HR: 08:30h
AN: GP41B-03    [Abstracts]
TI: Field Geometry During the Iceland Basin Event Observed from the North Atlantic Ocean, North Pacific Ocean and the South China Sea
AU: Laj, C
EM: laj@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS), Avenue de la Terrasse, Bat 12, Gif-sur-Yvette, 91198 France
AU: * Kissel, C
EM: kissel@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS), Avenue de la Terrasse, Bat 12, Gif-sur-Yvette, 91198 France
AU: Roberts, A P
EM: arob@mail.soc.soton.ac.uk
AF: Southampton Oceanography Centre, University of Southampton, European Way, Southampton, SO14 3ZH United Kingdom
AU: Hillaire-Marcel, C
EM: chm@uqam.ca
AF: GEOTOP-UQAM, C.P. 8888, succ. Centre-Ville, Montreal, H3C 3P8 Canada
AU: Cortijo, E
EM: cortijo@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS), Avenue de la Terrasse, Bat 12, Gif-sur-Yvette, 91198 France
AB: The Iceland Basin event (IBE), which is named for a record from ODP Site 983 in the North Atlantic Ocean (60.5øN), is a focus of growing interest in our community. This geomagnetic excursion is coeval with the marine oxygen isotope (MIS) stage 7/6 boundary at about 190 ka according to the orbitally tuned SPECMAP time scale. We have detailed new records of this excursion at two new sites from the North Atlantic (core MD99-2247; lat. 59øN, long. 31øW and core MD99-2242; lat. 59øN, long. 47øW), at one site from the North Pacific (ODP Site 884; lat. 51.5øN, long. 168.3øE), and in two others from the South China Sea (ODP Site 1146; lat. 19.5øN, long. 116.3øE and ODP Site 1145; lat. 19.6øN; long. 117.6øE). For all five sites, the event is identified at the MIS 7/6 boundary, which confirms its potential as a precise stratigraphic marker. The average sedimentation rate for this portion of the cores is 7.5, 10 and 15 cm/kyr in North Atlantic, North Pacific and South China sea cores, respectively, which allows high-resolution studies in this time interval. The event is characterized by a marked minimum in the relative paleointensity (sometimes with a double feature) and by large swings in inclination and declination. The VGP latitudes reach 78øS and 45øS for ODP sites 1146 and 1145, respectively, 37øS for ODP Site 884, and 74øS and 41øS for cores MD99-2247 and MD99-2242, respectively. The VGP paths for the four records from the North Atlantic and South China Sea cores are highly similar. For the most detailed of these records, the poles first pass over Africa, then they proceed to Antarctica and return northward over Australia. The paths are less well resolved for ODP Site 1145 and core MD99-2242, for which the poles cross the southern Indian Ocean rather than reaching Antarctica. The VGP paths for the two most detailed records (ODP Site 1146 and MD99-2247) are highly similar and are also similar to the path for ODP Site 983, which also has a high sedimentation rate and is precisely dated. In contrast, but in common with other published records of the IBE, the VGP path for ODP Site 884 loops in the opposite sense and passes from North to South America and then over the Pacific Ocean before returning to high northern latitudes. The striking similarities between multiple records for two observed sets of differing VGP paths for the IBE at locations spanning the northern hemisphere provides evidence for a non-dipolar, but relatively simple, geometry of the transitional field.
DE: 1714 Geomagnetism and paleomagnetism
DE: 1507 Core processes (8115)
DE: 1513 Geomagnetic excursions
DE: 1521 Paleointensity
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting