Structure and evolution of the Shihua Cave in Beijing

Of the known karst caves in northern China, the Shihua Cave in Beijing has the greatest scale and most kinds of secondary carbonate sediments. It is one of the most important caves in northern China in terms of its landscape sightseeing and scientific values. To determine its size and structure, a complete investigation including survey was conducted in July 2013. This work followed international survey standards and used various instruments including Leica laser rangefinders and Sunnto compasses and clinometers, in conjunction with Onstation and ArcMap 10 software. The results show that the Shihua Cave extends from NWW to SEE along the strike of the Ordovician limestone, indicating that the cave development is primarily controlled by strata. NE and NW-striking faults have influenced cave development to a less extent. The cave has a total length of 5,639 m and a floor projection area of 37,096 m2. In the vertical direction, the highest and lowest positions within the cave are 14 m above and 158 m below the entrance, respectively. The cave system consists of five levels of passages, of which the elevation is 249 m, 211 m, 154 m, 111 m and 95 m above sea level, respectively. Each level indicates a period of stable local base level, suggesting that this cave experienced five stages of development. The lowest level of it has a 1,638 m passage,which is characterized by seasonal water flow with three windows into a perennially inundated phreatic level. The seasonal underground river flows southeastward during the summer flood season. The downstream passage forks, one branch terminating in a sump pool while the other consists of chambers with a large amount of breakdown, implying the end of the underground river.The underground river may connect the Shihua Cave with Silver Fox cave to the northwest and the Kongshui Cave to the southeast. Exploration of nearby caves and tracer tests should be conducted to verify this connection in the future.