Çiğdem Saydam Eker

Petrography and Geochemistry of Eocene Sandstones from Eastern Pontides (NE TURKEY): Implications for Source Area Weathering, Provenance and Tectonic Setting

Subaerial weathering level, source area and tectonic environments were interpreted by using petrographic and geochemical characteristics of Eocene age sandstones found in the eastern Pontides. The thickness of Eocene age clastic rocks in the eastern Pontides ranges from 195 to 400 m. Mineralogical components of sandstones were mainly quartz, feldspar, rock fragments, and opaque and accessory minerals. Depending on their matrix and mineralogical content, Eocene age sandstones are identified as arkosic arenite-lithic arenite and feldspathic wacke-lithic wacke. CIA (Chemical Index of Alteration) values observed in the Eocene age sandstones (43–55) suggest that the source terrain of the sandstones was not affected by intense chemical weathering. Low CIW/CIA (Chemical Index of Weathering/Chemical Index of Alteration) values of the sandstones studied here suggest only slightly decomposed material and having undergone little transport until final deposition. Zr/Hf, Th/Sc, La/Sc and CIA ratios are low and demonstrate a mafic source; on the other hand, high LREE/HREE ratios and a slightly negative Eu anomaly indicate a subordinate fclsic source. Modal mineralogical and SiO2/Al2O3 and K2O/Na2O and Th, Zr, Co, Sc of Eocene age sandstone contents indicate that they are probably magmatic arc originated and deposited in the back arc basin.

Geochemical and isotopic characteristics of stream and terrace sediments of the Harsit Stream, NE Turkey

The current study compares and contrasts the elemental concentrations and the Nd, Sr and O isotopic compositions of sediments collected from the Harsit Stream bed sediments (HSBS) and terrace sediments (HSTS). There are positive correlations between Al2O3 and SiO2, TiO2, Na2O and Fe2O3, K2O in HSBS and between Al2O3 and Fe2O3, MnO in the HSTS samples. Major element components of HSBS and HSTS are comparable to average upper continental crust. Both types of sediments are generally classified as greywacke, based on chemical composition and O–Sr isotopic compositions. The ɛNd(0) and ɛSr(0) values range from −0.6 to −5.7 and from 7.1 to 45, respectively, in HSBS; and from −0.7 to −4.4 and from 20 to 54, respectively, in HSTS. The δ18O values range from 8.8 to 11.8 (average 10.8) in HSBS and from 11.3 to 13.3 (average 12.2) in HSTS, which are generally controlled by detrital or authigenic minerals in the studied samples. The average chemical index of alteration (CIA) and, plagioclase index of alteration (PIA) values are high in HSTS, whereas the index of compositional variability (ICV) and weathering index (WIP) values are high in HSBS. Several minor differences were observed between HSBS and HSTS in terms of geochemistry and isotopic compositions that reflect different processes involved in their sedimentation.

Concentrations of elements in Lias coals from the eastern Black Sea Region, NE-Turkey

ABSTRACT The element contents and organic matter-element relation between Lias-aged coals exposed in four fields in Gümüşhane and Bayburt were investigated. In general, fixed carbon and gross calorific values of the Edire and Balkaynak coals are higher than Güvercinlik and Çerçi coals. The highest ash yields were observed in the Çerçi coals. The concentrations of Mg, P, Ca, Mo, Y, Ni, U, Zn, Ga, Ba, W, Sr, Ta, and Be of the analysed coals are positively correlated with ash yield, indicating an organic affinity. The Lias-aged coals located in Gümüşhane and Bayburt are low-rank coals.

Organic Maturity and Hydrocarbon Potential of Liassic Coals from the Eastern Pontides, NE Turkey

Organic matter content, type of organic material, and thermal maturity of Lias-aged coals of the Gumushane and Bayburt areas were investigated. The total organic carbon contents of coals in the Gumushane area range from 0.39–35.46 wt%, and in the Bayburt area range from 0.02–50.64 wt%. The Gumushane (except Güvercinlik field) and Bayburt areas coals have low hydrogen index values. The coal samples contain a mixture of Type II and Type III kerogens. Based on average Tmax values Liassic coals in the Gumushane and Bayburt (except Cerci field) areas are mature, and potential yields are low.

Organic Geochemical Characteristics and Depositional Environments of the Eocene Deposits in the Eastern Black Sea Region, NE Turkey

Type of organic material, thermal maturity, depositional environment, and source rock potential of Eocene aged clastic rocks of the Eastern Black Sea Region were investigated. Based on total organic carbon values, clastic rocks range from weak-good source rock. Samples contain a mixture of Type I–Type III kerogen. Based on T max values, Eocene aged clastic rocks were thermally mature. Moretane/hopane ratio of samples <0.15, 22S/(22S + 22R) homohopane (C32), and 20S/(20S + 20R) sterane (C29) maturity parameters were equal or very close to equilibrium value of oil generation. The deposition environment was transitional marine environment and clastic rocks do not have the potential to form hydrocarbon.