Abstract

Reconnaissance air-gun seismic reflection profiles and sonobuoy refraction measurements were recorded in 17 perialpine lakes. Quaternary fill velocities derived from sonobuoy refraction records suggest a stratigraphic sequence consisting of two general elements. The upper interval with velocities between 1.5 and 1.9 km/sec may represent normal sedimentation of glaciolacustrine sediments, whereas higher velocities of 1.9 to 2.7 km/sec in a lower element probably result from glacier overriding and compaction. The refraction data also show bedrock velocities from 3.6 to 6.7 km/sec in concert with underlying geological formations. Reflection sections from the deep basins show modest overdeepening of the lakes north of the Alps and deep incision of the southern perialpine lakes. The data are consistent with an interpretation of glacial overdeepening of fluvially cut bedrock valleys, overriding of older glaciolacustrine deposits (Riss?), and limited erosion by the Würm glacier streams that seem to scoop but not downcut the basins. We found no evidence for late Quaternary faults.

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