HR: 17:20h
AN: GP44A-05    [Abstracts]
TI: Relative Paleointensity of the Geomagnetic Field 12-20 kyr. From Sediment Cores, Lake Moreno (Patagonia, Argentina)
AU: * Gogorza, C S
EM: cgogorza@exa.unicen.edu.ar
AF: CONICET, Rivadavia 1917, Buenos Aires, 1033, Argentina
AU: * Gogorza, C S
EM: cgogorza@exa.unicen.edu.ar
AF: Universidad Nacional del Centro, Pinto 399, Tandil, 7000, Argentina
AU: Irurzun, M A
EM: airurzun@exa.unicen.edu.ar
AF: CONICET, Rivadavia 1917, Buenos Aires, 1033, Argentina
AU: Irurzun, M A
EM: airurzun@exa.unicen.edu.ar
AF: Universidad Nacional del Centro, Pinto 399, Tandil, 7000, Argentina
AU: Chaparro, M A
EM: chapator@exa.unicen.edu.ar
AF: CONICET, Rivadavia 1917, Buenos Aires, 1033, Argentina
AU: Chaparro, M A
EM: chapator@exa.unicen.edu.ar
AF: Universidad Nacional del Centro, Pinto 399, Tandil, 7000, Argentina
AU: Lirio, J M
EM: liriojm@yahoo.com
AF: IAA, Cerrito 1248, Buenos Aires, 1033, Argentina
AU: Nunez, H
EM: hnunez@yahoo.com
AF: IAA, Cerrito 1248, Buenos Aires, 1033, Argentina
AU: Sinito, A M
EM: asinito@exa.unicen.edu.ar
AF: CONICET, Rivadavia 1917, Buenos Aires, 1033, Argentina
AU: Sinito, A M
EM: asinito@exa.unicen.edu.ar
AF: Universidad Nacional del Centro, Pinto 399, Tandil, 7000, Argentina
AB: Four cores labeled Lmor1, Lmor2, Lmor3, Lmor98-1, Lmor98-2 from the bottom sediments of Lake Moreno (south-western Argentina) have been used to estimate regional geomagnetic paleointensity. Lake Moreno is on the east side of the Andean Cordillera Patagónica; it is located in the Llao Llao area, San Carlos de Bariloche, Argentina (41° S, 71° 30'W). The following measurements were performed: Natural Remanent Magnetization (NRM), magnetic susceptibility at low and high frequency (specific, X and volumetric, k), Isothermal Remanent Magnetization (IRM) reaching the Saturation Isothermal Remanent Magnetization (SIRM), Back Field, Anhysteric Remanent Magnetization with a direct field of 0.1mT and an alternating field between 2.5 and 100mT (ARM_100mT). Associated parameters were calculated: S-ratio, Remanent Coercitive Field (B_CR, anhysteric volumetric susceptibility (k_anh), SIRM/k, ARM_100mT/k, and SIRM/ ARM_100mT. The rock magnetic studies indicate that the magnetic mineralogy of the clay-rich sediments is dominated by pseudo- single domain magnetite in a narrow range of grain size (between 1 and 4μm) and concentration (between 0.05 and 0.1%), thereby meeting established criteria for relative paleointensity studies. The remanent magnetization at 20mT (NRM_20mT) has been normalized using the anhysteric remanent magnetization at 20mT (ARM_20mT), the saturation of the isothermal remanent magnetization at 20mT (SIRM_20mT) and k. A comparison of these results with relative paleointensity records obtained in previous works, Lake Escondido (Gogorza et al., 2004) and Lake El Trébol (Gogorza et al., 2006) allows obtaining detailed information about the disagreement observed in the period 12-20 kyr between both records. References Gogorza, C.S.G., J.M. Lirio, H. Nunez, M.A.E. Chaparro, H.R. Bertorello, A.M. Sinito. Paleointensity studies on Holocene-Pleistocene sediments from Lake Escondido, Argentina, Phys. Earth and Planet. Inter. 145: 219-238, 2004. Gogorza, C.S.G., M.A. Irurzun, M.A.E. Chaparro, J.M. Lirio, H. Nunez, P.G. Bercoff, A.M. Sinito. Relative paleointensity of the geomagnetic field over the last 21,000 years BP from sediment cores, Lake El Trébol (Patagonia, Argentina). Earth Planet Space. 58: 1323-1332, 2006.
DE: 1521 Paleointensity
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly