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Abstract:

Karst phenomena of headstreams of the Lena River in Eastern Siberia between junctions of the Zolotokan Creek and  Chanchur River are described in the paper. Wide spreading of karst is determined by: areal occurrence of marine carbonate rocks  of the Lower and Middle Cambrian, their monoclinal bedding, increased tectonical fracturing of karstiferous rocks, relatively high  roughness of surface topography, flattened dividing ranges, relatively humid climate (precipitation 400-500 mm per year), and long  history of continental regime of the area. The relics of ancient gently sloped river valleys at dividing ranges are the most karstified.  There is no surface drainage in their limits, and groups of dolines up to 40-80 individuals per square kilometer are common. Karst  development determines an existence of vast meadows covered with the dwarf birch, reindeer moss and herbs (Trollius asiaticus Scutellaria baiñalensis, Rhodiola rosea, Veratrum lobelianum, Gentiana sp., Allium sp. è äð.) among stocked coniferous taiga at  the altitude of 1080-1150 m a.s.l. at the watershed divides of the Lena and Levaya Tongoda rivers (Mongolian Steppe Stow), and  Lena and Pankucha-2nd rivers. On the rest of the territory, dolines do not form large groups, but they occur as isolated individuals  or scattered clusters consisting of 3 to 5 individuals. Karst dry valleys are widely spread. Their total length is not less than 397  km, and 126 km of them belongs to the watershed of the Yukhta-1st River. Residual hills having morphology of pillars, towers and  ridges were observed. Descriptions of two karst caves and two crevice caves are given