Geoscience Reference
In-Depth Information
known from the inland parts of northern Sweden so that, until the 1970s, the
region was thought to be of little archaeological significance. The situation changed
recently when a model simulating early Holocene land uplift was created. This
meant that the positions of contemporaneous lake shorelines could be reconstructed.
These were used on field surveys and finally led to the discovery of a large number
of Mesolithic settlements (Olofsson
2003
, Bergman et al.
2003
).
In the south-western part of the Baltic Sea, where the maritime landscape and
settlement areas have been inundated and now lie on the seabed, shore-displacement
models can be used to obtain an initial idea of the chronological classification of the
submerged sites: here, the rule of thumb is 'the deeper the site below sea level, the
older the site'. However, unlike the areas with decreasing relative sea levels, they
are only of limited value as a starting point for underwater surveys in the search for
new sites.
15.2.2 Archaeological Sites as Sea-Level Index Points
The quality of the sea-level curves and shore-displacement models greatly depends
on the data used to compile them. Traditionally, they are based on geological
and palynological investigations of stratified sequences of sediments from differ-
ent deposits in the coastal area, which are analysed and interpreted. However, in
some cases, data from archaeological sites are also integrated - or at least referred
to - usually in order to prove the quality of the models (Lübke
2002
).
The remains of settlements that were originally on the coast can be used as fossil
sea-level index points, provided that the relevant parts of the sites were originally
situated near the shore or constructed with specific reference to sea level (Fig.
15.2
;
for a summary see Behre
2004
,
2007
). In such cases, it can be assumed that the
settlement facilities on the site, e.g. houses, hearths and pits, were above the mean
sea level and, in general, secure from inundation by storm surges. In addition, it
has to be ensured that the dated material represents the lowest parts of the site
(Olsson and Risberg
1995
). On the other hand, fish traps, fishing fences or the
foundations of piers and other harbour facilities must originally have been under
water.
Thus, the reliable dating of these settlement remains by archaeological methods,
dendrochronology or radiocarbon analysis can help us to reconstruct the sea level
at a specific point in time. This is especially valid in the case of archaeological
sites that were flooded during storm surges, when their remains were covered with
sediments that preserved them from erosion and conserved them in some fortunate
cases for thousands of years, until today. Almost without exception, such favourable
conditions only exist on sites that were inundated immediately after they were
abandoned or while they were still occupied. Most of these are still under water
today. This is first and foremost true of those areas in the south-western part of the
Baltic Sea that were rapidly inundated during the Littorina transgression and were
not affected by the glacio-isostatic uplift so that the drowned landscapes and sites
