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Abstract
Strong consolidation of fine-grained fluvial and glaciolacustrine deposits in formerly glaciated mountain ranges, such as in the Alps of Vorarlberg, Austria, may be entirely due to ice loading during the Late-Pleistocene.
Consolidation values can be used, in principle, to reconstruct ice thicknesses, surface heights, and surface gradients of (temperate) Pleistocene valley glaciers. In order to test this technique, 11 sediment samples were collected at various sites, roughly following a line parallel to the main direction of ice flow of the Pleistocene Rhine glacier in Vorarlberg. Grain size distribution, consolidation values, shear strength, and Atterberg consistency limits were determined; thin sections were studied by microscope.
Rounded consolidation values varied from 3800 to 5250 kN m-2, representing ice thicknesses of 400 to 500 m. On average this is lower than expected from geomorphologic evidence, though the results fit gradually better towards the north of Vorarlberg, where relief diminishes and valleys become wide and open.
The validity of the method and the various factors that may cause discrepancies with the results of geomorphologic reconstructions are discussed. In spite of the noted uncertainties, the method's further use in reconstructing ice thickness in Pleistocene valley glaciers and ice sheets is recommended.