SUBAQUEOUS STALACTOIDS IN THE DAL’NEE VERKHNEE LAKE OF THE SHULGAN-TASH CAVE (SOUTHERN URALS)
The relevance of the work is conditioned by the need for a comprehensive study of the mineralogical and microbiological parameters of the Shulgan-Tash (Kapova) cave, which is an archeological monument of universal importance.The purpose of the work: to describe findings of subaquatic stalactites in the Shulgan-Tash cave and to solve mineralogical and genetic issues.Research methodology: hydrochemical, electron microscopic and microbiological techniques of research were used in the present work. Results. This article describes subaqueous stalactoids for the first time in Russia. In the foreign literature they are called “Pool Fingers”. They are the carbonate forming with the origin, which is not yet definitely installed. They are emerging in the coastal zones of the cave waters. Subaqueous stalactoids were found in the Dal'nee Verkhnee lake on the second floor of the Shulgan-Tash cave 700 meters from the entrance. Subaqueous stalactoids are widespread along the Eastern and Western shores of the lake. They are thin and elongated aggregates of cream-colored up to a length of 30 cm, composed of calcite. They were formed in the lake of calcium bicarbonate type water with total mineralization of 390-510 mg/l, their hydrogen index is close to neutral (pH 6.8-7.3) and minor (not more than 5 mg/l) magnesium, sulfates and chlorides. Stalactitical surfaces are covered with the biofilm of the extracellular polymeric substances (EPS) and microorganisms. In their environment, the crystallization of calcite takes place. The “filaments”, whose taxonomic affiliation is not clear are found inside the units in the flattened strands of biological origin. Calcite is a block crystal subindividuals, which possess the elements of splitting. Their size is about 200-300 µm. The manifestation of skeletal crystal growth happens rather often. Researches prove the participation of microorganisms in the origin of subaqueous stalactoids. Apparently, filamentous bacterial mats play the role of the primers and a “framework", which provides a gravity-oriented growth of the aggregates. Extracellular polymeric substance (EPS) has the ability to form complex compounds with ions of Ca2+. It may indirectly lead to the precipitation of calcite.Conclusions. The microbial mediated genesis, similar to that described in the literature of the North American counterparts, was substantiated for thesubaqueous stalactoids (Pool Fingers).