After the world war II, the needs of applied earth sciences such as engineering geology, hydrogeology, applied geomorphology etc. has been emphasized in Japan. It is mainly due to the requests of engineers who constructed high ways, railway roads, tunnels, bridges, high buildings and deep wells of large diameters. It is partly due to the requests of agricultural engineers who did reclamation works of large scale. These necessities stimulated to the developement of applied earth sciences. It is easily imagined that applied earth sciences are closely connected to the study of Quaternary research in Japan. For example, one aspect of engineering geology related to soil mechanics will not be formed without standing on the basis of sound study of Quaternary geology. The writer demonstrated some of the Quaternary researches in Japan contributed to the applied earth sciences and wishes active collaboration of Quaternary research with applied earth sciences.
A brief review of the formation of coastal dunes is presented below. 1) Some ancient eolian sands are found only in the definite horizons of a Quaternary sequence; i. e., the Riss-Würm, late Würm, and later Holocene in age. 2) The deposition of some eolian sands is probably related with the fall in sea level. Others may indicate strong wind-action or arid climate. 3) The first appearance of the extensive emerged bars composed of the Quaternary marine and eolian sediments was probably due to the tectonic movement which generally produced an anticline. The Riss-Würm Interglacial transgression played the most important role in the development of the emerged sand bars where the eolian sands were deposited to conform closely to the pre-existing form of them.
This paper is mainly concerned with the river terraces and their deposits developed in Osaki Plain and along the Nanakita River, north of Sendai, Miyagi Prefecture. The basement rocks of this area consist mainly of Pliocene sediments and partly of Pleistocene pyroclastic flow deposits of Kitagawa dacite. The Pliocene sediments are a part of those, which are widely distributed in the northern part of Miyagi Prefecture. The river terraces of the area are grouped into four horizons, that is, from the older to the younger, IV, III, II and I. The IV, III and II terrace surfaces in Osaki Plain are covered with volcanic ash layers. The writer accomplished a tephrochronological study using these layers and made clear the development of the terraces. On the basis of the geomorphological features and the sequence of the terraces, the IV, III, II and I can be correlated with the Aobayama, Dainohara, Upper and Middle Sendai, and Lower Sendai (or Miyagino Plain) terraces in Sendai respectively. The successive developement of the IV, III, II and I terraces in this area is considered to be conformable with the opinion of Nakagawa (1961) and the succession of the IV, III, II and I Plains of him. Along the northeastern and southwestern margins of Osaki Plain, we can observe vertical dislocations of the IV and III terrace surfaces. The writer regards them as due to northwest-southeast trending faults and flexures. The Honjo-Sendai tectonic line detected in the Tertiary System of the area (Kitamura, 1963, and others) may not affect the terrace surfaces.
The auther investigated terraces developing along the Iwami River, southeast of Akita City. The results are summerized as follows. (Refer to Figure 7, a model cross section of terraces.) The terrace surfaces of this region are classified into 8 levels. The highest and Tsubakidai (the fourth from the higher) terrace surfaces were formed at the stages of transgression. Each of them is the upper surface of littoral or estuarine deposits about 50m thick. Most of the other terraces are of fluvial origin and top of them consists of a veneer of gravel. Their surfaces were formed at the stages of regression. The properties of the terraces of this region, near the coast of Japan Sea, resemble to those of some regions on the coast of the Pacific Ocean, where the formation of terraces is often considered to have relations to the glacial eustacy.