Abstract

Thermal, alternating field (AF), and two-stage (AF followed by thermal) experiments performed on one Silurian (Mascarene Group) and two Devonian (St. George and St. Stephen plutons) rock units indicate that considerable polar movement relative to New Brunswick took place in Siluro-Devonian times. The Mascarene Group yields a pole at 122°E, 02°S, the St. Stephen pluton, a pole at 136°E, 43°S, and the St. George pluton, two poles at 085°E, 38°S and 093°E, 29°N respectively. Although the southern poles lie some 70° south of most North American Silurian and Devonian poles, they are in agreement with poles obtained from two recent studies of Newfoundland rock units. It is unknown if this apparent polar displacement is representative of the entire North American craton or of its eastern margin only. A graphic representation of all available North American data is disconcerting and shows that little is known about the behaviour of the Lower Paleozoic field relative to North America and that many more data are needed to reconstruct the paleomagnetic record.The St. George pluton carries two dual polarity remanences which often are not easily discernible, especially since one of the remanences has an intensity much weaker than the other. The usefulness of vector diagrams for the analysis of multicomponent remanences is demonstrated. Examples are shown where the dual polarity of the weaker remanence, which might otherwise escape notice, can be readily detected on enlarged scale vector diagrams.

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