Evolutionary events of Cainozoic Ostracoda of western Philippine Sea and paleoceanographical implications

The Oligocene ostracod fauna of IISDP Site 292 of the western Philippine Sea was marked by high density, diversity and origination, probably reflecting a favorable period for deep-sea Ostraroda; while the sharp decrease in dtmsity and diversity as well as the repeatedly occurring vxtinctions in thc. Neogene may indicate the deterioration in bottom-water environmcnts at that tlme. Five rriajor faunal changes have been recognized in terms of density, diversity and evolutionary artivity (origination and extinction), occurring in the earliest Oligocene (PI8), mid-Oligocene (P21), earliest Miocene (N4), early Middle Miocene (N8) and late Pliocene (N21). respectively. These changes in ostracod faunas are suggested to represent short-term events related to global paleoceanographical changes and to record the Cainozoic cooling history of the West Pacific Ocean and Philippine Sea deep-water.

The Oligocene ostracod fauna of DSDP Site 292 of the western Philippine Sea was marked by high density, diversity and origination, probably reflecting a favorable period for deep sea Ostracoda; while the sharp decrease in density and diversity as well as the repeatedly occurring extinctions in the Neogene may indicate the deterioration in bottom water environments at that time. Five major faunal changes have been recognized in terms of density, diversity and evolutionary activity (origination and extinction), occurring in the earliest Oligocene (P18), mid Oligocene (P21), earliest Miocene (N4), early Middle Miocene (N8) and late Pliocene (N21), respectively. These changes in ostracod faunas are suggested to represent short term events related to global paleoceanographical changes and to record the Cainozoic cooling history of the West Pacific Ocean and Philippine Sea deep water.