4. Pliocene-Pleistocene Opal Records off Southwest Africa, Sites 1082 and 1084: a Comparison of Analytical Techniques1

M. Elena Pérez,2 Hui-Ling Lin,3 Carina B. Lange,2 and Ralph Schneider4


Two sites of the Ocean Drilling Program Leg 175 (Sites 1082 and 1084) in the Benguela Current system were investigated for their biogenic opal content in upper Pliocene and lower Pleistocene sediments. Both sites show a remarkable opal maximum, which corresponds to a distinct diatom maximum. The maximum spans the lower half of the Matuyama reversed polarity chron. Two different methods were used to measure opal abundance; similar variations in amplitude are found despite an offset in absolute values. We show that the different data sets can be merged, even though sample spacing differs. The results from the opal determinations are quite similar to the overall diatom abundance. In these sediments, therefore, diatoms are the chief contributors to the opal fraction.

1Pérez, M.E., Lin, H.-L., Lange, C.B., and Schneider, R., 2001. Pliocene–Pleistocene opal records off southwest Africa, Sites 1082 and 1084: a comparison of analytical techniques. 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_04/chap_04.htm>. [Cited YYYY-MM-DD]

2Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla CA 92093, USA. meperez@ucsd.edu

3Institute of Marine Geology and Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan 804.

4Bremen University, Geowissenschaften, PO Box 330440, 28334 Bremen, Federal Republic of Germany.

Initial receipt: 14 March 2000
Acceptance: 8 September 2000
Web publication: 28 February 2001
Ms 175SR-221