TECTONIC EVOLUTION OF WESTERN ANATOLIAN EXTENSIONAL PROVINCE DURING THE NEOGENE AND QUATERNARY

In western Anatolia there are about ten approximately East-West trending grabens. They are about 100-150 km long and 5-15 km wide. The data obtained on timing and history of development of the grabens, as a result of an extensive geological mapping, revealed the following evolutionary history; during the Early-Middle Miocene period thick volcano- sedimentary associations were formed within approximately North-South trending fault- bounded continental basins under in East-West extensional regime. The coeval sedimentary rocks of similar lithofacial characteristics cropping out extensively suggest that interconnected lake basins invaded the entire Western Anatolia in which low energy lacustrine sediments were deposited. During this period magmas were emplaced along the North-South trending tensional openings. The magmatic associations of this first phase are high-K, calk-alkaline and hybid.

During the late Miocene North-South extension started. During this period major breakaway faults began to form around Bozdag, located in the central part of the region. Consequently Bozdag began to rise. The depositional respons of this elevation is red, coarse clastics deposited along the periphery of Bozdag. Away from the Bozdag high clastic rocks pass laterally into white lacustrine limestones.

During the Late Miocene-Early Pliocene period sporadically developed alkaline basalts were formed. The North-South extension ceased for a brief period to the end of Early Pliocene, and a regionwide erosional surface was formed consequently. When the North- South extension was reactivated the present graben system began to form. The East-West trending graben-bounding faults cut and disconnected continuity of the previously developed N-S grabens. As a result they remained as hanging grabens on the footwall blocks of the East-West grabens.