Strandförskjutning under mesolitikum på centrala Södertörn, östra Mellansverige: Kvartärgeologiska undersökningar längs väg 73, Överfors - Västnora
2007 (Swedish)Report (Other academic)
The aim with this study was to reconstruct the shore displacement on central Södertörn, eastern middle Sweden. The achieved curve is supposed to serve as a base for archaeological discussions regarding dating and settlement location.
By determining the isolation ages of local bogs and fens at different altitudes, a new shore displacement curve was compiled. The thresholds of five ancient lakes (Borgbergetmossen 50.1 m a.s.l., Långmossen 45.3 m a.s.l., Millingsmossen 44.8 m a.s.l., Vimossen 43.0 m a.s.l., and Malmbergamossen 38.7 m a.s.l.) were levelled and their isolations were determined on the basis of lithology, diatom analysis, organic carbon analysis and AMS radiocarbon dating of terrestrial macrofossils.
At about 6800 BC, the Litorina Sea shore laid at a level that is now uplifted to c. 50 m above sea level. The shore displacement was regressive during the early Litorina Sea, e.g. the isostatic uplift was greater than the eustatic sea level rise, but a transgressive Litorina stage (L1) stopped the process of land gaining between 6800–5950 BC. Analyses of cores from Borgbergetmossen indicate that the basin had begun to isolate from sea due to regression and that this process disrupted by an increase in water depth. The transgression is also observed as a layer of clay at Vimossen, indicating greater water depth. During the following regressive period, c. 5950–5600 BC, with a relative uplift of c. 13 mm/yr, Borgbergetmossen, Långmossen and Millingsmossen became isolated lakes. A second transgression (L2) is recorded in the following century, when gyttja clay and clay was accumulated in Vimossen and Malmbergamossen, respectively. After c. 5500 BC, the shore displacement shows a regressive trend at a rate of c. 6mm/yr. Malmbergamossen became isolated from the sea at c. 4500 BC. This basin is now uplifted to c. 39 m a.s.l.
Comparison with archaeological data indicates that the nearby Mesolithic sites were established along the former shore lines. Even though the general trend of the shore displacement was regressive, the inhabitants continued to live at the sites long after direct contact with the shore had ceased. This is explained by the topographically pronounced fissure-valley landscape; long vertical distance does not result in long horizontal distance.
We have used the chronological timing of L1 and L2 for correlation with periods of increased summer temperatures in western Fennoscandia. Melting of glaciers resulted in a eustatic sea level rise that neutralized the isostatic uplift.
Place, publisher, year, edition, pages
Arkeologikonsult, Stockholm , 2007. , 57 p.
, Rapporter från Arkeologikonsult, 2006:2037
"strandförskjutning", "landhöjning", "Södertörn", "mesolitikum", "stenålder", "diatoméanalys"
IdentifiersURN: urn:nbn:se:su:diva-21088OAI: oai:DiVA.org:su-21088DiVA: diva2:187614