identification of subaerial taliks by geophysical methods in the middle part of the lena river basin, central yakutia

In autumn 2023, comprehensive geophysical surveys were conducted in the experimental section of the shestakovka river basin (central yakutia) to identify structural features of the near-surface part of the geological section, in particular permafrost rocks and talik zones. the work objectives included ground penetrating radar (gpr) studies and electrical resistivity survey. drilling and well temperature logging data were used in the interpretation. the work is relevant due to the importance of studying the processes occurring in the cryolithic zone due to global climate change, and the novelty lies in clarifying the structure of the study area. the average permittivity of rocks across the section on the right and left banks of the river is 15.5 and 6.9, respectively. the differences are due to moisture saturation and the degree of soil freezing. the depth of the talik base on the right bank of the river is from 2 to 14 m with an average value of 6.1 m. on the left bank of the river, it varies from 3 to 7.1 m with an average value of 4.2 m. according to electrical exploration, the medium is a four-layer section. the upper layer about 2 m thick is the most heterogeneous in electrical resistivity and corresponds to seasonally frozen soils. the base of the underlying talik on the geoelectric section is traced at a depth of 4 to 7 m, which is consistent with drilling and gpr data. the third high-resistivity layer corresponds to permafrost rocks. the electrical resistivity in them increases by an order of magnitude compared to the talik zone and is about 2000 ohm·m against the background of 100-270 ohm·m. the underlying lower layer is characterized by a decrease in electrical resistivity to 220 ohm·m, which may be associated with a change in the lithological composition or with the groundwater circulation.