On conductivity of permafrost

The bulk of the work was carried out by the integral method of routeradio-comparing, allowing to explore large areas for a short time. Measurements of the earth's wave tension were conducted by 16emitters CB-IR band (160-1000 kHz). The length of individual lines is 100 km to 1130 km. The number of detected frequencies perroute varied from 1 to 5, depending on the location of the route that allowed us to obtain a total of 94 curves of the modulus of theattenuation function of the distance. Tests were held by methods of sounding, Ramsey held on the Peninsula Chelyuskin (1986, 1988),in the area Gurievsk (Kemerovo region, 1989), Norilsk (1990), and profiles - Norilsk-Khatanga (1988), Sverdlovsk (at present -Ekaterinburg) - Kamyshlov (1989). Variations in radiofield intensity were studied on rf frequencies of 162-675 kHz. Simultaneously,we measured the temperature of air and soil, as well as the electrical conductivity of the upper part of the geoelectric section bysounding methods, Ramsey and the electrical conductivity of wood in the temperature range from -27 to +27 degrees Celsius. Theaccumulated experimental material on radiofield intensity variations and variations in intensity of rf conductivity of wood (bothhardwood and softwood) became the basis for the solution of the so-called "winter" anomaly in the propagation of medium radio wavesin middle latitudes. The work identified and experimentally proved wide distribution of low-resistance (30-200 ohm m) formations inthe area of permafrost. The presence of low-resistivity layer allowed to use the method of Ramsey (REMP) (according to anotherclassification - SDVR method) at high latitudes to determine the thickness of unconsolidated alluvial deposits in the search for mineraldeposits. The drilling of L-210 profile on the Arctic coast of the Peninsula Chelyuskin is given as an example of such work. In 1986 acomplex of geophysical methods - VES with AB/2 up to 500 meters, two-dimensional electric profiling symmetrical with AB/2 11 and100 meters, two-frequency electromagnetic profiling at frequencies 16.4 and 19.0 kHz, magnetic prospecting - was held here. Thespecific electrical resistance (resistivity) of the first layer corresponding to the zone of seasonal defrost varies in the range 15-50 . 100-300 Ohm m. The thickness of this layer varies from 10 to 70 cm. The second horizon is characterized not only by high resistivity, butalso by a greater variation of electrical resistance in the sequence (11 000 . 89 000 ohm m, with single "bounces" up to 120,000 ohm m). Geologically, this layer corresponds to frozen marine Quaternary sediments, traced over the entire profile. Variability of theresistivity is explained by the varying ice content in these formations, and maximum values correspond to ice interlayers, which areobserved in the section. The thickness of the layer varies from 2 to 5 meters. The third layer has the greatest interest: it is characterizedby a low impedance of 30-200 Ohm m. Decreased resistance of these rocks is explained by the presence of high salt content. Thethickness of these structures is 5-50 m. Work on L-210 profile showed that the low-lying areas of the buried relief are characterized byreduced (absolute) values of the reduced surface impedance phase (φ). The phase of impedance value is close to 45° in those places,where the bedrock is almost out to the surface, which corresponds to a uniform cross-section. At the same time, the reduced modulus ofthe surface impedance (pef.) in such places has a sawtooth character and a higher value (zone of quartz veins). Radioimpedancemeasurements in permafrost (Yakutia, Northeast Russia) fulfilled in recent years confirm the wide distribution of areas with lowelectrical resistance, which can be considered today as an established fact.

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