BLOCK ROTATIONS AND STRIKE-SLIP TECTONICS IN WEST ANATOLIAN EXTENSIONAL PROVINCE: PRELIMINARY PALEOMAGNETIC, GEOCHRONOLOGICAL AND STRUCTURAL RESULTS FROM ÝZMIR BAY AREA

The West Anatolian Extensional Province is an important element of the Africa-Eurasia collision. It is dominantly shaped by a series of E–W-trending detachment and high-angle normal faults currently experiencing an approximately N–S continental extension. Field-based studies carried out in Izmir Bay area have revealed a NE-trending crustal scale zone of weakness defined in a region located between Izmir and Balıkesir which is in good agreement with these features: the Izmir-Balıkesir Transfer Zone. It bounds the E-W trending Gediz, Küçük Menderes and Büyük Menderes grabens, the Menderes metamorphic core complex and related detachment faults from the west. Recent paleomagnetic studies have revealed that the area is characterized by incoherent block rotations and is proposed to be the evidence of strike-slip nature of the zone. At least two generations of basins are superimposed in the Izmir bay area. The older basin is represented by a NE-SW trending depression that filled with lower to upper Miocene lacustrine sedimentary units intercalated with calc-alkaline to alkaline volcanic rocks. The younger basin cut across the older one and is characterized by the E-W to NW-SE trending Izmir bay filled with Plio-Quaternary alluvial fan-fan delta to shallow marine sediments. In order to better understand the timing and distribution of deformation and block rotations, we have initiated a comprehensive study in the region using paleomagnetic, geochronological (⁴⁰Ar/³⁹Ar) and structural methods mainly concentrated on the Neogene units including Miocene lavas and sedimentary rocks. In this contribution we will discuss the preliminary results of these studies.