Bio- and chronostratigraphic significance of the Older Dryas Chronozone — on the basis of new radiocarbon dates

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Abstract
Six radiocarbon datings have been carried out on water mosses from a Late Weichselian sequence in Lake Sännen, Blekinge, SE Sweden. Three of the dates seem, from pollen-stratigraphical point of view, to correspond to the Older Dryas Chronozone and the very beginning of the Allerød Chronozone. As no contamination of the dated material can be demonstrated the dates are considered reliable. An age of 12 100–12 250 years B.P. is indicated for the Older Dryas, which is older than thought before. Added to the local varve chronology these dates suggest that SE Sweden was deglaciated 12500–12600 yr B.P. The climatic amelioration at the beginning of the Allerød interstadial is placed at about 12 100 yr B.P., but whether it was preceded by a distinct cold phase or not, is still doubtful. Because of that and its short duration the Older Dryas is proposed omitted as a chronozone.