Staroplejstoceńskie osady organogeniczne w Ceteniu i ich związek z serią preglacjalną południowego Mazowsza

Abstract

OLD-PLEISTOCENE ORGANOGENOUS DEPOSITS AT CETEŃ AND THEIR CONNECTION WITH THE PREGLACIAL SERIES OFSOUTHERN MAZOVIASummaryIn the course of geological mapping, conducted in southern Mazovia in 1964–1967, the author described what was known at that time in Polish literature as “preglacial” deposits. The description was based on borehole material and on many outcrops of these deposits identified by the author for the first time in this area. These so-called “preglacial” deposits are fluvial sediments accumulated in southern Mazovian by rivers flowing down from the Central-Polish Uplands. A large content of quartz is one of the most characteristic features of these deposits; until decently the lack of Scandinavian material was also regarded as another characteristic feature.“Preglacial” deposits occupy almost the whole area of southern Mazovia described here, except for elevations exceeding150 mabove sea level and those where these parts where these deposits were removed by later Pleistocene erosion (Fig. 1). The relief of the basement of “preglacial” deposits is erosional. The basement is composed of Tertiary, Cretaceous, and Jurassic rocks (Fig. 2).The development of the “preglacial” series, which is about30 mthick, shows considerable differentiation. The series consists of fluvial, river-bed deposits (sandy-gravel) flood and lacustrine deposits (silty-clayey), cyclically bedded (Figs. 3 and 4).The age of these deposits has not been clearly defined yet, described as Tertiary by some authors and as Quaternary by others. Until recently no dating of this series was available. Thus an important site of these tentatively called “preglacial” deposits occurs at Ceteń, near Nowe Miasto, where they are exposed at the edge of high ground and an overflood terrace in the valley of the River Drzewiczka(Fig. 5). These rocks are composed of sands, silts and accumulated in four sedimentation cycles. A bed of peat gyttia,80 cmthick (Figs. 6–9), occurs in the sediments of the third cycle. Palynological analyses by Z. Borówko-Dłużakowa (1968) show that the deposits concerned are of  Old-Pleistocene probably Cromerian age. The results of mineralogical and grain-size analyses by B. Kosmowska-Ceranowicz (1976) were compared with the recently published descriptions of the sequence of “preglacial” deposits from Ponurzyca (M. D. Baraniecka, 1975; L. Stuchlik, 1975); this comparison seems to indicate that the deposits from Ceteń are still older, probably Waalian.Studies of the deposits from Ceteń show that the “preglacial” series of southern Mazovia might have been formed during a long period, from the Pliocene to the Cromerian Interglacial inclusive. It is thus in this series that the boundary between the Tertiary and the Quaternary is found.