Svante Bjôrck

Abstract

The absolute dating of the deglaciation in South Sweden has been based on a number of different methods. Among those are ¹⁴C-dates on a) marine molluscs, algae, mammals, and sediments, b) limnic sediments and macrofossils, and c) terréstric macrofossils and mammals. Other methods have been to use varved clay connected with the present or local varve-chronologies added to the l4C-chronology. Correlations between the differently dated regions have therefore appeared to be difficult. A correlation method based only on glacial deposits and striations indicated a time-discrepancy between the differently dated deglaciation ages on the west and east coasts. Recent research on the difference between ¹⁴C-years and varve-years during the Late Weichselian suggests that much of the found differences between differently dated regions can be explained by steadily increasing ^l4C production during the deglaciation of South Sweden. The hitherto available data indicate that the time-scales "meet" sometime between 12 700 and 12 800 BP. During the following millennia the gradually higher ^l4C-activity led to gradually younger radiocarbon dates (relative to varve dates). A partly new, preliminary deglaciation chronology, taking these new data into account, is presented with correlations between the west and east coasts. Differences between regions, regarding deglaciation pattern, are discussed as well as possible glaciodynamic and climatic reasons for these anomalies.

Svante Bjôrck, Department of Quaternary Geology. Lund University, Tornav, 13, S-223 63 Lund, Sweden
Björn E. Berglund, Department of Quaternary Geology. Lund University. Tornav. 13 S- 223 63 Lund. Sweden
Gunnar Digerfeldt, Department of Quaternary Geology. Lund University, Tornav, 13, S-223 63 Lund, Sweden

Abstract

Marine hydroacoustic and stratigraphic studies were carried out on Late Quaternary deposits in the Hand Bay, combined with sampling and 14 C datings of pine stumps and peat deposits, pollen analyses of peat and soil horizons and mapping of the sea-bottom by divers. It shows that major water-level changes of the Baltic have been the most important factor for understanding the occurrence and absence of deposits in the Hano Bay. The most spectacular phases in the history of the area is a "pine-phase" between c. 9700-9300 BP when forest spread to areas which today are situated c. 40 m below sea level and a "peat-phase" between c. 8800-7000 BP when peat accumulated rapidly inside the shore bank of that time in areas which today are situated between —7 and —14 m. These quite dramatic water-level changes caused extensive erosion and resedimentation which have resulted in a stratigraphy characterized by many and long hiatuses. No evidences for recent sedimentation of fine-grained sediments have been found in waters of less than c. 60 m water depth.

Svante Bjôrck, Department of Quaternary Geology. Lund University, Tornav, 13, S-223 63 Lund, Sweden
Benneth Dennegârd, Department of Marine Geology, Box 7064, S-402 32 Göteborg and Department of Geology, University of Göteborg and Chalmers University of Technology, S—412 96 Göteborg, Sweden