Other
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmgp21a0776b&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #GP21A-0776
Other
1513 Geomagnetic Excursions, 1521 Paleointensity, 1522 Paleomagnetic Secular Variation, 1560 Time Variations: Secular And Longer
Scientific paper
New paleodirectional and initial paleointensity results from a re-sampled Brunhes age sequence of 34 basaltic lava flows at Agua Nova, Santo Antão, Cape Verde are linked with precise ages determined using the 40Ar/39Ar incremental heating method on groundmass separated from oriented hand samples originally studied by Knudsen et al. (Earth Planet. Sci. Lett., 206, 199-214, 2003). Alternating field demagnetization experiments on one sample per flow by Knudsen et al. (2003) suggested that two directional excursions may have been recorded. Five new 40Ar/39Ar isochron ages, which bracket and include the two excursional flows, are indistinguishable from one another and imply that a single complex period of excursional behavior took place at about 480 ± 13 ka. This excursion is the first to be revealed in a terrestrial volcanic sequence of this age and could correspond to cryptochron C1n-1 (504 to 493 ka) in the marine magnetic anomaly record (Cande and Kent, J. Geophys. Res., 100, 6093-6095, 1995). It is too young to be associated with the widely recorded Big Lost excursion, which is 40Ar/39Ar dated at 579 ± 6 ka, or any of the five West Eifel excursions dated between 722 and 528 ka (Singer et al., Phys. Earth Planet. Inter., in press, 2008). Neither is it clearly correlative with significant directional or paleointensity features observed in several high sedimentation rate ODP cores. Accurate paleodirections and paleointenities will enable us to define the full vector behavior of the geomagnetic field during this brief period of geomagnetic instability and will help us to better understand the processes within the Earth's core that give rise to such events.
Brown Charles Max
Faurschou Knudsen Mads
Feinberg Joshua M.
Singer Brad S.
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