PETROGRAPHY AND ORIGIN OF DOLOMITES OF YANIKTEPE FORMATION (UPPER CRETACEOUS) IN GÜRÜN AUTOCHTHONOUS, EASTERN TAURUS TURKEY

Abstract

The purpose of this study was to reveal the petrography and origin of the Upper Cretaceous dolomites in the Gürün autochthonous in eastern Taurus The Upper Cretaceous (Upper Santonian-Campanian) dolomites in the Gürün autochthonous belong to the Yanıktepe formation and are restricted to outcrops near Salyurt Yaylası, southern slope of Kavunağılı Tepe and Toycu Tepe The Yanıktepe formation is represented by the interfingering limestone and dolomite fades, which can be identified in the field The limestones are massive and exhibit texture of wackestone that contains foraminifera-macro shells (rudist). The dolomites formed as a result of dolomitization of foraminifera-macro shell-bearing wackestones. Three types of texture can be petrographically identified in these dolomites Type: Clear dolomite crystals, Type 2: Filthy (blurry) dolomite crystals, Type 3: Zoned dolomite crystals Of these, Type 1 is euhedral and subhedral, and very fine-to fine-grained; Type 2 anhedral and subhedral, and fine-to medium-grained; Type 3 subhedral and euhedral, and fine-to medium-grained These data support that the Upper Cretaceous dolomites in the study area could have been formed at two different stages, early and late diagenetic The early diagenetic dolomites (Type 1 and Type 2) are likely to form as a result of structural changes that occurred concurrently with sedimentation in the basin during the Upper Cretaceous The sea water fresh water mixing zones over uplifted submarine masses (rudist-bearing limestones) are probably the most favoured environments for dolomitization The late diagenetic ones (Type 3 texture) are wholly tectonically controlled and correspond to the dolomites which are controlled by fractures associated with nappe tectonics in the region