1st Istanbul International Geography Congress Proceedings Book
The controlling factors to the establishment and formation of Kızılırmak drainage around the North Anatolian Fault (NAF) ZoneMustafa Arıkan, Topçu Ahmet Ertek
The Kızılırmak River, the longest stream in Turkey, while flowing from Northeast to Southwest between İmranlı/Sivas and Nevşehir region, makes a large curve in central Anatolia between Nevşehir and Kırıkkale and turns from Southwest to Northeast. After passing through Çankırı region, it abandons Central Anatolian plateaus, plains and runs into the valleys the high mountain chain of Central Anatolia. 1355-kilometers journey from İmranlı to Bafra, which also passes through the North Anatolian Fault Zone and reaches the Black Sea, is a journey that begins and ends within Anatolia. In terms of its masses and being the longest and oldest water flow in Anatolia, it has had a great importance. From this respect, The Kızılırmak River, with its remarkable impact on the formation of river drainage and water basins in the region, and the connection of the Central Anatolian basins to the external drainage, sheds light on the paleo-geographical evolution of Anatolia. The Kızılırmak River, from Central Anatolian plains to the Northern Anatolian Mountains, and from there to Northern Anatolian Fault Zone, and the drainage, formation and development of it during the period of its connection to the Black Sea, and the effects of paleotectonic and neotectonic period movements and changing paleo-geographical environment conditions on that process have been investigated. In this study has benefited from the characteristics of lithological units, tectonic movements that have affected the development of the region, fieldwork observations, morphometric analysis, and previous studies. The region is located in Northern Anatolia, at the conjunction of the Anatolide - Pontide masses formed by the subduction of the Neotethys Ocean under the Sakarya continent and the İzmir - Ankara - Erzincan Suture Zone which developed between the two continent platforms. The extension of these tectonic units, of pre-Eocene foundation in the region, also constitutes the main direction of current topography. The region continued to be affected by N-S directional compression in the Miocene- Pliocene period after the collision and the Anatolites were fragmented by NE-SW trending faults. The courses of Kızılırmak’s flow in the Central Anatolian Plateau, on a large scale, follows the tectonic lines formed by these movements. In the formation of the general topographic structure of the region, important tectonic and paleo-geographical developments have been observed in the Eocene and the later period. In this process, the Eocene Sea, covering vast areas in the region, was later replaced by shallow lakes. After the Eocene, widespread andesitic volcanism shaped important heights of the region, and in a region between the Eocene and Oligocene, there was a paroxysmal phase of the Alpine Orogeny. These movements also determined the direction of the fold axis of the anticlines, and hence, the topographic direction of extensions. During the Miocene period, the lakes, covering large areas in Pliocene, shrunk and disappeared and were replaced by the Kızılırmak River drainage. In the region, the strike-slip morphology created by neotectonic movements, and shrinkage of Miocene-Pliocene lakes gave rise to a new impetus to the paleo-drainage; the E-W extending rift valley in the NAF Zone, which developed in this period, took full control of the paleo-drainage from Pliocene and onward by creating a regional base level. It has been determinant in the formation of the current drainage and the associated fluvial morphology. In the formation of drainage in the region, the direction of the main tectonic units determined by paleotectonic processes and the extension of weak tectonic lines caused by neotectonics have been effective, and the current drainage has been shaped by the ongoing neotectonic movements.