Paleomagnetism of the Gowganda and Chibougamau Formations: Evidence for 2,200-m.y.-old folding and remagnetization event of the southern province

Paleomagnetic analysis of 175 cores from three regions in the Huronian Gowganda Formation of Ontario and from one area in the probably equivalent Chibougamau Formation of Quebec yielded two remanence directions. Remanence A with a pole at lat 66°N, long 035°E (A95 = 5) predates folding of the Huronian rocks; remanence B (pole at lat 74°N, long 209°E, A95 = 6°) is posttectonic. Together with other Aphebian paleomagnetic results, these data indicate that an event of folding and subsequent remagnetization affected the whole region from Quebec to Minnesota prior to intrusion of the Nipissing diabase at approximately 2,150 m.y. B.P. Similar to other major events in the Canadian Shield, this event is represented in the paleomagnetic record by a closed loop, designated hairpin 50.