The paleomagnetism of the Great Slave Supergroup: the Akaitcho River Formation

Abstract

Results are reported from 120 oriented samples collected from 40 stratigraphic horizons spanning the Akaitcho River Formation of the Great Slave Supergroup. Thermal demagnetization experiments reveal the presence of multiphase remanence. Difference vectors indicate that the lower blocking temperatures carry a magnetic component attributable to the present field. The remanence remaining above 500–600 °C defines two polarity groups, but the two groups are not exactly antiparallel. This is interpreted in terms of a previously recognised widespread magnetic overprint acquired during uplift and cooling in the Coronation Geosyncline. A compilation of appropriate overprint data from the Great Slave Supergroup yields a mean direction of D = 152°, I = +64 °(N = 75 sites, k = 30, α95 = 3°), with a corresponding pole at 91°W, 21°N (K = 14, A95 = 5°). A statistical procedure is employed to remove this overprint and obtain a best estimate of the original magnetization, which corresponds to a paleomagnetic pole on the western limb of the Coronation loop (92°W, 4°S, N = 35 sites, K = 13, A95 = 7°).