Stratigrafi och överplöjning i Bussjösjöområdet, Ystad

Sammanfattning: Summary: Lake Bussjö is an 0.3 hectare large kettle hole in a hummocky morain landscape four kilometers north of Ystad. The purpose of this study is to investigate the stratigraphy and reconstruct the highest water level. Another task is to estimate the rate of farmland advance on earlier grazingland and swamps. Furthermore, to calculate the future development of the lake. To make the stratigraphy clear, six sections have been made, including 59 sediment profiles, which six have been done earlier (Dearing et al 1986 unpublished). Mainly Russian sampler and helical auger were used to penetrate the ground. In the laboratory a minerogenic magnetic method, IRM, has been used to correlate some of the sediment profiles. Correlation has been completed with pollen analyses. Studying of maps is an important part of our work, not least in order to find out the advance of cultivated land during the last two centuries. The results show that the highest water level of lake Bussjö has been three to four meters above the recent level during early postglacial. Mainly fine detritus gyttja deposition is recorded. But the upper part has a considerable amount of minerogenic content, according to a higher erosion level since agricultural work has been developed. The lake is surrounded by carr peat depositions. According to the macrofossil content and the pollen analyses, these were formed in an alder swamp forest. Farmer land is gradually moving over the former wet lands towards the lake, due to ploughing and water transport. This process is strongly varying in different conditions. In the lake Bussjö area the advance has a mean rate of about 0.4 meter/year. The sedimentation rate is estimated at 15 millimeters/year in recent time and is expected to increase in the future. Altogether, this means that the lake will be filled and incorporated with ploughed land within 100-150 years.