Nowe stanowiska osadów górnoeoceńskich na obszarze północnej Lubelszczyzny

Abstract

W wyniku przeprowadzonych badań przedstawiono najpełniejszy, znany obecnie, profil udokumentowanych paleontologicznie osadów górnego eocenu na obszarze północnej Lubelszczyzny i wydzielono w nim trzy wyróżniające się litologicznie odcinki. Na podstawie wyników badań mikropaleontologicznych oraz dyskusji tych wyników osady górnoeoceńskie północnej Lubelszczyzny zaliczono do poziomu z Truncorotaloides rohri, podkreślając, że stanowi on w rejonie badań najniższy poziom górnego eocenu.

NEW LOCALITIES OF THE UPPER EOCENE IN NORTHERN PARTS OF THE LUBLIN REGION

The boreholes recently made at Branica, Antonin and Michów in northern parts of the Lublin region (central part of the eastern Poland) have revealed the most complete profiles of the Upper Eocene of that region. The Late Eocene age of phosphate-bearing series stretching out between Kock and Puławy (Fig. 1), assumed on the basis of scanty evidence, is now fully confirmed by paleontological datings of deposits occurring directly below that series at Michów (Fig. 2). This evidences Late Eocene age of the series throughout the region.

The thickness of calcareous Upper Eocene deposits with good microfaunal record approaches 14 m in the Radzyń Podlaski area (boreholes Antonin and Branica). The Upper Eocene may be .divided into three parts. The lower part resting on waste of Upper Maestrichtian rocks consists of quartz-glauconitic sands with phosphatic nodules at the base passing upwards into day sands and subsequently dark, gray-green silty-sandy clays. The clays pass upwards into gray-green silty sands and quartz-glauconitic sands with single phosphatic nodules. The deposits yield microfaunal elements characteristic of the Late Eocene (Table 1). The middle part is represented by a layer characterized by concentration of phosphatic nodules and also with micropaleontological record. The upper part also comprises some glauconitic calcareous sediments overlied by noncalcareous clay silts, gaizes and sandy silts almost 10 in thick. The noncalcareous deposits yield hardly identifiable moulds of foraminifer tests and debris of Upper Eocene macrofauna.

In the profile of the borehole Michów gray mads of the Upper Maestrichtian are overlied by fine-grained thinly-bedded marls yielding very poorly preserved foraminifer tests. The foraminifers differ from those occurring in underlying marls and it is fairly possible that they were derived from Paleocene strata cropping out in the neighborhood. Upper part of the profile comprises calcareous silts laminated with marly layers a few millimeters in thickness, and silts poorer in calcium carbonate. These strata about 1.2 m thick yield Eocene microfauna discussed in the Polish text. The foraminifer assemblage found here comprise, some species known also from the Ledim and Wemmelian; bearing this in mind the authors are inclined to assign these strata to lower part of the Upper Eocene, similarly as it was done by K. Pożaryska and S. Locker (1972) in the case of strata from Siemień. At Michów the silty series with microfaunal record is overlied by phosphate-bearing deposits 3.35 m in thickness. Phosphatic clusters occurring at the top of these deposits yield innumerous phosphatized shells of snails and pelecypods indicative of the Late Eocene. A series of glauconitic deposits 12 m in thickness, resting on the phosphate-bearing ones, may also be of the Late Eocene age.

The problem of stratigraphic position of glauconite-bearing deposits from the northern part of the Lublin region is discussed. Deposits from the area of Radzyń Podlaski (boreholes Antonin and Branica)  and those with Eocene microfauna from Michów are assigned to the Truncorotaloides rohri zone. However, it should be noted that when tripartite subdivision of the Eocene is accepted it is still debatable to which part the above mentioned zone belongs. This follows from differences between the subdivisions proposed by W. A. Berggren (1971), J. A. Postuma (1971) and K. Pożaryska and S. Looker (1972), discussed in the paper.