Granica między retykiem i liasem w Polsce pozakarpackiej na podstawie badań florystycznych

Abstract

BOUNDARY BETWEEN RHAETIC AND LIAS IN THE EXTRA-CARPATHIAN AREA OF POLAND, DETERMINED ON FLORISTIC BASIS

Summary

The Wielichowo beds of West Poland, laid down in a limnic environment, are built up of clay and silty deposits, grey in colour, with coal interbeddings in their upper part (R. Dadlez, J. Kopik, 1963). The megaspore analysis of these deposits demonstrates the presence of a characteristic megaspore assemblage called here the Trileites pinguis assemblage. Such species as Trileites pinguis (Harris) Pot., T. pedinacron (Harris) Pot., Bacutriletes tylotus (Hards) Pot., and Verrutriletes litchi (Harris) Pot. are helpful in carrelating the Wielichowo beds with the Rhaetic Zone Lepidopteris, similarly as the form Nathorstisporites hopliticus Jung found to occur in the overlying Mechowo beds points to their connection with the Liassic Zone Thaumatopteris. It appears that the presence of such species as Ricciisporites tuberculatus Lundblad, Selaginella hallei Lundblad, Cornutisporites seebergensis Schulz, Limbosporites lundbladii Nilsson (T. Orłowska-Zwolińska, 1966, 1967) also allows us to refer the Wielichowo beds to the Rbaetic. In addition, the Rhaetic age of the Wielichowo beds is proved by the occurrence in them of cuticula fragments of Pterophyllum compressum Lundblad (= P. Schenki Zeiller) – a species characteristic, according to T. M. Harris and B. Lundblad, of the Zone Lepidopteris. In the underlying Gorzów beds, parallelized by J. Kopik (1967) with the Zone Rhaetavicula contorta, are found, besides leaf imprints of Lepidopteris ottonis (Goepp) Schimper, also megaspores Trileites pinguis (Harris) Pot. and microspores Ricciisporites tuberculatus Lundblad, Selaginella hallei Lundblad and others, which point to the relation of those beds with the Rhaetic Zone Lepidopteris. Thus, the Lepidopterls flora had, probably, appeared at the time of the transgression, together with the form Rhaetavicula contorta, as already suggested by T. M. Harris. It seems also that the flora of Lepidoipteris is characterized by two stages of evolution. The first stage of this flora may be observed in the Gorzów beds, the second one - in the Wielichowo beds. It results from the above that the boundary between the epicontinental Rhaetic and Lias deposits in Poland runs between the Wielichowo and Mechowo beds that, according to the microfloristic examinations, are equivalents of the Zone Lepidopteris and Thaumatopteris.