Yonabaru Clay, Shimajiri Formation, Okinawa (Miocene of Japan)

Where: Okinawa, Japan (26.5° N, 127.5° E: paleocoordinates 27.1° N, 126.5° E)

• coordinate estimated from map

• basin-level geographic resolution

When: Yonabaru Clay Member (Shimajiri Formation), Late/Upper Miocene (11.6 - 5.3 Ma)

• The Yonabaru Clay includes all Shimajiri Formation exposed below the upper tuffaceous pumiceous zone. The Yonabaru consists of bluish to gray silty to sandy clay, commonly with hackly to conchoidal fracture and fine dark-colored laminated to massive sand, weathering brown to gray, and in places contains large lime indurated concretions of sand. Most macrofossils are found in sandy beds intercalated with the clays. The Yonabaru passes under the cover of the basal gravels of the Naha limestone, and lap onto or are faukted against Paleozoic basement rocks.

• formation-level stratigraphic resolution

Environment/lithology: deep-water; poorly lithified, silty, sandy claystone and concretionary, brown, gray sandstone

• Molluscs found in assemblages of the Yonabaru Clay indicate moderately shallow to moderately deep water. Probably a depth of less than 100 fathoms in shallow facies and probably not more than 300 fathoms in deeper facies.
• Bluish to gray silty to sandy clay, commonly with hackly to conchoidal fracture and fine dark-colored laminated to massive sand, weathering brown to gray, and in places contains large lime indurated concretions of sand.

Size class: macrofossils

Preservation: original aragonite

Collection methods: quarrying,

• Collections held in USNM and UGSG repositories.

Primary reference: F. S. MacNeil. 1960. Tertiary and Quaternary Gastropoda of Okinawa: A comparison of the late Miocene, Pliocene, and Pleistocene Gastropoda of Okinawa with related faunas of East Asia together with a resume of the geological setting of the fossiliferous deposits. United States Geological Survey Professional Paper 339:1-148 [A. Miller/C. Ferguson/P. Wagner]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 42384: authorized by Austin Hendy, entered by Austin Hendy on 28.07.2004

Creative Commons license: CC BY (attribution)

Taxonomic list

• Taxa described in text, but not listed for specific localities. Importantly this list contains bivalvia
Bivalvia
 Arcida - Limopsidae
Limopsis cf. tajimae clam
Listed as "species closely related to L. tajimae"