Dolnoliasowy wiek warstw wielichowskich na tle badań sporowo-pyłkowych na Niżu Polskim

Abstract

LOWER LIASSIC AGE OF THE WIELICHOWO BEDS IN THE LIGHT OF SPORE-AND-POLLEN ANALYSIS (POLISH LOWLAND)

Summary

The paper presents a detailed spore-and-pollen characteristic of the Wielichowo beds and a discussion of age of these beds based on this characteristic. The Wielichowo beds (an equivalent of the Triletes Schichten in Germany) represent - according to the subdivision of the epicontinental Rhaetian in the Polish Lowland area (R. Dadlez, J. Kopik, 1963) - the Upper Rhaetian. During the Jurassic Colloquy, held in Warsaw in 1964, J. Kopik (1966) referred the Wielichowo beds to the Lower Liassic, basing his opinion on their lithological character and on the encountered organic remains. The Wieliochowo beds, distinctly differing in their lithology from the underlying Zbąszynek Beds, are built up of dark grey loamy claystones containing intercalations of coal. A palynological analysis of the Wielichowo beds shows the presence of a rich spore-and-pollen spectrum. The character of the spore-and-pollen spectrum of these beds and the boundary between them and the overlying Mechowo beds are presented in Fig. l. The spore-and-pollen spectrum of the Wielichowo beds, uniform in all the sections investigated, is made by three groups of sporomorphs. The first group embraces the sporomorphs characteristic of the Wielichowo beds only. This group contains 9 new species described in the present paper, 6 species known from the Upper Rhaetian of Germany (equivalent of the Wielichowo beds), and 5 species morphologically resembling Carboniferous sporomorphs. The second group embraces the spores occurring in both the Wielichowo beds and the Mechowo beds. Some of them are more frequently found in the Wielichowo beds, as f. ex. Ricciisporites tuberculatus Lundbl. To the third, richest group embracing 56 species belong the sporomorphs (alphabetically arranged), which are common to both the Wielichowo and the Mechowo beds and prove the presence of similar climatic conditions existing during the formation of the deposits under consideration. The occurrence of the sporomorphs characteristic of the Wielichowo or of the Mechowo beds only (Fig. l) allows to draw microfloristic boundary between these beds, which are similarly developed in their lithology. Extents of the Upper Keuper, Rhaetian and Lower Liassic sporomorphs and changes in their percentage (T. Orłowska-Zwolińska, 1966) show that the spore-and-pollen spectrum of the Wielichowo beds distinctly differs from that of the Lower Rhaetian, and is strongly connected with the Lower Liassic spectrum of the Mechowo beds. This fact allows to refer the Wielichowo beds to the Lower Liassic.