Tectonic Results from Paleomagnetism of the Aphebian Nipissing Diabase at Gowganda, Ontario

Abstract

A total of 30 sites (150 cores, 300 specimens) of the 2165 ± ~25 m.y. Nipissing diabase were collected from around the Miller Lake basin at Gowganda. After alternating field demagnetization a stable primary remanence was isolated at 10 sites of which eight were reversely polarized. A fold test shows that the basinal structure is primary at the 95% confidence level. The pole position of 106°W, 14°S (P0.05:9°, 14°) is statistically indistinguishable from previous Nipissing poles from the Cobalt and Elliot Lake areas. The evident conclusion is that the Superior and Southern geologic provinces have not undergone significant relative tectonic translation or rotation in the last 2165 m.y. Combining the remanence directions from the 37 available reliable sites of Nipissing diabase, they give a highly reliable pole position of 94.1°W, 14.5°S (P0.05:5.7°, 8.8°) for Nipissing time on the polar wander curve for these two provinces of the Canadian Precambrian Shield. Only four of the 37 sites are normally polarized suggesting that the Nipissing event reflects a dominantly reversed paleofield.