Schematy litostratygraficzne trzeciorzędu Niżu Polskiego

Abstract

LITHOSTRATIGRAPHICAL SCHEMES OF THE TERTIARY FROM THE POLISH LOWLAND AREA

Summary

Lithostratigraphical division of the Tertiary formations has for the first time been made for West and Middle Poland, along a section from the Lower Oligocene to the Pliocene inclusive. The section comprises several beds, the age·of which has·been determined on the basis of palaeontological evidences, mainly from palynological examinations.

The scheme of this division is as follows. Lower Oligocene – Upper Eocene (?) are represented by the Lower Mosina Beds. These are greenish quartz-glauconite sands with gravels (“bean-gravel”) phosphorites and sphaerosiderites with pelecypod, gastropod and foraminifer fauna. As the shallow-sea transgressive deposits they may be parallelized with the SchØnewald Beds, and with the Wittenberg Beds from the German Democratic Republic. Middle Oligocene comprises the Czempin Beds, which area, complex of siltstone-like, silty, shaly, silt-sandy and micaceous sediments, dark grey or dark brown-grey in colour, intercalated with green marine glauconite sands. These beds are an equivalent of the formations previously called “Toruń clays”. The age of the Middle Oligocene deposits has been documented both palynologically and with the aid of foraminifer fauna. The complex consists of 4–6 biostratigraphical horizons, and contains thin coal seams that are referred to the Czempin group of coal seams (V). These are regressive, marine, brackish or continental formations with the sediments of repeated marine ingressions. They rest unconformably on the Lower Mosinra Beds and correspond to the Calau Beds from the German Democratic Republic. Upper Oligocene is represented by the Upper Mosina Beds, Leszno Beds and Dąbrowa Beds.
The Upper Mosina Beds rest unconformable on the Czempin Beds. They consist of quartz-glauconite sands and gravels. Among the gravels are found quartz, lydite, quartz schists, and Mesozoic rocks. Frequently, phosphorite concretions and small pyrite nodules are encountered, too. Fauna remains are represented by otoliths, fish teeth and fragments of mollusc shells. The deposits are of marine origin and correspond to the Lower Cottbus Beds from the Lusatia area of the German Democratic Republic.
The Leszno Beds are built of silty and fine-grained quartz sands, light grey in colour, locally with light grey day intercalations. They may be divided into two series: the lower series, which consists of strongly micaceous·cross-bedded silt sands, and the upper series, built of quartz sands, too, but of coarser fraction, less micaceous, horizontally bedded, with bands of coal dust. At the boundary of these series a layer of grey-brown sand occurs, revealing coal dust and plant fragments (stalks, branches, roots). The Leszno Beds rest here discordantly on the·Upper Mosina Beds. In their development, they resemble German “light micaceous sands” (helle Glimmersande), and correspond to the Upper Cottbus Beds.
The Dąbrowa Beds of uniform development make the uppermost part of the Upper Oligocene. They consist mainly of a complex of coal-siltstone-sand deposits, from 6 to 11 m in thickness. The Upper Oligocene age of the coal seams has been determined on the basis of palynological examinations. The Dąbrowa Beds have been laid down under the sea-shore-and-continental, and continental conditions within the wide marshland areas (coal seams) left after the recession of the Upper Oligocene sea. The coal seams belong to the Dąbrowa group of coal seams (IV) which, in the German Democratic Republic, correspond to the IV Lusatia seam from Bitterfeld.
Lower Miocene consists of the Rawicz Beds, which make a complex, mainly of fat clay and siltstone, light grey and whitish in colour, locally coal-bearing, intercalated with quartz sands. In the sandy formations are found white, strongly weathered feldspars. At places one or two dark-red variegated clay horizons occur, disclosing druses of coarse-clastic gypsum and veins of silver-white aragonite. Palynological examinations point to the Lower Miocene age of the coals found in the beds considered. The clay formations contain thin coal seams, which belong to the Rawicz group of coal seams (III). In the German Democratic Republic, they correspond to the Brieske Beds, or to the Lower Brieske Beds, and in the south-eastern part of the Lusatia – to the Spremberg Beds. Within these beds there occurs the III series of the Lusatia seams, too, and the light colours of the clay deposits of these beds is responsible for an additional name of these beds, i.e. “helle Serie”. Midd1e Miocene is represented by the Ścinawka Beds and Pawłowice Beds.
The Ścinawka Beds make a complex of coal-clay-sand deposits developed in several coal seams, intercalated with clays, silts, shales or sands. They comprise the Ścinawka group of coal seams (II) of the Tertiary in Poland, and practically may be of great economical importance, mainly due to their thick coal seams found in them, and to their widespread occurrence, particularly in the western areas of Poland. According to the palynological examinations, the age of the coal seams has been determined as Middle Miocene. At the lower part of these beds are found glauconite and planctonic forms of Hystrichosphaeridae, similarly as the fragments of the Miocene marine pelecypods in the quartzite sandstones from the vicinity of Bolesławiec. Thus, the Ścinawka Beds are continental sediments, disclosing traces of a marine ingression that approached from west, and invaded the south-eastern part of West Poland. In the German Democratic Republic these beds correspond to the Lower Brieske Beds with the Lusatia coal seam. The Pawłowice Beds are represented by arenaceous, siltstone and micaceous formations, strongly charred in the upper part, with plant remains. Locally, a thin coal seam occurs, called Lubin seam II-A. Both glauconite and sponge spicules seem to point here to marine influences. The Pawłowice Beds correspond in the German Democratic Republic to the Lower Rauno A Beds, and the Lubin coal seam – to the upper accompanying seam (oberbegleiter FlØz). Upper Miocene consists of the Adamów Beds, Middle-Polish Beds and Lower Poznań Beds.
The Adamów Beds rest discordantly on the Pawłowice Beds, locally also on the older beds (Ścinawka Beds and even Rawicz Beds), in the places of a strong erosion of the deposits older than those at Adamów. The unconformity is stressed here by the presence of coarse-grained quartz or lydite sands and gravels, and even of quartz pebbles, up to 15 cm in diameter. At the lower part, they are developed as silty, micaceous or fine-grained sands, in which thin intercalations with few glauconite grains and sponge spicules occur. At the upper part in turn they appear as sands with coal dust. In the Lusatia area (GDR) they correspond to the Rauno B Beds.
The Middle-Polish Beds are built of clays and silts, grey or greenish-grey in colour, disclosing numerous plant fragments. In the central areas of Poland, these clays are interbedded with a coal seam, locally also even with 2 or 3 contiguous seams. Now, this seam is called the Middle-Polish seam. Locally, in the south-western area of Poland, the Middle-Polish Beds contain large coal lenses that correspond to the Oczkowice seam I, which, in relation to the Middle-Polish seam, would be characterized by a diachronic arrangement. At the top of the Middle-Polish seam the Upper Miocene deciduous flora appears.
The Lower Poznań Beds make a thick complex of grey, green-grey or olive-green clays, and disclose abundant plant remains observed mainly in the form of plant detritus, or fragments of stalks, branches and roots. The plant remains markedly separate them from the green clays with glauconite. The Lower Poznań clays may be correlated with the Rauno Beds from the German Democratic Republic.
Both Upper Miocene and Pliocen eara represented by the Upper Poznań Beds. They are built of a thick series of clayey formations, the lower part of which consists of green, fat an silty-arenaceous days with sand intercalations, and the upper part – mainly of variegated clays, previously called mottled clays (Flammentone). In the lower part of the Upper Poznań Beds, there occur glauconite and Tortonian microfauna. Most probably, these elements are related to a marine ingression from South Poland, caused by uplifting movements of the Carpathian foredeep. In the Lower Silesia and Sudetes areas, the Late Pliocene is represented by a series of white, kaolin clays with quartz gravels, quartz-feldspar sands and gravels with kaolin clays, and quartz-feldspar sand and gravels.
Both western and central areas of the country lack these formations, and the Quaternary deposits rest here immediately on the variegated or green Upper Poznań Beds.