This study focuses on the Pleistocene Golbasi-Harmanh coal deposit located in the East Anatolian Fault Zone (EAFZ), SE Turkey. The principal aim of the study is to determine factors that controlled peat accumulation by means of palaeontological data, routine coal analyses (proximate-ultimate), mineralogical composition based on XRD and SEM-EDX, and coal petrography. The basin-infillings consist of alluvial, fluvial, and lacustrine sediments. Palaeolake levels along with sedimentation were presumably controlled by the EAFZ during Late Pliocene to Holocene times. The investigated coal-bearing zone is composed of a thick coal seam (up to 39 m) with thin clastic intercalations of fossiliferous claystones. Palaeontological data from these clastic bands imply that the coal accumulated during Middle Pleistocene times, an uncommon period for the formation of thick coals in Turkey.