PALEOENVIRONMENTAL IMPLICATIONS OF ROCK-MAGNETIC PROPERTIES OF LATE QUATERNARY SEDIMENT CORES FROM THE EASTERN EQUATORIAL ATLANTIC

Rapid and nondestructive rock-magnetic measurements of late Quaternary sediment cores from the Senegal continental slope and the Sierra Leone Rise in the eastern equatorial Atlantic correlate strongly with the SPECMAP oxygen isotope master curve and carbonate content. The rock-magnetic-paleoclimatic relationship results from differences in the concentration, accumulation rate, grain size, and composition of magnetic minerals between glacials and interglacials. At both sites, magnetic mineral assemblages of glacial episodes are characterized by higher concentrations (and accumulation rates) of magnetic minerals, by coarser-grained ferrimagnetic minerals, e. g., magnetite, and by a lower ratio of ferrimagnetic to antiferromagnetic, e. g., goethite, hematite, minerals. By serving as a sensitive tracer for various deep-sea sedimentary components, rock-magnetic properties can provide insights into changing sediment sources and fluxes and therefore are a useful addition to more traditional chemically and mineralogically based paleoceanographic techniques.