| Abstract |
A thick series of the Miocene sediments, about 1800 m in thickness, is widely distributed in the Kii Peninsula, Southwest Japan, and is called the Kumano Group. This group lies on the Shimanto Supergr...oup with an unconformity and comprises three formations, namely the Onuma, the Koguchi and the Mitsuno Formation in ascending order. This group is characterized by a noticeable variation of lithological facies, but generally represents an upward-coarsening sedimentation. The lowermost formation, Onuma, is limitedly existent to the northern half of the area in which this group is distributed. Workable coal seams mined formerly are inserted in the lowermost horizon of the Mitsuno Formation. Based on the lithofacies, the Koguchi Formation is divided into three members which are found in the whole distributed area of the formation, whereas the Mitsuno Formation is subdivided into four members in the northern district and into seven members in the southern one, respectively. The sedimentary basin of the Kumano Group had been initially generated under offshore circumstance, and, hence forward, had continuously been under the progradational one. In the later stage of development of the basin, however, it was separated into northern and southern districts. The clastics of the Mitsuno Formation were, in the northern district, accumulated in lagoonal swamps in which coaly matter or fluviatile sediments deposited, but, in the southern one, the littoral environments had been persisted and thick beach sediments or shallow marine sediments were formed.show more
|
Export Mendeley
24_03_p155