Badania geochemiczne lessów Wyżyny Lubelskiej

Abstract

GEOCHEMICAL EXAMINATIONS OF LOESSES IN THE LUBLIN UPLANDSummaryThe purpose of the researches was to give preliminary geochemical estimation of loess and fossil soil horizons of various age in the Lublin Upland. The loesses of the Lublin Upland are divided into four stratigraphical horizons of various age. Loess I, the oldest one, belongs to the Middle Polish Glaciation. The remaining three horizons belong to the last North Polish Glaciation, loess II being related to the Szczecin stage, loess III to the pre-Paudorf Phase and loess IV to the Leszno, Poznań and Pomeranian Phases of the Main Stage. Although in various amounts, three main loess facies occur in each of the horizons. Subaerial facies predominates in the horizons I, II and IV, solifluction loess is found mainly in the horizon III, and alluvial loess - in the horizons II and IV. The loess horizons are separated with fossil soils. The lowermost soil belongs to the Eemian Interglacial. It resembles forest soil of considerable thickness, showing distinct gley horizon and periglacial deformations at the top. The middle soil was formed during the Brørup Interstadial. It resembles strongly degraded chernozem, but numerous features prove a complicated genesis of soil profile. The uppermost soil, referred to the Paudorf Interphase, is built up of relatively thin decalcified loess beds, brown in colour. Lithological and stratigrarphical description of the loesses and fossil soils of the Lublin Upland, given more in detail, was presented by the latter of the authors (J. E. Mojski, 1965, 1967). The discussion of the geochemical examinations was preceded by the analyses of granulometric and mineral composition. Table 1 presents the percentage of the main fraction (0.0l-0.05 mm) in the individual loess occurrence sites in the Lublin Upland, and the Table 2 – CaCO3 contents. Stratigraphically, to the most complete sections belongs that at Nieledew, thus the largest amount of geochemical analyses was made of its samples. Here, also radiometric analysis was made by W. K. Łukaszew (Table 3). Microelement content was determined using spectrograph of ISP-28 type, by means of quantitative emission spectral analysis. These examinations were made by W. K. Łukaszew. The results obtained are presented in Figs. 2-5, and in Tables 4 and 5. Irrespective of the lower soil at Hulcze (Fig. 4), we may observe that Ti, Zr, Cu and Cr contents decrease downward to the Brørup soil. An increase in these microelements, particularly Ti, Zr and Cr, can be observed again below, i.e. in soil of the Eemian Interglacial. In particular position rests here the lower soil at Hulcze, where a distinct increase in Ti, Zr and Cr can be noted. The soil of the Brørup Interstadial at Nieledew resembles, as concerns Mn content and distribution in the section, the alluvial-meadow soil of flood terrace in the Byelorussian Polesie Region. As concerns the fossil soils examined, it has been ascertained that the soil of the Eemian Interglacial is, due to its geochemical features, more approximate to the contemporaneous one, than to the soils formed during the North-Polish Glaciation. As a rule, the latter resemble rather loesses. On the other hand, the lower soil at Hulcze is of other character. Geochemical resemblances and differences prove that the conditions of loess weathering should be considered also from the geochemical point of view of this formation, thus, geochemical examinations should concern the individual fossil soil horizons. The researches allow us to explain in part the conditions of formation of fossil soils in the loesses of the Lublin Upland. This mainly concerns the soil of the Brørup Interstadial, which, partly at least, may have formed under conditions of high level of ground waters.