Earth’s Cryosphere, 2019, Vol. XXIII, No. 5, p. 31-43
ICE COMPLEX STRUCTURE INFERRED FROM VERTICAL ELECTRICAL SOUNDING (SOUTHERN MARGIN OF THE LENA-AMGA INTERFLUVE)
L.G. Neradovskii
Melnikov Permafrost Institute, SB RAS,
36, Merzlotnaya str., Yakutsk, 677010, Russia; leoner@mpi.ysn.ru
Discussed are the results of a cluster analysis of vertical electrical sounding (VES) data with an aim to characterize the Ice Complex structure in its southern margin stretching along the Berkakit–Tommot–Yakutsk railway corridor (the Tommot–Kerdyom section). In this area, the geoelectrical section is strongly variable and generally reflects a 5-layer structure of the Ice Complex. Ice contents are higher in the upper 30 m of the Ice Complex (horizons 1–3) composed of very ice-rich silts with relict syngenetic ice wedges. Horizons 4 and 5 occurring lower (to depths of 50–60 m) contain massive ice bodies of unknown origin, which does not rule out the presence of firn ice in Quaternary–Tertiary sediments. The data obtained by vertical electrical sounding and electromagnetic profiling indicate a strong decrease in volumetric ice content in the upper 10–15 m silts (705-th track kilometer) at the boundary between the Maganskaya and Emilskaya terraces in the Lena-Amga watershed, which is the southern end of the vast alas province (thermokarst basins) of the low to medium-height terraces along the right bank of the Lena River valley. A drastic reduction in the amount of relict massive ice bodies in the upper layers of the southern margin section and their complete disappearance in lower part of the section occur at the 697-th km point, on the top of the Emilskaya terrace. Within a 3 km distance further south, the presence of ice bodies in the upper 10 m from the terrace surface is ranked as sporadic, with the occurrence probability of 0.1%.
Boreholes, Ice Complex, massive ice, vertical electrical sounding, geoelectric section, cluster analysis, electrical resistivity