Miocene C-isotope signature from the central Apennine successions (Italy): Monterey versus regional controlling factors.

The C-isotope composition of a Miocene carbonate succession from the Latium-Abruzzi sector of the Central Apennines was studied to evaluate the influence of local vs. global factors in changing d13C. We propose that the Oligo-Miocene igneous activity of the Western Mediterranean and the closure of the Indo-Pacific connection influenced climate change and Mediterranean sea-water circulation. The huge Aquitanian- Burdigalian volcanic activity during the formation of the Ligurian-Provenc¸al Basin, with related increase in atmospheric CO2, may have accelerated weathering and hydrological cycling of nutrient inputs in coastal environments. The closure of the Indo-Pacific connection altered the circulation by changing and reversing the western exchange flow. The existence of warm and seasonally humid climate favoured the development of estuarine circulation, which was to lead to a dramatic increase in productivity in the euphotic zone.