ESTUDO PALEOMAGNÉTICO DO VULCANISMO TERCIÁRIO DO ARQUIPÉLAGO DE FERNANDO DE NORONHA

ORLANDO TADEU LIMA DE SOUZA, SÔNIA DIAS CAVALCANTE GUERREIRO

Resumo


The Fernando de Noronha archipelago lies in the Atlantic Equatorial Ocean at 3º50'S latitude and 32º26'W longitude. It comprises a big volcaníc complex consisting of unweathered volcanic rocks of Tertíary age. Three geological formations can be separated: Quixaba, Remédios, and São José. Using a compass and a clinometer, 100 samplee were collected in the formations in a total of 15 sites. However, with the results obtained in the laboratory, it was impossible to make use of all studied sites because five out of the 15 sítes presented weak magnetíc intensity relative to the employed magnetometer preventíng the cleaning process of the secondary magnetizations of these sites. Therefore, the 10 studied sítes presented a magnetízation with D = 350°, I=-9°, a95 = 6,8°, and k = 51,2. The cleaning process employed was the magnetic alternate field. Just one site prevented reversed polarization. The paleomagnetic pole was computed as 81°N and 232°E (A95 = 5°), which agrees with the results for peles having the same age in the South America.

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