GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.2 ___ GNGTS 2023 horizons interpreted along GPR profiles and causing high amount of energy to be reflected, also generating multiple reflections. We argue that such a high-amplitude could not be related just to the electromagnetic contrast between ice and moraine, but it could be rather related to a brine level on the top of the moraine (i.e. on the bottom lake). In addition, especially on FIG. 2B, it is enquiring that below the top moraine reflection, where it becomes almost horizontal, there is a transparent facies, most probably associated to a lack of signal. Such characteristics and the high amplitude of the top moraine reflection could move toward the hypothesis of some at least partially liquid brine occurrence ( Forte et al., 2016 ). FIG. 2 Two exemplary interpretated GPR profiles (A, B) highlighting the boundaries between different EM facies: lake bottom (blue), top of circular moraine (orange), glacier bedrock (olive green) and layered unit limit (pink dotted). The question mark indicates the unclear connection between the layered facies and the glacier. Vertical exaggeration 2x The GPR data highlighted also a layered facies located below the lake whose interpretation was not so straightforward. This layered unit has a mean thickness of 2.5 m and its extension covers up to 40% of the entire area of the lake. It is evident that the high contrast of electromagnetic impedance between the layered unit and the lake ice above it suggests, with a high level of confidence, a different material, characterized by a high difference of dielectric permittivity