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Late Miocene to Recent Drainage Evolution in Turkey: Major Provenance for the Eastern Mediterranean Basin

Abstract

Turkey is one of the main source areas for the Black Sea and eastern Mediterranean seas. It is characterized by three main morpho-tectonic domains; the Pontides in the north, the Taurides in the south and the Anatolides in the center. The Anatolides are characterized by Mesozoic to early Cainozoic metamorphic rocks constituting the Central Anatolian Plateau (CAP). Based on our topographical analysis, it seems that the drainage network in Turkey is directed to the NW at present. However, prior to the rise of the Taurides, it was directed oppositely towards the SE during which western Anatolia and the Pontides were topographical highs while the southern and the eastern Anatolia were lowlands if not covered by sea, evidenced by the presence of Late Miocene marine deposits as far north as Konya-Karapınar-Niğde area, placing the late Miocene coastline north of the Taurus Mountains that rise up to 2200m above mean sea level. In eastern and southeastern Anatolia, the marine conditions prevailed until the end of Serravalian (~10Ma) hence the CAP and much of Turkey was part of the Eastern Mediterranean hinterland. Nowadays, the CAP is characterized partly by several large scale isolated (internally drained) drainage basins like Tuzgölü and Konya that have accumulated lacustrine marls and limestones overlain by actively accumulating salt deposits while other parts of the CAP drain to the Black Sea Basin via severely deflected river valleys of the Sakarya, Kızılırmak, and Yeşilırmak rivers. This change took place around 6 My ago due to uplift of the Taurides in response to the slab-edge processes related to northwards subducting oceanic lithosphere of the African Plate along the South Aegean-Cyprian subduction system below Anatolia. These processes gave way to the tilt of the CAP thereby reversing the flow directions of all drainages from SE to NW into the Marmara and Black Sea basins. All of these processes collectively resulted in not only the drainage reversal but also in the shrinking of hinterland of Adana-Cilicia and Antalya basins while the CAP got severely incised. Wind-gaps (drainage beheading) and associated drainage characteristics preserved in the present drainage divides, accompanied by high angle stream segments (of same Strahler Order) and downstream located water-gaps (drainage capture) provide evidence for the reorganization of the drainage within the CAP. The major consequence of this reorganization is the change in the type and volume of the sediment load that has been transported to their ultimate location, the Black Sea and the eastern Mediterranean basins. Since, the petrography of the sediments strongly controls the quality of reservoir rocks, the known hydrocarbon exploration provinces like the Adana-Cilicia and Antalya basins have experienced such changes in the type of the supplied sediments and provenance characteristics. In this contribution, we present one of the many examples of how the reorganization of drainage has taken place as a consequence of the uplift of the Taurides in Turkey.