Investigations on buried soils and colluvial layers around Bronze Age burial mounds at Bornhoeved (northern Germany): an approach to test the hypothesis of 'landscape openness' by the incidence of colluviation

摘要

The idea of open landscapes around prehistoric burial mounds is founded on their topographical position and findings of plaggen clots within the hills at some sites. We have investigated the surroundings of four Bronze Age burial mounds at Bornhoeved (northern Germany) to test whether this assumed landscape openness enabled soil erosion and colluviation or not. The soils and colluvia within a watershed below the burial mounds were investigated in six large exposures and additional auger cores. The chronology is based on 21 AMS-radio-carbon dates, complemented by charcoal analysis and the content of selected heavy metals in the sediments. Colluvia were deposited in the Late Neolithic (～2500-2200 cal. bc), Roman Emperor Times (～ 250-400 cal. ad), Mediaeval Times (～ ad 600-1400) and Modern Times (～ ad 1800-2000). Our findings indicate that the soil surfaces were protected against soil erosion during the phase of Bronze Age funeral use (～ cal. 1800-600 bc). Either the prehistoric gravediggers practised a well suited form of pasturing to keep the scenery open or the surroundings of the burial mounds were forested at the time of funeral use. The results of charcoal analysis reflect the known succession of woody taxa in the region and underline the great potential of anthracology on colluvial layers for palaeoenvironmental reconstructions apart from traditional archives such as lakes or mires. Bulk radiocarbon dating of organic matter overestimated the time of burial of a buried soil as well as the time of deposition of colluvial layers considerably.