Paper No. 1
Presentation Time: 8:05 AM


STOLZE, Susann, Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO 80303, NELLE, Oliver, Aix-Marseille Université (AMU), Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix-Marseille, 13284, France and DÖRFLER, Walter, Institute of Prehistoric and Protohistoric Archaeology, Kiel University, Kiel, Germany,

Climatic variability during the fourth millennium BC was inferred from variations in lake level, vegetation and geochemical data obtained from two small lakes and a wetland site at different elevations in the vicinity of the Neolithic megalithic complex of Carrowkeel-Keshcorran, Co. Sligo, northwest Ireland. The palaeoecological evidence along with high-resolution chronologies indicates that the initial opening of the post-glacial woodland, which was accompanied by a noticeable decline in the elm population, occurred at the beginning of the fourth millennium BC. The subsequent expansion of grasses and the anthropogenic indicator Plantago lanceolata demonstrates that human activity increased notably in the area and was most pronounced sometime between ca. 3750-3600 BC. Simultaneously with the formation of open space, wheat cultivation was established in the pollen catchment area of the lowland lake and practiced over a period of ca. 140 years. Despite the increasing availability of cleared terrain, influx of terrigenous material into the lake basins did not increase. A concomitant decline in lake levels and hiatus formation suggest that drier and somewhat warmer climatic conditions coincided with this Early Neolithic period of increased human impact.

At around 3600 BC marking the transition to the Middle Neolithic, human activity declined notably in the area and continued thereafter at a smaller scale than during the Early Neolithic. This phase was dominated by pastoral farming. The decline in human impact overlapped with the onset of generally wetter and cooler conditions. Elevated amounts of inwashed material despite an increased woodland cover and higher lake levels suggest intervals of substantial rainfall at ca.3550 BC and between 3345-3075 BC. Coinciding with the climatic deterioration, the woodland cover attained pre-elm decline extent at the beginning of the Late Neolithic (ca. 3000 BC). This implies a marked decrease in human population density at the time.

The climatic shifts inferred from the Carrowkeel-Keshcorran area occurred simultaneously with those across the eastern North Atlantic region, suggesting a large-scale climate forcing. As the timing of climatic shifts corresponds to changes in solar activity, the Sun appears to be an important driver of the climate system during this time.