Varve chronology and palynology of the Lateglacial in Northwest Germany from lacustrine sediments of Hamelsee in Lower Saxony

The Hamelsee is a dolina from a collapse over Permian salt that occurred at the end of the Pleniglacial. It is more than 21 m deep and contains 18 m o f lacustrine sediments. The Lateglacial sediments in the central parr of th e lake consist of 2.7 m (from 15 to 17.7 m) of sapropelic and silty muds wh ich are mostly laminated and partly bioturbated. Minor slumps occur mainly during colder phases. The subdivision of the Lateglacial is based on pollen zones. Multidisciplinary studies of the microfacies from thin sections, ge ochemistry, pollen analysis and rotifer analysis allow environmental and pa laeoclimatological interpretations to be made. The biozones of the Lateglac ial and their boundaries are marked by rapid climatic changes. Though cover ing comparatively short periods of time, they are not monotonous but charac terized by minor internal climatic fluctuations. The sediments of the Meien dorf and Oldest Dryas are not laminated. The Allerod sediment is seasonally varved without interruption and encompasses 625 yr. The eruption of the La acher-See volcano (12,900 cat BP) had an impact on the climate during the f ollowing 10 yr. The transition from the Allerod to the Younger Dryas took s ome 50 yr and it occurred 200 yr after the eruption of the Laacher See volc ano. The abrupt change at the end of the Lateglacial (11,560 cal BP) occurr ed within less than 10 yr; however, many proxies reacted with a time lapse of 15 to 30 yr. (C) 2000 Elsevier Science Ltd and INQUA. All rights reserve d.