2006 Volume 112 Issue 4 Pages 257-272
The Cretaceous Hidakagawa Group of the Shimanto Belt in the western coast of the Kii Peninsula is divided into the Yukawa Unit consisting of only terrigenous deposits and the Miyama Unit consisting of terrigenous deposits with chert and basalt. The Yukawa Unit is subdivided into two sub-units; the Ogui Sub-unit composed largely of age-unknown thick-bedded sandstone and the Nagasaki Sub-unit largely of late Albian to late Cenomanian sandstone-rich alternating beds of sandstone and shale. The Miyama Unit is subdivided into four sub-units from the north to the south; the Karakozaki Sub-unit composed largely of Coniacian shale-rich alternating beds of sandstone and shale, the Chidenohana Sub-unit largely of Santonian to early Campanian thick-bedded sandstone, the Shiofukiiwa Sub-unit largely of Santonian to early Campanian shale-rich alternating beds of sandstone and shale, and the Hinomisaki Sub-unit largely of early Coniacian to early Campanian thick-bedded sandstone.
These six sub-units are correlated with the formations of Hidakagawa Group in the central part of the Kii Peninsula in general. The Ogui and Nagasaki Sub-units are correlated to the Y3 and Y1 Members of the Yukawa Formation, respectively. The Karakozaki, Chidenohana, Shiofukiiwa and Hinomisaki Sub-units correspond to the M1, M2b, M2a and M2b Members of the Miyama Formation, respectively.
