Paleomagnetism of Metamorphic Rocks from de Piquete Region - Ribeira Valley, Southeastern Brazil

Abstract

Paleomagnetic data are presented corresponding to 42 hand samples of metamorphic rocks exposed in the Piquete region (Ribeira Valley, Southeastern Brazil - 22º 35'S, 45º 15'W). K-Ar age determinations suggest a Late Cambrian - Early Ordovician age for the cooling phase of these metamorphic rocks. After paleomagnetic treatment, a reversed direction in 20 samples from 9 sites was isolated (D_m = 60.4, I_m = 68.0, α₉₅=6.8) which yielded a paleomagnetic pole at Lat. = 0.8° N, Long. = 346.5º E (α ₉₅=10.2). Most of the remaining samples present unstable remanence. It is shown that this reversed direction may be representative of the cooling phase of these metamorphic rocks.

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