HR: 0800h
AN: GP41C-03    [Abstracts]
TI: Archeointensity from 1300-200 BP Brazilian Pottery
AU: * Hartmann, G A
EM: gelvam@iag.usp.br
AF: Departamento de Geofisica, Universidade de Sao Paulo, Rua do Matao, 1226, Sao Paulo, SP 05508-090, Brazil
AU: Trindade, R I
EM: rtrindad@iag.usp.br
AF: Departamento de Geofisica, Universidade de Sao Paulo, Rua do Matao, 1226, Sao Paulo, SP 05508-090, Brazil
AU: Goguitchaichvili, A
EM: avto@geofisica.unam.mx
AF: Instituto de Geofisica, UNAM, Tzintzuntzan, 310, Morelia, 58098, Mexico
AU: Afonso, M C
EM: marisa@br2001.com.br
AF: Museu de Arqueologia e Etnologia da Universidade de Sao Paulo, Av. Prof. Almeida Prado, 1466, Sao Paulo, 05508-090, Brazil
AB: The evolution of the Earth's magnetic field in the 10 to 100s of years time-period can provide important information about geodynamo variations. Accurate curves for the last 2000 years have been developed for Europe and Western Asia. In contrast, continents in the southern hemisphere count much less data; South America contributes with less than 1% of the world archeointensity database. In order to derive a South American archeointensity master-curve, we have initiated a systematic paleointensity survey in well-dated (TL and/or 14C methods) ceramic fragments from southeast and northeast Brazil. Here we report the first results on pottery collected in 24 Guarani sites with ages from 1300 BP up to 200 BP, and colonial historical sites with ages from 350 BP to 200 BP. Rock magnetic measurements indicated that the main magnetic carrier in all pottery samples is magnetite in the SD state domain. Paleointensity measurements were performed using the double-heating Thellier-Thellier method and pTRM (partial thermoremanent magnetization) checks with success rates of 60%. Results were consistent within sites and between potteries of similar ages. Archeointensity values vary from 30 μT at around 870 BP up to two peaks of 52 μT at 900 BP and 540 BP, and decrease continuously towards the present-day value of ~30 μT.
DE: 1503 Archeomagnetism
DE: 1521 Paleointensity
DE: 1522 Paleomagnetic secular variation
DE: 1560 Time variations: secular and longer
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly