Late Quaternary Evolution of Gravel Deposits in Tromper Wiek, South-western Baltic Sea

The Late Quaternary history of the Baltic Sea is marked by a complex sequence of glacial lacustine and marine phases (late Pleistocene Baltic Ice Lake Yoldia Like Ancylus Lake Littorina Sea) Boomer data acquired in October 2004 permitted to improve the knowledge of the late Quaternary geological evolution of Tiomper Wick a semi enclosed bay located in the north-eastern part of Rugen Island The sedimentary deposits can be subdivided in 6 seismic units (U1 to U6) The upper part of the lowest unit (U1) corresponds to Pleistocene till Channels incise the top of this till (surface S2) probably created during the fist drainage of the Baltic Sea during the 1 ate Glacial Subsequent channel filling (U2) occurred in two phases beginning with chaotic deposits probably fluviatile of origin followed by graded deposits This filling was stopped by an erosive period with the formation of surface SI showing channels at the same location as S2 The facies of the channel filling (U3 and U4) during a second phase is similar to the first one but resembles a prograding sediment body intercalated between the two units in the shallower part U3 shows a bar shaped deposit at its top The facies of U4 is very similar to a barrier/back barrier facies similar to the facies of unit U5 partly composed of gravel The deposits of U6 correspond to the post Littorina Sea deposits The presence of gravel is linked to coastal cliffs in which chalk layers pushed up by glaciers alternate with sections of till and meltwater deposits and with submarine outcrops of till Gravel deposits are present in unit U5 They tie strongly linked to the presence of a barrier Four of the six units show a barrier facies (U2 U3 U4 and U5) gravel deposits could be present inside all of these units and would represent a larger deposit than estimated previously