This study provides the fi rst quantitative carbonate production estimate of an ancient debris reef, represented by the Upper Jurassic reef complex of the central Apennines. The components of carbonate production (Pnet, Psed, and Pgross) have been defi ned entirely on the basis of outcrop data. The reef volume (Pnet) was reconstructed based on the present distribution of the Upper Jurassic reef complex and its relationship with coeval successions of platform and slope. The volume of sediment exported along the slope (Psed) was obtained through the reconstruction of the thickness reduction pattern of the reef-derived sediments, at increasing distances from the platform margin. Several variables have been introduced to overcome the lack of data in some areas.The estimates obtained indicate that the Upper Jurassic reef complex produced a total amount of calcium carbonate equal to 1.7-2.3 times the amount of material retained in the reef complex. This excess volume of sediment produced was redistributed along the slopebasin system, up to a distance of ~55 km from the platform margin. According to the indices commonly used for quantifying carbonate production, the Upper Jurassic reef shows values that are consistently lower than other ancient and Holocene reef systems. The interaction between the sedimentologic characteristics of the reef structure and the hydrodynamic processes is ultimately seen as the main mechanism responsible for the low growth potential and reduced export of reef material. The methodology and the procedure used were designed specifi cally for the site being studied but could potentially be adapted for use in other regions where the data required are diffi cult to access. Isolated coral colonies are a few decimeters to 1 m wide, in life position, toppled or as large coral fragments, apparently without an evident preferential direction of dispersion. Preserved coral colonies have branching and massive morphologies. Bioerosion and microencrusters represent relevant features. They are mainly present in the back-reef zone and are more rare in the reef fl at.Calcifi ed demosponges are present as whole specimens or as large fragments with variable dimensions, growth fabric, degree of reworking, and distribution across the reef complex. Chaetetids are generally more abundant, larger, and better preserved in the back reef, where they form closely packed colonies, whereas they are fairly scarce in the external zones of the reef complex. Stromatopores show the opposite distribution pattern: They are very rare and small in the back reef, whereas they increase in frequency, degree of preservation, and dimensions toward the external reef zones, where several tens of whole stromatopore specimens form densely packed, moundshaped structures, 0.5 to 10 m 2 wide (stromatopore mounds).Microencrustations actively contribute to the reef construction by binding and cementing sediment and other reef components. They are micropeloidal microbialites, organized into different structures (stromatolitic, trombolitic, leioli...
