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Earth Planets Space, Vol. 58 (No. 10), pp. 1323-1332 2006

Relative paleointensity of the geomagnetic field over the last 21,000 years BP from sediment cores, Lake El Trébol (Patagonia, Argentina)

C. S. G. Gogorza1,2, M. A. Irurzun1,2, M. A. E. Chaparro1,2, J. M. Lirio3, H. Nunez3, P. G. Bercoff2,4, and A. M. Sinito1,2

1IFAS- Universidad Nacional del Centro, Pinto 399, 7000 Tandil, Argentina
2CONICET. Rivadavia 1917-1033 Buenos Aires, Argentina
3Instituto Antártico Argentino - Cerrito 1248 - Buenos Aires, Argentina
4Fac. de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ob. Trejo 242, Córdoba, Argentina

(Received November 30, 2005; Revised May 5, 2006; Accepted May 8, 2006; Online published November 8, 2006)

Abstract: Four cores from Lake El Trébol (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) versus age curve shows good agreement with published record from another lake in Argentina and with records from other parts of the world, suggesting that, in suitable sediments, paleointensity of the geomagnetic field can give a globally coherent, dominantly dipolar signal.
Key words: Relative paleointensity, sediment cores, South America, Lake El Trébol, coherence.


Corresponding author E-mail: cgogorza@exa.unicen.edu.ar


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