Yorimatsu Formation, Chikanaga area (Cretaceous of Japan)

Where: Japan (33.3° N, 132.8° E: paleocoordinates 42.9° N, 123.6° E)

• local area-level geographic resolution

When: Yorimatsu Formation (Shimanto Group), Santonian (86.3 - 83.6 Ma)

• STRATIGRAPHIC RELATIONS: From the Yorimatsu Fm (Coniacian) of the lower Shimanto Group and Shimanto Supergroup, overlying the Ishibiki Fm (Coniacian) and overlain by the Miocene granites. AGE: Santonian. STRATIGRAPHIC POSITION: List not specified to any part of the formation.

• formation-level stratigraphic resolution

Environment/lithology: offshore; siliciclastic sediments

• STRATIGRAPHY and STRUCTURE: The Shimanto Supergroup is a thick clastic sequence with minor basic volcanic rocks, chert and limestone. The Aptian, Albian, Turonian, and Conacian to Santonian strata are in fault contact with one another. The Lower Cretaceous, except for the Lower Aptian is regarded as rather deep offshore deposits, while the Upper Cretaceous as neritic, shelf deposits.
• SPECIFIC LITHOLOGY: Lithology, unknown, presumably siliciclastic. LITHIFICATION: No evidence for lithification.

Size class: macrofossils

Collection methods: COLLECTOR: Collector unknown. REPOSITORY: Repository unknown.

Primary reference: Y. Teraoka, I. Obata, and I. Mizuno. 1980. Stratigraphy of the Shimanto Supergroup in the Chikanaga area, west Shikoku, with special reference to the Miyakoan and Gyliakian Series. Bulletin of the Geological Survey of Japan 31(7):307-319 [A. Hendy/A. Hendy]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 65025: authorized by Austin Hendy, entered by Austin Hendy on 18.09.2006

Creative Commons license: CC BY (attribution)

Taxonomic list

• COVERAGE: Suspected to only include biostratigraphically important taxonomic groups (i.e. inoceramids and ammonoids). NOMENCLATURE: Not an authoritative publication, but using subgeneric and species-level designations.
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Bivalvia
 Arcida - Parallelodontidae
Nanonavis sachalinensis
 Myalinida - Inoceramidae
Inoceramus cf. vanuxemiformis, Inoceramus sp., Inoceramus cf. ezoensis, Inoceramus cf. amakusensis, Inoceramus balticus, "Inoceramus naumanni" = Sphenoceramus naumanni, "Inoceramus orientalis" = Sphenoceramus orientalis
Inoceramus sp. Sowerby 1814 clam
Inoceramus cf. ezoensis Yokoyama 1890 clam
Inoceramus cf. amakusensis Nagao and Matsumoto 1940 clam
Inoceramus balticus Bohm 1907 clam
"Inoceramus naumanni" = Sphenoceramus naumanni Yokoyama 1890 clam
"Inoceramus orientalis" = Sphenoceramus orientalis Sokolov 1914 clam
I. orientalis nagaoi
 Pectinida - Propeamussiidae
Propeamussium cowperi
Propeamussium cowperi Waring 1917 mud scallop
Subspecies: P. cowperi yubarensis
Cephalopoda
 Ammonitida - Desmoceratidae
"Neopuzosia sp." = Kitchinites (Neopuzosia)
"Neopuzosia sp." = Kitchinites (Neopuzosia) Matsumoto 1954 ammonite
 Ammonitida - Collignoniceratidae
Protexanites fukazawai