In the vicinity of the Bakony Mountains (Hungary) Upper Cretaceous (Senonian) brown coal deposits are known. Within the original sedimentary basin three depressions of northeast-southwest direction were formed prior to the Senonian. These depressions were the sites of fluvial sedimentation and swamp facies.

The accumulation of coal deposits was controlled by climatic conditions, rate of subsidence, paleohydrology, marine transgression, and mainly the rate of terrigenous sediment input. Due to reduced terrigenous input in the Ajka area the coal-swamp environment persisted for a long period of time, while in the Magyarpolány and Devecser areas of the Devecser zone the large coal swamp was replaced by a fluvial environment prograding from the northeast to the southeast. The optimal condition for coal accumulation in the Devecser zone came into being in the Gyepükaján area where the terrigenous input already decreased but the marine influence was not yet strong during the first period of Senonian sedimentation.