—Paleoenvironmenal reconstructions have been made from a multidisciplinary study of a borehole permafrost record on Kurungnakh Island (Lena delta). According to data on palynomorphs and ostracods, the clay silt units from the 10.58 to 13.54 m and 1.58 to 10.3 m core depth intervals were deposited in the Late Pleistocene (during the Karginian interstadial) and Early–Middle Holocene, respectively. The sediments were studied in terms of moisture contents, grain size distribution, mineralogy, and magnetic susceptibility, and the results were compared with published evidence from nearby natural outcrops. Quite a cold oligotrophic lake existed in the area during the Karginian period, and the deposition was interrupted by a gap recorded at a core depth of about 11 m. In the Early and Middle Holocene, the area was covered with shrub tundra vegetation.

A new system has been designed for laboratory physical modeling of hydrate-bearing sand samples and measuring their acoustic properties at different temperatures and pressures. The system includes a pressure vessel, units of temperature control, external pressure, and gas/liquid delivery, and a unit for measuring velocities of acoustic waves. Measurements are carried out in 10–50 mm high cylindrical specimens 30 mm in diameter. The system provides methane hydrate formation in sand samples and their acoustic measurements for as long as several days due to automatic control. Hydrate-bearing samples are prepared by pressurized methane injection into pores of wet sand and are exposed to several cooling/heating cycles to increase hydrate formation rates. Hydrate-bearing samples have been prepared and travel times of acoustic P and S waves have been measured in dozens of successful experiments. Acoustic data confirm the formation of hydrates, with the related increase in wave velocities to values about those in frozen sediments. The prepared gas hydrates are inferred to be of “cementing” type, i.e., they form as cement at the boundaries of mineral grains. The obtained velocities of acoustic waves show a positive linear correlation with hydrate contents in sand samples.

This work provides the results of the complex relative dielectric permittivity ε  =  ε′  −  iε″ (CRP) measurement and nuclear magnetic resonance (NMR) response of the quartz powders and cores of different porosity at stepped moistening and drainage. It is shown that CRP and NMR responses are ambiguous functions on water. The character of the CRP hysteresis depends on the electromagnetic field frequency, on the particle size and water salinity. The analysis of the NMR data shows that firstly the larger pores are filled with water at moistening and they are also drained first. Thus at the same water content, which is obtained in both the processes of moistening and drainage, pores of different sizes are filled. Herewith the water droplets have different curvature radiuses and different wetting contact angles which is the main cause of the hysteresis in the CRP and NMR response.

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