Radiolarian biozonation for the upper Quaternary in the Japan Sea

Abstract

Rapid and drastic changes in radiolarian assemblages during the last 33 kyr were revealed in three sediment cores from the eastern and northeastern Japan Sea. Such changes occurred synchronously over the Sea according to the correlation by TL layers and AMS¹⁴C dating. On the basis of these bio-events, four radiolarian biozones were established : Ceratospyris borealis Interval Biozone (33 to 15¹⁴C kyr BP), Stylochlamydium venustum Interval Biozone (15 to 12¹⁴C kyr BP), Cycladophora davisiana Interval Biozone (12 to 10.5¹⁴C kyr BP), and Larcopyle butschlii Interval Biozone (10.5¹⁴C kyr BP to Present) . These radiolarian biozones are useful for correlating the upper Quaternary sediments in the Japan Sea, where carbonate fossils are poorly preserved below the calcium carbonate compensation depth (CCD) .