Relationship between the Cretaceous? “black shales” and Cretaceous oceanic red beds of the Grajcarek Succession – a geochemical approach (Pieniny Klippen Belt, west Carpathians, Poland)

In the Polish Outer Carpathians, the contact zone of the Magura Nappe and the Pieniny Klippen Belt is known as the Grajcarek Succession (Unit). This succession contains the “black flysch” deposits, with controversial age, overlain by the Cenomanian radiolarian shales (CRS), followed by the Turonian through Campanian variegated shales (CORB). All these deposits have been sampled. The major and trace elements were analyzed, as well as relation of trace metals with organic matter content (TOC) was recognized. The studies performed by authors reveal that deposition of the CRS took place under oxygen deficiency condition. The trace-element distribution characterizes the hemipelagic regime of sedimentation of both the upper portion of the “black flysch” (spotty shales) as well as the CRS, which were deposited during increasing sea-level. Enrichment in redox-sensitive elements match was probably due to scavenging by H₂S-rich pore fluids. It suggests that spotty shales and the CRS were deposited under very similar sedimentary conditions. During the Late Cretaceous, crucial change in oceanic sedimentation occurred in the Tethys. The Mid-Cretaceous “black shale” facies were passed into Upper Cretaceous oceanic red beds (CORBs).