Environmental changes of a shallow kettle lake catchment in a young glacial landscape (Sumowskie Lake catchment), North-Central Poland

Abstract On the basis of detailed analysis (sedimentological, palynological, macroremains, geochemical and GIS analysis) the development of the Sumowskie Paleolake was reconstructed. Obtained results led to distinguish three main stages of the evolution of the basin and its catchment during the Late Glacial and the Holocene: the lacustrine stage, the lake overgrowth stage and the post lacustrine stage. Study site is located in the western part of the Brodnica Lakeland, North-Eastern Poland, within the former Sumowskie Lake bottom. Multidisciplinary research was conducted for two cores (sedimentological, palynological, plant macroremains): SUM A (149 cm) and SUM C (51 cm) and the soil profile – SUM 3 (sedimentological, geochemical). GIS analyses (land cover and water level changes) were carried out for the nowadays Sumowskie Lakes catchment. It was confirmed, that climate was the most important factor influencing the evolution of the lake and its surrounding. Although the role of this factor decreased in the Neo-Holocene period in favor of rapidly growing human impact. Changes of the water level were much more abrupt and lasted longer (e.g. 9500? – 5000? BP hiatus caused by the water level decrease) than in other described basins of the region due to the specific geomorphologic situation. Shallow kettle basins could alternately act as lakes and wetlands. As they are well-spread in the young glacial area, the strong influence of this abrupt and long term events should be reconsidered.