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Inorganic geochemical records of local palaeoenvironmental variability in the Jaworki Formation (Upper Cretaceous) of the Niedzica Succession, Pieniny Klippen Belt (Western Carpathians)

Wójcik-Tabol P.

Studia Geologica Polonica

2008

Vol. 131

269-280

The Cenomanian sequence of marls and marly shales interbedded by black shales (Jaworki Formation) from the Niedzica Succession was investigated. These organic carbon-rich horizons may correspond to the event of global anoxity OAE 1d. Major and trace element profiles mirror changing environments of deposition of black shales. In black shales, the content of SiO2, Al2O3, Fe2O3, K2O, TiO2, P2O5 increases at the expense of CaO. All samples are characterised as mixtures of terrigenous- detrital matter with varying amount of calcium carbonate. A good correlation between SiO2, Al2O3, K2O, TiO2, and the correlation with the minor elements Zr, Rb and Nb, point to the detrital origin of these elements. Detrital input was rather scarce. The high trace element/Al ratios in the black shales can be explained either by the adsorption onto organic matter or through the sulphides precipitation. Some black shale-samples are poorer in transitional metals. The studied sediments were deposited under oxic/suboxic conditions interrupted by irregular anoxic periods resulted from expansion of oxygen minimum zone (OMZ).