Tectonic Evolution of the Kiraz Basin, Küçük Menderes Graben: Evidence for Compression/Uplift-related Basin Formation Overprinted by Extensional Tectonics in West Anatolia

Authors: TAHİR EMRE, HASAN SÖZBİLİR

Abstract: The Kiraz Basin which is located at the eastern end of the Küçük Menderes Graben was previously considered to be an extensional basin. However, the data presented here allow us to infer that the tectonic evolution of the Kiraz Basin could be explained by an alternate model which suggests compression/uplift-related basin formation at the early stage of basin evolution followed, later, by block faulting in an extensional neotectonic regime. The successive compressional and extensional strain is accommodated by a predominantly NE-trending strike-slip fault system. The new model is based on the detailed mapping, field-cross sections and kinematic analyses of the studied faults. The new model requires a revision of the current regional approaches to the tectonic setting of the west Anatolian basins. The Kiraz Basin is filled by two contrasting sedimentary packages. The older one (the uppermost Middle Miocene-Upper Miocene Suludere Formation) is developed in relation to N-S-trending compressional tectonics and uplift along the northern margin of the basin, which is controlled by reverse and strike-slip faults. During this stage, the main sedimentary trough was located along the northern margin where metamorphic rocks of the Menderes Massif and Middle Miocene andesitic volcanism (Başova andesites) form the basement. The basal unconformity with the basement rocks has been tilted to vertical, even if overturned, thus recording the uplift linked to the activity along the margin-bounding reverse/thrust fault. The Miocene strata are nearly horizontal over most of their extent and highly deformed only along the northern margin of the basin where syntectonic activity is recorded by the development of intraformational unconformities. Following the Late Miocene, thrusting of Menderes Massif rocks onto the Miocene sediments indicates that the compressional regime was active after the sedimentation of the Suludere Formation. The development of the Plio-Pleistocene Aydoğdu Formation, under the control of the Suludere and Halıköy faults that bound the Kiraz Basin to the north and south, demonstrates that the extensional tectonic regime initiated the second stage sedimentation within the Kiraz Basin. This phase corresponds to a widening of the basin in N-S direction, a process which continues up to the present. On the basis of kinematic data collected from faults observed in the Kiraz Basin, four deformation phases have been recognized: (i) D_1 and D_2 deformations indicate north- and south-directed tectonic transport that pre-date the formation of the Kiraz Basin; (ii) D_3 deformation, reflecting syn- to post-sedimentary tectonics, is represented by intraformational unconformities and related reverse faulting; (iii) D_4 deformation gave rise to normal faults that cut and displace early structures and shapes the Kiraz basin's present-day configuration. It is therefore proposed here that the Kiraz Basin evolved in response to two discrete stages of tectonic activity: an early phase of latest Middle Miocene-Late Miocene reverse and strike-slip faulting along only the northern margin and a later phase of Plio-Pleistocene to Recent normal faulting affecting the margins of the basin.

Keywords: Küçük Menderes Graben, Kiraz Basin, syn-compressional sedimentation, extensional tectonics, W Anatolia

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