DIATOM-INFERRED PRODUCTIVITY CHANGES IN THE EASTERN EQUATORIAL PACIFIC - THE QUATERNARY RECORD OF ODP LEG 111, SITE 677

Recent marine planktonic diatom assemblages from 47 sediment surface s amples retrieved from the eastern equatorial Pacific yielded four sign ificant Q-mode factors that are related to surface water properties. T hey include a northern subtropical (Factor 1), a southern subtropical (Factor 2), a Peru Current (Factor 3) and an eastern Equatorial Pacifi c (Factor 4) factor. A transfer function (based on 42 surface sediment samples) with a productivity range of 109 to 210 gC m(-2)y(-1) was de fined using the geographic distribution of the northern and southern s ubtropical assemblages (Factor 1 and 2) and their relation to ''mapped '' surface water primary productivity. This transfer function has a st andard error of estimate of 11.9 gC m(-1) y(-1) and it is used to esti mate late Pleistocene paleo-productivity changes at ODP Leg 111 Site 6 77 off Ecuador. The Site 677 samples (usually spaced 10 cm apart and w ith a linear sedimentation rate of 4.3 cm y(-3)) were the same samples that were used for stable oxygen/carbon isotopic analysis from plankt onic Foraminifera. The well constrained oxygen isotope stratigraphy pe rmitted assignment of accurate ages to downcore samples. The interval between oxygen isotope stages 3 and 9 had variable productivity that i s generally higher than present values of 175 gC m(-2) y(-1). A major decline in paleo-productivity below the present value occurred in stag e 9, the early part of stage 8 and in the early and late stage 5.