Özet:

The Kızılırmak is the longest river in Turkey, extending from the western part of eastern Anatolia to the Black Sea, and crossing the orogenic Central Anatolian Plateau (CAP) and Black Sea Mountains. This study focuses on the formation period of the drainage system of the Kızılırmak River in the Cappadocia region, which is situated in the middle of the CAP. The Upper Pliocene-Quaternary geological and geomorphological stratigraphy of the Cappadocia region was revised with new findings and those of previous studies. In this study, the oldest terrace (Sünnetli Tepe Terrace, T0) of the Kızılırmak River was identified 214 m above the current river level. The terrace deposit is located between the Pliocene lacustrine Kışladağ Limestone Member (~5-2.7 Ma) and the ~2.7 Ma Valibaba Tepe ignimbrite. A minimum age for the terrace deposits was provided by the Valibaba Tepe ignimbrite, which caps the terrace. Therefore, the terrace T0 revealed that the Kızılırmak River drainage system existed in the eastern part of the CAP after the deposition of the Kışladağ Limestone Member (~5-2.7 Ma ago) and before the formation of the Valibaba Tepe ignimbrite 2.7 Myr ago. Contrary to most previous studies, this finding shows that Valibaba Tepe ignimbrite cannot be included in the Late Miocene-Pliocene Ürgüp Formation, which formed under an extensional tectonic regime and was incised by the Kızılırmak River. The data obtained showed that 17 of the Kızılırmak River terraces that have formed since ~2.7 Ma have been preserved to the present day.

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