Topographical and geological characteristics of Sofugan Tectonic Line (STL) area, Izu-Ogasawara Arc. Izumi SAKAMOTO Toshiya FUJIWARA and Osamu ISHIZUKA Sofugan Tectonic Line STL locates on the middle part of Izu-Ogasawara Arc IOA, and divides it into Northernand Southern part. Four major topographical characters such as seamounts, knolls, and trough and fault are observed in this area. And three major fault tectonic direction are confirmed such as NE-SW, NW-SE, and N-S trending. The investigated area is classified into four gedogical units such as fore volcanic front zone, volcanic front zone, back-arc knolls zone, and back-arc seamounts on the basis of their geological phenomenon. These topographical and geological characters indicate each stages for developing activity of Oceanic Island Arc. Keywords : Izu-Ogasawara Arc, Sofugan Tectonic Line, Seamount, Knoll, Fault OD OD Program Office, JAMSTEC Deep Sea Research Dept., JAMSTEC Geochemical Dept., GSJ
Km Km - Yuasa, Sakamoto et al,.. m WGS YK- JAM- STEC, YK- JAMSTEC, YK- JAMSTEC, YK- YK- Jarvis Jarvis YK- - Km. Km Km m m m m m /m Yuasa et al. NW Km m Km m Km m m S- m KmKm m -
Fig. Location and indexmap of around Sofugan Tectonic Line.
YK- YK- Fig. Bathymetric map of around study area using the YK- to YK- cruise data. Contour interval is m.
m Kmm Km m Km m Km m m Km m / m Km m Km m m m m m Km m km mm m m m GOKaS Fig. Bathymetric map of around the northern part of Shichiyo seamount chain. G Getsuyo seamount, O Ohomachi seamount, Ka Kayo seamount, S Suiyo seamount. Contour interval is m.
S-S- S- Km K m - Km NW - Km Km Km N ENE /m m / m m m S-S- Km Kmm m m /ms- NE Fig MKiD Bathymetric map of around the southern part of Shichiyo seamount chain. M Mokuyo seamount, Ki Kinyo seamount, D Doyo seamount. Contour interval is m.
S-S- Km KmKm m / m NS NE S-Km Km S-S- S- S-S- Km S- Km m S-S- S- S-S- S- Km Km m - - - Fig. Bathymetric map of around Sofu Block so-called. Contour interval is m.
S- Km KmKmm NE Km KmKm m m /m /m Km KmKmm / m m Mn Km KmKmm m m - Mn Km KmKm m /m Km KmKm m /m S-Km Km Km KmKm KmKm m /m /m S- -, - - Km m -South -North S- Km KmS- S-m S-
Fig. Bathymetric map of around the NW-SE trending small knolls and Sofu depression. Contour interval is m. KmKm Km m m Fig. Rose diagram for long axis direction of small knolls where locates around the Sofugan Tectonic Line m Km Km Km m S- m/m m /m
Fig. Distribution map of depression and fault around the survey area m m NW m Km Km Km m Km Kmm m S- S- m m NW S-
S-S- KmKm m m S-S- Km Km S- S- m S- Km Km m S- -.... Ma SiO.% Yuasa et al., Honza and Tamaki, Yuasa and Nohara, Fig. Geological columnar section from around Sofugan Tectonic Line after Sakamoto et al.,
Yuasa and Nohara, m m S- CNb-b. -. Ma CNb. Ma HFSNb. Ma K-Ar in-situ S- + + S-S- - Ma S- Mn Mn S- Mn S- NW S- CNb.-.Ma S- Ma Ar-Ar CNb.Ma S- m HFS Nb Ma Ar-Ar S- m S-S- Km m -
Fig. Geological tectonic map around Sofugan Tectonic Line - - S- S- - -
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