Charakterystyka palinologiczna osadów preglacjalnych z Ponurzycy (rejon Otwocka)

Abstract

PALYNOLOGICAL CHARACTERISTICS OF THE PREGLACIAL SEDIMENTS OF PONURZYCA (OTWOCK AREA)SummaryA pollen diagram has been established on the basis of palynological spectra of 38 samples of preglacial sediments from the Ponurzyca sequence (geological material provided by the Geological Institute). In this diagram four periods of vegetation development can be distinguished.Period I (bottom part of the diagram) characterized by a highly differentiated plant assemblage has been defined as the oak-alder period. Then mesophilous forest of interglacial type prevailed. In dry habitats these were oak-hornbeam forests with elm, Pterocarya, and Carya admixtures on wet ground. Wet river valleys were occupied by alder forests with trees of the Taxodiaceae-Cupressaceae group. The share of herbaceous plants did not exceed 30% and the Tertiary elements, with the exception of Pterocarya, Carya and the Taxodiaceae-Cupressaceae group, were of minor significance. Then the climate was moderately warm typical of younger interglacial periods.In period II/III (the middle part of the diagram) sporomorphs of coniferous trees clearly prevail over the deciduous plants being very abundant (up to 60%). The mesophilous deciduous forests were replaced by pine-spruce  forests with a considerable birch admixture. Outside the forests patches of brush vegetation with Betula nana and grass communities with Artemisia, Chenopodiaceae, Caryophyllaceae, and Thalictrum developed. In this period the climate was cool and close to subarctic.During period IV the mesophilous of inlerglacial character returned.However, these forests were poorer than those of period I and the herbaceous plants were more abundant (up to 40%). Tertiary plants occurred only in trace amounts. The climate was warmer than that of the middle portion of period II/III but cooler than of period I.Comparative studies of the vegetation of the periods distinguished at Ponurzyca and other Early Pleistocene vegetation of Western Europe and Lithuania revealed that the palynologically documented portions of the preglacial series of the Otwock area embrace a part of the Tiglian Interglacial (period I), the Eburonian Glaciation (period II/III), and a part of the Waalian Interglacial (period IV).No affinities exist to the so-called preglacial sediments of Warsaw (Ochota) and the two sequences differ clearly in their palynology. In the Ochota sequence the Tertiary element plays a substantial role in the pollen spectra (more than 50%), whereas in the Ponurzyca sequence it is of minor significance.