New insights on diapirism in the Adriatic Sea: the Tremiti salt structure (Apulia offshore, southeastern Italy)

The reinterpretation of public seismic profiles in the Adriatic offshore of Gargano (Apulia, southern Italy) allowed the detection of a kilometre-scale salt-anticline, the Tremiti diapir, within the larger Tremiti Structure. This anticline was generated by diapirism of Upper Triassic anhydrites within a thick Mesozoic to Quaternary basinal sedimentary succession. Both internal stratal patterns and shapes of Plio-Quaternary units, and the occurrence of an angular unconformity between early Tortonian and Pliocene rocks on the Tremiti Islands, suggest that halokinesis began during the late Miocene and is still active today. An ancient extensional SE dipping fault, cutting an older Mesozoic low-amplitude anhydritic ridge, played an important role during salt mobilization, which was promoted by NW-SE shortening. The diapir grew in the footwall of this fault, causing its upward propagation. In some places, the ancient fault served as a preferential channel for the upward migration of the anhydrites.