Late Cainozoic ostracod faunas and paleoenvironmental changes at ODP Site 1148, South China Sea

Measures of evolutionary activity (origination, extinction and diversity) have been applied to detecting the environmental change and their relationship to global events. Five peaks of evolutionary activity occurred in the Oligocene (P18, P21a and P22) and in the earlier mid-Miocene N8 and late Pliocene-Quaternary N21-N22, respectively. The peaks in P18 and P21a are the possible response respectively to the global cooling events Oi-1 and Oi-2, which occurred in the early Oligocene. The marked increase in extinction, origination and diversity was synchronous with the major enrichment in benthic δ18O in the late Pliocene N21, suggesting a reaction of the ostracod faunas to the rapid cooling of the bottom water and the initiation of the North Hemispheric Glaciation during the period of 3-2.5 Ma.