21. Walvis Paradox Confirmed for the Early Quaternary at the Southern End of the Namibia Upwelling System, ODP Site 10851

Patricia A. Anderson,2 Christopher D. Charles,2 and
Wolfgang H. Berger2


The Walvis Paradox states that opal accumulation fluctuates in counterphase to general productivity on Walvis Ridge, off northern Namibia. Sediments of early Quaternary age from Site 1085 (Cores 175-1085A-7H to 10H, off South Africa) were studied to check the phase relationships of general productivity and opal deposition in the region off the Oranje River, near the southern end of the Namibia upwelling system. The proxies used are 18O of Cibicidoides wuellerstorfi, 13C of C. wuellerstorfi, benthic foraminifers per gram (BF/g), Uvigerina spp. per gram (U/g), estimated diatom abundance (EDA) and sulfide and oxide aggregates (SOA) in the coarse fraction. EDA and BF/g are taken to indicate diatom and organic matter productivity, respectively. Oxygen isotopes were used to determine phase within the glacial-interglacial cycles.

The phase relationships between the different proxies emerge when applying internal stacking methods. For Core 175-1085A-7H, five prescribed 41-k.y. cycles were combined into an average 41-k.y. cycle for the different indices. Productivity indices (BF/g and U/g) tend to follow 18O in the accustomed manner (with glacial periods showing maximum productivity), but not EDA, whose maximum appears closer to interglacials, offset toward cooling. Thus, phase relationships are similar to those on Walvis Ridge, extending the Walvis Paradox to the southern end of the Namibia upwelling system for the early Quaternary. A tentative reconstruction of the phase of intensity of mixing is given, based on the two productivity indicators EDA and BF/g. Mixing is strongest during the glacial maximum.

1Anderson, P.A., Charles, C.D., and Berger, W.H., 2001. Walvis Paradox confirmed for the early Quaternary at the southern end of the Namibia upwelling system, ODP Site 1085. 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/VOLUME/chap_21/chap_21.htm>. [Cited YYYY-MM-DD]

2Scripps Institution of Oceanography, University of California, San Diego, La Jolla CA 92093, USA. Correspondence author: wberger@ucsd.edu

Initial receipt: 5 July 2000
Acceptance: 14 June 2001
Web publication: 13 September 2001
Ms 175SR-201