On the Investigation of the Buried Hill in Jôban Coalfields (2)

Geological Significance of "Greenish Mudstone Zone", Formed Around the Buried Hill

Abstract

The Pre-Tertiary basement underlying the main coal bearing strata, Hanakawa Formation, developed in the Joban coal-fields, often produced buried hills in the overlying beds. The develop-ment of the workable coal seams has been influenced by the existence of the buried hills; namely, the main coal seams all tend to become thinner as they approach the hills and thin out abruptly or gradually at the tops of them. Accordingly, predicting the location of the hills is important to the coal mine engineers.
The author, co-operating with the field technicians, has recently discovered a technical wise saying "a discovery of grey-greenish schistose mudstone and angular schist fragments in the boring core give us a definite hint on the existence of the buried hills around the boring stations".
This is due to the development of the dark-grey-greenish schistose mudstone zone which proba-bly resulted from the direct transportation of eroded materials derived from the buried hills. If we recognize this characteristic facies in the boring core, irrespective of the distance to the Pre-Tertiary basemant, we can determine concretely the same zone and consequently discover the presence of a buried hill.