Revisiting the Tremiti Islands structural high in the central Adriatic Sea (Italy), new insights from gravity anomaly modelling

In this study we investigate the Tremiti Islands structural high (TISH), north of the Gargano Promontory, to evaluate the possible implications of salt walls and diapirs in the formation and evolution of the archipelago. A series of different datasets, including seismic, gravity, magnetic, and well-log data, were integrated and modelled to unravel the geological and structural setting of the Tremiti Islands. Although detailed modelling of the observed gravity and magnetic anomaly was never attempted, most of the available literature traditionally relates the origin of the TISH to salt diapirism in the wider framework of the Apennine orogenesis during the Plio-Quaternary.

The analysis of seismic profiles combined with gravity anomaly modelling, contrary to the general view, suggest possible but very limited halokinetic salt underneath the TISH. Based on our interpretations, we propose that the TISH structure could be linked to inherited fault reactivation during recent compressional foreland deformation. To support this interpretative view, we test several modelling hypotheses finding that the best-fitting solutions support a configuration with minimal evaporites at depths greater than 5 km. This result contrasts with larger and shallower salt diapirs hypothesized in previous studies. Additionally, the structural interpretation suggests that the TISH features, influenced by both normal and reverse faults, are likely associated with deformation related to at least two tectonic phases in the Paleogene and Late Pliocene-Quaternary times that have affected the Adriatic foreland. Altogether these findings suggest that the structural high possibly developed through positive fault inversion rather than extensional halokinetic structures.