Traces of coral reefs at Kargı and Sütçüler have been dated to Late Tortonian times. Around 5.6 MYA, the Mediterranean region was hit by the Messinian salinity crisis. Sea levels dropped tremendously, and there was rapid erosion and desiccation. Growth of the fan deltas stopped as the receding coastline left the entire Aksu Basin on land. Deep gorges were carved in the areas that were now exposed as dry land. One of them, now a deep undersea canyon in the Gulf of Antalya, is still traceable in front of the present day Düden and Karaman river mouths. A similar canyon likely existed on the Aksu, but it has since been buried by Quaternary sedimentation on the marine shelf. Poisson et al reconstructed the course of the Aksu River around the end of the Messinian ( 5.3 MYA) this way: the river flowed through the Eskiköy Canyon, then "crossed the Antalya alluvial plain before joining the Antalya abyssal plain, through the actively cutting Antalya canyon". Poisson et al also argued that the Gebiz Limestone was formed during the Messinian, implying that there was still at least a pocket of sea in the Aksu Basin even while the sea retreated. They characterize this environment as "very shallow marine", with coral reefs, which then gradually became more restricted as it gave way to land and eventually dried up completely. This characterization is disputed – Üner et al instead describe the Gebiz Limestone as being deposited after sea levels rose again; Kaya attributes the Gebiz Limestone to the "latest Miocene-early Pliocene", describing it as being deposited by a NW-SE-oriented lake that formed during this period. Kaya's interpretation: the Aksu Basin was a "fluvial, fluvial-delta, beach setting" during the Middle Miocene ( 16-11 MYA), then "a lacustrine and lagoon environment" by the end of the Miocene (i.e. 5.3 MYA). Then, during the early Pliocene ( 5.3-3.6 MYA), there was a relatively brief (at least geologically speaking) period of tidal flat and very shallow marine conditions. Later, there was a "return to entirely terrestrial conditions", and deposition by the ancient Aksu River formed the Belkis Conglomerate during the Pleistocene period. Pliocene Sea levels rose again in the early Pliocene, during the Zanclean period ( 5.3-3.6 MYA). The southern part of the Aksu Basin was submerged, while the northern part remained dry land. The Messinian canyons became filled in by new deposition. The Eskiköy canyon was at