Streamlined topographical features in and around the Gulf of Riga as evidence of Late Weichselian glacial dynamics

Abstract

Based on various cartographic sources, a digital terrain model and acoustic profiling data, linear relief features of glacial origin have been distinguished and analysed in the Gulf of Riga and adjacent mainland areas in order to reconstruct the dynamics and pathways of former ice streams. North-east-south-west oriented features in the till topography prevail in the central part of the gulf and along the southern coast of the island of Saaremaa, which corroborate the previously known south/south-east direction of the main Riga ice stream. North-east to south-west directed features dominate in the Pärnu Bay and around the Irbe Strait. Similar deviations from the Riga ice stream are most likely due to ice divide zones, namely the Sakala Upland in Southern Estonia and Kurzeme in northwestern Latvia, which locally changed the course of the main ice flow. The influence of the Kurzeme ice divide is traceable at the bottom of the gulf up to the southern coast of Saaremaa. There is no evidence of an ice-marginal zone crossing the central part of the Gulf of Riga as was supposed earlier. The Pandivere-Neva and Palivere ice-marginal zones, which merge on the Strve Peninsula, probably continue offshore into the Irbe Strait. As the age of the glacier relief features is poorly contained, the chronological reconstruction of the ice dynamics is tentative.