What is it about?
Four cores from Lake El Trebol (Patagonia, Argentina) have been used to estimate regional geomagnetic paleointensity. The rock magnetic studies indicate that the magnetic mineralogy of the clay-rich sediments is dominated by pseudo-single domain magnetite in a range of grain sizes and concentration which are suitable for paleointensity studies. The remanent magnetisation at 20 mT (NRM20 mT) has been normalised using the anhysteric remanent magnetisation at 20 mT (ARM20 mT), the saturation of the isothermal remanent magnetisation at 20 mT (SIRM20 mT) and the low field magnetic susceptibility (k). Coherence function analysis indicates that the normalised records are free of environmental influences. Our paleointensity (NRM20 mT/ARM20 mT) versusage curve shows good agreement with published record from another lake in Argentina and with records fromother parts of the world, suggesting that, in suitable sediments, paleointensity of the geomagnetic field can give a globally coherent, dominantly dipolar signal.
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Why is it important?
The composite NRM/ARM curve represents an estimate of geomagnetic paleointensity variations in South Western Argentina. The obtained records meet the strictest criteria for relative paleointensity records: the most commonly applied mineral magnetic criteria, paleomagnetic stability, agreement between results of different paleomagnetic normalisation and agreement with records obtained from other geographical areas.
Perspectives
From the comparison of the relative paleointensity records was observed that the (millennial-scale) longer wavelength (∼1000 –10000 year) features can be correlated over many thousands of kilometres suggesting that the longer period content is controlled by the global-scale geomagnetic field. More records should be analyzed to arrive to more precise conclusions
Dr María A Irurzun
CIFICEN
Read the Original
This page is a summary of: Relative paleointensity of the geomagnetic field over the last 21,000 years BP from sediment cores, Lake El Trébol (Patagonia, Argentina), Earth Planets and Space, October 2006, Springer Science + Business Media,
DOI: 10.1186/bf03352628.
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