Neotectonic Characteristics of the Inonu-Eskisehir Fault System in the Kaymaz (Eskisehir) Region: Influence on the Development of the Mahmudiye-Cifteler Basin

Abstract

The Inonu-Eskisehir Fault System (IEFS) is a NW- to WNW-trending zone of active deformation about 15-25 km wide, 400 km long and characterized predominatly by strike-slip faulting. In this study, the Yorukkaracaoren (SE of Eskisehir)-Sivrihisar section of the IEFS was investigated. The system consists of three fault zones, namely the Alpu Fault Zone (AFZ), the Eskisehir Fault Zone (EFZ) and the Orhaniye Fault Zone (OFZ) in the study area. The EFZ is made up mostly of N30 degrees W-trending right-lateral strike-slip fault segments with normal components. However, the AFZ and OFZ are composed of E-W-trending normal and NE- to NW-trending strike-slip fault segments. The Mahmudiye-Cifteler-Emirdag basin is one of several strike-slip pull-apart basins along the Inonu-Eskisehir Fault System. It is an actively-subsiding NW-trending depression about 25 km wide, 85 km long located between Yortikkaracaoren and Emirdag. It contains two infills. The older and deformed (tilted and folded) mull, which rests with angular unconformity on the erosional surfaces of pre-Miocene metamorphic and non-metamorphic rocks, consists predominatly of lacustrine carbonates. The younger and undeformed basin infill (neotectonic mull) is composed of upper Pliocene-Holocene terrace deposits, alternations of sandstones, lacustrine mudstone to thin limestones and alluvial fans. The two basin infills separated by an angular unconformity, the deformation pattern of the older basin infill and the active bounding strike-slip faults all indicate the superimposed character of the Mahmudiye-cifteler-Emirdag pull-apart basin.