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Geological Society, London, Special Publications; 1992; v. 64; p. 331-342;
DOI: 10.1144/GSL.SP.1992.064.01.22
© 1992 Geological Society of London

The Geological Record of Upwelling Evolution

The Benguela Current and associated upwelling on the southwest African Margin: a synthesis of the Neogene-Quaternary sedimentary record at DSDP sites 362 and 532

Liselotte Diester-Haass1, Philip A. Meyers2 & Peter Rothe3

1 Alfred-Wegener-Institut 2850 Bremerhaven, Germany
2 The University of Michigan Ann Arbor, Michigan, USA
3 Universität Mannheim 6800 Mannheim, Germany

Sediments cored at DSDP Sites 362 and 532 on the Walvis Ridge provide a Neogene-Quaternary history of the development of the upwelling system on the southwest African margin. Upwelling occurs principally on the landward side of the Benguela Current. The upwelling centres have shifted northward since the Middle Miocene as the current has intensified and has flowed farther to the north. Changes in productivity are recorded in the types, proportions and preservation of foraminifera, radiolaria, diatoms, organic matter, and clay minerals in the sedimentary record. Prior to the Late Miocene (10 Ma), the Benguela Current did not reach the Walvis Ridge, and enhanced productivity is not evident in the sediments at this location. Between 10 to 5.2 Ma, upwelling was recorded in the DSDP sites in glacial periods, indicating that the Benguela Current intensified during glacial periods and transported evidence of upwelling to Sites 362/532 from near-coastal areas. During interglacial periods the current was not as strong and did not reach the Walvis Ridge, turning instead to the west within the Cape Basin. Strengthening of the current continued such that by the Pliocene and Quarternary the upwelling signal is contained in interglacial sediments. Sediments deposited in these more recent glacial times contain a weak or absent upwelling signal because glacial intensification shifts the Benguela Current system northward to reach the Angola Basin before it turns westward away from its coast-parallel direction.





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R. C. Preece, M. A. Kaminski, and T. W. Dignes
Miocene benthonic foraminiferal morphogroups in an oxygen minimum zone, offshore Cabinda
Geological Society, London, Special Publications, 1999; 153: 267 - 282.
[Abstract] [PDF]