Bisetun Aquifer hosts of a noteworthy example of deep endokarst system in the world which is largely unknown to the scientific community. Several caves with up to 1316.6 m depth and the world's second deepest shaft were discovered in this aquifer during recent years. This research tries to give a scientific explanation from geology, hydrogeology, geomorphology, and hydrochemistry to the questions about formation of this endokarst system. The aquifer is composed of about 3000 m thick Bisetun Limestone with more than 80% carbonate minerals. Existing of massive pure limestone together with the local cold weather and high precipitation at the area enhance karst development, but it seems that formation of deep endokarst in the aquifer is mainly related to the tectonic features. The Bisetun Limestone has experienced about 50–70 km displacement during Eocene, providing suitable structural conditions and near 2000 m relief for deep water circulation. All the caves and shafts are epigenic since they were formed by autogenic water movement from the high-elevation recharge zone toward the springs in nearby valleys. Caves and shafts morphology together with the analysis of structural features indicates that passage development was directed along the W–E-oriented successive thrust faults, subsequently dissected by the NE–SW- and NW–SE-oriented traversing faults. Water chemistry and high recession coefficients of spring's hydrographs show fast groundwater movement via karst conduits, mainly developed along the faults and fractures. Considering hydrogeological setting, it seems possible that even deeper endokarst features would be waiting to be explored at the aquifer.

中文翻译：

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Bisetun 含水层（伊朗西北部）的水文地质和地貌：深层内岩溶的有趣例子

比塞通含水层拥有世界上一个值得注意的深层内岩溶系统例子，科学界在很大程度上不知道。近年来，在该含水层中发现了几个深达 1316.6 m 的洞穴和世界第二深的竖井。本研究力图从地质学、水文地质学、地貌学、水化学等方面对这一内溶岩系统的形成问题作出科学解释。含水层由约 3000 m 厚的 Bisetun 石灰岩组成，碳酸盐矿物超过 80%。块状纯石灰岩的存在，加上该地区局部寒冷天气和高降水量促进了岩溶发育，但似乎含水层深层内岩溶的形成主要与构造特征有关。Bisetun 石灰岩在始新世经历了约 50-70 公里的位移，为深水循环提供了合适的构造条件和近 2000 米的浮雕。所有的洞穴和竖井都是后生的，因为它们是由高海拔补给区向附近山谷中的泉水的自生水运动形成的。洞穴和竖井形态以及构造特征分析表明，通道发育是沿着 W-E 向的连续逆冲断层，随后被 NE-SW-和 NW-SE 向的横断断层切割。春季水文过程线的水化学和高衰退系数表明地下水通过岩溶管道快速移动，主要沿断层和裂缝发育。考虑到水文地质环境，