Abstract

Results are reported from 59 stratigraphic horizons spanning an aggregate of some 2000 m of sedimentary rocks of the Great Slave Supergroup, mostly located in the Kahochella Group. Partial demagnetization experiments and vector differences indicate that the magnetization involved is multicomponent, with a well-defined overprint masking an underlying magnetic component. The overprint has now been recognized in many formations of the Great Slave Supergroup and is interpreted as having been acquired in response to uplift and cooling following orogeny in the Coronation Geosyncline. It corresponds to a paleomagnetic pole at 91°W, 21°N (A95 = 5°). Removal of this overprint reveals the underlying, presumed primary, magnetization, which has a mean direction of D = 129°, I = +21° (N = 18 sites, k = 12, α95 = 10°) and a corresponding pole at 62°W, 7°S (K = 15, A95 = 9°). The ages of these poles cannot be fixed precisely, but the available data suggest that the "primary" remanence was acquired about −1.8 Ga, and the overprint about −1.7 Ga. The two poles thus help define the Precambrian polar wander curve for Laurentia. In particular they help define the so-called Coronation loop, which reflects the response of Laurentia to the major orogeny in the Coronation Geosyncline.

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