Ice-Pushed Boulders on the Shores of Gotland, Sweden

Abstract

Boulder acclumulation and movements are described from four localities on Gotland. Two types of cliff-platform relationship and associated boulder accumulation are represented on the NW coast, illustrated by examples from Hall and Stenkyrka. Due to morphological-limestone bedrock- and climatic conditions the movements on the wave-cut platform the pall or pallen are not traceable in detail. In contrast, the shallow water inlets Gansviken and Furillen on the E coast demonstrate the boulder movements in the form of tracks in the soft bottom sediment. The tracks were made when the boulders were ice-bound and the ice-floes were wind-pushed over the slightly thawed bottom: New tracks are easily seen from the air and can be recognized after several years despite later infilling with new sediment. The boulder movements are clearly Induced by ice-pushing related to certain climatic conditions in cold winters, whereas development and growth of beach ridges normally occur in mild winters.