A new early Holocene shoreline displacement record for Blekinge, southern Sweden, and implications for underwater archaeology

Abstract

We present evidence of a submerged early Holocene landscape off the Blekinge coastline in the Baltic Sea, dating to the Yoldia Sea and Initial Littorina Sea Stages when the water level was lower than at present. 14C dated wood remains obtained by surveillance diving and new archaeological findings in combination with bathymetric analyses and interpolations between other sites across the Baltic Sea were used for refinement of the shoreline displacement history of the region. The new results reveal a Yoldia Sea lowstand level at 20 m b.s.l., a subsequent Ancylus Lake highstand at 3 m a.s.l., and then a period of relatively stable water level at about 4 m b.s.l. during the Initial Littorina Sea Stage, several metres lower than previously concluded. The refined shoreline displacement record was used for palaeo‐reconstructions of the study area during four key periods, the Yoldia Sea lowstand phase, the Ancylus Lake transgression phase, the Ancylus Lake highstand phase and the Initial Littorina Sea lowstand phase, using elevation data and map algebra functions. A flow accumulation algorithm was used for reconstruction of the now submerged prehistoric river network in order to identify areas of high archaeological potential. Our revised shoreline displacement record, and especially its lowstand period during the Initial Littorina Sea Stage around 9500–8500 cal. a BP, raises future demands not only for specific archaeological shallow‐water surveys down to 4 m b.s.l. in the area, but also for a renewed cultural heritage management strategy. The results of this study fill an important gap in the early Holocene part of the shoreline displacement history of Blekinge, contributing to its completion since the deglaciation, which is unique for the Baltic Sea.

Shoreline Displacement, Coastal Environments and Human Subsistence in the Hanö Bay Region during The Mesolithic

“…Shoreline reconstructions were made using the ArcGIS 10.3 software based on the shoreline displacement records from Haväng [6] and Blekinge [93]. Five palaeo-shoreline maps, showing the shoreline configuration during five key periods, were created; the Yoldia Sea lowstand, the Ancylus Lake transgression phase, the Ancylus Lake maximum, the Initial Littorina Sea minimum and the Littorina Sea transgression phase.…”

Sweden: Submerged Landscapes of the Early Mesolithic

“…before 11,700 cal BP, and the Littorina transgressions, after 8000 cal BP, providing good evidence of fluctuations at levels above present sea level (cf. Hansson et al 2018c). Pine stumps dating to the Yoldia and Ancylus stages have been found sporadically in the Blekinge Archipelago.…”

“…The waters of south-western Sweden, such as the Öresund Strait between Denmark and Sweden, (Hansson et al 2018c). The trends are similar in both areas, but the levels are different due to differences in land uplift and the southernmost Kattegat Sea, are not part of the Baltic Sea proper, and have a different shoreline displacement history, as these areas have been connected to the Atlantic Ocean since the deglaciation.…”

“…Pine stumps dating to the Yoldia and Ancylus stages have been found sporadically in the Blekinge Archipelago. Diving and acoustic surveys throughout the last 5 years have revealed several remains of a submerged landscape in the study area (Holmlund et al 2017), and amateur divers have located several new areas with preserved tree stumps and terrestrial palaeosurfaces in adjacent areas (Hansson et al 2018c). Furthermore, a recently revised shoreline displacement record for Blekinge (Hansson et al 2018c) suggests that there exists a significantly long period (c. 9500-8500 cal BP) with a relatively stable sea level during the Initial Littorina Stage at 4 m depth, well below today's shoreline (Fig.…”

“…The sites are difficult to date typologically, but in the few cases where this has been possible, the dates range from late Early to early Middle Mesolithic (c. 9500-8000 cal BP), i.e. during the rather long lasting Littorina low-stand period (Hansson et al 2018c).…”