| Budget Amount *help |
¥7,100,000 (Direct Cost: ¥7,100,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2003: ¥4,700,000 (Direct Cost: ¥4,700,000)
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| Research Abstract |
This research was on cracks, which are one of the causes of disturbance in Paleolithic strata. I compared soil wedges in the Korean Peninsula, desiccation crack casts in Honshu, and ice wedge casts in Hokkaido by observation in the field, and some laboratory analysis. I examined differences and transitional characteristics in frost cracks and desiccation cracks with respect to structure and formation mechanism.
1. Correlation of the Upper Pleistocene in the Korean Peninsula
In the Upper Pleistocene, including in soil wedges from the Korean Peninsula, round quartz and other round minerals of less than very fine sand grain size were recognized near the upper limits of the cracks. Thus, the round minerals may have originated as aeolian loess. In addition, it became clear that volcanic glasses which came from AT volcanic ash are included comparatively large portion in the crack fillers. I suggest that most upper cracks were formed before and after the climax of the last glacial stage. Furthermore, I made up Upper Pleistocene into four period with cracks, volcanic glasses, the dark color zone, the dark reddish-brown zone and so on.
2. Structure and a formation factor of cracks
In both local observations and observations of undisturbed surfaces, except for the top portion, soil wedges on the Korean Peninsula and desiccation cracks on Honshu were only mud veins made visible by rainwater. This crack phenomenon is a structure not found in the ice wedge casts accompanying with the activity layer in Hokkaido. With regard to the fact that the main origin of the ice wedge casts depends on freezing, the soil wedges and desiccation crack casts were influenced by the chilly conditions of the last glacial stage, but it is thought that shrinking due to drying was the main factor in formation. It is concluded, therefore, that these cracks were another cracks which were different from so-called soil wedges.
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