Deposition of Organic Matter To The Modern and Pleistocene Equatorial Atlantic: Links with African Climate and Marine Productivity
WAGNER, THOMAS, University of Bremen, Geosciences, Germany
Modern and Pleistocene glacial/interglacial sedimentation in the eastern
and central Equatorial Atlantic is well documented to be effectively controlled
by changes in paleoproductivity and variable eolian dust supply from central
African areas. These changes in paleoenvironmental conditions caused cyclic
changes in the total amount and composition of sedimentary organic carbon
preserved in deep sea sediments. Elevated accumulation of organic carbon,
typically recorded during glacial periods, is commonly interpreted to record
enhanced paleoproductivity closely related to glacially enforced wind stress.
In order to calibrate organic petrological and organic geochemical characteristics
of past deep sea sediments to modern climatic and oceanographic conditions
in the eastern to central Equatorial Atlantic spatial distribution patterns
of various organic proxies, e.g. of TOC, terrigenous and marine macerals,
Rock-Eval, and d13Corg are presented for surface sediments.
Special emphasis is drawn to compare the interpretation based on the well
established organic carbon isotopic signal of marine sediments with new
qualitative and quantitative results from maceral analysis.
Glacial-interglacial changes in the deposition of organic matter are
discussed for late Quaternary to Pleistocene sequences of open pelagic
to near continental settings including new results from ODP Sites 664,
663, and 959. Lateral gradients in eolian supply of terrigenous organic
matter from the African continent and temporal changes in paleoproductivity
are recorded along the core transect. Quantitative data derived from maceral
analysis obviously contradict with measured d13Corg signals
probably indicating a variable overprint of the bulk d13Corg
signal by isotopically heavy C4 plant material.
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