This paper describes the cyclic sedimentation of the Tertiary coal-bearing formations in the Futaba district, Joban coal field., The Shiramizu group in the district is comprised of the Asamigawa formation, Asagai sandstone and Shirasaka shale, named in ascending order., The Asamigawa formation in this district is characterized by the abundance of coarse-grained sediments which represent eight cycles of sedimentation, separated from each other by an erosional surface or diastem., The sediments of the each cycle consist of conglomerates sandstones, shales and coal seams., These sediments are coarser and thinner than those of the Hanakawa formation in the Isohara district., However, the Shiramizu group, comprised of the Asagai sandstone and the Shirasaka shale, is quite uniform as to lithology and thickness in both areas., The Yunagaya group has a seguence similar to the Shiramizu group and may be divided into five formations: the Nagahata formation, Oyauchi sandstone, Mizunoya sandy shale, Kamenoo shale and Hon'ya shale, listed in ascending order., The cycles of the Nagahata formation are composed of conglomerates, sandstones, shales and thin coal seams., The Oyauchi sandstone, Mizunoya sandy shale, Kamenoo shales and Hon'ya shale constitute a megacycle which for the most part represents a marine facies., The Kasamatsu formation of the Cretaceous Futaba group and the Misawa sandstone of the Shirado group also consist of a cyclic alternation of sandstones, shales and carbonaceous shales with thin coal seams.,
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