Paleoenvironment of fossil ophiuroids in Plio-Pleistocene Hijikata Formation in Shizuoka Prefecture, Central Japan

摘要

The Paleoenvironment of Ophiura sarsii Lutken and Ophiozonella longispina (H.L. Clark) from the Plio-Pleistocene Hijikata Formation in Shizuoka Prefecture, central Japan was estimated on the basis of stable isotope ratio of oxygen in the ossicles. The ratios of the fossil O. Sarsii and O. longispina were similar to each extant conspecific living on the upper bathyal zone at 2-12°C and lower sublittoral zone at 8-16°Crespectively. SEM observations and X-ray diffraction analysis of fossil ossicles of both species showed that the specimens had scarcely undergone depositional diagenesis suggesting the results of stable isotope analysis show a good estimation of paleoenvironment.