Tasman Front shifts and associated paleoceanographic changes during the last 250,000 years: foraminiferal evidence from the Lord Howe Rise

The paleoceanography of the Tasman Sea over the past 250,000 years was studied using benthic (>75 mum size fraction) and planktonic foraminifera (>149 mum size fraction) from three cores collected along similar to 162 degreesE traverse between similar to 25 degreesS and similar to 30 degreesS on the Lord Howe Rise. Planktonic foraminiferal oxygen isotope stratigraphy dates the cores between OIS 1 and 11. R-mode cluster and Q-mode factor analyses were carried out on benthic foraminiferal faunas, and Q-mode factor analysis and the modem analog technique (MAT) were used in analyzing planktonic foraminiferal faunas. Distinct benthic faunas across latitude from north (similar to 25 degreesS) to south (similar to 30 degreesS and similar to 35 degreesS) reflects: the difference in primary productivity level in the overlying surface water. The MAT result is thought to express latitudinal shifts of the Tasman Front over the last 250.000 years with: (1) the Tasman Front at similar to 35 degreesS during the oxygen isotope stage (OIS) 1 (post-glacial period); (2) migration of the front nearby similar to 25 degreesS during the last glacial period (OIS 2-OIS 4) and slightly northward of its present position during the penultimate glacial period (OIS 6); and (3) a return of the front to near similar to 35 degreesS during OIS 5 and OIS 7. Based on time-series and spatial variations of benthic foraminiferal factor typified by Pseudoparrella exigua and Uvigerina peregrina and one variety, southern-winter mixing and convection along the Tasman Front may have strengthened during the interglacial OIS 7 in particular. (C) 2001 Elsevier Science B.V. All rights reserved.