Characteristic features and structural evolution of a post collisional basin: The Sivas Basin, Central Anatolia, Turkey

The ENE-SSW trending Sivas Basin is located at the easternmost wedge-like tip of the Central Anatolian Block and exhibits characteristics of two other basins, one in west-central Anatolia and the other in eastern Anatolia. The Sivas Basin started to form within a collisional mosaic during Maastrichtian time with the Pre-Maastrichtian basement, the latter composed of continental metamorphic rocks, Jurassic-Lower Cretaceous platform carbonates of the Tauride Belt, and ophiolites and ophiolitic melánge derived from closure of the northern branch of Neo-Tethys. Similar Tertiary basins were developed on comparable collisional mosaics in other parts of Anatolia.The Sivas Basin is asymmetrical in both the longitudinal and transversal directions. Its infill is dominated by a thick Maastrichtian-Tertiary shallow marine-continental succession resting unconformably on Pre-Maastrichtian basement rocks and dissected into several subbasins. This infill consists of post-collisional deposits which overlie paleotectonic units unconformably and each subbasin is bounded by northeast–southwest trending oblique-slip faults exhibiting dominant strike-slip. The subbasins are characterized by contrasting stratigraphic successions, although all are composed of interstratified continental and shallow-marine facies. Both the northern and southern margins of the subbasins include Upper Eocene olistostromes containing mega-blocks of varied origin. The latter are sourced in paleotectonic units and were reworked in a shallow-marine depositional setting. The fill of the middle subbasins exhibits strong vertical and lateral facies changes, characterized by local and regional unconformities and includes continental to shallow-marine volcanic rocks.This basin was deformed under north–south-directed compression during Late Pliocene-Quaternary times during the neotectonic phase of deformation. This deformation divided the basin into new, small-scale, mainly pull-apart subbasins including those at İmranlı, İşhanı, Altınyayla and Şarkışla. From stratigraphic and structural correlations, a post collisional intra-continental basin model for the Sivas Basin is preferred.