VGP-Paths of Extremely High-Resolution Records of the Laschamp and Mono Lake Geomagnetic Excursions in Sub-glacially Deposited Cave Sediments, W. Norway

Details VGP-Paths of Extremely High-Resolution Records of the Laschamp and Mono Lake Geomagnetic Excursions in Sub-glacially Deposited Cave Sediments, W. Norway VGP-Paths of Extremely High-Resolution Records of the Laschamp and Mono Lake Geomagnetic Excursions in Sub-glacially Deposited Cave Sediments, W. Norway

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmgp41b..06l&link_type=abstract

American Geophysical Union, Fall Meeting 2004, abstract #GP41B-06

Mathematics

Logic

1513 Geomagnetic Excursions, 1520 Magnetostratigraphy, 1522 Paleomagnetic Secular Variation

Scientific paper

High-amplitude variations of paleomagnetic directions retained in clay/silt-sediments deposited inside three wave abraded coastal caves have been interpreted to represent incomplete records of the Skjong (Laschamp) and Valderhaug (Mono Lake) excursions1,2,3. The clay-silt sediments deposited in calm waters during glacial periods when the caves were filled with fresh-water (lakes) dammed by advancing ice. Ages of these biologically barren sediments are constrained by C14 and U-Th dates of CaCO3 precipitates and bones of a rich fauna of birds and mammals. Differential post-depositional compaction of these these laminated (annual?) resulted in N-NW dips of 20°-40° in the Skjonghelleren cave sediments. High coercivities of remanent magnetisation (MDF: 50-70 mT) are carried by partially maghemitized magnetite, probably strained during glacier-abrasive erosion. VGP paths of the Laschamp excursion from the three caves partly overlap and define three near-equatorial clusters (90°W, 20°E and 160°E). A secular variation signal apparently prevails during the Skjong excursion (Laschamp), and It is speculated that these loops reflect genuine high-resolution records of the complex behaviour of the geomagnetic field during the development of excursions on decadal time scales. The high-resolution paleomagnetic records have been retained due to the absence of major post-depositional modification during deposition-consolidation of these temporal, sub-terranean `lakes'. 1Lovlie R. and Sandnes A., 1987. Palaeomagnetic excursions recorded in mid-Weichselian cave sediments from Skjonghelleren, Valderoy, W. Norway. Physics of the Earth and Planetary Interiors, 48, 337-348. 2Valen V. Larsen E. & Mangerud J., 1995. High-resolution paleomagnetic correlation of Middle-Weichselian ice-dammed lake sediments in two coastal caves, western Norway, Boreas, 24, 141-153. 3Mangerud J., Lovlie R., Gulliksen S., Hufthammer A-K., Larsen E. & Valen V., 2003. Paleomagnetic correlations between Scandinavian Ice-Sheet fluctuations and Greenland Dansgaard-Oeschger events, 45,000-25,000 yr B.P., Quaternary Research, 59, 213-222.

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