High resolution sediment and vegetation responses to Younger Dryas climate change in varved lake sediments from Meerfelder Maar, Germany

This work focuses on a 1900-year section of varved sediments from Lake Meerfelder Maar (MFM) extending from the Late Allerod to the Preboreal. Varve counting provides the chronological framework and determines the length of Younger Dryas to 1025-1090 years. A strong relation between climate change, environment response and depositional processes has been found. In consequence, varve microfacies variations are a sensitive proxy for environment changes. These are reflected, for example, in erosion processes within the lake's catchment (minerogenic input) and lake productivity (diatom blooms). The observed varve changes have been quantified by multiproxy analyses of physical and chemical sediment parameters with a resolution of between 8 and 40 years depending on sedimentation rate. In addition, high resolution palynological investigations provide the biostratigraphical subdivision based on changes in the vegetation occurring during the same time interval. Varve observations reveal that environment changes at the beginning and the end of the Younger Dryas occurred within 20-50 years. Furthermore, sediment and vegetation changes were synchronous. Within the actual precision of the MFM and GRIP chronologies (divergence of only a few decades) terrestrial responses in Western Europe occurred quasi-synchronous to temperature changes in Greenland. (C) 1999 Elsevier Science Ltd. All rights reserved.