EVIDENCE FOR THE CLIMATIC AND ANTHROPOGENIC CHANGES INFERRED FROM THE YOUNGEST SECTION OF LAMINATED SEDIMENT OF LAKE GOSCIAZ, POLAND

摘要

The catchment of Lake Gosciaz, a small lake in central Poland, was subject to direct anthropogenic changes during the last two hundred years. In the beginning of the 19th century settlement and farming close to the lake began. Around 1950 the catchment again became depopulated and forested.In this work we compare the changes of isotopic and chemical composition of sediment recorded for the last two centuries with the instrumental climatic data. Almost the whole profile of the lake sediment (18.5 m) is regularly laminated, revealing varve structure typical of annual calcareous lamination. The sediment, dated by varve counting, was used as an archive for high-resolution palaeoecological and palaeoclimatic reconstructions, e.g. at the late Glacial/Holocene transition [1]. The varve chronology for the section 0.5-2.45 m was elaborated using 20 short cores taken in frozen form in situ from the youngest part of the sediment, and precisely correlated with one another. Because of lack of annual lamination in the uppermost 0.5 m, the absolute age of this chronology was determined using other time markers, i.e. the peaks of ~(137)Cs and of abundance of charcoal. The isotopic composition of oxygen and the content of Na, Fe, Mn and other elements were measured in single varves in the sequence between 1825-1960.