Surface water conditions in the Northern Benguela Region (SE Atlantic) during the last 450 ky reconstructed from assemblages of planktonic foraminifera

• Published in: Marine Micropaleontology
• Main Authors: West, S., Jansen, J. H.F., Stuut, J. B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2004
• Subjects: Benguela Current; planktonic foraminifera; Pleistocene; South Atlantic Ocean; southeastern trade winds; upwelling; /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; name=SDG 14 - Life Below Water; Neogloboquadrina pachyderma; Planktonic foraminifera
• Online Access: https://research.vu.nl/en/publications/7e89162d-0cb1-4652-be61-e42c3a55ad5d; https://doi.org/10.1016/j.marmicro.2004.01.004; https://hdl.handle.net/1871.1/7e89162d-0cb1-4652-be61-e42c3a55ad5d; http://www.scopus.com/inward/record.url?scp=2942566652&partnerID=8YFLogxK; http://www.scopus.com/inward/citedby.url?scp=2942566652&partnerID=8YFLogxK

Planktonic foraminiferal records from Site 1083 (ODP Leg 175) were used to investigate changes in surface water conditions in the Northern Benguela Region over the past 450 ky. The assemblages of planktonic foraminifera are dominated by four species: sinistral coiling Neogloboquadrina pachyderma, dextral coiling N. pachyderma, Globigerina bulloides and Globorotalia inflata. Besides, tropical species deliver a small contribution to the assemblage. The most prominent temporal variations, displayed by N. pachyderma (s+d), represent changes in the coastal upwelling and the presence of cold, nutrient rich waters over the core site. Neogloboquadrina pachyderma (s+d) shows cyclic variability in the eccentricity and, to a less extent, precession frequencies. The changes indicate increased upwelling intensity in glacial maxima and precession maxima, and correlate well with the wind-strength record of Stuut et al. (2002). During glacial maxima, steep temperature gradients over the Southern Hemisphere caused strong SE trade winds and strong upwelling. Precession maxima cause a weak monsoonal circulation, more zonal SE trade winds, strong coastal upwelling, and nutrient-rich surface waters over ODP Site 1083. Advection of Angola Current (AC) surface water into the Walvis Basin, indicated by the tropical species, occurs when the Angola Benguela Front (ABF) is positioned southward. Occasionally, this happened during glacial maxima, as can be explained with the reconstructed and predicted meridional movements of the ABF. The amount of AC water was never sufficient to suppress the marine biological production at the core site. The contribution of Benguela Current (BC) water, reflected by Globorotalia inflata, is greatly determined by the upwelling. In periods of strong upwelling, the BC influence is suppressed. In several glacial substages, the temperature of the upwelling South Atlantic Central Water (SACW) may have been increased, as suggested by the dominance of Neogloboquadrina pachyderma (d) in the upwelling record. This ...