Stratygrafia młodszego trzeciorzędu Polski na podstawie badań paleobotanicznych

Abstract

STRATIGRAPHY OF LATE TERTIARY IN POLAND ON THE BASIS OF PALAEOBOTANICAL RESEARCHSummaryA general lack of fauna in the Late Tertiary formations of continental type is responsible for a fact that in most cases plant remains are the only stratigraphical evidences. Since in Poland the Tertiary formations are as a rule overlain with younger deposits, and in consequence of this they are known from drillings only, the spore-and-pollen analysis seems to be here the best method of study, especially when considering the small size of samples.Palynological-stratigraphic considerations presented here are based on the species of sporomorphs or on their groups: a – those with characteristic morphology; b – those occurring in greater amounts one or at most two times at the Late Tertiary period. Pollen grains of Angiospermae are here the main index form. Among Coniferae, stratigraphical value is related to pollen grains of Sciadopitys and Sequoia.In this paper the term phase, e.g. Alnus phase, is used for a period of time in which a characteristic pollen grain distinctly predominates in the spore-and-pollen spectrum.Materials from bore holes made in the region of Lulbin – Ścinawa and from the vicinity of Rawicz, Mosina and Szamotuły, are a basis for these considerations.Drillings have penetrated here 4 series of brown coal seams, called in this paper the Lusatian brown coal series. A correlation of the Miocene deposits has been made using the results of micropalaeobotanic research of the Carpathian foredeep deposits (Figs. 11 and 2). The results are presented in Figs. 5 and 6.The lowermost Lusatia brown coal series IV is characterized by pollen grains of Tricolporopollenites congulum subsp. pusillus (R. P o t.) T h et P f., and T. cingulum subsp. fusus (R. P o t.) T h. et Pf. In the spore-and-pollen spectra they make about 40%. The series under consideration was formed at the Upper Oligocene time.The palynological profile of the Lusaitia series III begins at the bottom with the abundant Alnus pollen grains, where five-pore grains (Alnus phase, Tables 1 and 2) predominate. The author suggests to accept horizon that lacks pollen grains of the group pusillus-fusus, but reveals the abundant pollen grains of Alnus, as a boundary between the Oligocene and Miocene. Upwards, this situation changes and ends with a phase of the pollen grains of Monocolpopozenites parareolatus W. K r. (maybe belonging to palms), amounting up to 28%. Above this series, some profiles disclose the presence of Hystrichosphaeridae.In the siliceous sandstones from Osieczów - synchronous with the formations that separate the Lusatian series III and II – are found the remains of marine fauna, a. o. Lima lima L. (Fig. 3). The adjacent, similar sandstones reveal fossil laurel-leaf flora that proves the development of moderate, warm-subtropical climate.The lower part of the Lusatian brown coal series II is characterized by the presence of pollen grains of Tricolporopollenites henrici (R. P o t.) Pf. This phase is particularly well developed within the North-Sudetic trough. In the upper part of the palynological profile of this series, the pollen grains of Myricaceae and Tricolporopollenites librarensis (T h) T h. et Pf. s. 1 predominate. The abundance of this form may exceed 40%. It is supposed that the formation of the organogenic deposits of the Lusatian series II may, together with the mown coals of the North-Sudetic trough and the upper seam at Turów, be related to the period of the Lower Miocene sea regression, prior to the Lower Tortonian transgression in the Carpathian foredeep, i. e. according to the new stratigraphical scheme (I. Cicha, J. Senes,1968). This thesis has been based on a comparison with the spore-and-pollen pattern of the deposits from Zalesie Antoniowskie (area of the Carpatian foredeep), and of the deposits from Rhineland. In the area of the Mużaków arc, and in the Ziemia Lubuska region, the series yields a somewhat different palynological picture, where Cyrillaceae pollen grains reach up to 19%. This may be only a variation in facies during the development of plant communities of the Lusatian brown coal series II; it has been called Cyrillaceae facies.The sedimentation of the Lusartian brown coal series II terminated in Poland earlier than in the Sernftenberg basin. On the other hand, the upper part of the Tertiary sequence of this basin may be synchronized with the initial formation periods of the Middle-Polish coal seam in the region of Konin. Its palynological picture, proved by macroscopic plant fragments, is characterized by a continuous curve of the pollen grain of Sciadopitys with its maxima up to 20%, accompanied in the whole section of this seam by more or less high percentages (up to 27%) of Ericaceae pollen grains (Sciadopitys – Ericaceae phase). The stratigraphical position of the Middle-Polish coal seam is between the II and the a Lusatian series.The palynological profile of the latter series shows a distinct bipartition. In the lower part, where the curves of Tricolporopollenites henrici and T. librarensis s. 1. distinctly decreases, a high percentage of the Sequoia pollen grains may be observed (up to 36%) – Sequoia Phase. In the upper part in turn there appears a predominance of Nyssa and Alnus forms, with a greater admixture of Quercus – Nyssa – Quercus phrase. This is related to the influences of the developing basin of the Poznań series.In the marginal portions of the basin both in the North and in the South, are found coal beds that disclose similar spore-and-pollen character, except for Quercus replaced here by Betula. In this horizon are found leaves of Byttneriophyllum tiliaefolium (A. Br.) K n o b l. et K v a c e k. Probably, this is already a Pliocene horizon.Comparing the cumulative palynological profiles from the Lowland areas, and those from the Carpathian foredeep (Fig. 5) we observe that, up to the Middle Miocene, they are similar. In the Upper Miocene, however, they disclose distinct differences caused in the Lowland area by specific ecologic conditions, affected by a huge basin of the Poznań series, favorable to the plant communities adapted for living in an area inundated for a long time with water.