GEOMORPHOLOGY OF THE SOUTHERN PART OF JOBAN COASTAL DISTRICT

Abstract

In the eastern foot of the Abukuma Plateau, the uplands known as “Foreland.” are distributed along the Pacific Ocean. In this rigion, the existence of the marine terraces was described by some geomorphologists, but several geologists reported that the Pleistocene deposits of this region were mostly fluvial origin. The writer researched the geomorpology of this area with special reference to the distribution and facies of deposits for the purpose of solving the discrepancy above mentioned and of explaining the forming process of geomorphic surfaces, especially of the marine terrace plain. The conclusions of this paper are as follows (1) In this region, the writer distinguished three major geomorphic surfaces having the altitudes of 120-130m (Upper), 50-70m (Middle) and 30-40m (Loner) (Fig. 1). They are correlated with Tama terrace, Musa-shino terrace and Interiuiediate terrace between Musashino and Post Kanto Loam terraces. (2) From the detailed survey of the sediments composing geomorphic surfaces (Figs. 1, 3 and 4 and Tab. 1), she inferred the environments of deposition and the forming processes of the surfaces, and classified them as showvn in Fig. 2. (3) It is presumed that the land has been intermittently elevating on the whole, rarely containing the partial subsidence in the north, and the movements of the northern part are more complicated than those of the south. In all surfaees, the boundaries of the geomorphic surfaces having different processes are situated along the courses of the River Miy ata and Juo, where the existence of the tectonic line. has been concluded from the Tertiary tectonic by certain geologists. Tendency of the crustal movements in Pleistocene above stated is similar to that of Tertiary.