GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.2 ___ GNGTS 2023 Evidence of past fluvial deposition within the Amorphous Lake (East Antarctica) by means of Ground Penetrating Radar: preliminary results I. Santin 1 , E. Forte 1 , M. Guglielmin 2 1 Department of Mathematics and Geosciences, University of Trieste, Trieste, Italy 2 Department of Theoretical and Applied Sciences, Insubria University, Varese, Italy Introduction In this work, we present the preliminary results of the processing and interpretation of a GPR dataset acquired on Amorphous Lake (Northern Victoria Land, East Antarctica) in 2014. It is an ongoing research, as the hypothesis outlined are still under validation, but we present here the most confident inferences on the electromagnetic facies characterization and on the reconstruction of subsurface geometries. We focused on the Amorphous Glacier area, and specifically on a perennial frozen pond, unofficially named Amorphous Lake. It is located in the Northern Foothills area (74° 42’ S, 163° 58’ E), an undulating upland terrain in Northern Victoria Land, East Antarctica, about 4.5 km West from the Italian Antarctic Station ( Orombelli et al., 1990 ) (FIG. 1A,B). The lake lies on the northern side of a frontal and circular morainic ridge ( Guglielmin et al., 2002 ), created by Amorphous Glacier dynamics, taking up a morphological bowl on the glacier surface. We chose this site as it is located in a well-studied zone of Northern Foothills, but its dynamics and geomorphology, both past and present, are still not fully understood. GPR proved once again its high applicability in glacial environments as it provided a detailed imaging of the internal structures within the lake and an accurate electromagnetic characterization of the different frozen materials. Methods During the XXX Italian Expedition in Antarctica (2014), a GPR dataset was acquired with a Malå Geoscience ProEx GPR system, equipped with 500 MHz shielded antennas. In FIG. 1C the GPR dataset location is shown it encompasses an irregular grid composed of 18 profiles with an overall length of about 2.3 km, covering almost all the lake surface and its surroundings. Although the quality of the data was itself very high, we applied anyway a basic processing flow including zero-time correction, band-pass filtering, amplitude recovery, depth conversion and topographic correction. A constant velocity of 17 cm/ns was chosen from the results of diffraction hyperbola fitting and by considering the expected ice characteristics. Exploiting the Petrel® (Schlumberger)