The Upper Cretaceous carbonates of the Gargano-Murge region, southern Italy: A model of platform-to-basin transition

Abstract

The outcrops in Gargano-Murge region are good examples of the Upper Cretaceous carbonate systems of the peri-Adriatic area. They enable the architecture and the processes of the platform-to-basin transition to be studied in detail. The platform carbonates are juxtaposed to the deeper marine carbonates by the intermediary of a faulted scarp. The base-of-slope is characterized by bioclastic and conglomeratic aprons interbedded with pelagic mudstones. The outer shelf domain, which was the prolific source of rudistid bioclastic aprons, is not preserved. The platform is mainly built of mud-dominated transgressive systems tracts, whereas highstand systems tracts are developed as bioclastic base-of-slope aprons. The volume of the resedimented bioclasts largely exceeds the volume of missing outer shelf, indicating that carbonate production and sediment bypass are more critical for this stratigraphic response than carbonate erosion. The lowstands, which were controlled by tectonic deformations, are characterized by base-of-slope breccia and blocks eroded from the shelf edge. This erosion resulted in the progressive retreat of the shelf edge. The best potentials for hydrocarbon reservoir are found in the bioclastic base-of-slope aprons formed during the Cenomanian and Maastrichtian highstands. This model is considered as an analog for the hydrocarbon reservoirs formed by the deep marine deposits of Cretaceous Tamabra limestone in the Gulf of Mexico.