GEOLOGY OF THE MASSIF

The geology of the Kugitangtau Ridge is rather simple. The ridge is a single horst-meganticline, which is almost not complicated by overlying tectonics, being cut by a cuesta on the eastern slope. The western slope is a flat plateau with a height from 300 to 3000m. The plateau is armored by limestones of the Kugitangtau series (Upper Jurassic, Callovian - Oxfordian )up to 500m thick, in which the caves inquestion are situated . The remnants of gypsum-anhydrite deposits of the Kimmeridgean - Titonian Gaurduck series, in which the karst is developed, are found from place to place. But the caves are not interesting there. A thick flysch bed, which does not appear to be waterproof, underlies the limestones. Beneath the cuesta , the flysch is intruded by a granite batholith and a volcanic massif, which, to all appearances, intruded even into an eroded part of the limestone and left agate pebbles in the canyon valleys that cut through the modern ridge. The plateau is cut by some hundreds of canyons up to 300-400m deep and up to 30km in length. Some canyons reveal the upper floors of the caves, but in general the caves are situated completely below the canyon level and spread freely under it. The surface karst forms, such as sinks, sinkholes and so on, are totally absent. Limestones are quite interesting, being represented by very massive, slightly marbled and intensively silicified varieties. The normal karst process could not develop in them, which is the reason the caves can progress several meters under the canyon floors without being intercepted even by small sinkholes. There are interlayers with sideritic concretions, separate sulfur inclusions and numerous veins of low-temperature calcite and fluorite. There are also some Pb-Zn sulfide veins, which were partly exploited before. Single veins with celestite are also present.

The tectonics of the ridge is also simple. The substantial role belongs to a system of upthrusts, which are almost parallel to the ridge axis, forming horst blocks. Each upthrust with a 40 - 300m height is well traced in the relief features and obliquely transsects a plateau, dividing it into well defined upper and lower blocks. Other fractures have a height of no move than a few meters.