Abstract:
The radiolarian zonation of ODP Site 1179 was accessed using core-catcher samples. The data indicate that the soft sediments analyzed range from late Miocene to Recent. The radiolaria biostratigraphy of ODP Site 1179 yielded reliable results even though only core-catcher samples were studied, as seen by the comparison of the radiolarian and magneto stratigraphy based sedimentation rates. Sedimentation rates at DSDP/ODP sites (578, 579, 580, 581, 881,1149 and 1179) range from 23.1 m/Ma in the north to 3 4 m/Ma in the south during the late Miocene. The sedimentation rates during the Pliocene range from 58.4 m/Ma in the north to 14.0 m/Ma in the south site and during the Quaternary they range from 65.4 m/Ma in the north to 27.7 m/Ma in the south The initiation of Miocene biosiliceous sedimentation in the Northwest Pacific Ocean, as recorded at DSDP Sites 578 and 581 and ODP Site 1179, indicates that this event was diachronous The onset of biosiliceous sedimentation began in the middle Miocene at DSDP Site 581 and moved southward during the late Miocene. Since this time the Kuroshio/Oyashio transition zone has been migrated north and south. The current path does not move straight to the east, instead its path is curved. The position of the Kuroshio/Oyashio transition zone during the late Quaternary as indicated by radiolarian data occurs between 39 to 41 degrees N; this is not consistent with Koizumi (1985). There is a slight drift in the apparent latitude of the Kuroshio/Oyashio convergence boundary based on paleoceanographic sea surface currents and sedimentation indicators.