Geology of the Yeşilyuva and Kocabaş region and its geotectonic significance

Abstract

Southwestern Turkey experienced a transition from crustal shortening to extension during Late Cenozoic, and evidence of this was recorded in different basin types in the east of Denizli region. The study area comprises a heterogeneous suite of Mesozoic to Recent igneous, metamorphic, and sedimentary rocks. Two main rock groups are distinguished in the area: the basement rocks of pre-Neogene age and the sedimentary cover of Neogene-Quaternary age. In the region, several Late Cenozoic structural basins are filled with terrestrial clastic and volcanic rocks. These basins are different in orientation, geometry, and nature of basin infills. In the studied area, the exposed basal units of the ophiolitic melange correspond to the Lycian Nappe complex. The first sedimentary cover unit, unconformably overlying the nappes, is represented by an E-W-trending basin that is filled with the Oligocene-Lower Miocene shallow marine-terrestrial deposits. The infill of the studied basin consists of the Caykavustu and the Akcay Formations which were deposited during the Late Oligocene and the Early Miocene, respectively. These basins developed as a piggy-back basin along the fault plane on the hanging wall blocks of normal faults. A graben basin (Yesilyuva-Kocabas) started to occur along with NE-SW-trending normal faults which were formed as a result of E-W extensional regime during the Late Miocene. The coarse clastics of the Kizilburun Formation of the Late Miocene age were deposited within an alluvial fan derived from the Elmadag Horst in the east of the basin. Whereas the coarse clastics of the Late Miocene basement were accumulated in front of the hanging fault blocks, the fine-grained clastics of the Saraykoy Formation overlie conformably the Kizilburun Formation. The sequence continues with the lacustrine limestones of the Aktepe Formation. Alkaline magmatics of Early-Late Pliocene cut all successions. E-W-trending fault systems formed with the N-S extensional regime affected the basin, and the recent E-W grabens (Curuksu and Acigol Graben) occurred during the Early Pliocene. The recent morphology of the studied area developed under the control of the Asagidagdere oblique fault zones which are located in the south of the Curuksu Graben.