Basal till genesis in relation to bedrock morphology in the Berghem area, southwestern Sweden

Abstract

Investigations of Late Weichselian deposits on the plateau north of Berghem, southwestern Sweden, constitute the basis for a detailed interpretation of basal tills above the marine limit. Deposition in relation to bedrock ridges perpendicular to ice flow occurred mainly on the stoss side. The content of locally derived bedrock increases with depth and the intensity of deformation within the ridge increases whengoing from the ice‐proximal to the distal position. Drumlinoid features around a rock hillock suggest that the depositional behaviour on the stoss side was slightly different in the central part compared with the flanks. In the ice‐proximal position the earliest deposition occurred in the centre of the drumlinoid, where the frequency of locally derived components is highest. The deformation in the central part was more intense than on the flank. The details of the till stratigraphy and structures cannot be attributed to one single process. Rather, an interaction of processes is proposed to account for this deposition. The processes involved are lodgement, basal melt‐out, deformation and subglacial meltwater sedimentation.