| 概要 |
1) At the later age of the Ariake, the Chikuho Coal Basin was formed as a "rift valley" extending NNW- SSE in direction, and in which the coal-bearing Paleogene, the Nogata and Otsuji groups of 1, 500...-2, 000m in total thickness were accumulated. While the northern limit of this rift valley could not been well assumed, the southern one might have been extended to the area of the Asakura Coal-field. By the advent of this rift valley the Paleo-Ariake bay, which had been spreaded out, at that time, to the northern part of the Miike Coal-field, further penetrated into this valley. According to fossil remains obtained and also to rock facies, salt water might have invaded to the utmost till in the Asakura Coal-field, and a greater part of the Chikuho Coal-field was, therefore, under fresh, partially brackish environment. Accompanying to the advent of the "Chikuho rift valley" several small ones having nearly the same character broke out in it's adjacent area; they are the Kokura, Kasuya and Fukuoka Coal-fields. Because these valleys had been in connection with the main valley "Chikuho" on the north, the same coal-bearing Paleogene deposits were also accumulated. 2) During the time of deposition of the Paleogene the down sinking movements of the Chikuho rift valley, in another word, the upheaval of the walls of the rift valley, had still been proceeded on. As the amount of the upheaval movement on the west margin was greater than that on the east, the characteristic geological structure, the "Chikuho-geostructure" was accomplished, resulting in that the relationship of the Paleogene to the basements is in "fault" on the east, and in unconformity on the west. By a great amount of upheaval of the western basement block, the geological structure in the Kasuya Coal-field, situated on the west side of the Chikuho, forms a striking contrast with that of the Chikuho. 3) The "boundary fault" between the Paleogene and the basements on the eastern periphery might essentially run nearly straight, NNW-SSE or N-S, but because it was removed by compressional force of NNE to SSW direction, several parts of this fault shifted south-southwestward, and finally the echelon fault system and the elongated basin and dome structures were constructed. It is very hard, however, to find out any proper reason for the creation of this compressional force, but it seems neccessary to make it clear, taking more detailed geological and geophysical data into consideration.続きを見る
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Mendeley出力
