During the Miocene a number of fault bounded basins developed in Central Anatolia, Turkey. One such basin at Cayirhan, near Beypazari, contains thick, laterally extensive lignite seams. This basin was filled initially with coarse elastic material. Upward fining of the clastics during basin fill, with an increase in the amount of clay and carbon content led to the development of relatively shallow limnic basins in which extensive peat deposits accumulated in low-lying mires. These lignites are characterized by their high sulphur and ash contents (up to 8.2% S and 68.3% ash on an air-dried basis). Studies of the sulphur and ash contents reveal three types of distribution; namely, vertical variation within individual seams, variation between the seams and lateral variation across the basin. In the case of the sulphur content, vertical variation within and between the seams is related to variations in the amount and source of the sulphate in the mire water, and the lateral variation is probably related to structural/topographic control of the mire at the time of formation. Variation in the ash content within the seams is probably the result of depositional processes at the time of mire development. Variation between seams is recognized due to the presence of ubiquitous zeolites in the mineral matter; namely heulandite in the first seam and analcime in the second seam. This is probably the result of variations in the chemistry of the original volcanoclastic or clastic material associated with the lignite or of variations in the chemistry of the circulating fluid. There is a broad east-west lateral variation across the basin in the ash content of the seams, probably resulting from variations in the amount and rate of elastic or volcanoclastic influx into the mire at the time of formation, related to structural/topographic controls.