The first geological record of a palaeotsunami on the southern coast of the Baltic Sea, Poland

Abstract

Tsunami deposits have not previously been recorded along the southern coast of the Baltic Sea. The results of present research provide evidence of high-energy event layers that occur on the bottom of two hemispherical hollows cut into glaciolimnic silt and glaciofluvial sand and gravel of Late Weichselian age. The event deposits are represented by poorly sorted marine sand with admixtures of pebbles and allochthonous biogenic detritus: marine, brackish and occasionally freshwater shells and shell debris of bivalves and snails, plant macrofossils from the nearshore zone, shreds and lumps of peaty material, gyttja and organogenic silt, lumps of charcoal, wood pieces and tree branches and trunks. All these features are commonly considered indicative of tsunamis. The age of the biogenic detritus found in the tsunami layer ranges from 6,630 to 10,390 cal. yr BP, whereas the oldest gyttja covering the event layers is 6,600 cal. yr BP old. This means that the tsunami occurred between 6,600 and 6,630 cal. yr BP. Various causes of the tsunami event are considered, including the impact of meteorites within the coastal plain ana the littoral zone of the southern Baltic Sea.