Magnetic properties of sediments in a Polish lake: evidence of a relation between the rock-magnetic record and environmental changes in late Pleistocene and Holocene sediments

Abstract

A study of mineral magnetic parameters was carried out on a Late Pleistocene and Holocene sedimentary sequence (of nearly 18 m) from Lake Bledowo. Sediments of Lake Bledowo have already been analysed for bulk sediment mineralogy and biogenic materials. The mineral magnetic stratigraphy confirms the major changes in palaeo-environmental conditions that have been deduced from other methods. The most important mineral magnetic change results from the authigenic formation of ferrimagnetic greigite, Fe3S4, during the beginning of lacustrine conditions. The data also indicate a detrital origin of overlying ferrimagnetic iron oxides. It is suggested that they originate from brown soils developed on the boulder clay constituting the west side of the lake shore. Variations of ferrimagnetic iron oxide size are related to the early diagenetic processes.