Integrated stratigraphy of Oligocene-Miocene phosphate-bearing layers in the frame of the Central Mediterranean paleoceanography. Insights from the western Hyblean Plateau sedimentary record (SE Sicily, Italy)

The late Oligocene to Early Miocene marked a critical phase in Earth's climate history characterized by the onset and evolution of the Icehouse climate mode, following the Antarctic glaciation at the Eocene-Oligocene transition. During this interval, the Antarctic ice volume fluctuated, driving global sea-level changes and reorganizing oceanic circulation. These changes are recorded by several glacial maxima, including the prominent Mi-1 event, which is associated with deep-sea cooling, sea level fall, and a major reorganization of the global carbon and nutrient cycles. The Early Miocene Carbon Maximum (EMCM) reflects enhanced primary productivity triggered by intensified ocean circulation and increased weathering. Meanwhile, the global carbon cycle became increasingly responsive to astronomic forcing, particularly eccentricity cycles. The phosphorus biogeochemical cycle also reorganized, with phosphogenesis events documented in both the Atlantic and Pacific oceans. This study investigates the Oligocene–Miocene interval in the Central Mediterranean, focusing on the largely investigated phosphatic layers of Southeastern Sicily (Hyblean Plateau). Through integrated calcareous plankton biostratigraphy and Strontium Isotope Stratigraphy, three main hiatuses are identified, corresponding to glacial events (Oi-2d, Mi-1, Mi-1a, Mi-1aa, and Mi-2). These hiatuses are locally associated with condensed, phosphate-rich layers linked to the upwelling of nutrient-rich waters and sea level fall. The occurrence and distribution of these layers highlight the Mediterranean's sensitivity to global climatic and biogeochemical shifts during the early Icehouse mode. This work provides new stratigraphic constraints and paleoceanographic interpretations, highlighting how glacial dynamics, ocean circulation, and regional tectonics influenced nutrient availability, phosphogenesis and sedimentary facies distribution during the Oligocene–Miocene.