Stratygrafia pstrego piaskowca w wierceniu Otyń IG-1 (Monoklina Przedsudecka)

Ryszard Fuglewicz


Stratygraphy of Buntsandstein in the Borehole Otyń IG-1 (Fore-Sudetic Monocline, Poland)

The paper deals with stratigraphy of Buntsandstein in a borehole Otyń IG-1 (Fore-Sudetic Monocline) on the ground of megaspores and cyclic succession of lithologie complexes. In the borehole a Buntsandstein series is complete and contains abundant meg a spores that allow to distinguish three index megaspore assemblages: Otynisporites eotriassicus assemblage of Lower Bunter, Pusulosporites populosus assemblage of Middle Bunter and Trileites validus assemblage that is an index for Roethian. Buntsandstein series in the borehole Otyń IG-1 has a cyclic succession, typical for almost the Whole territory of Poland. This succession is expressed by an alternating occurrence of red rocks with no megaspores and of grey-greenish rocks (with two inserts of oolitic beds) containing megaspotres £ig.l,pl. I—IV. In comparison with the north-eastern part of Poland there are more complete sedimentary cycles in the borehole Otyń IG-1 due to greater mobility of the Fore-Sudetic Monocline. It allowed to supplement the hitherto table of Buntsandstein (Fuglewicz 1973) with new stratigraphie units (Table 1, Fig. 1). The Sub-oolitic Beds include in the interval 933.0—970.0 m greenish-grey claystones and siltstones with miospores, hystrichospheres and megaspores of Otynisporites. The complex, distinguished as Otynisporites siltstone, allows to divide the cyclothem la into two smaller cyclothems: la 1 and la 2 (Table 1, Fig. 1). Inter-oolitic Beds compose of similar as in other parts of Poland, red and brown rocks without any palaeontological remains. A thickness of Upper-oolitic Beds in the borehole Otyń IG-1 is notably reduced. Inter-oolitic Beds and Upper-oolitic Beds form the lower part of the cyclothem lb, distinguished as cyclothem lb. Supra-oolitic Beds of the profile contain in the interval 492.0— 518.0 m a complex of grey and greenish claystones and siltstones with interbeds of sandstones with abundant plant remains. The complex, characteristic for its plentiful megaspores Pusulosporites, was distinguished as Pusulosporites siltstone. In the stratigraphie table of Buntsandstein of north-eastern Poland (Fuglewicz 1973) it is of the same age as the upper part of Upper-oolitic Beds (Table 1). The complex, together with the lower part of Upper-oolitic Beds, was distinguished as a cyclothem lb 2. Roethian is typical as in the Fore-Sudetic Monocline. Two lagoonal complexes allow to find two full cyclothems of Roethian i.e. lia and lib (Fig. 1). Each cyclothem begins with sediments of the open sea and ends with lagoonal facies. Cyclothem lie includes the uppermost Roethian (Supra-gypsum Beds) and the Lower Muschelkalk and ends with lagoonal facies of Middle Muschelkalk. According to previous papers of the author, dealing with Buntsandstein in Poland (Fuglewicz 1973, 1977), a full unequivocal feature of its subdivision into sedimentary cycles was proved. As in north-eastern and central Poland, there is also in the Fore-Sudetic Monocline an alternate occurrence of red or brown rocks with no organic remains and of greygreenish rocks with two inserts of oolitic limestones and with many megaspores. More distinct cyclic succession of Buntsandstein in the Fore-Sudetic Monocline, being an evidence of a considerable mobility of that area, allowed for more detailed stratigraphical division in comparison with the platform part of north-eastern Poland. A cyclic sedimentation is probably connected with differentiated epeirogenetic movements within the Polish-German Basin; the movements caused periodical ingressions of the sea in the semidesert areas of Central Europe. An expansion of water reservoirs was every time associated with flora development. A composition of megaspore assemblages is quite different in each cyclothem so the processes caused by climatic fluctuations must have been of great importance.

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