This article presents the results of geocryological studies of the Tokarikan and Guvilgra grabens of the Aldan Shield. Expedition research on the hard-to-rich region since 1996 has allowed us to determine the temperature regime, thickness, and nature of permafrost rock distribution and characterize its geocryological conditions for the first time. We have established that the lowest temperatures (up to –3.4 °С) are characteristic of peatmoss bog landscapes, whereas the highest (–0.5 °С) are for well-drained and watershed areas. The results of the measurements in deep wells, information on the process of drilling deep exploration wells, and the analysis of data on the thermophysical properties of rocks allowed us to estimate a permafrost thickness capacity that varied in the range of 40–260 m. The presented schematic permafrost and geological cross-sections and geocryological condition maps can be used to plan the industrial development of the territory.

The Suntar-Khayata Range includes numerous natural phenomena interacting with or depending on permafrost conditions. Here, we examine some patterns of deep permafrost and talik zones on adjacent sites. A 210 m deep borehole in siltstone bedrock was equipped for the temperature monitoring of the topmost 15 m and measurements of a deep permafrost temperature profile in July 2010. The temperature curvature in the upper part has a bend, which is consistent with the upper portion justified by climate warming, and shows a steady-state linear geothermal profile below 85 m depth with a high geothermal heat flux. A shallow borehole situated at the river floodplain was used to investigate the thaw zone's temperature regime. The temperatures down to 6.7 m deep have been monitored at 5 min intervals during heavy rainfall, and the temperature readings have behaved quite peculiarly. The thickness of the seasonal freezing layer reaches 5.7 m; moreover the ground temperature increases to 6 ^∘C at 6.7 m depth by groundwater heat transfer. This study provides some new insights into the permafrost condition at one of the coldest places in the Northern Hemisphere.