Research has been conducted on the permafrost in the Sentsa River valley for the first time. The investigated units of the permafrost are cryogenic structures of unconsolidated deposits and active layer temperature, morphology and cross-section of sizable frost mounds and chemical composition of ice core. The complex pilot studies included borehole drilling, detailed documentation of frost borehole samples, penetrated sections of frost mounds, and river terrace cusps, tachometric survey of the Sentsa river valley, GPS-anchoring of reference sections and boreholes, defining the ice content (humidity), and the lithological, grain-size and microaggregate composition of lacustrine-alluvial sediments. The analysis has been performed by the specialists of the Center for Geodynamics and Geochronology located at the Institute of the Earth's Crust, Irkutsk using modern methods. According to the preliminary data, frost mounds are cryogenic formations of mixed segregation-intrusive genesis. The permafrost thermal regime observations have shown that significant temperature variations occur in the layer 0-2 m, and below the rock temperature is negative in the two-year cycle. It varies from -1.6 °C (in winter) to -0.8 °C (in summer) at depth 4.4 m. The rock temperature is constant (-2.1°C) at depth 10 m.