Prehistoric man and the Baltic Sea at Pärnu, southwestern Estonia. Shifting coasts and a possible tsunami in the Baltic Sea 8400–8200 years BP
by
Siim Veski
Tallinn Technical University, Institute of Geology, Estonia pst. 7, 10143 Tallinn, Estonia
Coauthors: Atko Heinsalu (TTU Institute of Geology), Veiko Klassen (Tartu University, Institute of Geology), Aivar Kriiska (Tartu University, Department of History), Lembi Lõugas (Institute of History, Estonia), Ulla Saluäär (Pärnu Museum)

We have studied 16 sections of buried organic matter (pre-Ancylus Lake and pre-Litorina Sea) and associated Stone Age cultural layers in Pärnu area, southwestern Estonia. Buried organic beds are each part of a sedimentary sequence, which is repeated, forming two overlying sets of an orderly succession of five layers. The organic sedimentation of set 1 occurred about 10,800–10,200 years BP, that of set 2 about 9450–7800 years BP. Associated with set 1 is the Early-Mesolithic settlement Pulli, and with set 2 the Stone Age cultural layers at Sindi-Lodja. The Early- and Middle-Mesolithic sites in Estonia are concentrated on shores of rivers and lakes to make the use of a variability of resources. The hunters and fishermen followed downstream the ancient Pärnu River and the receding shoreline of the Yoldia Sea and since about 10,700 years BP, were forced to retreat inland in front of the transgressive Ancylus Lake shore which first inundated the Paikuse area about 10,400 years BP, and Pulli and higher sites about 10,200 years BP, the total amplitude of the transgression preceded 11 m and reached up to 14 m a.s.l. in the area. The Litorina Sea transgression reached 7 m a.s.l. after 8000–7800 years BP. The Mesolithic, Neolithic and modern sites on top of each other in the Pärnu area may suggest that, although years apart, they were inhabited by the same group of people who stayed in the area and moved back and forth together with the shifting shoreline of the Baltic Sea.

An anomalous 1–2 cm clear layer of light fine sand within the and pre-Litorina Sea buried organic matter containing brackish-water diatoms indicates a sudden short time ingression of the sea in the area. We have earlier suggested that this sand layer represents high storm water level on the eastern side of the Baltic Sea (Heinsalu et al., 1999). As a hypothesis, this event can be a result of tsunami-type sedimentation. Andrén & Andrén (2000) discuss possible tsunami wave evidence of the Second Storegga slide in Bornholm Basin at 7200 14C years BP, synchronous with the Paikuse sand layer. Alternatively, the tsunami wave could have been generated by a meteorite impact event at c. 7600–7500 14C years BP, the traces of which have been recorded as impact microspherules in several peat sequences all over the Western Estonian Archipelago (Raukas, 2000).

References:

Andrén T. & Andrén E. 2000. Did the Storegga tsunami reach the Baltic Sea? In. Sandgren, P., (ed.), Environmental changes in Fennoscandia during the Late Quaternary. Lundqua Report 37, 108.

Heinsalu A., Veski S. & Moora T. 1999. Bio- and chronostratigraphy of the Early Holocene site of double-storied buried organic matter at Paikuse, Southwestern Estonia. Proc. Estonian Acad. Sci. Geol. 48, 1, 48–66.

Raukas A. 2000. Investigation of impact spherules – a new promising method for the correlation of Quaternary deposits. Quat. Intern. 68–71, 241–252.

Date received: March 6, 2002