Egzotyki w paleogenie magurskim między Dunajcem a Popradem

Abstract

Exotic rocks in the Palaeogene of the Magura nappe between the Dunajec and Poprad Rivers (Carpathians, Poland) Pebbles of exotic rock's have been found in the Palaeogene of the Magura nappe at Kadcza, Zarzecze, Przysietnica and Tylmanowa (fig. 1). These localities are situated near Nowy Sącz, in the southernmost part of the Magura nappe (s.c. Krynica Zone). The exotic rocks have been recorded in Eocene deposits, above Middle Eocene variegated shales with Cyclammina amplectens Grzybowski. The variegated shales are overlain by a 700-metre series of thin-bedded flysch (Hieroglyphic beds) with intercalations of thick-bedded sandstones and conglomerates (fig. 2). The Hieroglyphic beds belong to the Middle Eocene, and are overlain by the Magura beds of the Middle?- Upper Eocene age. Exotic rocks from Kadcza, Zarzecze and Przysietnica appear in the Hieroglyphic beds whereas those from Tylmanowa are associated with the Magura beds. In all the localities except Tylmanowa pebbles of exotic rocks occur in beds formed by a mud-sandy flows. Moreover, the bed with exotic pebbles at Kadcza is deformed by a submarine slide (fig. 3). Near Tylmanowa exotic rocks have been found in a conglomerate bed. The present study is concerned with pebbles of exotic rocks having more than 10 mm in diameter. The shape of pebbles was determined (table 1) basing on Zingg’s classification (1935), the flatness index according to Cailieux (1945). The mean pétrographie composition of the beds is given in table 2 and fig. 2. A detailed description of the pebbles of exotic rocks is furnished in the Polish text. The pétrographie composition of the exotic material collected at various localities is very similar. Irf igneous rocks from Kadcza, Zarzecze and Przysietnica there are alaskite granites. At Przysietnica and Kadcza similar garnet gneisses and red conglomeratic gneisses have been found. In all the localities white, grey and pink-red quartzite gneisses have been recorded. Sedimentary rocks are represented everywhere by yellow dolomites and dolomitic limestones (Triassic?), white crinoid limestones (Dogger?) and white crystalline limestones (Dogger?) known from Kadcza, Zarzecze and Przysietnica. Micrite limestones, often organogenic (Globochaete, Calpionella, Radiolaria, Radiolaria-Nannoconus limestones), coming from sediments of Hoterivian-Eearly Tithonian age constitute another characteristic assemblage. Pebbles of Jurassic-Lower Cretaceous rocks correspond to those present in the Pieniny Klippen Belt (Central Carpathians). The other characteristic microfacies encountered in all the localities under study -are organogenic and detritic limestones, reef limestones (of Urgonian type) and sandy, spongy, sometimes glauconite limestones. Limestones of Urgonian type correspond to the Urgonian facies of the Tatra Mts. and of the Pieniny Klippen Belt. The youngest elements are Lithotamium limestones (Palaeocene?) and sandstones similar to those present in Inooeram'ian beds (flysch). Pebbles of exotic rocks from the discussed localities show a striking similarity to those occurring in the Senonian (Birkenmajer, 1958), Cretaceous and Palaeogene of the Pieniny Klippen Belt (Samuel, Borza, Köhler, 1972). In all the pétrographie groups the largest pebbles appear in the Hieroglyphic beds, the smallest ones in the Magura beds. A relation between the percentage of sedimentary rocks and the size of pebbles has been ascertained. The content of sedimentary rocks in a given fraction increases with the size of pebbles. The latter very likely depends on the density and velocity of the turbidity current and, in a lesser degree, on the length of transport and the intensity of erosion in the source area. In the individual pétrographie groups nearly .always discoidal pebbles prevail (table 1). All the pebbles are well rounded, which indicates a long transport. Current cast directions and pebble imbrication (fig. 2) imply that the exotic material was supplied to the Magura flysch basin from the southeastern border of the basin. Considering the appreciable similarities in the pétrographie composition of the exotic rocks, their common origin from one, in a broader sense, source is conceivable. The source area (table 3) was presumably made up of Early Palaeozoic metamorphic rocks with intrusions of Late Palaeozoic igneous rocks. According to Wieser (1970), such rocks are characteristic of the marginal parts of plutons. The presumable crystalline massif may have been covered with Permian variegated conglomerates and Werfenian quartzites. These formations show a considerable degree of metamorphism, which does not exclude their Palaeozoic origin. Also shales and variegated sandstones as well as yellow dolomites and dolomitic limestones may be Triassic in age. Jurassic and Lower Cretaceous sediments are much better represented by white crinoidal limestones, white crystalline limestones, green radiolarites, Globochaete limestones, Calpionella limestones and limestones displaying Radiolaria-Nannoconus microfacies. The presence of Malm-Neocomian pelagic sediments indicates that the sedimentary basin had a good connection with the Alpine geosyncline. A change in sedimentation occurred most likely in the Barremian-Aptian, when organodetrital limestones of Urgonian type could have been formed. Spongy sandy limestones belonging may be to the Albien and Organodetrital limestones, sandstones and marly shales, representing the Senonian?-Palaeogene period of sedimentation, may be regarded as a successive stratigraphie units. The source massif was probably situated near the northern border of the Pieniny Klippen Beltarc (Leśko, Samuel, 1968; Sikora, 1971; Książkiewicz, 1972). During the Middle Eocene the massif was elevated above the sea level, supplying substantial amounts of exotic material to the Magura basin.