SUBPERMAFROST GROUNDWATER IN THE NORTHEASTERN PART OF THE LENA-AMGA INTERFLUVE
M.A. Fedorov, A.A. Fedorov, N.A. Pavlova
Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Sciences, Yakutsk, Russia
Keywords: groundwater, Middle Cambrian aquifer system, Jurassic aquifer system, Tatta-Tompo fault, hydrostatic level, chemical composition
Abstract
The purpose of this work was to specify the hydrogeological conditions in the poorly studied northeastern part of the Lena-Amga interfluve. We analyzed archival (1965-1995) and published data on subpermafrost waters and permafrost thickness in the Churapcha and Tattinsky districts of the Republic of Sakha (Yakutia), including new field studies (2009-2022). The research was based on the data from 19 groundwater exploration wells, 450 to 650 m in depth. It is shown that the Jurassic and Middle Cambrian aquifer complexes differ in piezometric pressures and chemical composition. Based on the new information, it is suggested that the boundary between these two aquifer complexes should be shifted northward by 50-80 km. A zone with distinct specific hydrogeological conditions confined to the Tatta-Tompo fault was identified. Presumably, the fault was formed under conditions of horizontal compression, which resulted in the compaction of the rocks and their reduced permeability along the fault, as well as in the increased freezing intensity in the strata with a low water content during periods of decreased global temperatures.
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