Paleostress inversion of fault-slip in the Ayhan Basin, Kırşehir Block (Turkey) since the Late Cretaceous: Insights into the Neotethys closure

Abstract

Kırşehir Block, a large triangular continental domain exposed in Central Anatolia, is surrounded by ophiolitic melanges that mark former subduction zones associated with the closure of the northern and southern branches of the Neotethys Ocean. Notably, the Ayhan Basin, located in the inner part of the block, is one of the few locations containing a geological record from the Upper Cretaceous to the Pliocene. It provides a unique opportunity to examine the crustal deformation and the temporal and spatial stress distribution over the Central Anatolian orogen. This study encompasses a comprehensive analysis of the Ayhan Basin’s stratigraphy and structure, combined with the paleostress inversion solutions derived from over 400 fault-slip data. The findings reveal that the Ayhan Basin underwent three distinct tectonic phases: (1) ∼ NE-SW extensional phase from Late Cretaceous to Lutetian, which refers to the main basin-forming stress configuration. Importantly, this extensional phase is crucial to delineate the spatial extent of the concurrent collision in the north. (2) ∼ N-S compressional phase during the Lutetian, mainly governed by the shortening of the Kırşehir Block. This compressional phase caused the inversion of the inherited normal faults in the basin; and (3) ∼ NE-SW extensional phase active since the Late Miocene was accompanied by volcanism and uplift in the region. The Cyprus Slab’s southward retreat might be this extension’s triggering mechanism. Consequently, the temporal and spatial extent of the tectonic phases and their resultant deformations are crucial for understanding the underlying geodynamic processes and establishing their timing.