Late Neogene paleoceanography of the North Pacific DSDP Sites 173, 310, and 296

Major paleoclimatic/paleoceanographic fluctuations across the mid-latitudes of the North Pacific have been identified based on quantitative analysis of temperature sensitive planktonic foraminiferal biofacies at DSDP Sites 296, 310, and 173. In the marginal Northeast Pacific DSDP Site 173 temperature oscillations within the California Current System are marked by alternating cool and transitional faunal assemblages; cool paleowater masses are represented by high frequencies of predominantly sinistrally coiling Neogloboquadrina pachyderma and transitional water masses by high frequencies in the species of Globigerina and Globigerinita associated with predominantly dextrally coiling N. pachyderma. In the marginal Northwest Pacific DSDP Site 296 temperature oscillations within the Kuroshio Current System are characterized by alternating subtropical and transitional faunal assemblages. High abundance in temperate species of Globorotalia represent subtropical water masses; high frequencies in the species of Globigerina and Globigerinita represent transitional water masses. In the Central North Pacific cool, transitional, and subtropical assemblages are present permitting paleoclimatic/paleoceanographic correlation with the Northeast Pacific Site 173 based on frequency distribution of N. pachyderma and the Globigerina-Globigerinita group, and with the Northwest Pacific based on the Globorotalia and the Globigerina-Globigerinita groups. This paleoclimatic interpretation is supported by oxygen isotope studies of DSDP Site 310, and the Equatorial Pacific. A comparison of the quantitative distribution of temperate species of Globorotalia at DSDP Sites 310 and 296 suggests that paleoclimatic interpretation is not seriously complicated by calcium carbonate dissolution.