Tectonic impact on Pleistocene and Holocene erosional patterns in a formerly glaciated intra-plate area

Abstract

Deep-seated faults have for a long time been thought to have had an influence on the formation of valleys both in the subsurface and in the present-day terrain in and around former glaciated areas. To systematically investigate if, and if so, how faults may have impacted on the erosional patterns during the Pleistocene and the Holocene in Denmark, three separate vector datasets of mapped buried valleys, topographic valleys, and deep-seated faults have been compared with respect to orientations. Several correlations in the datasets were found. Correlations between tunnel valleys and deep-seated faults suggest that structural weaknesses along faults within the sedimentary succession may have altered the hydraulic properties of the sedimentary strata and thereby have created biased erosion patterns beneath the ice sheets. Correlations between deep-seated faults and erosional valleys in the modern landscape point to active tectonics enabling the erosion to mirror the tectonic framework in the present-day topography. We propose a model that invokes the mechanism of glacially triggered faulting in all of the Danish area, intermittently impacting on erosion. The erosion during the Quaternary seem to have favoured old and well-established patterns, and areas over active faults appear to represent zones more susceptible to erosion. Our findings suggest that recurrent impact on erosion patterns from glacially triggered faulting can be expected in and around former glaciated areas during the Pleistocene and the Holocene.