Early Holocene water level changes as recorded on the island of Senoren, eastern Blekinge, southeastern Sweden

University essay from Lunds universitet/Geologiska institutionen

Abstract: Popular scientific summary: This paper presents a study carried out in the fall of 1994 on Senoren, an island of the Karlskrona archipelago. Considering the aim of the study which was to record Early Holocene water level changes in the Baltic Sea, two bays, Sörevik and Norrevik on this island were chosen because they lie in the province of Blekinge in southeastern Sweden. The coastline of Blekinge is characterized by the fairly unique geological feature of being more or less parallel to the land uplift isobases (Berglund & Björck in press). This makes the area very suitable for shoreline studies, because large areas have experienced approximately the same amount of uplift since the last deglaciation, dated to approximately 12,600 14C years BP (Björck & Möller 1987). The area has experienced a number of transgressions and regressions ever since. The present Baltic Sea has changed from the Baltic Ice Lake (12,600-10,200 BP) through the Yoldia Sea (10,200-9500 BP), the Ancylus Lake (9500-8000 BP) and finally the Littorina Sea (8000-5000 BP) (e.g. Eronen 1988, Björck in press). Water level and other environmental changes throughout these geological episodes can be recorded by analyzing sea and lake sediments in this area. In this study the sediments were cored with a Russian peat sampler in along a 550 m longitudinal section trending between Sörevik and Norrevik and along a 130 m transverse section at Sörevik. Geological mapping was done in the field to include non-organic deposits like till, sandy till and boulder rich till. The oldest organic sediments collected in this study is a black drift peat which was dated to 9300±160 14C years BP. This drift peat represents the Yoldia Sea to the Ancylus Lake interphase. The clay gyttja and coarse detritus gyttja which follows respectively were deposited during the Ancylus transgression and the regression there after. Opening of the ocean connection took place about 8000 BP and caused the Littorina transgression during which time fine detritus gyttja and clayey gyttja were deposited. The younger strata namely sand and reed peat were deposited after the cease of Littorina transgression. The results from magnetic, organic content and minerogenic content analysis have been used for the correlation of the cores, determination of the stratigraphy, and recording of water level changes in the area.

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