Cover photograph In the middle part of the Boso Peninsula, central Japan, the upper part of the Neogene Awa Group, Amatsu, Kiyosumi and Anno formations, in ascending order, are widely distributed (upper-left figure). In this part, detailed geological structures and straigraphy have been studied based on the distribution of many key tuff beds intercalated in these formations except for the area around the Seiwa Prefectural Park (block C in upper-left figure), located along the upper stream of Koito River, due to the existence of the old Mishima-dam and Toyofusa-dam lakes. The geological survey using a motor boat (upper-right figure) was conducted to disclose the detailed straitigraphy and structure of this area (lower-left figure). At an locality, the channel deposits of the middle part of the Anno Formation, sandy conglomerate and pebbly sandstone, directly Overly the lower Amatsu Formation (lower-right figure). Please see Ishihara and Tokuhashi (2001) in this issue. (all figures: Yoshiro ISIHARA and Shuichi TOKUHASI)
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