发育在早二叠世栖霞组大理岩化夹硅质层和含硅质结核的石灰岩中的龙石空洞,是华东地区重要的风景旅游洞穴。是一个干洞与地下河相结合的洞穴系统。由于栖霞组石灰岩与上覆的童子岩夹煤层砂页岩、文笔山砂页岩及下伏的泥盆纪石英砂砾岩呈断层接触,断层接触带形成了地表沟谷。燕山晚期花岗岩侵入时导致栖霞灰岩变质。在地形上,夹煤层砂页岩不仅覆盖在栖霞灰岩上,而且出露部位比灰岩体高。出自煤系地层的水会顺坡或垂直流入灰岩体。出自煤系砂页岩的地下水pH值为3.78～4.73,SO4-2达到240mg/l。源自泥岩夹薄层砂岩和花岗岩地区的地表水,具有pH值6.85～7.25及低Ca2+、HCO3-值水也会流入灰岩体。直接出露灰岩体,雨水入渗土壤,溶解土壤CO2后再进入石灰岩。因此,龙石空洞系统是外源水与内源水共同作用的结果,是由碳酸水和硫酸水联合作用的新型洞穴双成因发育模式的一例。

The Longkong Cave, including the underground river and dry passages decorated by the solutional features and carbonate speleothems, is one of the well known show caves in Southeastern China. It developes in the Lower Permian Qixia limestone with siliceous layers and concretions. The Qixia limestone is contacted by faults with Lower Permian Tongzhiyan sandstone and shale with coal mines, Wenbishan sandtone and shales and Devonian silicarenite and conglomerate rock. The surface valleys developed along the faults. The Qixia limestone was metamorphosed by the Late Yanshan granite intrusion. Topograpgically, The sandstone and shale with coal and the granite on the mountain and the Qixia limestone on the lower slope. The surface water and groundwater from the sandstone and shale with coal and othe noncarbonates terrains flows into or down to the limestone. A part of limestone has been exposed as the noncarbonate rocks,which have been removed away. The fissure spring water discharging from the Tongzhiyan formation is with pH values in the range from 3.78 to 4.73, 240 mg/l of SO_4 -2 anions; the water with pH of 6.78～7.25 and lower contents of Ca 2+ and HCO_3 - sources from other noncarbonate rock terrains. These exotic waters, expecially with sulphuric acid aqueous,strongly dissolve the limestone to form the Longkong cave system. The endogenetic water penetrates into soil covering on the limestone from the rainwater and dissolves the CO_2 produced by vegetation roots breath, organism decomposion and biofunction of soil fauna and mcrobe to form the carbonatic acid aqueous. When the water flows into the limestone,it dissolves the limestone to enlarge the fissures and passages. The Longkong Cave is the typical genetic model for cave development by the sulphuric and carbonatic acid aqueous from the exotic and endogenetic waters.