Chemostratigraphy of the Upper Jurassic (Kimmeridgian–Tithonian) Pałuki Formation of central Poland and its correlation to organic-matter-rich deposits of Western Europe

Geochemical data derived from fine-grained, organic-rich deposits of the Pałuki Formation of central Poland, which are coeval with those of the Kimmeridge Clay of England, are presented. Precise biostratigraphical dating and correlations show strict simultaneity of occurrences of major (≤10.7 wt%) and minor (≤5.2 wt%) organic-rich horizons of the Pałuki Formation from the higher Eudoxus–Pseudoscythica zone interval with their equivalents known from NW Europe. This coincidence is despite a partially different sequence stratigraphic framework of the Pałuki Formation. The calculated chemical redox and palaeoproductivity indices show predominant suboxic and more oligotrophic settings in the lower part of the Pałuki Formation, which are followed by a gradual change of the depositional parameters to more anoxic and eutrophic ones. The uppermost portion of the studied strata is, however, characterized by a decrease in organic matter content and an increase in calcium carbonate content. This phenomenon is interpreted to be a result of gradual climate aridification, being in agreement with local and regional geochemical proxies of weathering intensity. The chemostratigraphical data reported point to orbital forcing of the latest Jurassic climate of NW and central Europe and to synchronicity of its high-amplitude variations.