The structure of the upper part of the Earth’s crust in the area of the Lena River delta: the first magnetotelluric data

Abstract

We present the first magnetotelluric sounding (MTS) data acquired in the southern part of the Lena River delta which is a junction zone of the Siberian Craton and the Verkhoyansk fold-and-thrust belt, in the transition zone from the Eurasian Continent to the shelf of the Laptev Sea. The MTS data were used to construct a vertical section of the bulk electrical resistivity (ER) structure of the Earth’s crust down to a depth of 8 km. The upper high-resistivity layer (320–000 Ohm m) corresponds to the permafrost rocks ranging in thickness from 1 km to 400 m under the channels of the Lena River. The underlying deformed Mesoproterozoic– Lower Triassic rocks can vary in composition, but they are poorly differentiated in ER values (110–40 Ohm m). We detected three low-resistivity anomalies (10–0 Ohm m) related to the fluid-saturated core and damage zones of active faults. A deep-lying high-resistivity anomaly (320–50 Ohm m) identified at the northeastern part of the section can correspond to the Lower Proterozoic or Archean metamorphic rocks.