Landscape mapping using ground-penetrating radar, electrical resistivity tomography survey and landscape profiling

This work aims to verify and correct the boundary between two landscapes—moraine and outwash plain—delineated earlier by the classical landscape approach. The initial interpretation of the boundary caused controversy due to the appearance of the thermokarst depression in the outwash landscape. The lithological structure is one of the main factors of landscape differentiation. The classical approach includes drilling to obtain the lithological and sedimentary data. However, the boreholes are usually shallow, while geophysical methods allow to look deeper into the subsurface and improve our knowledge about lithological structure and stratigraphy. In this study, we use ground-penetrating radar with a peak frequency of 250 and 50 MHz and detailed electrical resistivity tomography (with 1 m electrode spacing) in addition to the landscape mapping and drilling to correct the landscape boundary position. We conclude that it is primarily defined by the subsurface boundary between lithological complexes of clayish moraine deposits and sandy outwash deposits located at 7 m depth. Moving the boundary to the northeast by 70–100 m from the current position removes inconsistencies and clarifies the history of the area's formation in the Quaternary.