Neogene transitional carbonates: the link between the tropical and the temperate carbonate province

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Water temperature is a major controlling factor for neritic carbonate production. In warm waters, the photozoan association dominates, whereas cool water zones contain the heterozoan factory. Neritic carbonate formation also depends on nutrient levels. High nutrient contents trigger growth of heterozoan carbonate producers, low nutrient levels the formation of photozoan carbonates. Where these end members of carbonate depositional systems are more or less known in the recent and in the geological past, very little data and models exist for transitional systems. This projet addresses this point. Early to middle Miocene neritic temperate to subtropical carbonates in Sardinia will be analyzed in order to develop models for an "intermediate" type of carbonate system. Differences between such systems and true warm and cool water deposits will be presented. Sedimentological, petrological, diagenetical and geochemical analyses (stable oxygen and carbon isotopes) will show the dynamics of this type of carbonate depositional system as a response to sea level fluctuations and palaeoceanographic fluctuations. The sensitivity of neritic carbonates to environmental change will be used to decipher how the global Miocene climatic evolution affected these depositional systems.