Tetori Group

The Tetori Group is a stratigraphic group in Japan, found within several basins in and around Fukui Prefecture. It is Early Cretaceous in age.^[1] It primarily consists of freshwater continental deposits, with some beds of volcanic tuffite. It primarily overlies Jurassic marine sediments or gneiss basement. Some of the units within the group are noted for their fossil content, including dinosaurs, lizards mammals and other vertebrates.^[2]

Tetori Group
Stratigraphic range: Early Cretaceous PreꞒ Ꞓ O S D C P T J K Pg N
Type	Stratigraphic group
Sub-units	Fukui Area Kitadani Formation Akaiwa Formation Kuwajima Formation Gomijima Formation Shokawa Area Bessandani Formation Okura Formation Amagodani Formation Okurodani Formation Otaniyama Formation Mitarai Formation Ushimaru Formation
Underlies	Omichidani Formation
Overlies	Hida Gneiss, Kiritani Formation or Kuzuryu Group
Thickness	Over 1,000 metres (3,280 ft)
Lithology
Primary	Sandstone, Mudstone
Other	Tuffite
Location
Country	Japan
Type section
Named by	Oishi
Location	Areas along the Itoshirogawa River
Year defined	1933

Stratigraphy

The term "Tetori Group" was first used by Oishi in 1933. A significant revision was made by Maeda in 1961 which subdivided the Group into three subgroups, which in ascending order are the Kuzuryu Subgroup, the Itoshiro Subgroup and the Akaiwa Subgroup, alongside the Omichidani and Asuwa Formations, which were subsequently excluded from the group. Recent stratigraphic revisions have split off the Kuzuryu Subgroup into the Kuzuryu Group, which is Mid to Late Jurassic in age and is largely marine. There is significant lateral variation within the Tetori Group, with completely different sequences of formations in different areas, so it is difficult to correlate different sequences into the different subgroups, so the Itoshiro and Akaiwa subgroups are now considered depreciated.^[3]

References

1. Kusuhashi, Nao; Matsumoto, Ai; Murakami, Masaki; Tagami, Takahiro; Hirata, Takafumi; Iizuka, Tsuyoshi; Handa, Takeshi; Matsuoka, Hiroshige (2006-08-18). "Zircon U-Pb ages from tuff beds of the upper Mesozoic Tetori Group in the Shokawa district, Gifu Prefecture, central Japan†: U-Pb dating of the Tetori Group". Island Arc. 15 (3): 378–390. doi:10.1111/j.1440-1738.2006.00544.x.
2. Matsuoka, Hiroshige; Kusuhashi, Nao; Corfe, Ian J. (2016-07-03). "A new Early Cretaceous tritylodontid (Synapsida, Cynodontia, Mammaliamorpha) from the Kuwajima Formation (Tetori Group) of central Japan". Journal of Vertebrate Paleontology. 36 (4): e1112289. doi:10.1080/02724634.2016.1112289. ISSN 0272-4634.
3. Yamada, Toshihiro; Sano, Shin-ichi (2018). "Designation of the Type Section of the Tetori Group and Redefinition of the Kuzuryu Group distributed in Central Japan". Memoir of the Fukui Prefectural Dinosaur Museum. 17: 89–94.