云贵高原典型串珠状岩溶湿地水文地质演化研究

Hydrogeological evolution of typical moniliform karst wetland in the Yunnan-Guizhou Plateau

位于云贵高原面上宣威岩溶断陷盆地北东部的格宜镇,地貌类型为岩溶丘峰谷区,广泛分布碳酸盐岩地层,由于岩石建造和外地质应力的复杂性,在强烈的溶蚀作用下形成了多种多样的地貌形态,既有溶蚀形成的溶洞、洼地、谷地、落水洞等地表岩溶地貌,又有地下河管道等。通过水文地质学、岩溶学方法,对湖泊型串珠状湿地的构造、水文地质、岩溶发育特征进行研究,云贵高原面上串珠状岩溶湿地演化过程经历了地壳抬升期、南地壳稳定期、地壳再次抬升期三个阶段,在新构造运动作用下,由于地壳抬升,侵蚀基准下切等原因,岩溶管道在漫长的时间内垮塌、淤泥堵塞及岩溶发育的不均匀条件下了形成地表串珠状湿地。针对目前湿地面积的不断萎缩、减小问题,提出了具体的保护建议。

Geyi town,located in the northeast part of Xuanwei karst fault basin on the Yunnan-Guizhou Plateau,shows its geomorphic type of karst area of hump valley where carbonate strata are widely distributed.Because of the complexity of rock formations and external geological rock stress,various types of morphology are formed by strong dissolution in this area,not only including surface karst landforms such as karst caves,depressions,valleys and sinkholes,but also underground river pipelines and so on.The study area is intermittently uplifted during the neotectonic movement.A short quiet period during the intense uplifting process leads to the development of multi-layer(exactly four layers)horizontal karst caves in this karst area.The study area is distributed in the second layer with a distribution elevation between 2,020-2,050 m.In the typical moniliform wetland of this area,groundwater converges to the syncline structure of basin floor.The nuclear part of the syncline is located in the corrosion trough valley in the depression of the wetland.Eastward and westward groundwater,recharged through joint fissures and runoffs of karst groundwater,discharges to the nuclear part of syncline and converges to the soluble pond or lake wetland like Qiwen lake.Due to the shallowly buried groundwater level,this kind of lake wetland is rich in water resource.As a discharge area as well as a recharge area of the southern underground river system,corrosion trough valley in the depression of the lake wetland maintaines a close hydraulic link between groundwater and surface water in a constant cycle of suppy-discharge-supply of underground water.Under the condition of the same hydrological flow field,keeping the water balance can guarantee the continuous water displacement,and hence maintaining a good water quality in the lake wetland.Through the analysis of hydrological geology,a study on the structure,hydrological geology and karst development characteristics of moniliform lakes of lacustrine type has been conducted.The study shows that the moniliform wetland on the Yunnan-Guizhou Plateau surface experienced three stages.The first stage-the first phase of Nanpan river-is the stage of crustal uplift.In this stage,the sinkhole-karst tube fissure system was developed in terms of dissolution on the basis of structural fissure development.The second stage-the second phase of Nanpan river-is the stage of crust stablity.In this stage,depressions and funnel-cave underground river systems were developed maturely.The third stage is the stage of stone forest in which the new karst uplift led to degradation of the underground river in the layer caused by the capture of a newly developed underground river system;consequently,collapse,siltation and blockage occurred.With the effect of neotectonic movement,the moniliform wetland on the surface was formed under the condition of karst pipeline collapse,silt blockage and uneven karst development in a long time due to crustal uplift and erosion base sapping.In view of the shrinking wetland area at present,protection suggestions are also put forward in this study.These suggestions involve delimiting the water conservation area and the core area of wetland,strengthening wetland protection and its publicity,conducting the study on the evolution of karst wetland to improve the level of wetland scientific research and developing the tourism with characteristics of wetland and"red revolution bases".