Abstract: The main lithologies of Dodurga formation consist of clay stone, bituminous shale, dolomite and coals. Limestone and marls arerarely observed as intercalations. The dominant minerals are clays and uncommonly calcite and dolomite. Opal-CT is bounded upwith volcanogenic clay stones. The contents of quartz and feldspar are usually lower, altough they are determined in almost all levels.Pyrite and gypsum are commonly found in organic material-rich sediments. Analcime in one layer, jarosite in the uppermost coal zone and marcasite in the lower çoal zone are only encountered in the Kargı area. Huntite, siderite, barite and goetite appear in the Alpagut area. Magnesite are present in the Ayvaköy area. Dioctahedral smectite is a common clay mineral of all sub-basins. The amounts of illite, chlorite and kaolinite associated with this mineral partly increase at bottom of lower coal zone. Smectites have montmorillonite and beidellite compositions which are partly iron-rich and they could be distinguished from each other`s by means of hightemperature behaviours. Ideal calcite and Ca-dolomites are found as ideal rhombohedral crystals in the limestone and marls intercalated with clayey rocks, however high Mg calcites have non-ideal rhombohedral crystals in the coal zone. It seems that the variation in the species and habits of these minerals are controlled by the chemistry of micropores.