Bölling-Interstadial und Laacher Bimstuff in einem neuen Spatglazial-Profil aus dem Vallensgard Mose/Bornholm. Mit pollen-großenstatistischer Trennung der Birken

Sediments at Vallensgard Mose, Bornholm, Denmark , from pre-Alleröd to
Younger Dryas time are investigated by pollen-analysis. Pollen of dwarf- and broad leaved birches is separated by evaluation of size-frequency distributions. Jn accordance with Iversen (1954) most birch pollen in pre- and early Alleröd time is due to Betula nana. Contrary to lversen's presumption, Betula pubescens aggr. prevailed in birch pollen precipitation in late Alleröd time. In pre-Alleröd time, changing values of (dwarf-)birch together with corresponding variations of sediments (contents in lime and organic matter) indicate a warmer period followed by a cooler, i.e. Bölling and Older Dryas. The Alleröd period shows a threefold division caused by a cooler phase in the middle. High values of Juniperus before and after this phase seem to indicate climatic optima. Immediately above the cooler middle part of Alleröd time, tuff has been found be longing to volcanism of the Laacher See in the Eifel mountains. A hiatus at the boundary Alleröd/Younger Dryas established by stratigraphical features is considered to be the reason for the lack of pine dominated spectra of late Alleröd time, as recorded in lversen 's diagram.