新庄盆地の第四紀地殼変動

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The Pliocene and Lower Pleistocene formations are folded and the fluvial terraces are dislocated in the Shinjo Basin, northeastern part of Yamagata Prefecture, Northeastern Honshu, Japan. The folded structures, mainly of Miocene sediments, constitute a synclinorium developed between the Backbone Ranges of Northeastern Honshu and the Dewa Hillyland. In the southern part of the Shinjo Basin, the Pliocene and Lower Pleistocene formations are intensely folded and thrust faults are locally developed along the axial planes of the closed synclines which are inclined eastwards. The folds in the southern part of the basin plunge northwards and change into a gentle synclinorium through a broad syncline. Slightly reversed gradient of the fluvial terrace plains is recognized at several localities in the western and southern parts of the basin. The dislocation of the terraces accords with the folded structure of the basement formations. The lower part of the Upper Pliocene Izumikawa Formation is intercalated with sedimentary marine facies, which indicate clearly a post-Pliocene uplift amounting to more than 500 m of the Dewa Hillyland now separating the basin from the Japan Sea coastal area. Terraced graded plains are distributed on the foothills of the Backbone Ranges and Dewa Hillyland around the Shinjo Basin and suggest the principal duration of the uplift of the Dewa Hillyland preceding their development. Some problems in the structural development of the lowland zones of Northeastern Honshu are also discussed in this paper in connection with the Quaternary crustal movements in the Shinjo Basin.
東北大学の論文
1971-03-31

新庄盆地の第四紀地殼変動

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