The Role of Triassic Salt in the Deformation of the Ionian Zone (Albania and Greece)

The Ionian Zone (IZ) of Albania and north-western Greece forms part of the Albanides–Hellenides fold-and-thrust belt (FTB), one of the main mountain systems of the eastern Mediterranean. Its structure is strongly influenced by Upper Triassic evaporites, which acted both as detachments for thrusting and as mobile layers that developed into pillows, diapirs, and salt walls with small minibasins. Above a thick succession of Triassic to Eocene carbonates lies an Oligocene–Miocene flysch, all repeated by west-verging thrust sheets. Alpine deformation began in the late Oligocene and continues today in the external IZ. This study integrates field observations, borehole data, seismic profiles, and physical modelling to investigate how evaporites controlled deformation.

Seismic interpretation provides the most novel results, based on newly acquired profiles migrated to depth using velocities derived from borehole data and laboratory measurements. These sections offer the first image of the deep structure of the IZ by directly linking surface geology with subsurface architecture. They reveal salt detachments, welds, and deep-rooted diapirs incorporated into thrust stacks. The analysis shows how Triassic evaporites influenced both shallow and crustal-scale deformation. Borehole information further indicates systematic lateral variations in evaporite lithology, with halite-rich successions in the west and gypsum–anhydrite units to the east.

Experimental models of salt structures shortened under contraction closely reproduce the geometries observed in the seismic data and in the IZ. The agreement between analogue models and natural examples confirms that precursor diapirs were present and fundamental in localising later Alpine shortening.

These results emphasise the central role of Triassic salt in the deformation of the Ionian Zone and provide new insights into salt tectonics in fold-and-thrust belts, with implications for hydrocarbon exploration and potential geological storage.