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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
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.
In carbonate rocks, especially in those with high primary porosity such as most Cenozoic carbonates, the interaction between deeply derived rising flow through sub-vertical fracture-controlled conduits and intrastratal matrix flow of shallower systems can invoke mixing corrosion and result in prominent speleogenetic effects. This paper outlines a conceptual model of such interaction and provides instructive field examples of relevant morphological effects from two different regions within the Prichernomorsky (north Black Sea) basin, where karst features are developed in lower Pliocene, Eocene and Paleocene limestones. In the Crimean fore-mountain region, extensive steep to vertical limestone scarps formed through recent exposure of hypogenic fracture-controlled conduits provide outstanding possibilities to directly examine details of the original karstic porosity. The morphological effects of the conduit/matrix interaction, documented in both caves and exposed scarps, include lateral widening of sub-vertical conduits within the interaction intervals (formation of lateral notches and niches) and the development of side bedding-parallel conduits, pockets and vuggy-spongework zones. Natural convection circulation, invoked by interaction of the two flow systems, spreads the morphological effects throughout the conduit space above the interaction interval. Where the interaction of the two flow systems is particularly strongly localized, such as along junctions of two vertical fracture sets, the resultant morphological effect can take the form of isolated chambers. The variety of speleogenetic features developed through the conduit/matrix interaction, can be broadly grouped into two categories: 1) variously shaped swells of the major fracture conduit itself (morphological features of its walls – niches and pockets), and 2) features of the vuggy-spongework halo surrounding the conduit. This halo includes clustered and stratiform cavities, spongework zones and lateral side conduits. The speleogenetic features due to conduit/matrix flow interaction, especially the halo forms, often demonstrate distinct asymmetry between opposite walls of the conduits. The prominent phenomenon of the vuggy-spongework halo around fracture-controlled conduits has important hydrogeological implications. A comparison of karst features in different regions and rock formations clearly shows that in spite of some distinctions imposed by local structural, sedimentological and paleo-hydrogeological peculiarities, hypogenic speleoforms in limestones of different age and of different degree of diagenetic maturity demonstrate remarkable similarities.
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. Desc
The hydrogeological approach to defining hypogene speleogenesis (HS) relates it to ascending groundwater flow (AF). HS develops where AF causes local disequilibria conditions favoring dissolution and supports them during sufficiently long time in course of the geodynamic and hydrogeological evolution. The disequilibrium conditions at depth are invoked by changing physical-chemical parameters along an AF paths, or/and by the interaction between circulation systems of different scales and hydrody-namic regimes. The association of HS with AF suggests a possibility to discern regulari-ties of development and distribution of HS from the perspectives of the regional hy-drogeological analysis. In mature artesian basins of the cratonic type, settings favorable for AF and HS, are as follows: 1) marginal areas of discharge of the groundwaters of the 2nd hydrogeological story (H-story), 2) zones of topography-controlled upward cir-culation within the internal basin area (at the 1st and, in places, at the 2nd H-stories; 3) crests of anticlinal folds or uplifted tectonic blocs within the internal basin area where the upper regional aquitard is thinned or partially breached; 4) linear-local zones of deep-rooted cross-formational faults conducting AF from internal deep sources across the upper H-stories. Hydrodynamics in the 3rd and 4th stories is dominated by ascending circulation strongly controlled by cross-formational tectonic structures. Specific circula-tion pattern develops in large Cenozoic carbonate platforms (the Florida-type), side-open to the ocean, where AF across stratified sequences in the coastal parts, driven by both topography-induced head gradients and density gradients, involves mixing with the seawater. The latter can be drawn into a platform at deep levels and rise in the plat-form interior (the Kohout’s scheme). In folded regions, AF and HS are tightly con-trolled by faults, especially those at junctions between large tectonic structures. In young intramontaine basins with dominating geostatic regime, HS is favored at margin-al discharge areas where circulation systems of different origins and regimes may inter-act, such as meteoric waters flows from adjacent uplifted massifs, basinal fluids expelled from the basin’s interiors, and endogenous fluids rising along deep-rooted faults. Spe-cific and very favorable settings for HS are found in regions of young volcanism with carbonate formations in a sedimentary cover