Change in the accommodation space and implication on stratigraphic architecture of a carbonate ramp succession: Insight from the Oligo-Miocene carbonate ramp of Maiella, Central Apennines (Italy)

Accommodation is a fundamental concept in carbonate sedimentology. Pomar (2001a) distinguished physical accommodation, controlled by hydrodynamic processes, from ecological accommodation, which depends on the ability of carbonate-producing organisms to build a bioconstruction above the hydrodynamic equilibrium profile. Whereas changes in ecological accommodation explain the transition from carbonate ramps to reef-rimmed platforms, we propose that physical accommodation may also vary independently of relative sea-level change as a consequence of long-term palaeogeographic evolution. This hypothesis is tested using the Oligocene–Upper Miocene of the northern margin of the Apulian Carbonate Platform. The succession comprises three shallow-water carbonate units alternating with deeper-water deposits. All pre-Upper Miocene shallow-water units pinch out landward against the Paleogene substrate, whereas the Upper Miocene succession preserves a complete facies belt. The Oligocene–Middle Miocene architecture has been interpreted as the result of repeated reductions in physical accommodation during relative sea-level falls, when the inner ramp entered the wave-abrasion zone and previously deposited sediments were eroded and redistributed basinward. During Late Miocene, progressive restriction of the proto-Adriatic Basin reduced fetch and, consequently, the depth of wave abrasion. The resulting increase in physical accommodation allowed preservation of a complete carbonate-ramp profile despite subsequent sea-level fluctuations. These results indicate that, over geological time scales, tectonically driven palaeogeographic changes can modify physical accommodation by altering the deep of wave base independently of relative sea-level change. This process extends the accommodation concept of Pomar and provides a new framework for interpreting the stratigraphic architecture of shallow-water carbonate ramps in tectonically evolving basins.