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Lewis Jonathan, Loughborough University (United Kingdom)
David Ryves, Loughborough University (United Kingdom)
Peter Rasmussen, GEUS (Denmark)
Petersen Kaj Strand, GEUS (Denmark)
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Historical and archaeological evidence attests the importance of marine resources to cultures and societies living in coastal regions of Denmark throughout the Holocene. Such cultures and societies were often heavily dependent upon the dynamic Baltic Sea, yet our knowledge of this complex interplay remains fragmentary. The Baltic Sea was perhaps at its most dynamic during the Littorina Sea Stage where it is characterised by a complex series of high sea level stands (trangressions) and low stands (regressions). Inevitably bound to these alterations in sea level is change in important environmental parameters such as salinity, temperature and nutrient status at both local (e.g. within individual fjords) and regional scales (e.g. the entire Baltic basin). Such changes are likely to have disrupted ecosystem structure and functioning within the coastal waters and may have affected the presence and availability of important marine resources to these societies.
Perhaps the most important of these complex interplays between sea and society occurs at the Mesolithic-Neolithic transition (∼5,900 BP). Here it has been suggested that changes in the marine environment may have forced the long-delayed introduction of agriculture into Denmark to compensate for a reduction in important resources; numerous Stone Age shell middens document an abrupt decline in the number of oysters present in the Mesolithic layers compared to the overlying Neolithic layers. A potential causal factor is a salinity decline in the inner Danish waters, possibly due to a lowering of sea level and subsequent reduced input of more saline nutrient-rich water from the North Sea.
Whereas much research has focussed on accurately reconstructing the sea level history of the Baltic Sea, far less attention has been given to assessing independently how these key environmental parameters change accordingly. The few salinity reconstructions that have taken place in the Danish coastal waters to date based on biological proxies are semi-quantitative, of low temporal resolution and often suffer from poor dating control.
Here we present diatom and molluscan data from natural sedimentary archives at multi-decadal resolution for the period covering the Mesolithic-Neolithic transition from three Danish coastal sites situated in close proximity to important archaeological sites and settings. These sites are Kilen, situated in the Limfjord and Norsminde and Korup Sø, situated along the east coast of Jutland. For each site, a quantitative reconstruction of salinity is attempted on the fossil diatom data using a diatom-salinity model based on a large, pan-Baltic training set. All site chronologies are based on AMS 14C dating of terrestrial macrofossils, thus avoiding problems associated with the marine reservoir effect.
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