The karst of the Gissarski Khrebet Uzbekistan - Central Asia
The Gissarski Khrebet, between Uzbekistanand Tagikistan State in central Asia, is a mountain range extended for about 100 km. Its altitude goes from 2500 to 4000 m.
The chain consists of a NNE vergin fold-and-thrust-belt, developed over a predeformed crystallin basement of Paleozoic age. A stratigraphic succession of shale and sandstone constitutes the local water table level, for overlying 300 m of thickness of the karstic stratificated gray limestone of the Giurassic age, with facies of grainstone and mudstone.
On top of the limestone are present about 100 m of thickness of red/brown clay with gypsum level, where several suffosion dolines develop. The climate of the area is continental and arid without vegetation cover, with dry summer and a lare winter snow cover.
The karstic plateau of about 100 km2 is localized in the south of the village of Tashkurgan between Samarkand and Dushanbe.
It was investigated by the PAMIR 91 italian/sovietic expedition. The main superficial and underground karst is localized in a wide and flat syncline, cut in the middle by a deep canyon.
The main morphological landforms are characterized by an altitude denudated and nival karst, represented on the limestone beds by small scale solution sculptures as karren and microkarren. They are preferentially organized along a system of fractures oriented in the N-S direction. Several dolines, tenths of solution shafts and snow-wells connect the epikarst zone with underground karst.
The hypogean karst are costituted by shafts of tens of meters of depth, partially infilled with ice, that connect several narrow passages developed along main tectonic features. In the lower part are often present clay and debris deposits. The main cave is represented by the system of Gissarskaya, that develops for over1000 m with a depth of about 200 m. In the lower part of the central canyon a spring, Reka Caves explored for 250 m, costitutes one of the main drainage systems of the karstic plateau.