東北地方における第四紀地殻変動

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The Tohoku Region is the most favorable area to investigate the Quaternary crustal movements in the Japanese Islands on account of the well developed Neogene as the basement of the Quaternary System and there is large accumulation of geological information on them. The Pliocene and Quaternary sediments and most of the terrace topography are restricted in their distribution to four hilly land zones running parallel with the direction of the Japanese Islands, each of which are separated from one another by mountainlands consisting largely of pre-Pliocene rocks. The Quaternary crustal movements in the Tohoku Region are characterized by the superposition of folding with the axes of N-S direction on the northward tilted blocks with NW-SE axes, caused the alternating arrangement of low plains and hilly lands along the low land zones developed on the synclinorium. The Pacific coastal area is the most stable and the folding became more intensified towards the Japan Sea side during the Quaternary. The accordant summit area of the hilly lands have been developed mostly as a denudational graded plain during the early Middle Pleistocene. Truncation of the folded structure of the underlying strata including the Pliocene and the Lower Pleistocene by this graded plain suggests that the rate of the folding is inferior to the development of the denudational graded plain. This is a striking contrast to northern part of the 'Fossa Magna' area where folded Pliocene and Lower Pleistocene rise far above the base-level control and to the sedimentary basin in the central part of the Kanto Region where marine sedimentation survived through the Pliocene and Early Pleistocene until the beginning of the distinct lowering of sea level during the Late Pleistocene.
日本地質学会の論文

東北地方における第四紀地殻変動

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