The Yalvaç Basin is a sedimentary basin in Turkey, around Lake Beyşehir and the present-day town of Yalvaç. It lies within the geological region known as the Isparta Angle. It has existed since Miocene times.
General description.
The Yalvaç Basin is a sedimentary basin located in the northern tip of the Isparta Angle. It generally runs from northwest to southeast and is about 55 km long and 15 km wide. Lake Beyşehir occupies its southern part, while at its northwestern end is the village of Yarıkkaya. To the north, east, and west, the Yalvaç Basin is bounded by mountains, such as the Sultandağları mountains.
The Yalvaç Basin's shape and size have been mostly the same since its formation, either during or shortly before the Middle Miocene, and sedimentary deposition has been occurring here since then.
Stratigraphy.
The Yalvaç Basin consists of four main geological formations, from oldest to youngest: the Bağkonak Formation, the Yarıkkaya Formation, the Göksöğüt Formation, and the Kırkbaş Formation. Their total thickness is about 800 m. Below these are basement rocks of diverse origin including ophiolites, metamorphic rocks from the Afyon zone, and non-metamorphic rocks that originally came from the Tauride fold and thrust belt and were thrust here in Cretaceous through Eocene times.
Faults.
The edges of the Yalvaç Basin are marked by various large-scale normal faults. Within the basin, there are many medium-sized faults with displacements of a few centimeters to a few meters. The primary fault directions are northwest–southeast and northeast–southwest, indicating that the local tectonics are controlled by two main "zones of weakness".
The most prominent fault zone in the area is the Yarıkkaya Fault Zone. It runs west toward the Karacaören Fault and east toward the Sultandağları mountains, where it dies out. Another zone is the Çakırçal Fault Zone, which goes northwest–southeast for over 15 km and is itself interrupted by the eastern part of the Yarıkkaya Fault Zone. Then there is the Sağır Fault Zone, which forms an 18 km-long valley running northwest–southeast west of Sağır. It is also cut up by the Yarıkkaya Fault Zone, as well as by the northeast–southwest-trending Kumdanlı Fault Zone. The Kumdanlı Fault Zone itself runs for about 20 km, from Mısırlı in the northeast to south of Aşağıtırtar in the southwest before disappearing into Lake Hoyran. Its northeastern end disappears into the Yalvaç Basin's sedimentary infill. Another fault zone is the northeast-southwest Yaka Fault zone, which is about 6 km wide and over 20 km long. It runs from south of Gelendost at its southwestern end to near Madenli in the northeast. The Yaka Fault Zone controls the southern margin of the Yalvaç Basin and separates the Yarıkkaya Formation from the underlying basement rocks.
References.
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