Dolomity i dolomityczne brekcje triasowe w Skałce Maruszyńskiej

Ludwik Watycha




Dolomites and dolomitic breccias occur in situ at Maruszyna in the northern slope of the Tutkowska Rola hill, where they form a lense approximately 350 m long and 2-26 m thick in its middle portion. In the south, to the steeply inclined rocks (60-65°) adhere Posidonia and Super-Pasidonia beds (Dogger) that grade upwards into radiolarites and cherty limestones (Malm-Neocomian) overlain by Globigerina-radiolaria and Globatruncana marls (Cretaceous) (Fig. 1). All these rocks occur in a lense-like form extending E - W, and tectonically compressed. Its elements wedge out between shear surfaces. The whole sequence is classified into the Pieniny series. In the north Globotruncana marls belonging to the Branisko series adhere to the dolomites. Within these marls lenses of Jarmuta conglomerates occur that contain very abundant and differently rounded dolomite fragments. Within the Maruszyna dolomites breccias prevail, the size of their constituents ranging from fine argillaceous flour, through sand, to rubble. Locally they are cemented to compact blocks or beds. In these breccias, disintegrated at the surface, a few layers of hard very heavily fractured dolomites have been preserved. The dolomites are light in colour, ocher-yellow and locally attain a grey colouring due to algal accumulations. Occasionally a faint banding may be seen. Within these biogenic dolomites the micrite-sparite and micrite varieties have been distinguished by A. Maliszewska (1974). The elipsoidal, frequently blurred, algal concentrations are less abundant (up to 30%) in the fine-crystalline micrite-sparite dolomites than in the micrite varieties (80% and over) that, in addition, contain more clay matter and pseudomorphs traces after shell remnants and occasionally iron hydroxides concentrations. Some dolomites of these layers have rounded caverns and pores partly filled with dolomitic-ferruginous substance and partly void (cavernous dolomites). Like the caverns, the fissures are filled with yellow-brown dolomite containing hydrated iron oxides admixtures and occasionally calcite crystals. According to A. Maliszewska (1974) the Maruszyna dolomites are algal dolomites laid down far from the shore of their marine depositional basin in considerably saline waters. The fine grain size indicates these dolomites to have been formed simultaneously with the deposition of the entire carbonate series or slightly later. The carbonates were subject to recrystallization during the period of diagenetic alterations but prior to the brecciation. According to A.Maliszewska the lithofacies development points to the Triassic age of the rocks. In absence of palaeontological evidence this assumption has been based on lithological analogies, chiefly to the Lower Campilian sediments distinguished by Z. Kotański (1963) in the Haligovce K1ippe. The Maruszyna dolomites are the lowest and the oldest stratigraphic member not only of the Pieniny series, but also of all the remaining series of the Polish part of the Pieniny Klippen Belt. Despite the macroscopic similarities to the Tatra series the dolomites - as to their facies development - are closer to the Triassic sediments of the Cracow-Silesia region (A. Maliszewska, 1974). The distinctness of the dolomites, and even of the entire Pieniny Mesozoic, from the rocks of the Tatra region (despite certain analogies) has been confirmed by geochemical examinations (J. Calikowski, B. Gondek, K. Szpanier, 1968) that revealed the hydrocarbons of the Pieniny series and its basement to differ from those of the Podhale Palaeogene and its basement. Consequently the rock groups (of Triassic-Jurassic age) had a different history and were laid down in different depositional basins between which no communication existed.

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