Abstract
The Quaternary system in South Kanto is supposed to be a standard succession of middle-upper Pleistocene in Japan. However, there are many problems especially in its lower half. The authors have progressd reexamination about these problems, based on the study by Y. Otuka(1973), Y. Naruse (1960) and others, and succeded to Kanto Loam Research Group (1965). In our previous work in 1970, we have discussed on the Tsurumi Formation which was covered by Shimosueyoshi Formation unconformably. However the relation to the Byobugaura Formation was not certain in that time. So the necessity to reexamine the so-called Byobugaura Formation, has happened in order to establish and clarify the Quaternary system, especially middle Pleistocene, which had been regarded as the transgressive deposit before the Shimosueyoshi stage in South Kanto. The conclusion introduced by our investigation are as follows. 1) So-called Byobugaura Formation is distinguished into several units showed in following table. Each unit is composed of the neritic deposit (printed in Gothic letter) and is succeded by thick volcanic ash (so-called loam) on its upper part. Though, in some cases, especially in Totsuka Formation and Maioka Formation, neritic deposit and loam change into each other in laterally. 2) Each neritic deposit gradually changes its facies from bottom to top, mud facies (burying the -bottom of valleys with peaty silt and fossil shell) -coarse grained facies (granule-pebble sized gravel or sand)^loam. Such cyclic change of facise is seen in each unit. 3) The development of these units in this area suggests repeated sea-level changes, and the transitional change of sedimentary basin effected by crustal movements in the Quaternary history of South Kanto.
