Sedimentological and geochemical investigation of the lower eocene-upper oligocene Gaziantep formation at Egil and surrounding area (Diyarbakir)

The Lower Eocene-Upper Oligocene Gaziantep formation consists of cream, beige, gray, white, dirty white colours, medium to thick, very thick bedded stratas, solid, well porous, abundant fossiliferous limestones. The carbonate rocks of Gaziantep formation dominate limestone and presents dolomitic features on the basement. The Gaziantep formation is divided into three microfacies. These are grainstone, packstone and microdimensional anhedral dolomite facies. Heterostegina sp. Myogypsinoides complanatus (SCHLUMBERGER), Miogypsina polymorpha (RUTTEN), Miogypsina sp., Operculina sp., Globoigerinoides sp., Amphistegina sp., And Lepidocyclina sp. type of bentic foraminifera fossils are found in the limestones. The CaCO3 content of the dolomites between 55 to 99 mol%, the MgCO3 content between 1 to 45 mol%, the main oxide contents are; SiO2 content is 0.07-1.27%, Al2O3 content is 0-0.40%, Fe2O3 content is 0.01-0.22%. Dolomites are Ca-rich (Ca55-56, Mg52-53), non-stoichiometric dolomite. Ba content of carbonate rocks is <60 ppm (avarage 6 ppm). This is shown that carbonates in here were derived from marine origin. The limestones of the Gaziantep formation have δ18O values which are between -7.83%o and -5.33%o PDB (mean -6.80%o PDB), δ13C values are between -0.17%o and -6.90%o PDB (-3.29%o Lt; / RTI & gt; The δ18O values of the dolomites vary from -7.74%o to -1.23 %o PDB (averages -5.36%o PDB), δ13C values vary from -6.79%o to -0.68%o PDB (-4.10 %o) (PDB) . The dolomites of Gaziantep formation have been formed by the dolomitization of the limestones formed in the peripheral environment in the late diagenetic (mixing zone) and shallow buried environment.