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Carbonate platforms grow through the precipitation, transport, and final deposition of carbonate sediment out of seawater. Quantifying the relative contributions of initial production versus subsequent transport in determining the growth rates and geometries of platforms remains a significant challenge. In this study, stratigraphic forward modeling is used to quantify the roles of sediment production, transport, and deposition during each growth stage of a Permian-Triassic carbonate platform with a complex growth history. Parameter optimization and sensitivity analysis show that, within the range of reasonable values, the morphology of the platform is most sensitive to sediment transport, moderately sensitive to maximum carbonate production rate, and least sensitive to the productivity-depth curve. The ramp-to-high relief, steep-sloped platform transition during Early Triassic time can be explained by any factor that limits sediment transport from shallow water areas of high production to the slope and basin. Reefs may play a role in limiting sediment transport on many platforms but other processes, such as early marine cementation or carbonate production along the slope, may be equally capable of yielding this shift in platform geometry. In this particular case, early lithification of ooid and skeletal shoals on the platform margin, perhaps facilitated by unusually high carbonate saturation state of seawater, may have inhibited sediment transport into the basin prior to the development of a reef on the platform margin. Later, Anisian progradation of the platform margin can be explained by the development of a slope factory rather than requiring increased sediment transport from the platform top. The development of an escarpment margin in the Ladinian is mainly influenced by accommodation in the slope profile created by antecedent Anisian topography. A general implication from the model results is that the growth of steep-sloped carbonate platforms lacking slope factories may often be limited by transport of sediment from the platform top to accommodation on the slope rather than by the intrinsic production capacity of the platform top factory.

The most different faunal and floral assemblages have experienced several events of extinction, diversity reduction and diversification during Cretaceous. Such events are basically coeval to rapid reorganizations of the regional-to-global hydrosphere/atmosphere systems following relevant geotectonic pulses. Biotic assemblages shifted repeatedly among phases of carbonate production modes dominated by oligotrophic specialized and meso-eutrophic opportunistic taxa, namely k- and r-mode forms, as a consequence of major turning points in the evolving paleoceanographic conditions. Stratigraphic data on several Cretaceous successions of southern Apennines and Apulia (southern Italy) have demonstrated that brachiopods were a main component of r-mode assemblages which developed in Latemost Valanginian, late Early Aptian, earlymost Cenomanian, and latemost Campanian. With the exception of the latemost Campanian event, all of these time intervals correspond to severe global environmental disruptions of the oceans and climate coupled to biocalcification crises. However, all of them correlate to Tethyan oceanic anoxic events (Weissert and Selli OAEs) and/or platform drownings (Late Valanginian, late Early Aptian, Early Cenomanian and latemost Campanian). Noteworthy, all of the investigated events reflect regional shifts among chlorozoan, foramol and microbial production modes of the mediterranean shallow-water carbonate factories. The remarkable association of brachiopoda with cyanobacteria, though in complex stratigraphic relationships, especially in Late Valanginian, late Early Aptian, and Early Cenomanian times accounts for drastic environmental deterioration of the surface oceanic waters which were highly unfavourable for oligotrophic, k-mode organisms. We assume that such a relevant correlation between Cretaceous brachiopod beds and disruptions of the paleoceanographic conditions may provide an additional tool to improve the comprehension of the internal structure of major paleoecologic changes due to the environmental collapse of oceanic waters during drowning events of carbonate platforms and/or OAEs.

Volume dei Proceedings del COFIN 2000 (vedi titolo del libro) presentati in occasione del Workshop tenuto a Pozzuoli (NA) il 25-27 Febbraio 2003.