Loc. 138 [Okinoshima Fm] (Eocene of Japan)

Where: Japan (32.9° N, 129.6° E: paleocoordinates 38.1° N, 124.0° E)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Okinoshima Formation, Bartonian (41.3 - 38.0 Ma)

• STRATIGRAPHIC RELATIONS: From the Okinoshima Fm, which conformably overlies the Hashima Fm and is unconformably overlain by the Iojima Fm. AGE: Late Eocene according to foraminiferal biostratigraphy in Asano (1958), and correlated to the Sakasegawa Shale. Kobayashi and Kamada (1959) suggest that the formation could even range from Middle-Late Eocene. According to foraminiferal and molluscan biostratigraphy, the formation is assigned in age to the Auverisian to the Bartonian (Upper Eocene). The Okinoshima Formation falls within calcareous nannofossil Subzones CP14a–CP15b of Okada and Bukry (1980) and planktic foraminiferal Zones E10–E13 of Berggren and Pearson (2005), dating to the middle Eocene. The Okinoshima Formation including calcareous nannofossils such as Reticulofenestra umbilica and Discoaster barbadiensis, indicating Zones CP14–CP15 and planktic foraminifer, Acarinina primitiva, representing Zone P14 or older (Yamaguchi et al. 2004). These biozones of planktic microfossils assign the Okinoshima Formation to 43.5–39.0 Ma (Yamaguchi & Kamiya, 2007).

•STRATIGRAPHIC POSITION: From bed of unknown thickness within 150 m thick formation.

• bed-level stratigraphic resolution

Environment/lithology: offshore; lithified siliciclastic sediments

• ENVIRONMENT: The biofacies consists of samples from muddy sandstones, sandy mudstones, and mudstones, which represent bioturbation and include few sedimentary structures that indicate wave and tidal influences. The planktic/total foraminifer ratios (P/T ratios) from the Okinoshima Formation is less than 0.03, suggesting water depths shallower than about 100–150 m. The lithofacies, P/T ratios, and molluscan assemblages indicate shallow-marine environments with little to no influence by wave and tidal action. Hence, the biofacies correlates with outer-shelf environments under warm-water conditions.
• SPECIFIC LITHOLOGY: Lithology not stated in text, but is likely siliciclastic. LITHIFICATION: Lithified, on the basis of figured specimens.

Size class: macrofossils

Preservation: cast, mold/impression

Collected by Kamada

Collection methods: surface (in situ),

• COLLECTOR: Y. Kamada and graduates students Nagasaki University, c. 1950's. REPOSITORY: Nagasaki and Tokyo University.

Primary reference: T. Kobayashi and Y. Kamada. 1959. An Eocene Nautiloid from Kyushu, Japan. Japanese Journal of Geology and Geography 30:105-125 [A. Hendy/A. Hendy]more details

Purpose of describing collection: paleoecologic analysis

PaleoDB collection 81229: authorized by Austin Hendy, entered by Austin Hendy on 11.06.2008

Creative Commons license: CC BY (attribution)

Taxonomic list

• COVERAGE: Exhaustive for Bivalvia, Gastropoda, and Cephalopoda. NOMENCLATURE: Authoritative publication for cephalopods, but general for other taxa. Nomenclature is somewhat antiquated, but identified to species-resolution.
 Carditida - Carditidae
"Venericardia nipponica" = Venericardia (Venericor) nipponica
"Venericardia nipponica" = Venericardia (Venericor) nipponica Yokoyama 1911 clam
 Cardiida - Veneridae
 Pholadomyida - Pholadomyidae
"Pholadomya margaritacea" = Pholadomya (Bucardiomya) margaritacea
"Pholadomya margaritacea" = Pholadomya (Bucardiomya) margaritacea Sowerby 1821 clam
 Neogastropoda - Tudiclidae
Pseudoperissolax blakei Conrad 1855 snail
 Nautilida - Nautilidae
"Eutrephoceras japonicum" = Eutrephoceras japonicus
"Eutrephoceras japonicum" = Eutrephoceras japonicus Shimizu 1926 nautiloid