Research of the Karatsu Coal-field. No. 1.

On the Coal Bearing Formation and its Marine Facies of the Karatsu Coal-field, Kyushu.

Abstract

It is well known that for the Nogata Stage, one of the main coal-bearing stages of Palaeogene Tertiary in Northern Kyushu, a marine facies corresponding to it is present. However, for the Otuji Stage, the upper coal-bearing stage of Nogata Stage, the presence of a corresponding marine facies has not yet been reported. The writer and his colleague have discovered the missing marine facies by the observation and studies of date from many borings made by a few coal mining companies in Karatsu Coal-field, Saga Prefecture. The Yoshinotani Beds, the main coal-bearing beds of Karatsu Coal-field and correlative to the Otsuji Stage, have been demonstrated to be overlain unconformablly by the Kishima Beds. The Yoshinotani Beds, have also, been demonstrated, with four zones of marine fossil-bearing beds. Three of these lie each above the main coal seams or groups of seams, and the fourth occupies the uppermost horizon of Yoshinotani Beds. In the Ureshino district, the southern margin of Karatsu Coal-fields, the coal seams of the Yoshinotani Beds are entirely absent, only the marine facies of them are present. The change in facies of deposition of Yoshinotani Beds from north to south, i.e. offshore, is summarized as follows : the normal coal-bearing formation with workable coal seams—interfingers of marine beds and terrestrial coal bearing beds—pure marine beds of same stage. The writer and his colleague have proposed the name "Kawago Beds" for this marine facies of the Otsuji Stage of the Karatsu Coal-field. The name is derived from the locality of Kawago in City Takeo.