Bulletin of the Mizunami Fossil Museum No. 49
Subsurface stratigraphy of widespread tephra in the late Pleistocene to Holocene sediments under the coastal area of Nohbi Plain, and further problems, central Japan
- BMFM49-014Makinouchietal（PDF 10.39MB）
- BMFM49-014Makinouchietal-s（PDF 2.33MB）
Makinouchi et al. (2022) print-version
Makinouchi et al. (2022) small-version
Published: 2022/12/27 Page: 145–165
Tephra analysis of borehole core samples (NB core) recovered from the coastal area of Nohbi Plain (Nabeta, Yatomi City, Aichi Prefecture) was performed, and several widespread tephra were identified. Based on the identified tephra, some problems have newly derived. Its contents are as follows. 1) Stratigraphy of the NB core consists of the Nan-yo (Holocene), Nohbi and First Gravel (latest Pleistocene), tephra in the bottom sediments of Lake Biwa. 3) Three ash-fall horizons were identified in the marine clay member of Nan-yo Formation. These are correlated with the Ulreung-Oki (U-Oki), Kikai-Akahoya (K-Ah), and Amagi Kawago-daira (Kg) tephra. 4) According to Hori et al. (2019), the First Gravel (=BG) and Nohbi Formations do not appear to date back to about 30 ka. 5) Content ratio of volcanic glass shape in muddy sediments suggests that the Nohbi Formation can be divided into the lower half containing the Aira-Tn tephra (AT) and the upper half without AT. 6) Thickness from the base to K-Ah horizon in the marine clay of Nan-yo Formation represents a period of time between the beginning of marine clay deposition and the K-Ah ash falling. Thicker localities are distributed along the longitudinal axis of Nohbi Plain. These data imply that the deposition of marine clay started from the longitudinal axis. A similar case is seen in the marine clay of the lower part of Atsuta Formation, where thickness from the base to the Nagashima tephra is greater in the east. It is further problem whether this marine clay began to be deposited from the east side.