Transition and change in pollen diagrams and pollen-charcoal diagrams at and around the Atlantic/Subboreal border

Abstract

Three "C-dated pollen diagram sections which start during Late Atlantic Time are presented and compared with each other. Two of the diagrams are from western Ostergotland - the large Dags Mosse bog and the extremely small kettle hole at Niissja - while the third diagram is from Lake Bjiirsjoholmssjon in southernmost Scania. In the Niissja diagram not only pollen but also macrofossils (charcoal, seeds) are registered in the lowermost part. In this kettle hole the sedimentation started during the Late Atlantic (charcoal of burnt Tilia stems has been found and dated) and accelerated at or above the elm-decline level: charcoal particles ofburnt stems ofBetula, Corylus, Alnus, Salix, Pomoideae, Tilia and Quercus were deposited during the Early Subboreal. The Scanian early subboreal "indexhorizons" found in Lake Bjiirsjoholmssjon are easy to observe and fix also in the Dags Mosse diagram. These index horizons are synchronous from Scania in the south to Ostergotland in the north - and very likely over much larger areas (from Ireland in
the west into, not unlikely, western Russia in the east). Thus the vegetational changes between the elm-decline level (5150 BP) and the beginning ofthe Regeneration (4500 BP) ought to be caused by factors lying beyond man's control. It is also de-monstrated that the "sudden" rise ofthe Betula curve in Lake Bjiirsjoholmssjon is not a reflection ofa "very early landnam" in this area. This "sudden" spread ofbirch is nothing but an illusion - the sedimentation stopped for some decades above the elm-decline level.