PALAEOMAGNETISM AND K/AR AGES OF SOME IGNEOUS ROCKS OF THE TRINDADE COMPLEX AND THE VALADO FORMATION, FROM TRINDADE ISLAND, BRAZIL

Abstract

Palaeomagnetic and radiometric data of seven igneous units from Trindade Island are,given. They support the age of2.41 ± 0.05 m.y. for the polarity transition between the Matuyama reversed an'd the Gauss normal epochs. On the, basis of the mean direction of cleaned remanent magnetization of each igneous unit a virtual geomagnetic pole is computed; the mean of these virtual geomagnetic poles is 86°S, 5°E, lX 9 5 = 4; it would represent the Late Cenozoic palaeomagnetic pole for the Trindade Island. It is suggested that the normal polarity found in igneous rocks from Argentina would represent a continental evidence for the existence of the short normal polarity event at the beginning of the Matuyama reversed epoch suggested on the basis of seafloor spreading data.