23. Reconstructing the Climatic History of the Western Coast of Africa over the Past 1.5 m.y.: A Comparison of Proxy Records from the Congo Basin and the Walvis Ridge and the Search for Evidence of the Mid-Pleistocene Revolution1

E.L. Durham,2 M.A. Maslin,2 E. Platzman,3 A. Rosell-Melé,4 J.R. Marlow,5 M. Leng,6 D. Lowry,7 S.J. Burns,8 and the ODP Leg 175 Shipboard Scientific Party9


A multiproxy approach including the use of stable isotopes, magnetic characterization analyses, and organic geochemistry has been adopted to consider factors such as productivity and terrigenous input over the past 1.5 m.y. at two areas off the western coast of Africa. These factors can, in turn, be used to consider variability in ocean circulation and upwelling in addition to changes in climate on the African continent. In particular, studies focused on the influence of glacial-interglacial cycles and evidence for the mid-Pleistocene revolution (MPR), a complex change in climate that occurred at ~1 Ma. A comparison of the records from the two areas drilled during Ocean Drilling Program Leg 175, the Congo Basin, at a latitude of 5°S (Holes 1076A and 1077A), and the Walvis Ridge, at 17°S (Hole 1081A), demonstrates that these sites are affected by different localized factors. The sites in the Congo Basin are strongly influenced by freshwater and sediment from the Congo River, whereas the site at the Walvis Ridge is located in the center of oceanic upwelling and contains a more marine signal. Evidence also suggests that the two sites responded differently to both long- and short-term climatic variations. In particular, the response at the Walvis Ridge to the MPR occurred over an extended period, from 1.1 to 0.8 Ma, and was associated with a change in the dominant source of terrigenous input to the site in conjunction with a change in the productivity signal. In the Congo Basin, the response to the MPR was more rapid, occurring between 0.9 and 0.8 Ma. During this period, the influence of the Congo River became significant. However, productivity records only began to respond toward the end of this interval, at 0.8 Ma.

1Durham, E.L., Maslin, M.A., Platzman, E., Rosell-Melé, A., Marlow, J.R., Leng, M., Lowry, D., Burns, S.J., and the ODP Leg 175 Shipboard Scientific Party, 2001. Reconstructing the climatic history of the western coast of Africa over the past 1.5 m.y.: a comparison of proxy records from the Congo Basin and the Walvis Ridge and the search for evidence of the mid-Pleistocene revolution. 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_23/chap_23.htm> [Cited YYYY-MM-DD]

2Environmental Change Research Centre, Department of Geography, University College London, 26 Bedford Way, London WC1H 0AP, United Kingdom. Correspondence author: emma.durham@jncc.gov.uk

3Department of Geology, University College London, Gower Street, London WC1E 6BT, United Kingdom.

4Department of Geography, University of Durham, Durham, United Kingdom.

5FFEG, Newcastle Research Group, Drummond Building, University of Newcastle, Newcastle upon Tyne NE1 7RU, United Kingdom.

6NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottingham, United Kingdom.

7Geology Department, Royal Holloway, University of London, Egham, Surrey TW20 0EX, United Kingdom.

8Stable Isotope Laboratory, Geological Institute, University of Berne, Baltzerstrasse 1, CH-3012 Berne, Switzerland.

9Shipboard Scientific Party addresses can be found under "Shipboard Scientific Party" in the preliminary pages of the volume.

Initial receipt: 23 February 2000
Acceptance: 21 June 2001
Web Publication: 24 October 2001
Ms 175SR-229