HR: 09:15h
AN: GP51A-06 INVITED    [Abstracts]
TI: Magnetochemical Features in Recent Marine Sediments Across the Galician Atlantic Margin and their Stratigraphic Significance
AU: * Rey, D
EM: danirey@uvigo.es
AF: Dpto. Geociencias Marinas, Universidad de Vigo, Vigo, 36210, Spain
AB: A significant part of the sedimentary magnetochemical signal in the marine realm is controlled by the variability of detrital inputs; especially ice-rafted debris (IRD), fall-outs from nepheloid layers (NL) and wind blow-outs; which have been widely reported in the scientific literature. Their magnetic properties have been commonly and quite successfully used to establish the stratigraphic correlation of cores from a given location, or more intently, as proxies that document climatically forced events. Soon after deposition, the balance between oxygen diffusion from oxic bottom waters into the sediment; sea bed remobilization by benthic organisms and currents; primary productivity; and sediment accumulation rates will determine the degree of alteration of these detrital signals during redoxomorphic diagenesis and subsequently, the degree and conditions of preservation of their detritally-based environmental information (mostly held by magnetite) and the addition of new information during the authigenesis of magnetically-interesting minerals (chiefly goethite, greigite and pyrite). The correct interpretation of the magnetochemical properties and their environmental significance depends on our ability to asses the intensity and nature of magnetic-sensitive early-diagenetic processes resulting from changes in the sediment accumulation rates and on the palaeoceanographic conditions affecting productivity through time. Much of the changes that took place over the last 30 ky in the different depositional and diagenetic realms of the Galician Continental Margin -spanning from high productivity low depth Rías, storm swept continent shelf, and down slope turbiditic aprons, and abyssal plain- can be assessed estimating the concentration and half life of magnetite; which is respectivelly controlled by detrital forcements and the balance between C/S and the site sedimentation rate. This paper will deal with the magnetochemical expression of these changes in the depositional and/or diagenetic environment from the point of view of the enviromagnetism, solid-phase geochemistry, with the additional support of radiometric dating and scanning electron microscopy texture analysis; and of how these information have been used to reconstruct the Late Pleistocene to Holocene sedimentation history across the Galician Atlantic Margin.
DE: 1512 Environmental magnetism
DE: 1540 Rock and mineral magnetism
DE: 1834 Human impacts
DE: 1861 Sedimentation (4863)
DE: 1890 Wetlands (0497)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting