10. Marine and Terrigenous Lipids in Southeast Atlantic Sediments (Leg 175) as Paleoenvironmental Indicators: Initial Results¹

Enno Schefuss,² Gerard J.M. Versteegh,² J.H. Fred Jansen,² and Jaap S. Sinninghe Damsté^2,3

ABSTRACT

Lipid compositions of sediments recovered during Ocean Drilling Program Leg 175 in the eastern South Atlantic reflect a variety of oceanographic and climatological environments. Most of the identified lipids can be ascribed to marine sources, notably haptophytes, eustigmatophytes, dinoflagellates, archaea, and diatoms. Elevated concentrations of cholesterol suggest zooplankton herbivory, characteristic for sites influenced by upwelling. At these sites, sulfurized highly branched isoprenoids from diatoms are also present in high amounts. Sterols, sterol ethers, hopanoids, and midchain hydroxy fatty acids could also be detected. Terrigenous lipids are n-alkanes, fatty acids, n-alcohols, and triterpenoid compounds like taraxerol and -amyrine. n-Alkanes, fatty acids, and n-alcohols are derived from leaf waxes of higher land plants and transported to the sea by airborne dust or fresh water. Triterpenoid compounds are most probably derived from mangroves and transported solely by rivers. Lipid compositions below the Congo low-salinity plume are strongly influenced by terrigenous material from the Congo River. Elevated organic carbon contents and predominantly marine lipid distributions at the Angola margin may indicate a highly productive plankton population, probably sustained by the Angola Dome. Sedimentary lipids in the Walvis Basin contain an upwelling signal, likely transported by the Benguela Current. Sedimentary lipids off Lüderitz Bay and in the southern Cape Basin are dominated by plankton lipids in high to intermediate amounts, reflecting persistent and seasonal upwelling, respectively.

¹Schefuss, E., Versteegh G.J.M, Jansen, J.H.F, and Sinninghe Damsté, J.S., 2001. Marine and terrigenous lipids in southeast Atlantic sediments (Leg 175) as paleoenvironmental indicators: initial results. 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_10/chap_10.htm>. [Cited YYYY-MM-DD]

²Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands. Correspondence author: schefuss@nioz.nl

³Utrecht University, Institute of Earth Sciences, PO Box 80021, 3508 TA Utrecht, The Netherlands.

Initial receipt: 21 February 2000
Accepted: 14 September 2000
Web publication: 10 April 2001
Ms 175SR-228