The late Miocene onset of high productivity in the Benguela Current upwelling system as part of a global pattern Liselotte Diester-Haass a; *, Philip A. Meyers b , Laurence Vidal c ; 1 a Zentrum fu «r Umweltforschung der Universita «t, 66041 Saarbru «cken, Germany b Department of Geological Sciences, The University of Michigan, Ann Arbor, MI 48109-1063, USA c Fachbereich Geowissenschaften der Universita «t Bremen, 28334 Bremen, Germany Received 1 July 2000; received in revised form 10 January 2001; accepted 25 May 2001 Abstract We have examined the history of the elevated primary productivity associated with the Benguela Current upwelling system off southwest Africa using sediments from 7.5 to 4.8 Ma at Ocean Drilling Program Site 1085 in the middle Cape Basin. Sedimentation rates are low until 6.9 Ma. Low accumulation rates of benthic foraminifers and organic carbon indicate that biological productivity was also low. Paleoproductivity dramatically increased at 6.7^6.5 Ma and was highly variable until 4.8 Ma with productivity maxima during cooler periods. The presence of radiolarian opal only between 5.8 and 5.2 Ma suggests an interlude of silica-rich intermediate water in the Cape Basin. The onset of heightened productivity under the Benguela Current is mirrored by similar increases reported between 6.9 and 6.7 Ma in the tropical eastern Pacific, the western and northern Pacific, and the Indian Ocean. The similarity between the patterns at Site 1085 and in the Pacific and Indian Oceans suggests that the dramatic productivity increase off southwest Africa is part of a global response to paleoceanographic changes. ß 2002 Elsevier Science B.V. All rights reserved. Keywords: late Miocene; export productivity; upwelling; CaCO 3 MAR; organic carbon MAR; benthic foraminiferal accumulation rates 1. Introduction A major increase in marine biological produc- tivity during the late Miocene^early Pliocene has been documented in widespread areas of the glob- al ocean. Locations include upwelling areas in the equatorial Paci¢c and Indian Oceans, where dra- matic increases in mass accumulation rates of opal, organic and inorganic carbon, phosphorus, and barium (Van Andel et al., 1975; Peterson et al., 1992; Berger et al., 1993; Farrell et al., 1995; Schroeder et al., 1997; Dickens and Owen, 1999) and expansion of the oxygen minimum zone (Dickens and Owen, 1999) have been noted be- tween 7 and 6 Ma. Evidence of similar late Mio- cene increases in productivity has been described at high latitudes in the northwest Paci¢c (Rea et al., 1995) and subpolar South Atlantic Ocean (Froelich et al., 1991). The widespread occurrence 0025-3227 / 02 / $ ^ see front matter ß 2002 Elsevier Science B.V. All rights reserved. PII:S0025-3227(01)00207-9 1 Present address: CEREGE, Europo ªle de l'Arbois, BP 80, 13545 Aix en Provence, France. * Corresponding author. E-mail address: a.l.haass@t-online.de (L. Diester-Haass). Marine Geology 180 (2002) 87^103 www.elsevier.com/locate/margeo