The shallow water record of the "Monterey Event" within the Central Mediterranean area: a major controlling factor of the carbonate platforms evolution

The middle Miocene is a key time to understand modern global climate evolution and its consequences on oceanographic and marine systems. It is characterised by the so called Mid-Miocene Climatic Optimum (17-13.5 Ma) within... [ view full abstract ]

The middle Miocene is a key time to understand modern global climate evolution and its consequences on oceanographic and marine systems. It is characterised by the so called Mid-Miocene Climatic Optimum (17-13.5 Ma) within which a long-term positive carbon isotope shift, known in literature as the “Monterey Excursion”, is recorded. This work analyses the lower to middle Miocene carbon isotope record of three different domains of the Central Mediterranean, two of them representative of shallow water settings (Latium-Abruzzi and Apulian Platforms), and one representative of an hemipelagic setting (Umbria-Marche Basin). The record identifies the local carbonate platform response to this major global carbon cycle perturbation. Carbon and Oxygen isotope ratios have been measured on whole-rock samples. The stratigraphic framework is provided, by calcareous nannofossil biostratigraphy for the Apulian Platform succession, and through Sr isotope stratigraphy for the Latium-Abruzzi succession, due to the lack of any biostratigraphic marker. Sr isotope ratios have been measured on selected pectinid shells, after a detailed diagenetic screening that allowed to rule out any significant diagenetic overprint. Both platform successions record the Monterey Carbon Isotope Excursion, which coincides with a spread of bryozoans over other carbonate-producing biota due to enhanced nutrient availability and water fertility. The high productivity of the bryozoan dominated factory in the aphotic zone had an important control on their depositional profile. In particular, the high rates of sediment production in the deeper oligophotic and aphotic zones produced a depositional profile of a low-angle ramp.