阿讃山脈における高位緩斜面の分布とその特性
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概要
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There are many high-level gentle slopes in the Asan (Sanuki) Mountains, north-eastern Shikoku. The writer classified them into three ; top gentle slopes (T slopes), top-flank gentle slopes (TF slopes), and flank gentle slopes (F slopes). He surveyed mainly their distribution and characteristics, and discussed their formation. Following are conclusions; 1. High-level gentle slopes occupy 31.9% area in the western part of the Mountains, 50. 9 % in the central, 17. 6% in the eastern. When seen in the N-S direction, at the right angle with the base-line along the Median Dislocation Line, which is one of the 1st class tectonic lines in Japan, 88% of the high-level gentle slopes are in the zone between the base-line and 6 km north of it, especially 56. 1% of the whole are in the zone 2 to 4 km north of the base-line. 2. There are many relationships between distribution of the high-level gentle slopes and the geological structure of the Izumi Group constituting their base rock. The large portion of F slopes are near its synclinal axis, and many of TF slopes are near the southern limb of the syncline. The greater part of F slopes have steep cliffs at their back-ground and small mounds and slight depressions on their surfaces. As to the geological profiles observed at many outcrops showing deposition of detritus and some bedding of base rock, it is probable that F slopes were resulted from the mass sliding on the back slopes of cuesta. The characteristics of T slopes are different from those of F slopes, but it is not yet solved whether T slopes are the relics of uplifted peneplains or not. 3. Although it was reported that some portion of the high-level gentle slopes belonged to the piedmonttreppen, the writer cannot discover the clear evidences, but at the present stage he cannot deny the piedmonttreppen theory, because some high-level gentle slopes, e. g. those in the north of the Awa-Ikeda Station or in the north of Kamiitacho, have the accordant levels and it is more reasonable to attribute their formation other than landslide. 4. The asymmetric distribution of the high-level gentle slopes in the N-S direction is one of the notable characteristics. The earlier upwarping in the northern part has the high-level gentle slopes eroded out and the later upheaval in the southern part along the Median Line made the slopes……T slopes perhapss……remained without dissection. 5. Relationships between the high-level gentle slopes and facies of the Izumi Group are not clear at present.
- 地理科学学会の論文
- 1969-12-15
地理科学学会 | 論文
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