Distribution, geometry, age and origin of overdeepened valleys and basins in the Alps and their foreland |
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| Authors: | Frank Preusser Jürgen M Reitner Christian Schlüchter |
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| Institution: | 1. Institut für Geologie, Universit?t Bern, Baltzerstrasse 1+3, 3012, Bern, Switzerland
2. Geologische Bundesanstalt, Neulinggasse 38, 1030, Wien, Austria
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| Abstract: | Overdeepened valleys and basins are commonly found below the present landscape surface in areas that were affected by Quaternary
glaciations. Overdeepened troughs and their sedimentary fillings are important in applied geology, for example, for geotechnics
of deep foundations and tunnelling, groundwater resource management, and radioactive waste disposal. This publication is an
overview of the areal distribution and the geometry of overdeepened troughs in the Alps and their foreland, and summarises
the present knowledge of the age and potential processes that may have caused deep erosion. It is shown that overdeepened
features within the Alps concur mainly with tectonic structures and/or weak lithologies as well as with Pleistocene ice confluence
and partly also diffluence situations. In the foreland, overdeepening is found as elongated buried valleys, mainly oriented
in the direction of former ice flow, and glacially scoured basins in the ablation area of glaciers. Some buried deeply incised
valleys were generated by fluvial down-cutting during the Messinian crisis but this mechanism of formation applies only for
the southern side of the Alps. Lithostratigraphic records and dating evidence reveal that overdeepened valleys were repeatedly
occupied and excavated by glaciers during past glaciations. However, the age of the original formation of (non-Messinian)
overdeepened structures remains unknown. The mechanisms causing overdeepening also remain unidentified and it can only be
speculated that pressurised meltwater played an important role in this context. |
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