GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.2 ___ GNGTS 2023 interpretation suite, we interpreted several horizons corresponding to the topographic surface, the lake bottom and some glaciological features such as snow layers, crevasses and the circular moraine boundary, using a semi-automated picking procedure. In order to calculate the lake thickness, all interpreted horizons were imported in Surfer (Golden Software) environment and a Kriging algorithm was applied in order to preserve the original values at their own locations. We obtained a regular grid of square cells (2 m by 2 m) and calculated the depth of the lake by subtracting the lake bottom horizon from the topographic surface one. The lake border was set by joining information from both GPR dataset and satellite images, provided by Google Earth, which were essential in no geophysically-covered areas to fix the border of the lake. In order to improve the facies characterization, GPR interpretation was supported by GPR attribute analysis, which allowed to better image and understand the boundaries and the geometries of the electromagnetic facies and horizons on GPR data. We focused on amplitude-, phase- and frequency-related attributes, integrating them during data interpretation. In particular, frequency-related attributes allowed to discriminate glacial and morphological domains as the circular moraine, the glacier ice and the glacier bedrock. FIG. 1 (A) Location map of Amorphous Lake (yellow star) in East Antarctica. (B) Location of Amorphous Lake (yellow circle) compared to the Italian Antarctic Station (black circle). (C) Satellite photo from Google Earth (taken on 07-11-2014) with superimposed the GPR dataset location (blue lines) and GPS points (green dots). Results and discussions On the basis of the responses to the electromagnetic signal and the strength of amplitude reflections, we identified several electromagnetic facies, including the lake bottom, the frontal morainic ridge, the snow cover, the interconnections with the Amorphous Glacier and its underlying bedrock (FIG. 2). The lake bottom reflection is interpreted at the base of a transparent facies contaminated by background noise especially close to the surface. The lake lies partly upon the glacier and partly upon the morainic ridge, which was identified extending below the lake along all the GPR profiles. It presents a bowl shape, with steep flanks on South and East, where it lies directly upon the moraine. On the other hand, toward North and West the slope of the lake bottom is more gently connected to the glacier. It is remarkable to notice the unusual high amplitude of the morainic ridge, reaching more than three times the amplitude of all the other