HR: 16:45h
AN: GP22B-04 INVITED     [PDF]
TI: Holocene Paleomagnetic Secular Variation From Iceland (MD99-2269) : New Observations on Millennial to Centennial Scale Field Dynamics From North America to Europe
AU: * Stoner, J S
EM: Joseph.Stoner@colorado.edu
AF: INSTAAR, University of Colorado, Boulder, CO 80309-0450 United States
AU: St-Onge, G
EM:
AF: GEOTOP-UQAM-McGill, Case postale 8888, Succursale Centre-Ville, Montreal, H3C 3P8 Canada
AU: Kristjansdottir, G B
EM:
AF: INSTAAR, University of Colorado, Boulder, CO 80309-0450 United States
AU: Andrews, J T
EM:
AF: INSTAAR, University of Colorado, Boulder, CO 80309-0450 United States
AU: Hardadottir, J
EM:
AF: National Energy Authority, Grensasvegur 9, Reykjavik, 108 Iceland
AU: Koc, N
EM:
AF: Norsk Polar Institute, Polarmiljosenteret, Tromso, N-9296 Norway
AB: Recent studies of lacustrine and estuarine sediments have demonstrated coherence millennial-scale paleomagnetic secular variations (PSV) patterns across North America. New archeomagnetic observations now show centennial-scale PSV impulse changes across Europe and suggesting a new class of geomagnetic behavior at a presently unknown spatial scale. Our knowledge of how PSV continues and evolves between North America and Europe are, however, poorly constrained as there are few studies from the intervening 60 degrees of longitude. We present a new high resolution Holocene PSV record from Iceland that allows us to bridge this geographic gap. MD99-2269 (Lat: 66.37.53 N. Long. 23.51.16 W, water depth 365 m, length 2530 cm) was collected from a 25-30-m thick post-glacially derived shelf sediment body off N/NW Iceland. The sediments of 2269 are generally homogenous siliciclastic rich, silty muds with no evidence for reductive diagenesis. The chronology for 2269 is based on 18 AMS radiocarbon dates constrained by Hekla and Saksunarvatn tephras. A simple linear age model satisfies (r = 0.99) all eighteen radiocarbon dates and the Saksunvatn tephra. Therefore, 2269 extends to 12,300 cal yr BP with each centimeter of sediment representing about 5 years. The natural remanent magnetization (NRM) was studied by progressive alternating field (AF) demagnetization of u-channel samples, which indicated a strong, stable, single component magnetization. Inclinations are consistent with the expected values for the site latitude and comparisons with other regional records (Iceland \& East Greenland) support the geomagnetic origin of the observed directional changes. Therefore, 2269 provides a well-dated high temporal resolution PSV record for Iceland that extends through the Holocene. Comparison of Icelandic PSV to records from North America and Europe demonstrates that declination patterns show two distinct modes during the Holocene. Over the last 2,000 years millennial-scale declination swings in Iceland are correlative with those in North America, but clearly distinct from those in Europe. While prior to around 2,500 cal yr BP declinations swings are similar from North America to Iceland to Europe. Centennial-scale impulse changes documented in European archeomagnetic records are also observed in Iceland with some traceable to North America. The most dramatic impulse occurs around 2,500 cal yr BP, observed from North America to Europe and may mark a major transition in Holocene geomagnetic field behavior. The implications of these observations will be discussed.
DE: 1503 Archeomagnetism
DE: 1507 Core processes (8115)
DE: 1522 Paleomagnetic secular variation
DE: 1545 Spatial variations (all harmonics and anomalies)
DE: 1560 Time variations--secular and long term
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting