新潟縣南蒲原郡森町村に見られる同時褶曲の一例

抄録

In July and August of 1949, the writer carried out a precise geological survey over a part of margin land of Niigata oil field, east of omo oil field, jointly with K. Ida, Y. Ishiwada and T. Mitsunashi. The general stratigraphic succession is as follows:
In the area under discussion, the Imogawa black mudstone formation is interfingered by the Niwazuki pyroclastic member. The latter consists mainly of dacite-pumiceous tuff, partially including subangular pebble or boulder of the dacite and black mudstone. The boundaries between them are remarkably clear and uneven, and a lot of blocks of black mudstone and hard black shale are scattered in the tuff near on the boundaries to the mudstone. As shown in the figure, the distribution of the pyroclastic member is quite different between on the both wings of the anticline or syncline. This geologic structure has no connection with the "Niigata trend", and might be produced by volcanic activities simultaneous with deposition, resulting in the unusual distribution and shape of the tuff.