Geoscience Reference
In-Depth Information
Chapter 11
Drowned Forests in the Gulf of Gda nsk
(Southern Baltic) as an Indicator of the
Holocene Shoreline Changes
Szymon Uscinowicz, Grazyna Miotk-Szpiganowicz, Marek Kr apiec,
Małgorzata Witak, Jan Harff, Harald Lübke, and Franz Tauber
Abstract This chapter presents a newly discovered locality of tree stumps occur-
ring in situ at the bottom of the Gulf of Gdansk. It focuses in particular on the age
of the stumps and characterization of the palaeoenvironment, i.e. the nature of the
plant communities in which the trees grew and also on their position in relation to
the palaeo sea level. Tree stumps occurring in situ on the sea floor along with peat
deposits are the most reliable indicators of sea level changes. The site is located
about 6-7 km NE of the entrance to the Gdansk harbour, in water depth of 16-17 m.
The thickness of marine sand at the site is from a few to a dozen centimetres. Below
the sand, gyttja with peat intercalations and wood fragments occur. Sixteen frag-
ments of alder trunks and one oak trunk's fragment were extracted. Radiocarbon
ages of the tree trunk fragments are 7,920
±
50 BP, 7,940
±
40 BP, 7,960
±
40
BP and 8,000
50 BP. The age of gyttja, according to pollen analyses, is of early
Atlantic period. The characteristic forest composition of that time was the broad
deciduous forest with oak ( Quercus ), elm ( Ulmus ) and lime ( Tilia ). The climate was
characterized by good thermal and moisture conditions, which is confirmed by the
presence of pollen grains of mistletoe ( Viscum ) and ivy ( Hedera ). The obtained data
about the time of accumulation of the investigated sediments indicate that the sea
level at that time was about 19-20 m lower than at present.
±
14 C dating
Keywords Shoreline displacement
·
Drowned forest
·
·
Pollen and
diatom analyses
·
Middle Holocene
·
Baltic Sea
·
Gulf of Gdansk
11.1 Introduction
Stumps of trees occurring in situ on the sea bed are known from many places in the
world. The first scientific reports about “sunken forests” appeared in the nineteenth
century in Great Britain, where many of them were discovered in coastal areas (e.g.
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