Characteristics And Origin Analysis Of North-China-type Karst Landform In Yanqing Geopark

Longqingxia Scenic Area,located in the west of the proposed Yanqing Global Geopark,is about 10 km far from Yanqing urban area,covering an area of about 108.63 km2.This scenic area is dominated by the typical North-China-type karst landforms developed in the Precambrian dolostone of Wumishan Fm,which are the representative of karst landforms in the north China..Longqingxia Scenic Area takes the neritic dolostone of the Mesoproterozoic Wumishan Fm about 1.4 billion years ago as its basis,with perfect marine depositional structures,such as horizontal beddings,stromatolites,tempestite and others.In this scenic area,the dense structural joints and faults are developed in the Precambrian marine carbonates due to the effect of the Mesozoic Yanshanian movement.Since the Cenozoic,the beautiful karst landscapes have been shaped by the karstification.As an important component of Yanqing Geopark,Longqingxia Scenic Area is rich in geoheritage,dominated by the typical North-China-type karst landforms,and it also rovides the evidence of the Mesozoic Yanshanian movement.Based on the field investigations and data collection,this paper describes the characteristics,origin and evolutionary process of the karst landforms.discusses the geological background of major geosites,and focuses on the mutual relationship between the karstification and Yanshanian Movement-induced structural joints in its material basis.The major results are as follows:(1)Longqingxia scenic area had experienced a long-term exposure after the deposition of Meso-to Neoproterozoic Wumishan Fm;(2)The unconformity in this area between the Precambrian Wumishan Fm and Upper Jurassic Tuchengzi Fm is coincident with other areas but still with some differences;(3)The Yanshanian movement-induced joints and faults in the Precambrian Wumishan Fm are mainly formed in the first phase of Yanshanian Movement;(4)Since the Neotectonic movement,the study area has dominated by the vertical uplift,the flowing water mainly flowed and eroded along the two nearly vertical joints,and finally formed the karst valley..Longqingxia Scenica Area is not only an important component of Yanqing Geopark,but also a main studying area of the Yanshanian movement.The research on the karstification process and landforms has important significance both in studying the geological history of Yanqing Geopark,and providing scientific evidence for rational and scientific development of Longqingxia Scenic Area of the geopark.