Spits and Tombolos in the Southwest Archipelago of Finland

Approximately one-third of the 73,000 islands in coastal Finland comprise the southwest archipelago. This region of recent marine sedimentation and late-Pleistocene glacial deposition is superimposed upon a southwesterly-sloping, dissected Precambrian peneplain surface of the Fennoscandian Shield that is undergoing postglacial rebound of 4-5 mm/yr. Most of the islands are rocky; beaches are found mainly on those islands mantled by glaciofluvial deposits in the form of eskers or from end moraines. Coastal processes have reworked the beach sediment into spits and tombolos in accordance with the predominant wave and fetch regimes. Sites where 9 spits and 10 tombolos were found in the study area are at islands in the Rymattyla and Parainen parishes and along the Salpausselka III ridge.