Planktonic foraminiferal sea surface temperature variations in the southeast Atlantic Ocean: A high-resolution record MD962085 of the past 400,000 years from the IMAGES II-NAUSICAA cruise

A high-resolution (similar to 4 - 5cm/kyr) giant piston core record (MD9620 85) retrieved during an IMAGES II - NAUSICAA cruise from the continental sl ope of the southeast Atlantic Ocean reveal striking variations in planktoni c foraminifer faunal abundances and sea-surface temperatures (SST) during t he past 400,000 years. The location and high-quality sedimentary record of the core provide a good opportunity to assess changes in the intensity and position of the Benguela Current System and the Subtropical Convergence, tw o key features of the ocean-climate system in the south Atlantic. This reco rd can be also used to evaluate the possible influence of Agulhas Current f rom the throughflow of the Indian Ocean into the South Atlantic. The plankt onic foraminifer faunal abundances of the core are dominated by three assem blages: (1) N. pachyderma (right coiling) + N. dutertrei, (2) G. bulloides, and (3) G. inflata. The assemblage of N.pachyderma (right coiling) + N. du tertrei shows distinctive abundance changes which are nearly in-phase with glacial-interglacial variations. High abundances of this assemblage are ass ociated with major glacial conditions, possibly representing low SST I high nutrient level conditions in the southwestern Africa margin. In contrast, the assemblages of G. bulloides and G. inflata show more high-frequency abu ndance change patterns, which are not well-parallel to glacial-interglacial changes. These patterns may indicate rapid oceanic frontal movements from the south, and a rapid change in the intensity of Benguela upwelling system from the east. A winter-season SST estimate using transfer function techni ques for this record shows primarily glacial-interglacial variations. The S ST reaches maxima during the transitions from the major glacial to intergla cial stages (Termination II, HI, IV), and is associated with the abundance maxima of a warm water species indicator G. ruber. The relationship shown b y the SST and planktonic foraminifer partial derivative(18)O implies that t he SST maxims lead the partial derivative(18)O minima by approximately 3-5 kyr.