Comparison study about formation mechanism of frost cracks and sun cracks, cause of stratigraphic disturbance on the last glacial stage

这项研究是关于裂缝的，裂缝是旧石器时代地层中扰动的原因之一。我通过实地观察和一些实验室分析，比较了朝鲜半岛的土壤楔形、本州的干裂铸件和北海道的冰楔铸件。研究了冻裂和干裂在结构和形成机理上的差异和过渡特征。朝鲜半岛上更新世对比在上更新世，包括朝鲜半岛的土壤楔体中，在裂缝的上限附近发现了圆形石英和其他小于很细砂粒粒度的圆形矿物。因此，圆形矿物可能起源于风成黄土。此外，很明显，来自AT火山灰的火山玻璃在裂缝填充物中占了相对较大的比例。我认为，大多数上裂缝形成于末次冰期高潮前后。在此基础上，将上更新世划分为裂缝、火山玻璃、深色带、暗红棕色带等四个时期。结构和裂缝的形成因素在当地和对未受干扰的表面的观测中，除了顶部，朝鲜半岛的土壤楔子和本州的干燥裂缝只是雨水可以看到的泥脉。这种破裂现象是北海道伴随活动层的冰楔铸件中所没有的一种结构。关于冰楔铸模的主要来源取决于冰冻，土壤楔形和干燥裂隙铸模受末次冰期寒冷条件的影响，但认为干燥收缩是形成的主要因素。因此，这些裂缝是不同于所谓的土楔的另一种裂缝。

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 PeninsulaIn 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 cracksIn 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.