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- MakaleAçık Erişim2025Geochemical evaluation of black limestones in the Early Cretaceous platform carbonates of Gümüşhane (NE Turkey): An insight into petroleum source rock potential and palaeoenvironment conditions
Saydam Eker, Çiğdem; Arı, Uğur Volkan; Alemdağ, Selçuk
This study assesses the organic matter (OM) content, kerogen type, maturity, depositional environment conditions and sedimentation model of Early Cretaceous (Berriasian–Aptian) black limestones in NE Turkey using geochemical analyses, including Rock-Eval/total organic carbon (TOC), gas chromatography–mass spectrometry, gas chromatography, major and trace elements and stable carbon isotope of OM measurements. The investigated black limestones' TOC, hydrogen index and potential yield values range from 0.07 to 2.91 wt%, 76 to 636 mg HC/g TOC and 0.15 to 11.17 mg HC/g rock, respectively. These results indicate that the examined limestones have variable source rock potential, ranging from low to high. Tmax values, calculated saturated biomarkers and aromatic components suggest that the OM contained in the black limestones varies between thermally immature and mature, consistent with the potential index values. The OM found in the black limestone contained kerogen varying between type I and III. It is a composition of marine and terrigenous OM, as shown by the δ13C isotope values, biomarker components and n-alkane distributions and their parameters. This OM was deposited in a salinity water environment with marine–terrigenous (transitional) surroundings under oxic, suboxic to anoxic and arid–hot climate conditions. These findings provide critical insights for assessing the hydrocarbon potential of carbonate platforms in similar geological settings.
- MakaleAçık Erişim2024Geochemical characteristic of the Lutetian black shale (Bayburt, NE-Turkey): amount, nature, origin of organic matter and palaeo-environment conditions
Eker, Çiğdem Saydam
To define the amount, thermal maturity and type of organic matter (OM), a comprehensive analysis of major and trace elements, organic carbon isotope and organic geochemistry was conducted on Lutetian black shales found in the Everek (Bayburt) region of northeastern Turkey. Total organic carbon (TOC) levels in the shale samples range from 0.62% to 6.75%, and type II–III to type III kerogen is generated, displaying a combination of high terrigenous and low marine OM. The δ13C values (ranging from –28.22 to –28.23), aromatic hydrocarbon compounds (methyl phenanthrene, dibenzothiophene, tri-aromatic and monoaromatic steroids), saturated hydrocarbon compounds (sterane and terpane), acyclic isoprenoids, n-alkane distribution (n-C13–n-C36) and inorganic geochemical characterization support that the black shales were deposited in a terrestrial-marine transition environment and had a high proportion of terrestrial OM with small amounts of marine OM preserved in relatively arid to hot climate and oxic to suboxic conditions. The analysis of biomarker thermal maturity markers, Tmax (ranging from 449–458oC) and estimated vitrinite reflectance (varying from 0.92 to 1.08%) values suggest that the black shales have reached the oil window. As a result, black shales are thought to contain low to high amounts of TOC, have a mixed kerogen type, reach a high thermal maturity level and produce little hydrocarbons.
- MakaleYalnız künye2016Concentrations of elements in Lias coals from the eastern Black Sea Region, NE-Turkey
Eker, Çiğdem Saydam; Akpınar, İbrahim; Sipahi, Ferkan; Yapıcı, Ejder
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.
- MakaleYayıncıda açık erişim2016Organic geochemistry and element distribution in coals formed in eocene lagoon facies from the Eastern Black Sea Region,NE Turkey
Saydam Eker, Çiğdem; Akpinar, İbrahim; Sipahi, Ferkan
The amount and type,the inorganic element content,and the maturity of organic materials of Eocene coals,shaly coals,and coaly shales exposed in the Gümüşhane and Bayburt districts of the Eastern Black Sea Region of Turkey were investigated. The depositional environments and hydrocarbon potentials were also interpreted. The total organic carbon concentrations in the studied samples ranged from 0.50% to 63.08%. The samples from Özyurt,Kayadibi,and Tarhanas contained types II and III kerogen,and those from Sökmen and Manas contained type III kerogen. The samples contained Co,Cs,Ga,Hf,Th,U,Y,Mo,Be,Cd,Sb,and La,with average values similar to those of standard brown coals. The samples showed average contents of Co,Ga,Nb,Rb,V,Y,Cu,Pb,Zn,As,Be,and Se,similar to those of other Turkish coals. The sediment source of Eocene samples in the five areas was characterized by rocks with intermediate or mafic geochemical characteristics. The terrigenous/aquatic ratio of coal and shaly coal samples of the areas in question is >1. The sterane distribution was C29 > C28 > C27 and C29 > C27 > C28 for the Özyurt and Tarhanas areas,respectively. The average Tmax values for samples are between 424 °C and 460 °C. For samples Oz-1 and Ta-2,22S/(22S + 22R) homohopane (C32) ratios are 0.48 and 0.61,respectively; 20S/(20S + 20R) sterane (C29) ratios are 0.18 and 0.53,respectively; and Ts/(Ts + Tm) ratios are 0.015 and 0.64,respectively. The Pr/Ph ratios of the samples are >3. The studied samples have low sterane/hopane and high (C19+C20)/C23) ratios without anoxic biomarkers (17α(H)-28,30-bisnorhopane). Based on these data,the coals,shaly coals,and coaly shales were probably deposited under an oxic-suboxic mixture of marine and terrestrial environment conditions; these materials contain terrestrial organic matter and cannot generate hydrocarbon.