Stratygrafia dewonu antykliny Dębnika

Abstract

Na podstawie nowych otworów wiertniczych oraz obserwacji odsłonięć i dotychczasowej literatury przedstawiono schemat lifostratygraficzny dewonu okolic Dębnika. Wyróżniono 6 nieformalnych jednostek (od dołu): dolomity ze Zbrzy, wapienie dębnickie, wapienie gruzłowe, wapienie ziarniste, wapienie płytowe oraz wapienie ziarniste i mikrytowe. Przedyskutowano również aspekty bio- i chronostratygraficzne dokonanego podziału. Granica eiflu z żywetem przebiega w obrębie lub poniżej dolomitów ze Zbrzy, żywetu z franem - w pobliżu kontaktu wapieni dębnickich i gruzłowych oraz franu z famenem – w obrębie wapieni płytowych. STRATIGRAPHY OF THE DEVONIAN OF THE DĘBNIK ANTICLINE The Devonian and Carboniferous carbonates outcropping near Dębnik in southern Poland (Fig. 1) form a unique reference section which is important for detailed correlations with similar deposits covered by the Carpathian nappes and underlying the Upper Silesian Coal Basin. Basing on the cored borings (Figs. 2-3) and on outcrops six informal lithostratigraphic units have been described representing the Devonian sequence of this area (from base to top):1. Zbrza Dolostone - thickness over 260 m (PI. II, Figs. 8-11).2. Dębnik Limestone - 35 m (PI. III. Figs. 12-15; PI. IV, Fig. 17).3. Nodular Limestone - 28 m (PI. I, Fig. 5; PI. IV, Figs. 16, 18).4. Grained Limestone - over 34 m (PI. V, Figs. 19-21).5. Platy Limestone - over 70 m (PI. I, Fig. 6; PI. V, Fig. 22).6. Grained and Micritic Limestone - thickness unknown (PI. I, Fig. 7; PI. VI, Figs. 23-26).The described carbonates rest discordantly on the quartz porphyry intrusion of the post-Devonian age. Their upper boundary is unknown and overlying Lower Carboniferous strata are developed in highly comparable carbonate platform lithofacies.The lack of key fossils precludes dating of the basal part of the profile. The lowermost biostratigraphic data were obtained from near the contact of the Zbrza Dolostones with the Dębnik Limestone. They point to the Givetian age, just below the Polygnathus asymmetricus conodont Zone. Basing on the conodonts the Givetian/Frasnian boundary corresponds more or less to a lithologic transition between the Dębnik Lst. and the Nodular Lst. The Frasnian/Famennian boundary runs within the Platy Lst. unit. The youngest conodont fauna found within the lower Grained and Micritic Lst. unit corresponds to the crepida-rhomboidea Zones of the standard conodont division.