HR: 09:00h
AN: GP41A-05    [PDF]
TI: A 3-Myr Mineral Magnetic Record of Saharan Dust Input Into the Eastern Mediterranean: Linking Magnetic Data With Climate Variability Over Northern Africa
AU: Larrasoana, J
EM: jcl1@soc.soton.ac.uk
AF: Southampton Oceanography Centre, University of Southampton European Way, Southampton, SO14 3 ZH United Kingdom
AU: * Roberts, A P
EM: arob@soc.soton.ac.uk
AF: Southampton Oceanography Centre, University of Southampton European Way, Southampton, SO14 3 ZH United Kingdom
AU: Rohling, E J
EM: ejr@soc.soton.ac.uk
AF: Southampton Oceanography Centre, University of Southampton European Way, Southampton, SO14 3 ZH United Kingdom
AU: Winklhofer, M
EM: mw99@soc.soton.ac.uk
AF: Southampton Oceanography Centre, University of Southampton European Way, Southampton, SO14 3 ZH United Kingdom
AU: Wehausen, R
AF: Institut fuer Chemie und Biologie des Meeres, Carl-von-Ossietzky-Universitaet, Oldenburg, D-26111 Germany
AB: We have produced a high resolution, 3-million-year mineral magnetic record for eastern Mediterranean sediments from Ocean Drilling Program Site 967. Rock magnetic analyses indicate that hematite dominates the high coercivity fraction of the sediments. We have developed a proxy (IRM0.9T@AF120mT) for the concentration of hematite by AF demagnetizing the IRM0.9T at 120 mT. A comparison of this proxy with Ti/Al data and other geochemical data indicates that variations in the concentration of hematite are related to the input of aeolian Saharan dust, regardless of non-steady-state diagenetic processes associated with organic-rich (sapropel) layers. We deduce that the eolian hematite in eastern Mediterranean sediments derives from the northern Sahara and relate dust production in this area with penetration of the African summer monsoon front to the north of the central Saharan watershed. Long-term variations in the penetration of the monsoon front would have led to changes in soil humidity and vegetation cover, and hence in the amount of dust production. Spectral analyses of our dust record reveal strong power at the precession, obliquity and eccentricity bands, which indicates that the northward penetration of the African monsoon, and thus northern African climate, is driven by a combination of low and high latitude mechanisms. We also observe a marked increase in dust supply and sub-Milankovitch variability around the mid-Pleistocene transition (~0.95 Ma), which suggests a link between millennial-scale climate variability, including monsoon dynamics, and the size of northern hemisphere ice sheets.
DE: 1512 Environmental magnetism
DE: 1620 Climate dynamics (3309)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting