Early Miocene freshwater diatom flora from the Yamato Rise, the Sea of Japan

Abstract

Fossil freshwater diatoms from tuffaceous–terrigenous deposits of the Yamato Rise, the Sea of Japan are described. The diatom flora includes 133 species and intraspecific taxa belonging to 44 genera. Species of Aulacoseira (19 taxa) and Tetracyclus (17 taxa) are highly diversified, and species of Aulacoseira and Actinocyclus occur very abundantly. Aulacoseira is mainly represented by extinct taxa, including those with elliptic valves that are characteristic of the Early Miocene (23–16 Ma). Such findings of numerous fossil freshwater diatoms in the Yamato Rise deposits strongly suggest that, during the Early Miocene, the Yamato Rise contained a lake basin within a terrestrial environment. Fifty-seven diatom taxa are illustrated.

Keywords:

• freshwater diatoms
• Early Miocene
• Yamato Rise
• Aulacoseira
• Tetracyclus

Acknowledgements

The author thanks very much F. Akiba (Diatom MiniLab Akiba Ltd., Japan) for critically reviewing the manuscript and providing useful discussion and suggestions. I am grateful to my colleagues from the Il’ichev Pacific Oceanological Institute for collecting geological samples from the Yamato Rise and L.V. Osipova for the processing of the samples for the diatom analysis.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by the Far Eastern Branch of the Russian Academy of Sciences [grant numbers 15-I-1-003, 15-I-1-004о] and partly by the programme of basic scientific research of the Il’ichev Pacific Oceanological Institute (theme 75.7).