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

• STRATIGRAPHIC RELATIONS: From Hiragishi Fm, which overlies the Ikushunbetsu and underlies the Ashibetsu Fm, all of the Ishikari Gp (Middle Eocene). THICKNESS: From unit which reaches a thickness of 120-700 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: fluvial; lithified sandstone and lithified siltstone

• ENVIRONMENT: Marine and brackish faunal assemblage.
• SPECIFIC LITHOLOGY: Sandstone and siltstone. 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 70905: 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.
unclassified
  -
Gastropoda
 Cerithioidea - Thiaridae
 Architaenioglossa - Viviparidae
Bivalvia
 Cardiida - Corbiculidae
 Unionida - Unionidae
Anodonta subjapanensis freshwater mussel
Hyriopsis mabutii freshwater mussel