Geomorphology and Geology of Eastern Musasino and Tephrochronology of Diluvial Uplands in Southern Kanto

Abstract

Tertiary hill, diluvial upland and alluvial plain are landform elements of the southern Kanto, and the former two are overlain by Kant-CI Loam (volcanic ashes). WE st part cf Tokyo, so-called Yamanote, is situated on eastern Musasino upland that is one of the diluvial coastal, plains. In this paper, cur geomorphological and stratigraphical observations on eastern Musasino, as well as former descriptions on the same region by others have been summarized, and the chronological arrangement of upland surfaces in the southern Kanto have been done by the use of Kanto Loam (namely tephrochronology).The main conclusions are as follows 1. Yamanote upland can be divided into three levels.Upper level ; depositional surface of Tokyo formation. (Uplifted coastal plain).Middle and lower level ; erosional surfaces formed by extended rivers. (River terraces).2. The deposition of Kanto Loam, that is, fall of volcanic ashes had a time interval, by which the Kanto Loam is divided into upper and lower one.3. The horizons of many levels of Musasino and adjacent uplands have been determined as shown in our chronological table.4. It is likely that before the birth of Tokyo Bay or the appearance of ancient Uraga Strait the deposition of upper Kanto Loam had finished.