THE BIG FLUSH - PALEOMAGNETIC SIGNATURE OF A 70 MA REGIONAL HYDROTHERMAL EVENT IN DISPLACED ROCKS OF THE NORTHERN CANADIAN CORDILLERA

The 70 Ma Carmacks Group, a subaerial volcanic succession which once c overed much of central southwest Yukon, has a paleomagnetic remanent d irection which passes the fold test and the reversal test. A new colle ction of 13 sites, combined with 13 sites from a previous study, rende rs a pole (088.6 degrees E, 78.4 degrees N, A(95) = 7.8 degrees) which is far-sided with respect to the pole for cratonic North America and implies a displacement from the south of 1900 +/- 700 km. Late Triassi c Mandanna Member red beds and Early Jurassic Nordenskiold Formation t uffs, deformed in the Late Jurassic, fail the fold test and conglomera te test but pass a contact test with Eocene dykes. The postdeformation al remanent direction is identical to that isolated from the Carmacks Group. The magnetic signature contained in these older formations is p robably an overprint produced by an extensive hydrothermal system acti ve during Carmacks extrusion. Geological work indicates that the Carma cks Group is plume related. Given its paleomagnetic latitude and geolo gical nature, we hypothesize that the Carmacks Group is a displaced se gment of the Yellowstone hot-spot track, and the hydrothermal system w hich remagnetized the older rocks was established by mantle upwelling below the region.