Akabira Formation, Ishikari Group (Eocene of Japan)

Where: Japan (43.5° N, 142.0° E: paleocoordinates 46.2° N, 137.6° E)

• coordinate based on nearby landmark

• local area-level geographic resolution

When: Akabira Formation (Ishikari Group), Bartonian (41.3 - 38.0 Ma)

• STRATIGRAPHIC RELATIONS: From Akabira Fm, which overlies the Bibai and underlies the Ikushunbetsu Fm, all of the Ishikari Gp (Middle Eocene). THICKNESS: From unit which reaches a thickness of 350-600 m. AGE: late Middle Eocene according to Takano and Waseda (2003). Referred only to Eocene in Mizuno (1964). STRATIGRAPHIC POSITION: Composite checklist for formation from local area.

• formation-level stratigraphic resolution

Environment/lithology: marginal marine; lithified sandstone and lithified siltstone

• ENVIRONMENT: Marine and non-marine faunal assemblage.
• SPECIFIC LITHOLOGY: Sandstone and siltstone wth many coal seams. LITHIFICATION: Assume to be lithified on the basis of age and photgraphic plates of Takano and Osamu (2003).

Size class: macrofossils

Preservation: cast, mold/impression

Collection methods: COLLECTOR: T. Mizuno (c. 1960's). REPOSITORY: Unknown, not stated in text.

Primary reference: A. Mizuno. 1964. Summary of the Paleogene molluscan faunas in North Japan. Geological Survey of Japan Report 207 [A. Hendy/A. Hendy/A. Hendy]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 70903: authorized by Austin Hendy, entered by Austin Hendy on 11.04.2007

Creative Commons license: CC BY (attribution)

Taxonomic list

• COVERAGE: Exhaustive for bivalvia and gastropoda. NOMENCLATURE: Somewhat antiquated, but with species-level identifications.
 Ostreida - Ostreidae
Ostrea eorivularis Oyama and Mizuno 1958 oyster
 Ostreida - Pteriidae
"Margaritifera perdahurica" = Pinctada
"Margaritifera perdahurica" = Pinctada pearl oyster
 Mytilida - Mytilidae
 Carditida - Crassatellidae
"Crassatellites yessoensis" = Crassatella
"Crassatellites yessoensis" = Crassatella clam
 Carditida - Carditidae
"Venericardia cf. yoshidai" = Cyclocardia yoshidai
"Venericardia cf. yoshidai" = Cyclocardia yoshidai Nagao 1928 clam
 Pholadida - Myidae
Mya ezoensis Nagao and Inoue 1941 softshell clam
COMMENTS: Includes Mya ezoensis akabirensis
 Cardiida - Corbiculidae
Corbicula tokudai, "Geloina hokkaidoensis" = Polymesoda (Geloina)
"Geloina hokkaidoensis" = Polymesoda (Geloina) clam
 Cardiida - Veneridae
"Microcallista munroei" = Callista (Microcallista)
"Microcallista munroei" = Callista (Microcallista) venus clam
 Thraciida - Periplomatidae
 Thraciida - Thraciidae
 Lucinida - Thyasiridae
"Thyasira bisecta" = Conchocele conradii
"Thyasira bisecta" = Conchocele conradii Rosenkrantz 1942 clam
SUBSPECIES: Thyasira bisecta omauri
 Unionida - Unionidae
Unio uryuensis freshwater mussel
Anodonta subjapanensis freshwater mussel
 Nuculida - Nuculidae
Acila shimoyamai Oyama and Mizuno 1958 divaricate nutclam
 Protobranchia - Sareptidae
 Protobranchia - Yoldiidae
 Neogastropoda - Perissityidae
 Neogastropoda - Buccinidae
"Siphonalia" sakakurai Mizuno 1954 true whelk
 Naticoidea - Naticidae