阿讃山地のPitching的曲隆に関する地形学的研究

抄録

In the northeastern Shikoku, the Asan Mountainland, whose southern boundary coincides with the Median Dislocation Line dividing southwestern Japan into the Outer and the Inner Geological Zones, is a recently elevated massif preserving several steps of relatively flat erosion surfaces on its foot.
The writer tried to make clear the Plio-Pleistocene tectonic movement of this mountainland through the study of these erosion surfaces. He classified these surfaces into 3 grouper, where sedimentary remnants are classfied into 6 layers on the northern side and 9 on the southern side of the massif. Moreover, 6 types of the conditions of contact between each surface and other ones are identified. Analysing these geomor-phological factors and fault structures, the writer reaches the following conclusions.
The Asan Mountainland is presumabjy a tilted block with some fresh fault scarps on its southern side as on the northwestern side, and has swollen up as a landwave of pitching with an axis upwarping at its central part linking Inohana with Sarusaka. Thus, the central part of the massif has been brought higher than its western or eastern ends. The movement mentioned above develops a system of radial faults with such depression areas as some parts of Takamatsu and Marugame Plain.
Considering the fresh fault cutting the lowest terrace gravels seen on the southern side of the mountain, this orogenic movement may have continued to grow up to the recent time.