GEOMORPHOLOGICAL DEVELOPMENT OF THE AREA ALONG THE UPPER STREAM OF THE JOGANJI RIVER

概要

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The writer has surveyed the glacial topography of the Tateyama Range in the northwestern part of the Hida Mountains, the lava plateau of Tateyama Volcano (Fig. 1) and the river terraces (Fig. 2) along the upper stream of the Joganji River. The results may be summarized as follows. (1) The gravel beds of Awasuno and Ashikuraji terraces (Fig. 3) were deposited After Midagahara lava plateau had been formed (Table 1) and the western side of the crater wall had been almost destroyed -by breakdown and erosion. (2) The explosion of the Mikurigaike took place after Midagahara lava plateau had been formed, was an event in the latter half of Tateyarns ice age (=Hida ice age) which may be correlated to Würm ice age. (3) In the gravel beds of Chigaki and Yokoe terraces (Fig. 4) huge boulders can be found, while in those of higher and older ones of Awasuno and Ashikuraji they can't. Comparing the gradient of the present river-flow with those terraces, it may be said that those gravel beds were deposited by the increse of the river-water. The writer has concluded, therefore, it was probably at ice age or its melt-water stage that these gravel beds were deposited. Basing upon the facts as stated above, the writer has mad the chronologi-cal table of the geomorphological development of the area treated (Table 2).
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