Coupled primary production, benthic foraminiferal assemblage, and sulfur diagenesis in organic-rich sediments of the Benguela upwelling system

Author(s): Brüchert, Volker; Pérez, M. Elena; Lange, Carina B.
Author Affiliation(s): Primary:
Max Planck Institute for Marine Microbiology, Bremen, Federal Republic of Germany
Scripps Institution of Oceanography, La Jolla, CA, United States
Volume Title: Marine Geology
Source: Marine Geology, 163(1-4), p.27-40. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0025-3227 CODEN: MAGEA6
Note: In English. 61 refs.; illus., incl. 2 tables, sketch map
Summary: Episodically deposited, dark, organic-rich Pleistocene and Late Pliocene sediments from the lower continental slope off southwest Africa reveal complex interactions between changes in primary production, benthic foraminiferal assemblage, and anaerobic microbial processes. The organic-rich layers contain diatom assemblages characteristic of intense seasonal coastal upwelling whereas stratigraphically adjacent sediments reflect pelagic primary production. Coastal upwelling-dominated depositional intervals coincide with periods of enhanced carbon flux to the seafloor. Enhanced organic carbon export during dark layer deposition was accompanied by decreases in the diversity of benthic foraminifera to few opportunistic species adapted to high phytodetritus accumulation rates and low O2 conditions. In all sediments the sulfur isotopic composition of pyrite indicates redox cycling of sulfide close to the sediment/water interface. The sulfur isotopic evidence and the permanent presence of abundant low O2-adapted benthic foraminifera throughout the organic-rich layers suggest an oxygenated benthic environment. Efficient oxidation of sulfide and removal of sulfide by sulfidization of organic matter inhibited buildup of toxic hydrogen sulfide from bacterial sulfate reduction at the sediment/water interface. These data imply that in continental slope sediments underneath productive surface waters benthic dysoxic conditions are maintained by the lateral advection of dissolved oxygen to support a small, but well-adapted benthic community. Abstract Copyright (2000) Elsevier, B.V.
Year of Publication: 2000
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Aerobic environment; Africa; Algae; Anaerobic environment; Assemblages; Atlantic Ocean; Benguela Current; Benthic taxa; Biochemical sedimentation; Bioclastic sedimentation; Biogenic processes; Biostratigraphy; Calcium carbonate; Carbon; Cenozoic; Coastal environment; Coccolithophoraceae; Continental margin sedimentation; Continental slope; Coupling; Currents; Depositional environment; Diagenesis; Diatoms; Ecology; Foraminifera; Geochemistry; Gephyrocapsa caribbeanica; Invertebrata; Isotope ratios; Isotopes; Leg 175; Marine environment; Namibia; Nannofossils; Neogene; ODP Site 1084; Ocean Drilling Program; Ocean circulation; Ocean currents; Organic carbon; Oxygen; Paleo-oceanography; Paleocurrents; Pelagic environment; Plantae; Pleistocene; Pliocene; Productivity; Protista; Quaternary; S-34/S-32; Seasonal variations; Sedimentation; Sedimentation rates; South Atlantic; Southeast Atlantic; Southern Africa; Stable isotopes; Sulfur; Tertiary; Upper Pliocene; Upwelling
Coordinates: S253049 S253049 E0130140 E0130140
Record ID: 2000034940
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands