Presented are the results of geophysical works carried out in the Lena river delta near Samoylov Research Station with the aim to evaluate the thickness of hydrogenic talik under the bed of one of delta channels. Three geophysical methods have been used – ground penetrating radar (GPR), transient electromagnetic (TEM) sounding and electrical resistivity tomography (ERT).
GPR survey proved to be inappropriate for the study of sub-bottom talik due to high water mineralization that leads to strong damping of radar signal. TEM voltage responses obtained in the Lena river delta are everywhere complicated by fast decaying induced polarization (IP) processes that can be explained only by specific cryogenic structure of frozen ground. In the onshore part of the profiles two polarization processes with different characteristic times were identified. The first IP process completely disappears in the responses obtained on the channels, whereas the second one remains visible. This means that permafrost is apparently presented under the channels.
ERT measurements made in the continuous resistivity profiling (CRP) mode with the use of towed cable revealed substantial growth of resistivity values at the depth of 40 50 m below the bottom of the river. Joint consideration of TEM and ERT data makes the most possible the assumption, that underbed talik has limited (tens of meters) thickness under the channels of Lena river delta.