A multidisciplinary study of the Gölbaşı-Harmanlı coal seam, SE Turkey

Abstract

This study focuses on the Pleistocene Gölbaşı-Harmanlı 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 39m) 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.We suggest that the movements of the EAFZ caused rapid subsidence, and along with favourable climatic conditions, allowed large peat accumulation in a relatively short period of time. The results of proximate and ultimate analyses from 29 coal samples obtained from two cores show high ash yields (av. 32%), relatively low sulphur content (av. 1.8%), low net calorific value (av. 11.6MJ/kg) and low total carbon content (av. 35.5%) on an air-dry basis. The mean random reflectances of eu-ulminite B indicate a low-rank coal. Maceral compositions and maceral indices indicate that the peat accumulated under limno-telmatic, mesotrophic conditions, with peat-forming vegetation being composed of mainly herbaceous plants.Ostracoda and Mollusca fauna from intercalating clastic layers within the coal seam provide important information about the geographic distribution of fossil taxa, environmental evaluation of the intercalations, and the age of the studied coal seam. The Ostracoda species Gomphocythere geareyi was identified within the coal seam for the first time. Humphcypris subterranea is the first fossil record of this Ostracoda genus in Turkey. These, along with the presence of the Gastropoda subspecies Bithynia phialensis syriaca, imply a transport into the palaeomire via migratory birds from the Eastern Mediterranean areas. Discovery of Humphcypris subterranea, Bithynia phialensis syriaca, and the African originated genus Gomphocythere in the Gölbaşı-Harmanlı coal deposit marks their northernmost worldwide occurrence.