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Turkish Journal of Earth Sciences

DOI

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Abstract

The Gildirli Formation is the oldest Neogene rock unit in the Adana Basin and was formed prior to the regionally extensive Early Miocene marine transgression. These coarse clastic red-beds provide important evidence about the causes and early phases of filling in this large trough, because the Gildirli Formation sediments fill an irregular palaeotopography carved out of Palaeozoic and Mesozoic basement rocks. Detailed study of the Gildirli Formation reveals the existence of at least two alluvial fans supplied from different source areas. A northeastern fan, exposed around Gildirli Village, was fed by streams draining an area of ophiolitic mélange, Mesozoic and older limestones, and fills an irregular palaeomorphology around and northeast of Gildirli. The southwestern fan, in the Nergizlik area, is dominated by debris flow and sheet flow rudites derived from an area of entirely carbonate bedrock. The lower part of the southwestern fan is characterised by well-bedded carbonate breccias and conglomerates that occupy deep, steep-sided palaeovalleys with approximate E-W trends (parallelling the main basin-margin), whereas higher parts of this fan are muddier and show channelised fluvial and floodplain attributes. The two fans display different provenance characteristics and evidently were fed into an intervening pre-existing depression, probably tectonically controlled. The Lower to Middle Miocene sediments that succeed the Gildirli Formation fan clastics on this basin margin form a mosaic of facies associations, partly contemporaneous and partly diachronous. These include a mixed clastic-carbonate unit (Kaplankaya Formation) of mainly shallow marine character, a reefal to platform carbonate unit (Karaisalı Formation), and a coarse clastic submarine fan system (Cingöz Formation) together with its coeval deep-marine shales (Güvenç Formation). The limestone bodies of the Karaisalı Formation in this area display clinoformal geometries that accord with a backstepping pattern and also attest to pre-existing fault control of the steep basin margin. The western part of the partly contemporaneous Cingöz Formation submarine fan system has been supplied through a feeder-channel that now occupies the palaeovalley depression inherited from pre-Gildirli Formation times. The palaeovalley system shows a margin-parallel trend and might have been developed before the deposition of the Gildirli Formation by extensional tectonics. Thus the location, geometry and orientation of this sector of the mid-Miocene submarine fan appears to have been determined by the tectonically mediated pre-Miocene/Early Miocene palaeomorphology.

Keywords

Adana Basin, alluvial fan, submarine fan, palaeovalley, sediment bypassing, sequence stratigraphy

First Page

181

Last Page

209

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