Due to the availibility of high-quality lacustrine sediment records, the Moervaart depression in northwestern Belgium is a very suitable region from which to assess environmental responses to abrupt climate change during the late-glacial (ca. 14,5 – 11,5 ka cal BP). Multiple-proxy analyses of physical parameters (bulk sediment composition and magnetic susceptibility) and biotic remains (palynomorphs, plant macroremains, diatoms, freshwater molluscs, ostracods and chironomids) resulted in a considerable amount of valuable data concerning the climate and palaeoenvironment in this region. The climatic cycles observed in the late-glacial significantly affected the local vegetation and water shed. The milder Bølling interstadial (ca. 14,5-14,1 ka cal BP), characterized by shallow swamps and an open vegetation of mainly birch, grasses, willow and juniper, was abruptly interrupted by a short cold phase, the Older Dryas (ca. 14,1-13,8 ka cal BP), in which a dry and open grass tundra occurred. Based on the presence of Gloeotrichia colonies, known as nitrogen fixers, it is suggested that during the Older Dryas these cyanobacteria created more favourable conditions for aquatic plants to colonize the swampy areas. During the successive Allerød interstadial (ca. 13,8-12,6 ka cal BP), a shallow, large palaeolake with submerged vegetation (e.g., Nymphaea and Myriophyllum) developed, whereas a more dense birch forest (1st phase), accompanied by pine (2nd phase), was continuously present in the surroundings. Extreme cold climatic conditions during the Younger Dryas (ca. 12,6-11,5 ka cal BP), however, caused major hydrological changes, originating in the development of an east-west trending palaeochannel system across the (nearly-)desiccated lake area. In summary, our results clearly demonstrate strong and rapid environmental responses to abrupt climate change at the last glacial-interglacial transition in the Moervaart area.

Abstract of an Oral Presentation or a Poster