36th International Meeting of Sedimentology June 12–16, 2023 • Dubrovnik, Croatia

During the Eocene period, shallow-water carbonate systems were significantly influenced by climate fluctuations. Following the peak temperatures of the Early Eocene Climatic Optimum (EECO), a general cooling trend began, with short-lived (< 200 Kyr) warming events occurring alongside it. During the early Bartonian (around 40.1 Ma), a warming event known as the Middle Eocene Climatic Optimum (MECO) occurred, lasting approximately 500,000 years. In this scenario the types and calcification rates of marine organisms such as corals and larger benthic foraminifera (LBZ) were significantly impacted by the influence of global CO2 and oceanographic changes, which had a major effect on photic carbonate factories. To better understand the effects of these factors on carbonate factories, a detailed study of shallow-water facies types, distributions, and evolution was conducted. The Middle Eocene Monte Saraceno sequence, located on the eastern margin of the Apulia Carbonate Platform (Gargano Promontory, southern Italy), was selected as an ideal case study to investigate the relationships between carbonate factory types and climatic changes. This study identified two distinct intervals with different carbonate production, separated by a clear, sharp boundary. The lower interval consists of clinostratified thick beds of rudstone to floatstone, mostly made up of various large Nummulites tests, indicating an uppermost Lutetian to early Bartonian age (Shallow Benthic Zone 16–17). In contrast, the upper interval consists of coral floatstone to rudstone with a packstone matrix, rich in branching corals in association with gastropods, bivalves, and rare small LBF. The appearance of Heterostegina in this interval indicates a late Bartonian age (Shallow Benthic Zone 18). By integrating biostratigraphic and stable isotope data, the lower interval, mostly composed of Nummulites, was linked to the MECO and post-MECO intervals, during which higher global temperatures seemed to be tolerated by LBF, as occurred in the Early Eocene. However, the sharp transition to a coral-dominated carbonate factory during the late Bartonian could be attributed to a drop in temperature below the threshold for coral flourishment, rather than a simple facies shift caused by a relative sea-level drop.