RECENT PLANKTONIC FORAMINIFERA FROM DEEP-SEA SEDIMENTS FROM THE EASTERN EQUATORIAL PACIFIC: PROXIES OF THE EQUATORIAL FRONT IN THE LATE QUATERNARY

Abstract

Planktonic foraminifera recovered from 25 deep-sea sediment samples (core-lops) Irom the eastern Equatorial Pacific were analyzed tor thoir geographic distribution and possible environmental controls. Samples colloctod doopor than tho carbonato lysoclino (-2800 m) show significant signs of dissolution, - when compared to sediment-trap samples resulting in the increase of the solutionresistant species Neogloboquadrlna duterlrei. NeogOboquadnna pachyderma and Gioborotaha Cufrata and the reduction of tho soíuüon-suscoptiblo spocios Globigonmta glutmata. Globigennotdes ruber and Gtobigohnoidos saccuMor. Threo bioprovincos woro rocognizod by cluster analysis: (1) bioprovince I that occurs on tho Cocos Ridgo whore G. cultrata and N. pachyderma are dominant. (2) bioprovince II that occurs on the Carnegie Ridge where N. duterlrei, N. pachyderma and Globorolatia intlata aro dominant, and (3) bioprovince III that occurs in the Panama Basin whore G. saccuhtor and G. ruber aro dominant. Bioprovinces I and II reflect a shallow thormocllno inducod by upwelhng. although AOU, NO , and PO, and SiO, are significantly higher in tho lattor rogion. B-oprovinco III reflects a deeprrvxod layor and low nutriont contonts. Possiblo proxies ol tho Equatorial Front in the past are: (1) the Shannon diversity indox. ovonness and the number ot species that show a latitudinal break at -1.5*S and. (2J the G. cultrata / G. dutertrei ratio that decreases southward