Isotopic signatures of organic matter in the Upper Miocene–Pliocene Elbistan coal seam (Turkey): Insights from δ13C and δ15N variability

• First δ 13 C and δ 15 N isotope dataset from Elbistan coal seam is presented. • Isotopic data reveal dominant C 3 plant input and redox fluctuations. • Coal quality and isotope values vary systematically with depth. • Study highlights isotopic tools for coal paleoenvironmental reconstruction. This study examines the stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope compositions of coal samples from the Upper Miocene–Pliocene (Neogene) Elbistan Basin, Turkey, to constrain the sources of organic matter and the depositional conditions of peat formation. A vertical sequence of samples collected from the Kışlaköy open-pit mine was analysed for total carbon and nitrogen contents, C/N ratios, and δ 13 C–δ 15 N values. The δ 13 C values range from −28.09 ‰ to −16.99 ‰, while δ 15 N values vary between 1.97 ‰ and 4.99 ‰. The carbon isotope data indicate a predominantly C 3 -type plant origin for the organic matter, with minor C 4 contributions inferred from samples exhibiting enriched δ 13 C signatures. Although some δ 13 C enrichment may partly reflect microbial alteration of organic matter, the overall values remain consistent with a dominant C 3 vegetation signal. Elevated δ 15 N values suggest fluctuating redox conditions and microbial nitrogen cycling during peat accumulation. In comparison with other Turkish lignite basins and global coal deposits, the Elbistan samples display a broader isotopic range, reflecting a more complex paleoenvironmental evolution. The data suggest that the coal beds formed mainly in freshwater mire settings, where fluctuating water tables, variable redox conditions, and occasional inputs from C 4 plants influenced peat accumulation. These results provide new insights into the paleobotanical and geochemical history of the basin and demonstrate the value of stable isotope analysis for reconstructing depositional environments in coal-bearing successions.