STRUCTURAL ANATOMY AND TECTONIC EVOLUTION OF A LATE CENOZOIC TRANSTENSIONAL SEDIMENTARY BASIN, SW TURKEY

The Aksu Basin (AB) is one of a series of ~NNW–SSE-trending, late Cenozoic sedimentary depocenters within the Isparta Angle in SW Turkey, and is a product of transtensional deformation associated with the recent geodynamics of the eastern Mediterranean–Aegean region. The modern landscape and geology of the AB have been shaped by aggradation and incision of the Aksu River in the Plio-Quaternary. The middle Miocene clastic sedimentary rocks in the basin contain abundant limestone and chert–dolerite pebbles, derived from the Triassic rift-drift sequences exposed in the Anamas-Akseki carbonate platform to the east. These rocks are locally folded around NW–SE-trending fold axes as a result of middle to late Miocene shortening in the region. The Pliocene shallow water to lacustrine limestone, marl, calcareous sandstone and tuffaceous siltstone-sandstone display ENE–WSW-oriented, steeply dipping, syn-depositional oblique normal faults, indicating a NNW–SSE-directed, and dominantly tensional stress regime during the latest Cenozoic. Extensive distribution of fanglomerates and fluvial terrace deposits in the Pleistocene sequence points to accelerated transtensional tectonic activities along the edges of the AB and strong downcutting within the fluvial channels in and across the basin. There is no structural evidence for contractional deformation in the post-Miocene sequences within the AB. Extensive tufa deposits to the north and in the city of Antalya are bordering the AB to the SW, and form a series of subhorizontal terrace surfaces descending into the Aksu River Valley. Both the Antalya Tufa deposits and the AB continue offshore into the Bay of Antalya in the south in an asymmetric graben system with southward sediment transport. The Plio-Quaternary transtensional deformation recorded in the Aksu Basin strata has affected the structural architecture and tectonic evolution of the entire Western Tauride belt, which has been undergoing oblique rifting, transcurrent faulting and alkaline volcanism in response to the combined effects of the slab retreat at the Hellenic Trench to the west and the southwestward escape of the Anatolian microplate.