GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 positon of future boreholes while developing and approach that can be exploited even in other geological, geomorphological, and glaciological situatons. Fig. 1 – (A) Locaton map of CALM grid and Lake n.16 (light blue square) in Boulder Clay Glacier area (MZS: Mario Zucchelli Italian Staton). (B) Ortophoto with superimposed the GPR profles, in white, and the FDEM survey, in red. Yellow lines mark the positon of the gravel landing strip. Methods During the XXXVIII Italian Expediton in Antarctca (November 2022), two GPR surveys were performed on the CALM grid and the neighbouring Lake n.16. On the later, an FDEM survey was also collected. The 880 m-long FDEM dataset (red line in FIG.1B) was acquired with a CMD-2 probe (GF-Instruments), recording the mean conductvity value every 0.5 s, down to a maximum nominal depth of 2.5 m. The dataset is characterized by a high overall quality, with minimum and maximum values of 0.05 mS/m and 12 mS/m, respectvely. The conductvity values were interpolated on a regular grid (2 m by 2 m) with a Kriging algorithm, obtaining the apparent conductvity map, shown in FIG.2. As far as the GPR surveys (white lines in FIG.1B), they were both performed with a ProEx GPR system (Malå Geoscience), equipped with 500 MHz shielded antennas. A basic processing fow was applied, including zero-tme correcton, band-pass fltering, amplitude recovery, depth conversion and topographic correcton, considering a constant velocity of 0.17 m/ns (I.e. the typical value for pure clean glacial ice). To improve the EM characterizaton of brines pockets, the interpretaton of CALM grid GPR dataset was supported by GPR atribute analysis, which already demonstrated their efectveness in glacial environments (e.g. Zhao et al., 2016 ). We specifcally focused on frequency-, phase- and texture-related atributes, integratng them during data interpretaton.