Chemostratigraphy and mineralogical characterization of Piacenzian sapropels cluster A (2.75–2.57 Ma) in the Gelasian GSSP type-section of Monte San Nicola (Sicily, Italy): Paleoenvironmental and paleogeographic implications

Abstract

Mineralogical, geochemical and stable isotope (δ¹⁸O, δ¹³C) data from Marine Isotope Stages (MIS) G4 to 103 are here presented. The studied interval includes the sapropelic cluster A (A2-A5) from the Gelasian GSSP type-section, outcropping at Monte San Nicola (Sicily, Italy). The studied section exhibits a good response of the δ¹⁸O measured on the bulk carbonate to the Earth's astronomical parameters. The sapropelic red/brown layers (A2- A5) are alternated to grey marls and this cyclicity is clearly evident by the difference in colour, organic matter content, redox-sensitive elements and runoff indicators, tied to the precession/insolation cycles. Further, the obliquity signal is well evident in paleoproductivity indicators and mineralogical composition, driven by glacial-interglacial cycles. The obtained dataset has allowed the reconstruction of the paleoenvironmental conditions during marls/sapropels deposition, which appears to be influenced by the precessional forcing that induced strong changes in the marine water circulation. This scenario is also integrated by an original paleogeographic model including the presence of a high topographic structure in SE Sicily that limited water exchanges between the Ionian and Central Mediterranean Seas during sea level drawdowns, caused by glacial phases, triggered by obliquity minima.