Joint expedition to explore the terraces in the valleys of the rivers Katun’ and Inya, Gorny Altai

July 20, 2018

Until now, there is no unanimous opinion of scientists about the genesis of the Ynin formation in the valleys of the Gorny Altai rivers.

To study the amazing terraces in the valleys of the Katun’ and Inya using the equipment of high-resolution electrical exploration by the method of reflected electromagnetic waves (MREW) we went as part of a joint international expedition with scientists from the Geographical Faculty of Moscow State University and the Institute of Geography of the Russian Academy of Sciences.

Research is carried out within the framework of the Program of the Presidium of the Russian Academy of Sciences No. 19 "Fundamental problems of geological and geophysical study of lithospheric processes."

Previously, the geological section of the formation was studied through natural outcrops located along the valley of the river Katun’. For more information, adequate geophysical data were required.

The equipment MREW consisted of a transmitting device of increased power of 15-32kV, generating an ultra-wideband pulse, a receiving device based on the GROT 12 receiver and resistively loaded antennas 15 m, 10 m and 4 m long.

*Receiver with flexible antennas 10 m long*

Preliminary results of the interpretation of the MREW data showed that with the help of MREW it is possible to display a section of terraces with the definition of blocks and large boulders at different levels of the section of 180 and 70 meters’ deep terraces (ininsky and saldzharskaya, respectively - according to the regional stratigraphic scheme).

In general, a comparison of the geoelectric and geological sections showed that the thickness of the terraces corresponded to the outcrops was determined with MREW.

With the help of the GROT equipment, it became possible to record deep reflections at 180 meters corresponding to the edge of the river.

The analysis and interpretation of the MREW data allow uncovering the inner boundaries of the section corresponding to the sandstone-pebble formations of the Ininskaya and Bashkauskaya suites, distinguishing zones with different moisture in the upper layers and locating blocks and boulders.

Radarogram of the profile covered with antennas 10 m in min-max view

The same profile with a palette representation of the amplitude

The same profile with a palette view in a different palette

Comparison of data: radarogram of the WREW profile covered with a 4 m long antenna (above) and a geological section across the valley of the river Katun’, 500 m below the mouth of the river Inya (refering to [Parnachev S.V. Geologiya vy`sokix altajskix terras (Yalomano-Katunskaya zona) / S.V. Parnachev. – Tomsk: Izd-vo IPF TPU, 1999. – 137 p.])

We thank the organizers and participants of the expedition for their cooperation!