Geology and Lignite Seams in the Fukinodai District, Uryu-gun, Hokkaiko

Abstract

In 1957 and 1958, the writers have investigated the geology of the Fukinodai district, Uryu-gun, Hokkaido and discovered lignite seams which have never been officially reported. According to their investigation, the general geologic succession in the area is summarized as follows in descending order:
The Older agglomerate is mainly developed in the eastern and western parts of the mapped area; while the Chikubetsu formation, covered by the Older agglomerate with clino-unconformity, is exposed locally in the west. In the western half of the central area, the Epishuomapp-gawa formation, which is partly covered by the Younger agglomerate, shows a synclinorium with an axis of approximately N-S direction. On the contrary, in the eastern half, the Karuushinai-gawa formation which dips slightly is distributed broadly except for the fenster-shaped outcrops of the Epishuomapp-gawa formation.
Of these formations, the Epishuomapp-gawa formation is the most important lignite measure, and contains numerous lignite seams which vary locally in their thickness and number. That is, about 20 seams are more than 1m in thickness, while a few are about 10m in thickness.
The lower part of the Epishuomapp-gawa formation interfingers contemporaneously with a part of the Older agglomerate, whereas its upper part interfingers with a part of the Younger agglomerate, of which geologic age is the upper Miocene. The Epishuomapp-gawa formation is exposed in the area covering 7km from north to south and 2.5km from east to west. It is very likely that the formation is also distributed with the similar dimensions in the adjacent area beneath the Karuushinai-gawa formation.
These lignite seams have never been mined before because of their poor quality and accessibility.