NEOGENE STRATIGRAPHY AND PALEOGEOGRAPHIC EVOLUTION OF THE KARABURUN AREA, ‹ZM‹R, WESTERN TURKEY

Abstract

The western margin of the Foça Depression (FD) is located in the NE of the Karaburun Peninsula. Terrestrial Neogene sediments in the study area which partly representing the western margin of the FD and the mafic volcanics have NW-SE directions towards ‹zmir bay and are separated from the basement rocks by synthetic normal faults. During the Miocene deposition the basin’s boundaries became structurally narrower and two main sedimentary successions have been defined namely the Karaburun group and the Eflendere group which have been separated with angular unconformity in regional scale. The Karaburun group is represented with dominantly lacustrine deposition in Early-Middle Miocene period that includes Haseki and Hisarc›k formations and Karaburun volcanics. The Lower Miocene Haseki formation is represented by the Salman member developed in the alluvial fan environment and lacustrine deposits of algal-biostromal Yeniliman limestone and micritic limestone dominated Aktepe member. NW trending basin margin faults which formed a boundary between Karaburun high and the FD and caused the effective second stages of mafic volcanism did not interrupt the lacustrine deposition at the beggining of the Early Miocene. But it caused relative deepening of the basin, changed depositional conditions and lacustrine sedimentation continued with the Hisarc›k formation. The activity shaping the FD from the western part and partly coinciding with the Early Miocene basin margin faults has been documented with the unconformity showing no time gap between Haseki and Hisarc›k formations. Hac›hüseyintepe member has unconformity with the lavas that represent the second stage of Karaburun volcanics and laterally passes into the Karaba¤lar› member. The Karaba¤lar› member consists of green coloured lacustrine shoreface sediments which lie on the Aktepe succession with sublacustrine paraconformity. De¤irmentepe limestone transitionally lies on the top and it is the last member of the Karaburun group. Eflendere group lies on the Hisarc›k formation with regional scale angular uncoformity and presents the Late Miocene-early Early Pliocene(?) sedimentation grading from alluvial fan deposits of the Saip formation to lacustrine Çukurcak limestone. Calc-alkaline Karaburun volcanism which is represented with potassium rich andesitic products has three stages that laterally connected with the Early Miocene-early Middle Miocene deposition The first two stages have dual facies namely, pyroclastics at the base and lavas on the top. The first stage products are laterally discontinuous reference level that is separating Yeniliman limestone and Aktepe member. Second stage products are in/on the Aktepe member. The third stage lava flows are dated as K/Ar 16.0±1.3 Ma age which is thought to be located at the bottom of the De¤irmentepe limestone that is the last member of the Karaburun group.