Tectono-stratigraphic investigation of Yahşihan (Kirikkale) and it's surrondings

The Upper-Cretaceous/Lower-Tertiary Kırıkkale sedimentary basin is an ideal locality to study the tectono-stratigraphic evolution of a basin within a collisional tectonic setting. Located ca. 50 km east of Ankara, the basin lies in the İzmir-Ankara-Erzincan suture zone. This lineament marks the former boundaries of Gondwana-related microplates to the south (the Menderes-Tauride zone) and Eurasia-related plates to the north (Pontide zone). The basin abuts an inferred microcontinent (the Kırşehir Masif) and an accretionary complex (the classic Ankara Melange) ? a product of the northward subduction of the Northern Neo-Tethys Ocean during the Mesozoic. Structurally, the basin developed on the Ankara Melange, which is locally faulted against Palaeocene and Cretaceous basin sediments ?a result of regional contraction following Lower Tertiary continental collision. Previous work has modelled brittle thrust-faulting within the basin. This study, however, favours a model of soft syn-sedimentary folded deformation. Later (Miocene and younger) mainly SW-NE trending oblique-slip faults cut the basin. Basin sedimentation is as follows; 1) Upper-Cretaceous volcaniclastic grain flows inter-bedded with biotite-phyric lavas of intermediate composition (the Ilıcapınar Formation) pass into shales and sandstone turbidites (the Bölükdağ Formation); 2) Palaeocene volcaniclastic turbidites inter-bedded with carbonate olistostromes (limestone debris flows) and olistoliths (solid limestone blocks) make up the Dizilitaşlar Formation; 3) Lower Eocene shales and sandstone turbidites (Bulanıkdere Formation) pass upwards into deltaic sandstones (Mahmutlar Formation) then into fluvial/deltaic clastic conglomerates (Karagüney Formation) and transgressive nummulitic limestones (Bahşili Formation); 4) Oligo-Miocene clastic fluvial conglomerates and lacustrine evaporites. Further interest is added by the intrusion of a collision-related hornblende-phyric granitic plüton in the basin margin during the Palaeocene. The exhumation and unroofing of which formed the granitic clast-rich Mahmutlar Formation.