1 0 0 0 OA 埼玉県寿能泥炭層遺跡の概況と自然環境に関する2・3の問題
- 著者
- 堀口 万吉
- 出版者
- Japan Association for Quaternary Research
- 雑誌
- 第四紀研究 (ISSN:04182642)
- 巻号頁・発行日
- vol.22, no.3, pp.231-244, 1983-11-30 (Released:2009-08-21)
- 参考文献数
- 15
- 被引用文献数
- 4 4
The Juno Peaty Site is situated on the Shibakawa lowland in the eastern part of Omiya City, Saitama Prefecture, and was investigated on the field from 1977 to 1981. The investigation was conducted to examine the natural environment of this site by the cooporation of archaeologist, geologist and many biologists. As the results, archaeological remains were found abundantly and useful observations were carried out, and many samples for scientific analysis were obtained to reconstruct the Juno's natural environment.This paper deals with a summary of the Juno Peaty Site with mainly geological evidences and several points of the problem to reconstruct of natural environment of this site. Especially, height and age of the highest sea level on the Holocene Transgression (Jomon Transgression) and palaeovegetation in the Jomon Age are described.Rising of sea level of Jomon Transgression in this site stagnated temporarily in the Kurohama stage (ca. 5, 700y.B.P.) showh by Kurohama Sand Bed with wave cut platform and trace fossils at 1m height on recent sea level, and thereafter, more risen sea level reached ca. 3m height on recent sea level in Moroiso-a stage. This 3m height indicates a upper limit of marine deposit in the highest sea level stage. Therefore it is presumedthat the highest sea level of Jomon Transgression stay on 3m height or more in the Moroisoa stage (ca. 5, 300y.B.P.) of Early Jomon Age.On the palaeovegetation in Jomon Age it is thought generally that the laurel forest (Cyclobalanopsis) had covered on the Pacific coast of Japan from Early Jomon Age downward. In the site, however, it was found out that the deciduous broad-leaved forest (Lepidobalanus) was dominant during the Jomon Age. This aspect is in contrast with the viewpoint that the laurel forest covered on the area of the Pacific coast in Japan, and it is characteristic feature found over the central part of Kanto Plain.
The writers and their collaborators have made study on the distribution of seismic intensity in Kanto district. They inquire of a few thousand persons the intensity who live in the wooden houses with second story. The data on the intensity are collected so on after an earthquake occurs. In this paper, following earthquakes are refferred, i.e. local earthquakes of western Tokyo (1979) and east-off Chiba Prefecture (1979); destructive ones of Kanto (1923) and Nishi-Saitama (1931). Approximate location and magnitude of those earthquakes are as follows; [Table] The distribution of seismic intensity of those earthquakes hows that straight, long and narrow zones are severe or sensitive to the earthquakes which are named the abnormalous seismic vibrated zones (F. Tsunoda, 1980). For instance, violent motion was felt along the margins of diluvial uplandand fault zones in the Kanto mountainland in case of the western Tokyo earthquake. Similar distribution was shown in the destructive Nishi-Saitama earthquake. Severe vibrated zone was found along the northeast coast of Tokyo Bay in case of the east-off Chiba Prefecture. Similar irregular distribution of intensity is found in the Kanto earthquake. Most of those anormalous seismic vibrated zones runs in northwest-southeast direction which is the general trend of the basement complex of Kanto Plain, and under some of them, faults of the basement complex are found, for instance, the Ayasegawa fault. So it must be intimately related with the faults developed in the basement. While some zones such as the Iwatsuki-Kasukabe abnormalous seismic vibrated zone run in northeast-southwest direction. The geological meaning of these zones is left to be solved in future. As already pointed out, the shock is also severe in the area where thick peat is deposited.