Paleomagnetismo de um Enxame de Diques Toleíticos de Idade Meso-Cenozóica, localizados no Rio Grande do Norte

Sonia Dias Cavalcanti Guerreiro, Axel Schult

Abstract


Thirteen sites from a probably Lower Cretaceous tholeiitic dike swarm in Rio Grande do Norte (approx. 5.5ºS, 36.8ºW) have been sampled (128 samples). After the alternating field cleaning, their mean direction is D = 186.6º, I = + 20.6º with α95 = 14.0, K = 12.9, N = 10. This yields a pole at 80.6ºS, 274.8ºE with A95 = 9.5 and K = 26.8, which for South America is nearer to the Upper Cretaceous poles than to the Lower Cretaceous poles. This may reflect an uncertainty in determination of the age of the dikes: although some existing radiometric determinations indicate ages of about 130 m.y., some authors attribute a younger age (Upper Cretaceous or Tertiary) to the dikes. Rock magnetic investigations showed that the magnetic phase in the tholeiitic rocks is mainly magnetite and maghemite with poor titanium content.



Keywords


paleomagnetismo; enxame de diques toleíticos; idade meso-cenozóica

References


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DOI: http://dx.doi.org/10.22564/rbgf.v1i2.999

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