LATE PLEISTOCENE PALEOCEANOGRAPHY OF THE TASMAN SEA - IMPLICATIONS FOR THE DYNAMICS OF THE WARM POOL IN THE WESTERN PACIFIC

Quantitative analyses of planktonic foraminifera from 47 core-top samp les (spatially distributed through the Tasman Sea) and cores RC12-113, E36-23, DSDP Sites 588, 591, 592, 593, and ODP Site 828A (from a N-S transect), supplemented with stable-isotope analyses indicate that thr ee planktonic foraminiferal assemblages (defined by factor analysis on core-top material) correlate with three hydrographic modes defined on the basis of, sea-surface temperatures, temperature profiles, seasona l changes in temperature and mixed-layer depth. Similar assemblages we re found in down-core material along the Tasman Sea transect that, com bined with semi-quantitative analyses of foraminiferal assemblages (pr ovinces), and the coiling ratio of Globorotalia truncatulinoides, allo ws reconstruction of the position of the Tasman Front (or the Subtropi cal Divergence) during the late Brunhes Chron. The results indicate th at the Tasman Front migrated from its present position at similar to 3 0 degrees S to similar to 26 degrees S during the last glacial maximum . The northward migration of the Tasman Front may indicate a reduction in volume of the equatorial warm-pool and/or an increase in the stren gth of cool subtropical water masses. The late Pleistocene distributio n of G. truncatulinoides left-coiling form appears to be related to th e formation of Subantarctic Mode Water thermostads. This relationship may explain the evolutionary origin of this species in the Southwest P acific at 2.4 Ma simultaneously with the onset of late Pliocene glacia tions. The past position of the Subtropical Convergence is reconstruct ed by means of coiling directions in Neogloboquadrina pachyderma. The convergence apparently migrated slightly north of 43 degrees S (core E 36-23) during glacial stages 6, 10, and 12.