Nanjing University, China

Three layers of volcanic tephra, sampled from ODP Site 1143 in the South China Sea, were observed at the mcd depth of 5.55 m, 42.66 m, and 48.25 m, and named in this paper as layers A, B, and C, respectively. All of these tephra layers have an average thickness of ca. 2 cm. They were constrained in age of ca. 0.070 Ma, ca. 0.80 Ma, and ca. 1.00 Ma, respectively, by microbiostratigraphic data. These tephra layers were dominated by volcanic glass shards with a median grain size of 70-75 mu m in diameter. Their major chemical composition, analyzed by EMPA and compared with previous data from other scatter areas, suggests that these three layers of tephra may correspond to the three layers of Toba tephra, YTT, OTT, and HDT, respectively, which erupted during the Quaternary. The occurrence of these tephra layers in the South China Sea implies that the Toba eruptions often occurred in the summer monsoon seasons of the South China Sea during the Quaternary, and that the strength of these eruptions was probably stronger than previously estimated.