The mid-Cenozoic succession and evolution of the Mut basin, southern Turkey, and its regional significance

Abstract

The hitherto poorly known Mut basin occupies a position that is critical to our understanding of the later Cenozoic history of south central Turkey. The biostratigraphic and sedimentological study reported here reveals an extended and complex pattern of basin evolution and enables the history of this basin to be compared in detail with that of adjacent south Turkish basins. The oldest basin fill deposits are demonstrated to be Oligocene to earliest Miocene in age and comprise alluvial redbeds, thick lacustrine deposits and thin lagoonal sediments mainly supplied from northern (Tauride) sources This mainly terrestrial megasequence resulted from an early Oligocene phase of crustal extension, leading to rapid “trap-door” subsidence and the formation of narrow E–W trending troughs. This phase was terminated by a minor marine incursion and through reactivation of basement faults during renewed extension in the earliest Miocene. The overlying Miocene succession, thus, rests with local angular discordance upon tilted and gently deformed Oligocene (and older) rocks. Subsequent subaerial erosion created an irregular pre-Burdigalian palaeotopography that strongly influenced the nature, thickness and distribution of the early Miocene basin fill. In palaeotopographic depressions, the Miocene sequence commences with alluvial fan, braidplain and meander belt redbeds formed in river systems that flowed mainly south and southeast. These pass up (and laterally) into more extensive lagoonal and shallow marine mixed clastic/carbonate units yielding late Burdigalian to early Langhian microfaunas, marking the inception of the main Miocene marine transgression in this area. Episodic northwards marine advance led to isolation of the northerly source of siliciclastic detritus and resulted in periodic onlap of mid- to inner-shelf fine-grained carbonates (with thin clastic intercalations) that include isolated coralgal build-ups, calcarenite mounds and sand-waves. At the peak of Miocene transgression (mid-Serravallian), thick reefal limestones were deposited far to the north and also formed on top of basement highs forming the southern and eastern flanks of the basin. Significant influxes of coarse and fine siliciclastics from the north attest to periodic progradational events that are more conspicuous and protracted in the late Serravallian and Tortonian. However, muddy deeper shelf conditions prevailed throughout the middle Miocene in the central part of the basin, while stronger currents and unstable slopes characterise the constricted marine strait in the southeast of the basin near Silifke. In terms of their sequential arrangement, palaeoenvironmental and tectonic evolution the Oligo-Miocene sediments of the Mut basin closely resemble coeval sequences in the adjacent Ecemis–Aktoprak and Karsanti–northern Adana basins and share a similar history, involving complex interplay between regional tectonics and eustasism. Deeper water Oligo-Miocene sequences in the ‘outboard troughs,’ such as the southern Adana basin and the Kyrenia–Misis–Andirin complex, yield more subtle signatures of these tectonic and eustatic events. The differences between these basins are attributable to the influence of regional kinematic elements generated during the reorganisation of plate boundaries in the northeast Mediterranean that followed final suturing of the Arabian and Anatolide plates in the mid-Cenozoic.