Neotectonic evolution of an actively growing superimposed basin in Western Anatolia: The inner bay of i̇zmir, Turkey

Abstract

İzmir Bay is an actively growing shallow marine basin controlled by active faults trending NE, NW, N-S and E-W, in the West Anatolian Extensional Province. The bay of İzmir is a lazy L-shaped superimposed basin which is topographically divided into an E-W-trending inner bay and a NW-trending outer bay. The Inner Bay of İzmir is an asymmetric graben structure approximately 5-7 km wide and 25 km long containing (i) upper Cretaceous-Palaeocene basement, (ii) an older succession of lower to upper Miocene basin fill, overlain with angular unconformity by (iii) a younger Plio-Quaternary basin fill. The older succession contain a 0.5- to 1.5-km-thick, folded and coal-bearing continental volcano-sedimentary sequence. The younger succession of the Inner Bay of İzmir includes the upper Pliocene-Pleistocene Görece formation and Holocene to recent alluvial fan, fan delta to shallow marine deposits. The is study reveals that the İzmir Bay region was above sea level and the site of a NE-SW-trending lacustrine environment associated with calc-alkaline to alkaline volcanism during the early to late Miocene. By the late Pliocene the modern coastal areas of İzmir were inundated beneath the waters of the Aegean Sea by the creation of the E-Wtrending Inner Bay of İzmir. Detailed geological mapping, geomorphological evidence and computer-based kinematic analysis show that the tectonic evolution of the basin since the early Miocene can be divided into four stages. Two early extensional stages resulted in the formation of NE-SW-trending lacustrine volcano-sedimentary basins; the third stage, characterized by dip- to strike-slip faulting, deformed the older basin fill units, and the final extensional stage resulted in the opening of the Inner Bay of İzmir since the Late Pliocene. © Tübi̇tak.