GEOLOGY, GEOMORPHOLOGY AND TECTONIC EVOLUTION OF THE LATE CENOZOIC, TRANSTENSIONAL AKSU SEDIMENTARY BASIN, SW ANATOLIA – TURKEY

A series of ~NNW–SSE-trending, subparallel late Cenozoic sedimentary basins are nested within the Isparta Angle and the Anamas–Akseki platform in southern Anatolia. The Aksu Basin (AB), 80-km-long and 6- to 10-km-wide, represents a transtensional, intracontinental depocenter that is currently drained by the modern Aksu River. The landscape and the geology of the AB have been shaped by aggradation and incision of the Aksu River since the early Pliocene. The middle Miocene clastic sedimentary rocks contain abundant limestone and chert–dolerite pebbles, derived from the Triassic rift-drift sequences exposed in the Anamas-Akseki platform to the east. These rocks are locally folded around NW–SE-trending fold axes. Shallow water to lacustrine limestone, marl, calcareous sandstone and tuffaceous siltstone-sandstone become progressively widespread in the Pliocene strata. They display ENE–WSW-oriented, steeply dipping, oblique normal faults, indicating a NNW–SSE-directed and dominantly tensional stress regime across the AB. 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. We recognize in the AB the existence of two major subbasins, Gediz–Yenimahalle in the north and Aksu–Çalkaya in the south, in which lacustrine to fluvial deposits with numerous extensional normal faults occur. 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 the youngest rocks 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. We discuss the structural architecture and tectonic evolution of the AB within the regional tectonic framework of the eastern Mediterranean region.