35th Meeting of Sedimentology: Prague, Czech Republic 21–25 June 2021

During the middle and upper Eocene significant changes in the benthic communities occurred. The general dominance of large benthic foraminifers (LBF) in shallow-marine environments decreases sharply through the early-late Bartonian boundary (SBZ16–18a), and an abrupt shift to zooxanthellate corals-rich facies is observed, marked by a gradual increase in size, number, and diversity of coral-buildup ecosystems. The Tremiti Islands are located in the Adriatic Sea, less than 20 km northward the Gargano Promontory along the Italian coast and both belongs to the well-known Apulia Carbonate Platform. In this study, middle to upper Eocene LBF and coral facies of the San Domino Formation have been analyzed from sedimentologic, paleoclimatic and paleoecological significance, and finally compared to coeval facies of Monte Saraceno Formation cropping out mainland in the Gargano Promontory. The lower and middle San Domino Fm consists of porous massive, whitish and brownish limestones rich in skeletal floatstone to rudstone mainly dominated by LBF (nummulitids, orthofragminids), echinoids, red algae, bryozoan, small benthic foraminifera and acervulinids (Gypsina). According to the biota assemblage, this stratigraphic interval is indicative of the upper Lutetian to Bartonian p.p. (SBZ 14-16). Instead, the upper part consists of a coral boundstone with corals colonies (Favites, Montastrea, Astrocoenia, Astreopora, Alveopora, Antiguastrea, Actinacis sp., Goniopora sp.) and some solitary corals. They are also associated with scattered orthofragminids (Discocyclina, Orbitoclypeus). The skeletal components and the occurrence of Chapmanina gassinensis in this coral facies, seems to indicate the Bartonian–Priabonian boundary (SBZ 18a). A similar situation is also visible in the Monte Saraceno Fm (Gargano), where LBF are abruptly covered by coral-rich facies. On the contrary of the Tremiti Island, the coral facies have a less pronounced biodiversity and seems to be a little bit younger, as the presence of Heterostegina suggest (SBZ 17-18a middle-upper Bartonian). The stratigraphic and facies architecture in Tremiti Islands and Gargano Promontory suggest as a drastic change in carbonate factory occurs during the upper Lutetian and the Bartonian time interval. At the base LBF dominate, with big and very abundant Nummulites until the early Bartonian, abruptly covered by coralrich facies, not present before, during the early-late Bartonian and at transition with the Priabonian. We interpret this fast switch in carbonate production types as the result of paleoclimatic changes, from warmer interval during the Lutetian and early Bartonian, where LBF were dominant, culminating at ca. 40.1 Ma with the MECO event, and the progressive cooling, after this hyperthermal event, when corals start to thrive in more favorable conditions.