Abstract
The internal structures of a moraine complex mostly provide information about the manner in which they develop and thus they can transmit details about several processes long after they have taken place. While the occurrence of glacier–permafrost interactions during the formation of large thrust moraine complexes at polar and subpolar glaciers as well as at marginal positions of former ice sheets has been well understood, their role in the formation of moraines on comparatively small alpine glaciers is still very poorly investigated. Therefore, the question arises as to whether evidence of former glacier–permafrost interactions can still be found in glacier forefields of small alpine glaciers and to what extent these differ from the processes in finer materials at larger polar or subpolar glaciers. To investigate this, electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) surveys were carried out in the area of a presumed alpine thrust moraine complex in order to investigate internal moraine structures. The ERT data confirmed the presence of a massive ice core within the central and proximal parts of the moraine complex. Using GPR, linear internal structures were detected, which were interpreted as internal shear planes due to their extent and orientation. These shear planes lead to the assumption that the moraine complex is of glaciotectonic origin. Based on the detected internal structures and the high electrical resistivity values, it must also be assumed that the massive ice core is of sedimentary or polygenetic origin. The combined approach of the two methods enabled the authors of this study to detect different internal structures and to deduce a conceptual model of the thrust moraine formation.
Highlights
Glacier–permafrost relationships were initially studied on polar and subpolar glaciers more than 50 years ago
The use of ground-penetrating radar (GPR) should enable a more detailed investigation of sedimentological boundaries and internal shear planes [28,32]. These findings offered better knowledge of the thrust moraine formation, which allowed us to generate a conceptual model of the moraine genesis in the glacier forefield Muragl
The electrical resistivity tomography (ERT) cross profile C1 (Figure 3) shows a three-layered structure typical for thin permafrost resistivity values are between 5 and 15 kΩm, whereas the proximal area is characterized by a thicker occurrences
Summary
Glacier–permafrost relationships were initially studied on polar and subpolar glaciers more than 50 years ago. In the context of thrust moraine evolution at polar and subpolar glaciers, Kälin [2] provided evidence on glacier–permafrost interaction for the first time. Further important studies in this context dealt with the deformation of frozen sediments [3] or the interaction between frozen proglacial sediments and the subglacial hydraulic system [4,5]. Hambrey and Huddart [6] and Bennett [7] presented multi-processual models of moraine genesis through glacier–permafrost interaction. In these studies, the properties of the glacial stress field, glacial flow patterns, the sub- and proglacial hydrological system as well as the properties of the proglacial sediments were considered
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