Cenomanian carbonate depositional settings: case histories from central-southern Apennines (Italy).IN: SCOTT R.W. (ED.), CRETACEOUS RUDISTS AND CARBONATE PLATFORMS: ENVIRONMENTAL FEEDBACK-SEPM Special Pubbl.

During latest Aptian to latest Turonian time interval global changes triggered widespread crises that resulted in world-wide anoxic episodes and drastic variations in biogenic assemblages and lithofacies in carbonate sequences. The related carbonate depositional systems changed as well. In this context, the Cenomanian represents one of the keys to understanding the turnover of facies and biota observed in Cretaceous carbonate platforms. In particular, in this time interval, both the eustatic oscillations and the tectonic events of the Periadratic region produced localized emersions and deep physiographic alterations of the Apenninic carbonate platforms. Emersion phases resulted in reduced and discontinuous Cenomanian records in centralsouthernItaly. The Cenomanian strata generally show restricted peritidal deposits and more open lagoon facies, colonized by radiolitids, nerineids, and ostreids. These pass laterally into large, complex mosaics of molluscan bioclastic shoals, closely associated with small caprinid mounds. Cenomanian outcrops of rudist-bearing limestones have been selected to show differences in the sedimentological and/or paleontological characterization. Particular attention was given to the evolution of the different depositional areas that were characterized by shelf-margin conditions vs. areas which suffered restricted circulation. The lithofacies indicate a complex zonation corresponding to transitions from shelf-margin rudist patches and their related debris to semi-restricted areas and tidal flats. Sand-shoal-related deposits also occurred. These sediments built complex sand bodies or “small islands”. “Transition zones” between shelf-margin and semi-restricted environments were characterized by the intercalation of skeletal sands episodically washed back into the inner shelf from the high-energy shelf-margin belt and migrated across the colonized areas. Waves, currents, and/or storm-related events controlled the dispersion of the skeletal grains along active current pathways and/or tide-related small channel networks. Tectonics controlled the relationships between different areas and the creation of the related accommodation space. In addition, the presence of a tectonically induced irregular topography resulted in the coexistence of areas with very different hydrodynamic conditions, allowing colonization by different organic communities and complex distribution patterns of the skeletal debris. As a consequence, Cenomanian lithofacies architecture was significantly heterogeneous.