贵州落脚河峡谷景观特征及形成机制

On Landscape Characteristic and Formation Mechanism of Luojiao River Gorge in Guizhou Province

【目的】探讨以碳酸岩为基岩的贵州落脚河发育出庞大的河曲型岩溶峡谷景观的原因。【方法】根据落脚河峡谷系统的空间展布特征,通过分析区内地形地貌、地质构造和水文等自然条件,探讨落脚河峡谷群的景观特征及形成机制;同时,以区域新构造演进为主线,探讨落脚河峡谷群形成与演化。【结果】1)落脚河峡谷群全长61.33km,共发育了76个河曲,其中"Ω"型有6个,是岩溶区乃至世界少有大密度的河曲深切型峡谷系统;2)盆地地形和相对隔水层的存在,使区内形成一个相对封闭的古湖盆,从而为河曲的形成提供了孕育环境;3)地壳抬升,六冲河溯源侵蚀,使封闭湖盆打开,落脚河形成并在湖盆内形成自由河曲;4)区内平缓的岩层和极其发育北东、北西向的"X"节理,为自由河曲沿既有的方向溶蚀下切提供了水力通道;5)来自周围非碳酸岩山区的外源水,对研究区内基岩具有较强的溶蚀能力,是加速河流下切的动力之一。【结论】岩溶区存在像落脚河峡谷这样的高密度河曲型峡谷极为稀有,具有较高的旅游观赏价值。落脚河河曲型峡谷因地壳抬升并由早期自由河曲继承性下切而形成,主要经历了湖盆期(孕育期)、自由河曲发育期、河谷深切期等3个时期。

[Purposes]To discuss why there are a large meandering river with carbonate rock as the bedrock in Luojiao river,Guizhou province.[Methods]According to the spatial distribution characteristics of the Luojiao river gorge system,by comprehensively analyzed the natural conditions such as topography,geological structure and hydrology in the area to explore the landscape characteristics and formation mechanism of the Luojiao river gorge group.At the same time,taking the evolution of regional neotectonics as the main line,the formation and evolution of the Luojiao river gorge group are discussed.[Findings]1)The Luojiao river gorge group has a total length of 61.33 km and has 76 meanders,of which 6 are omega-shaped,which is a deep-seated canyon system with few high density in karst areas and even in the world;2)The topography of the basin and the existence of the relative aquiclude make the area form a relatively closed ancient lake basin,which provides a breeding environment for the formation of meanders;3)Earth’s crust is uplifted and the six red River erodes to its source,opening the closed lake basin,forming a resting river and forming a free meander in the lake basin;4)The gentle rock strata in the area and the extremely developed"X"joints in the north-east and north-west directions provide a hydraulic channel for the dissolution and undercutting of the free meander along the existing direction;5)Exogenous water from surrounding non-carbonated rock mountain areas has strong dissolution ability to bedrock in the study area and is one of the driving forces to accelerate river undercutting.[Conclusions]Such a high-density meandering valley in karst area is extremely rare and has high tourism and ornamental value.The Luojiao meander canyon is a crustal uplift formed by the inherited undercutting of the early free meander,which mainly experienced three periods,namely,the lake basin period,the free meander development period and the valley depth period.