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The Late Paleogene Çankırı Basin of Türkiye: The geologic record of lithospheric foundering beneath the Central Anatolian Plateau

Year: 2025

Type: article

Abstract: We hypothesized that the Çankırı Basin of Türkiye records lithospheric foundering beneath the Central Anatolian Plateau in Late Paleogene time. Geologic mapping and stratigraphic sections supplemented by detrital zircon U-Pb and Hf isotopic analyses demonstrate that a 7500 km2 saline lake developed within a 125 × 75 km box-fold along the İzmir-Ankara-Erzincan Suture Zone at ca. 37.5 Ma. Lacustrine environments mark the transition from polymodal to bimodal detrital zircon age spectra during the onset of a trend toward crustal εHf(t) values. Such geologic and geochemical changes are consistent with subsidence above thickening lithosphere. At ca. 32.5 Ma deposition transitioned to volcanogenic-alluvial, fluvial, and lacustrine environments along the northern margin of the Çankırı Basin. Detrital zircon from such deposits return to polymodal age spectra and record a 15-unit εHf(t) mixing array. Such changes are consistent with unroofing and multi-source melting during isostatic rebound above foundering lithosphere. Today, the Çankırı Basin resides within an elliptical ~750-m-high topographic depression that is bisected by the north-northeast flowing Kızılırmak River and surrounded by rugged landscapes reaching elevations of ~1500 m. Such radial physiographic symmetry exhibits a wavelength of ~250 km (50,000 km2) and further defines the Sarıcakaya-Kızılırmak and Yeşilırmak-Kızılırmak river drainage divides. Indeed, both drainage divides are underlain by a slow shear wave velocity geophysical anomaly. Thus, the geomorphological expression of drip tectonics endures today. Our results, therefore, demonstrate that upper plate lithospheric removal along the İzmir-Ankara-Erzincan Suture Zone began in Late Paleogene time and is tied to the ongoing development of the Central Anatolia Plateau.

Source: Geological Society of America Bulletin

DOI: 10.1130/b38453.1

Authors: C.F. Campbell, M.H. Taylor, M.A. Mueller, A. Licht, F. Ocakoğlu, K.C. Beard