Enigmatic ridges in Lake Vättern, Sweden

Abstract

The latest generation of high-resolution multibeam sonars reveal ever smaller subaqueous landforms, particularly in shallow marine and lake environments. High-resolution bathymetric data from the floor of Lake Vattern, Sweden, reveal fine-scale landforms on a bouldery sediment surface, which we attribute to ice-related processes. We explore subglacial, grounding-zone, crevasse infill and push/scour processes of grounded and floating ice in an attempt to explain the origin of these enigmatic features. Lake Vattern in south-central Sweden is a deep, elongate rift basin which lies amid regional landform and sediment assemblages produced during the retreat of the last Fennoscandian Ice Sheet (FIS). The regional retreating ice margin terminated in the large proglacial Baltic Ice Lake, to which the Vattern Basin was connected before its eventual drainage (Lundqvist & Wohlfarth 2001). A recent high-resolution multibeam survey of sectors of the Vattern lake floor revealed landforms associated with marginal ice grounding and retreat. On a mid-lake shoal at 30–40 m depth, a suite of fine-scale, enigmatic landforms have been formed in stiff sediment (Fig. 1). Fig. 1. ( a ) Multibeam bathymetry from Lake Vattern showing 1–2 m amplitude sediment ridges that are formed on a shoal, which comprise both parallel, linear components (L, L*) and sinuous ridges (S, S*) of …