Abstract: Deposition of Organic Matter To The Modern and Pleistocene Equatorial Atlantic: Links with African Climate and Marine Productivity

WAGNER, THOMAS

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.

AAPG Search and Discovery Article #90939©1997 AAPG Eastern Section and TSOP, Lexington, Kentucky