Lake in Wenxian, Gansu Province

The geological formation mechanism of permanent barrier lakes in carbonate areas is rarely studied. Systematic analysis is also lacking on the environmental effects of such barrier lakes in arid areas. Their geological fo rmation mechanism has theoretical and practical significance, but the mechanism is not very clearyet. Using detailed field surveys and C14 dating method, we conducted anin-depth study on the formation mechanism and environmental effects of Tianchi Barrier Lake in Wenxian County. The results showed that Tianchi Lake was formed when a strong earthquake struck the Tianchi region (6450±73) years ago, causing two high landslides in the right bank and left bank of Tiachi valley at the sametime, blocking the Tianchi valley . The "inverse grading structure feature" of the landslide deposit causes the particle size structure of the landslide dam material to show the features of"smaller below and larger above" and "smaller in the middle and larger on the sides" . This is the reason why the Tianchi Barrier Lake can stand long, becoming a natural reservoir, forming a unique microclimate, and generating a very rich, varied, and heterogeneous landscape type. The long existence of Tianchi Barrier Lake accelerated the erosion rate down the landslide dam, controlled the undercutting in the lake area, and had little effect on the undercut rate of the valley in the upper reaches of the lake, forming clearly contrasting landforms.