11. Siliceous Phytoplankton Productivity Fluctuations
in the Congo Basin over the Past 460,000 Years: Marine vs. Riverine Influence, ODP Site 10771

E. Uliana,2 C.B. Lange,3 B. Donner,2 and G. Wefer2


Accumulation rates, concentrations, and relative abundance of siliceous microfossils from Site 1077 are used to reconstruct changes in marine productivity and climate history of the Congo Fan area. The major contributors to siliceous productivity are marine diatoms, which show highest concentrations during glacial stages and cooler substages of the last interglacial. Abrupt changes are observed during Termination II (oxygen isotope Stage 5/6 boundary): (1) the marine diatom signal varies in amplitude and assemblage composition from predominantly marine to marine/brackish and (2) the environmental setting on land obtained from freshwater diatoms and chrysophycean cysts points to changes from more arid conditions accompanied by a large drainage area of the Congo River to more humid conditions and a decrease in the inland water content for the last 125 k.y.

1 Uliana, E., Lange, C.B., Donner, B., and Wefer, G., 2001. Siliceous phytoplankton productivity fluctuations in the Congo Basin over the past 460,000 years: marine vs. riverine influence, ODP Site 1077. In Wefer, G., Berger, W.H., and Richter, C. (Eds.), Proc. ODP, Sci. Results, 175, [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/175_SR/chap_11/chap_11.htm>. [Cited YYYY-MM-DD]

2 Fachbereich Geowissenschaften, Klagenfurter Strasse, Universitšt Bremen, 28359 Bremen, Federal Republic of Germany. Correspondence author: eleonora@uni-bremen.de

3 Scripps Institution of Oceanography, University of California at San Diego, Geosciences Research Division, La Jolla CA 92093-0244, USA.

Initial receipt: 7 March 2000
Accepted: 14 September 2000
Web publication: 26 April 2001
Ms 175SR-216