Paleogeography of the environment in north-eastern Poland recorded in an Eemian sedimentary basin, based on the example of the Jałówka site

Abstract

The paper presents the results of the research on biogenic sediments from the Jałówka profile (Podlasie region, NE Poland) situated at the foot of a dry valley slope. A 35 cm monolith of sediments was collected from the excavation pit. The sediments were deposited beneath 4 m thick mineral sediments. Interdisciplinary research helped to reconstruct the possible transformations of the local environment. Palynological, physical, and geochemical analyses were applied to organic sediments, and plant macroremains were examined. Five local pollen zones were identified in palynological terms and correlated with the late Warta Stadial (MIS 6) of the Odra Glaciation (Saalian), and four older periods of the Eemian Interglacial: MIS 5e (E1, E2, E3 and E4). Younger zones have not been preserved. They were eroded in the early Vistulian. During the late MIS 6, there was a eutrophic water body with highly transparent water, characterized by a relative stable water level. The landscape was dominated by tundra with a high proportion of Juniperus–Artemisia. Curves of oxygen (δ18O) and carbon (δ13C) stable isotopes confirmed the boundary between MIS 6 and MIS 5e. The beginning of the interglacial vegetation succession (E1) was characterized by expansion of birch–pine–spruce forests. Probably at the end of this period, the lake became shallower. E2 is distinguished by the dominance of pine and birch. The lake was replaced by a peat bog. The sequence of vegetation succession in the landscape was as follows: Quercus (E3), Corylus, Fraxinus-Alnus and Tilia (E4). Probably, the peat bog drained in the E4 and the water level rose again in the climate optimum of the Eemian Interglacial. The results of physical and geochemical analysis clearly corresponded with climatic changes determined by palynological analysis. They provided evidence of the changing redox conditions, variability and intensity of denudation, the scale of biological productivity, and fertility of the environment. The studied sediments were characterized by reducing conditions. The increase in terrigenous silica content and the relatively high N:K ratio indicated the predominance of mechanical denudation during the late glacial period of the Warta Stadial and the E2 period.