Electrical resistivity tomography (ERT) surveys on glacial deposits in Romanian Carpathians

Abstract

The study presents preliminary results regarding the use of electrical resistivity surveys in the assessment of the internal structure of the glacial deposits from the Romanian Carpathians. ERT is a geophysical method used to quantify changes in electrical resistivity of the ground towards passing electric current across an array of electrodes and simultaneous measurement of the induced potential gradient. Using specific software the measurements are further processed and correlated with the topography in order to obtain bedrock resistivity features. Therefore, the method is useful to evaluate the characteristics of geological strata and is widely used for mapping shallow subsurface geological structures. In the mountain regions ERT studies have been applied in different glacial and periglacial geomorphological studies - for permafrost detection (in Romanian Carpathians - Urdea et. al., 2008; Vespremeanu-Stroe et al., 2012), slope deformation analysis, the assessment of slip surface depths, sediment thickness, groundwater levels etc. One of the most commonly 2-D array used is the Wenner electrode configuration, which is moderately sensitive to both horizontal and vertical ground structures. Due to their elevations and Pleistocene’s climatic conditions, the Romanian Carpathians have been partially affected by Quaternary glaciations. The glaciers descended to about 1050-1200 m a.s.l. (Urdea and Reurther, 2009) in the Transylvanian Alps and Rodna Mountains (Eastern Carpathians) carving a large number of U-shaped valleys and glacial cirques (Mindrescu, 2006) and forming accumulations of unconsolidated glacial debris (moraines). Our study areas are two sites located in the northern (Rodna Mts.) and southern (Iezer Papusa Mts.) part of the mountain range.