RELATIONS BETWEEN KARST AND THE NEOGENE PALEO-BELAYA VALLEY NETWORK, SOUTHERN CIS-URALS REGION

Abstract

Miocene-Pliocene tectonic movements transformed considerably the landscape of South Urals and drove spatial patterns and intensity of Earth surface processes. Deepening of river valleys in Paleo-Volga and Paleo-Ural drainage systems facilitated ground water action. Geological section in paleo-valleys of Belaya, Ufa, Bystriy Tanysh, Dioma and other rivers includes up to 200 m thick Late Miocene – Pliocene clayey unit that may favor both drainage and screening of aquifers depending on local hydrogeological conditions. In the former case, karst processes are intensified due to the increased pressure gradients and ground water velocities along the sides of paleovalleys that are composed of Carboniferous and Lower Permian gypsum and limestones. In case of shielding, rising flows of highly mineralized water are discharged in the form of large karst springs (“Krasniy Klyuch”, and others.). Along with natural control factors (lithology, tectonics, hydrogeology, etc.), present-day karstic processes development are controlled by economic activity. Karst and suffosion (underground erosion) are often activated by growth of cities and development of new lands. Neogene and modern valleys promote karst development in Lower Permian gypsums in the Ufa agglomeration where 63 karstic fieds were found. In the last 25 years, 70–80% of hazardous cases related to kasrt intensification were induced by technogenic waterlogging. Karstic and suffusion processes threaten the exploitation of Yumaguzinskaya and – Pavlovskaya Hydropower stations that were constructed on karst prone carbonate rocks at the Belaya and Ufa palevalleys.