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Anais da Academia Brasileira de Ciências

versão impressa ISSN 0001-3765versão On-line ISSN 1678-2690

Resumo

TAMRAT, Endale  e  ERNESTO, Marcia. Paleomagnetic constraints on the age of the Botucatu Formation in Rio Grande do Sul, southern Brazil. An. Acad. Bras. Ciênc. [online]. 2006, vol.78, n.3, pp.591-605. ISSN 0001-3765.  http://dx.doi.org/10.1590/S0001-37652006000300016.

Paleomagnetic and rockmagnetic data are reported for the aeolian Botucatu Formation, in the southern Brazilian State of Rio Grande do Sul. Oriented samples were taken from a section located between the cities of Jaguari and Santiago. After thermal and alternating field demagnetization, both normal and reversed characteristic remanent magnetizations were found. These results yielded 13 reversed and 5 normal polarity sites, composing a magnetostratigraphic column displaying a sequence of reversed-normal-reversed polarity events. The paleomagnetic pole calculated for 18 sites is located at 114.7ºE, 78.5ºS (dp=8.1º; dm=1.2º), after restoring the strata to the paleohorizontal. This paleomagnetic pole indicates a Late Jurassic-Early Cretaceous age to the Botucatu Formation in the investigated area, and places the sampling sites at paleolatitudes as low as 21ºS.

Palavras-chave : paleomagnetism; Botucatu Formation; magnetostratigraphy; magnetic anisotropy; Late Jurassic.

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