地球物理方法探索隐伏岩溶古河道——以湖南郴州万华岩为例

为探讨湖南郴州万华岩景区上游岩溶古河道的存在性，丰富景区岩溶洞穴科普知识以推动地方旅游经济发展，探索性地应用高精度磁法、高密度电法、音频大地电磁测深法（EH4）等综合地球物理方法在景区上游进行了探测研究，其结果发现几处磁、电异常部位，并结合区内岩溶垮塌地貌形态、区域地质背景资料及野外地质调查成果，认为景区上游存在岩溶古河道，同时确定出岩溶古河道的剖面位置及平面走向。整个研究思路表明综合地球物理方法在研究岩溶古河道时具有可行性。 

Exploratory research on buried karst paleochannels by comprehensive geophysical methods:A case study of Wanhua cave system,Chenzhou,Hunan Province

The research area is located in the upstream of the Wanhuayan Scenic Area. The outcrop strata are the third to fourth member of Carboniferous Yanguanian Stage, upper member of Datangian Stage Shichengzi Formation, and Ceshui member of Datangian Stage Ceshui Formation,of which the lithologies are characterised by shallow-sea carbonate facies strata, i. e. micrite and limestone. It is structurally controlled by the northeast-south west trending compression-torsional fracture and the secondary fault of the New Neocathaysian system, and is also affected by north west-south east trending fault. In the southern part of the study area, there are large-scale intrusive fine grained-,and coarse grained granites and medium-coarse porphyry granite of the Indosinian stage. Groundwater mainly comprises karst water, pore water and a small amount of fissure water. To explore the existence and evolution history of karst ancient rivers in the upper reaches of Wanhua caves for enriching popular science knowledge of the karst caves, the researchers applied comprehensive geophysical methods of high-precision magnetic method, high-density electric method and audio frequency magnetotelluric sounding method (EH4) to explore the upper reaches of the scenic area. The results revealed several magnetic and electrical anomalies. We also have interpreted anomalies and made geological assumptions.The distribution of overburden layer thickness, geological structure and stratigraphic lithology in the study area are well presented by the results from both high density electric and audio geodetic sounding surveys. The high precision magnetic method reveals the granitic boulders deposited underground, which indirectly indicates the presence of karst ancient river channel and restores historical process of its evolution. The whole research idea is practical; and through this study, a approach to applying comprehensive geophysical methods to detect karst ancient river channels can be established.