Étude stratigraphique du Rosso Ammonitico du Monte Inici (domaine Trapanais, Sicile occidentale) : événements biosédimentaires au Jurassique moyen-Crétacé inférieur

The pelagic Jurassic successions of Western Sicily are dominated by the Tethyan Rosso Ammonitico. In the eastern sector of Monte Inici this lithofacies has been deposited during the Callovian-upper Berriasian interval. In the southwestern and northwestern sectors, it reached the middle Oxfordian and was followed by the deposition of silicified limestones which form a lateral equivalent of Tethyan radiolarites. The base of the studied pelagic succession reveals a high energy environment during the Callovian. It is followed by a low energy period until the upper Kimmeridgian-Berriasian interval, characterised by an intense and cyclic hydrodynamism. This energy decreases during the end of the Berriasian time. During the middle-upper Oxfordian a positive d 13 C peak (d 13 C = + 3 [[perthousand]]) coincides with the highest skeletal diversity, the appearance of the nodular facies in Monte Inici East and the deposition of the silicified limestones in the southern zone. This peak indicates a high biological productivity. On the other hand, the Planula Zone (upper Oxfordian) is characterised by a relative negative excursion of the d 13 C curve (+ 2.3 [[perthousand]]), a decrease of the biodiversity and the local disappearance of protoglobigerinids. The fluctuations of the d 13 C curve are interpreted as variations of global palaeoenvironmental conditions. The heteropy Rosso Ammonitico/radiolarites s.l. is controlled by local palaeotopographic gradients.