Hydrogeology and geomorphology of Bisetun Aquifer (NW Iran): interesting example of deep endokarst
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ORIGINAL ARTICLE
Hydrogeology and geomorphology of Bisetun Aquifer (NW Iran): interesting example of deep endokarst Morteza Mozafari1 · Maryam Sajjadian2 · Youssef Sorninia3 · Rahim Bagheri4 · Fatemeh Ghader5 Accepted: 9 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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–SWand 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. Keywords Bisetun aquifer · Endokarst · Hydrogeology · Geomorphology · Speleogenesis
Introduction * Morteza Mozafari [email protected] Maryam Sajjadian [email protected] Youssef Sorninia [email protected] Rahim Bagheri [email protected] Fatemeh Ghader [email protected]‑berlin.de 1
School of Geology, College of Science, University of Tehran, Tehran, Iran
2
Iran Ministry of Energy, Tehran, Iran
3
Surena Caving Team, Kermanshah, Iran
4
Faculty of Earth Sciences, Shahrood University of Technology, Shahrood, Iran
5
Department of Applied Geoscience, Hydrogeology Research Group, Technische Universität Berlin, Berlin, Germany
Karst is defined as a terrain with distinctive landforms and hydrology characterized by fluted and pitted rock surfaces, sinking streams, enclosed depressions, caves, dolines, shafts and large springs (Palmer 1991; White 2007; Ford and Williams 2007). The dominant morphogenetic process at karst regions is dissolution of rocks by water, resulting subsurface features from microscopic in size to thousand
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