著者

皆川 紘一 町田 端男

出版者

地学団体研究会

雑誌

地球科學 (ISSN:03666611)

巻号頁・発行日

vol.25, no.4, pp.164-176, 1971-07-25

被引用文献数

1

---

Correlation of the stratigraphic sections of the Tama Loam (tephra), by key beds of pumice layers, at some hills in South Kanto leads to some conclusions as the following. 1. The thickness of the Tama Loam totals about 40m, and it corresponds to that of all the loam units-Suarashi, Shimosueyoshi, Musashino and Tachikawa loams-younger than the socalled Tama Loam. The lower part of the Tama Loam unit is characterized by intercalations of dacitic pumices, whereas the upper part by andesitic pumices. 2. Such unconformable features as to be found near the boundary between Shimosueyoshi and Musashino loams are also found at two horizons within the Tama Loam. 3. From the facts mentioned above, the length of time through which the whole strata of the Tama Loam were deposited, may be inferred as being enough long to cover, for instance, whole time length implied by known several tephra units younger than the Tama Loam. Furthermore, the stratigraphic value of the Tama Loam may be on a par with that of the group including all the loam units younger than the Tama Loam. 4. The so-called Tama topographic surfaces which carries the Tama Loam upon them are tephrostratigraphically classified at least to four levels of terrace namely, from older to younger, the Sayama, Hodokubo, Kobiki and Oshinuma terraces.