5:15 PM - 6:30 PM
[SGL37-P02] Stratigraphic correlation of the middle and lower part of the Cretaceous Yezo Group by U-Pb geochronology of tuffaceous rocks, Hokkaido, northern Japan
Keywords:Cretaceous, Yezo Group, U-Pb geochronology
As a result by zircon U-Pb dating, the tuff layers, in the Shirataki Formation, in Teshionakagawa area show the youngest graphical age peaks of 96.3-103.4 Ma. On the other hand, the youngest age peak of 98.5±0.5 Ma are obtained from the tuff layer, in Shunbetsu area. Additionally, the petrological characteristics of these tuff and tuffaceous sandstone show felsic. In nature, it is reported that the depositional age of the Maruyama Formation is 102-105Ma by previous studies using planktonic foraminifera (Takashima et al., 1997b). In addition, sanidine Ar-Ar radiometric age of 98.98±0.38 Ma, 99.16±0.37 Ma were reported from the tuff layer in the Hikagenosawa Formation, in the Middle Yezo Group in the central Hokkaido (Obradovich et al., 2002). Therefore, we concluded that the dated tuff layers in Teshionakagawa and Shunbetsu areas are comparable to these Formations, because of the similarity of these depositional ages and petrological characteristics. It is concluded that the granitic rocks yielding 96-127 Ma K-Ar ages (ex. Shibata and Yamada, 1978), distributed in the Oshima Belt, and the volcanic rocks showing 100.6±3.3 Ma Ar-Ar age (ex. Takigami, 1984) in the Rebun-Kabato Belt are potentially related to source of these tuff layers because of similarity of the radiometric ages and petrological characteristics.