Stratigraphic correlation of the Neogene basins in southwestern Anatolia: Regional palaeogeographical, palaeoclimatic and tectonic implications

Abstract

The extensional intramontane grabens that formed in southwestern Anatolia in the Late Cenozoic bear the unique tectono-sedimentary, palaeontological and palynological record of a region that underwent rapid transition from the last compressional pulses of the Alpine orogeny to the tectonic phase of orogen collapse and the onset of neotectonic regime. The change in tectonic regime was accompanied by regional climatic changes, recorded by the sedimentary environments of the basins and evidenced by palaeontological and palynological data. The late Early to mid-Middle Miocene was characterized by a warm and humid subtropical climate with densely forested wetlands. The late Middle to Late Miocene witnessed a change to arid climatic conditions, with grass-dominated steppe ecosystems. The Pliocene climate was warm and humid, with savannah-type open habitats. In terms of their stratigraphic development, the southwestern Anatolian basins form two distinct groups. One group is represented by the Denizli, Söke and Yatağan basins, which commenced their development in the Early Burdigalian and underwent similar phases of environmental change: (1) the Burdigalian phase of alluvial environment and redbed deposition; (2) the Late Burdigalian–Langhian phase of alluvial sedimentation accompanied by the formation of “terminal” lakes; (3) the Serravallian–Middle Tortonian phase of the formation of shallow perennial lakes; (4) the Middle Tortonian–Messinian phase of lake expansion and deepening, followed by shrinking and shallowing; (5) the Pliocene phase of lake expansion and deepening; and (6) the erosional Quaternary phase of two-stage alluvial sedimentation separated by a high-relief erosional unconformity. The other, younger group of tectonic grabens is represented by the Karacasu, Bozdoğan, Çameli and Eşen basins, which commenced their development in the earliest Tortonian and underwent common environmental changes: (1) the Tortonian phase of alluvial environment and redbed deposition, coeval with the phase of lake drying in the Denizli, Söke and Yatağan basins; (2) the Messinian phase of the formation of “terminal” lakes, coeval with the re-establishment of shallow lakes in the three other basins; (3) the Zanclean phase of shallow perennial lakes, coeval with the expansion and deepening of lakes in the other basins; (4) the Piacenzian phase of deep lacustrine environments; (5) the Gelasian phase of shallow lacustrine environments; and (6) the erosional Quaternary phase of two-stage alluvial sedimentation, similar as in the other basins. In spite of the time offset in their development, the two basin groups have been strongly modulated by climate and hence show correlative responses to regional climatic changes. Despite the time offset in their tectonic development, the two basin groups showed correlative environmental changes imposed by regional climatic conditions. The basins were environmentally unified by the Quaternary alluvial phase of their development. In the Late Cenozoic, Anatolia was at the crossroads of fauna migration routes between Africa, Asia and Europe, and the palaeontological data from the southwestern Anatolian basins shed more light on this phenomenon. The study as a whole contributes to a better understanding of the Late Cenozoic environmental, climatical and biogeographical changes in the Eastern Mediterranean.