Depositional environments of Oligo/Miocene coal-bearing strata and coal quality from the Oltu-Balkaya Basin, northeastern Turkey

Abstract

This study addresses the depositional environments of the Oligo/Miocene coal-bearing Susuz Formation and Komurlu Formation from the Oltu-Balkaya Basin, northeastern Turkey, and coal quality of the Ince and Susuz seams from the Susuz Formation, which was formed in a mainly meandering fluvial environment. The Komurlu Formation that conformably overlies the Susuz Formation was developed in a mainly lacustrine environment. Six channel samples from the Ince seam and 13 channel samples from the Susuz seam exploited in the underground mines around Balkaya were collected and evaluated in this study. The samples show that the Ince and Susuz seams, on an air-dried basis, respectively, average high ash yields (38.9 and 31.2%), high total sulfur contents (3.49 and 2.89%), and relatively high calorific values (3956 and 4775 kcal/kg). The mean random ulminite reflectance (0.54 and 0.56% Rr) and nonagglomerating character imply that these coals are in a subbituminous-A coal rank. The mineral matter of the studied samples is made up of smectite, quartz, pyrite, calcite, feldspar, and traces of illite and gypsum. Petrographic studies show that some of pyrite and all calcites were detected in cleat and fracture infillings.