Recent planktonic foraminifera from deep-sea sediments from the eastern Equatorial Pacific: Proxies of the Equatorial Front in the late quaternary
Martinez, J.-Ignacio; Bedoya, G.
Boletin de Investigaciones Marinas y Costeras 30: 151-176
2001
ISSN/ISBN: 0122-9761
Accession: 011252720
Planktonic foraminifera recovered from 25 deep-sea sediment samples (core-tops) from the eastern Equatorial Pacific were analyzed for their geographic distribution and possible environmental controls. Samples collected deeper than the carbonate lysocline (apprx2800 m) show significant signs of dissolution, - when compared to sediment-trap samples -, resulting in the increase of the solution-resistant species Neogloboquadrina dutertrei, Neogloboquadrina pachyderma and Globorotalia cultrata and the reduction of the solution-susceptible species Globigerinita glutinata, Globigerinoides ruber and Globigerinoides sacculifer. Three bioprovinces were recognized by cluster analysis: (1) bioprovince I that occurs on the Cocos Ridge where G. cultrata and N. pachyderma are dominant, (2) bioprovince II that occurs on the Carnegie Ridge where N. dutertrei, N. pachyderma and Globorotalia inflata are dominant, and (3) bioprovince III that occurs in the Panama Basin where G. sacculifer and G. ruber are dominant. Bioprovinces I and II reflect a shallow thermocline induced by upwelling, although AOU, NO3 and PO4 and SiO2 are significantly higher in the latter region. Bioprovince III reflects a deep-mixed layer and low nutrient contents. Possible proxies of the Equatorial Front in the past are: (1) the Shannon diversity index, evenness and the number of species that show a latitudinal break at apprx1.5degreeS and, (2) the G. cultrata/G. dutertrei ratio that decreases southward.