Eemian and early Weichselian Lobelia lakes in northeastern Poland

The Eemian and early Weichselian (early Vistulian in Polish stratigraphy) Lobelia lakes were investigated in an attempt to reconstruct the palaeoenvironmental conditions of northern Podlasie, northeastern Poland. Lacustrine sediments from six palaeolakes (Choroszczewo, Solniki, Dzierniakowo, Sokółka, Bohoniki and Drahle) were investigated palynologically. Furthermore, macroscopic plant remains were analysed from Bohoniki. Lobelia-lake vegetation was represented by Isoëtes, whose microspores were identified in all analysed profiles. In Bohoniki, megaspores of Isoëtes lacustris L. were also detected. Patterns of Isoëtes occurrence are evidence that during the Eemian interglacial and early Weichselian the existence of Lobelia lakes in northeastern Poland coincided with the boreal climate and the presence of boreal pine forests, which developed in the direct surroundings of the water bodies studied. These communities had the best conditions to develop in the terminal pine phase of the Eemian interglacial (E7 Pinus R PAZ), as well as during the interstadials of the early Weichselian (Brørup and Odderade). All these parts of the Late Pleistocene were relatively cold and humid. There is a similarity in the occurrence of Isoëtes between the decline parts of the Eemian interglacial, and the Holocene.