Depositional features and coal potential of the Gölbaşı- Bahçeköy Neogene Basin, Ankara (Central Turkey)

Abstract

The Bahçeköy coal field, which is the subject of this study, is located in the Gölbaşı Neogene basin in the south of Ankara (central Turkey). The pre-Neogene basement rocks located in the west and south of the basin are mostly composed of Permo-Triassic carbonate rocks, Cretaceous ophiolites, and Eocene turbidites. The coals in the Bahçeköy area are observed in the lower part of the Pliocene lacustrine sedimentary sequence which fills the basin. In the western part of the basin, the basalts and the lacustrine sediments, which contain coal, show intrusive contact relations in the lateral direction, during the Pliocene period, with the effect of the volcanism developing at the same time with sedimentation. Diatomite intercalations were formed at the upper parts of the lacustrine sequence which reached 12 m. The widespread observation of diatomites is quite important and it implies that the silicon-rich solutions associated with volcanism are involved in the lacustrine environment. The thickness of the economic coal level in Bahçeköy area varies between 4 and 12 m. According to these thicknesses, the total coal reserves calculated for the Bahçeköy area reach up to 16 million tons. The obtained drilling data shows that Bahçeköy coals exhibit rapid thickness and quality changes in the lateral direction. The chemical analyses point out these coals have average calorific value ranging from 7762 to 12,413 kJ/kg and ash content ranging from 44 to 65%.