Neogene structural evolution of the area between Mihaliccik and Sivrihisar (Eskisehir, Turkey)

During the post-Cretaceus evolution of Tethys Ocean, Central Anatolia Basins showing intense deformations in Central Anatolia Region have been experienced different tectono-stratigraphic evolutions as a result of the collision of Pontide and Anatolide-Tauride blocks. These basins are also the best examples showing spatial and temporal deformation varieties of the neotectonic regime effects in Anatolia. Study area located in the Sivrihisar Neogene Basin, is represented with the Mesozoic basement rocks of Tavşanlı Zone and the Neogene fluvial sedimentary units lying uncomformably on top. During the deposition of Neogene units, climatic changes and effects of the tectonism caused to the mostly successional and sometimes transitional deposition of clastics, carbonates and evaporitic units. In the beginning of its evolution, the study area was an inter-mountain basin due to the collision of the Anatolide- Tauride and Pontide blocks. Because it is located between the North Anatolian Fault System and İnönü-Eskişehir Fault System, tectonism has been controlling the evolution of the study area. When the field investigations, paleo-stress analyzes and earthquake analyzes are evaluated together, it can be stated that the study area is under the influence of three different tectonic regimes in the neotectonic period. These are the nearly N-S extensional regime affecting the Miocene-Pliocene interval of the region, and the transgressional regime effective from the Pliocene, and the transpressional regime which is active today. Considering the earthquakes that are effective in the region, it may be seen that the region continues its seismic activity nowadays.