HR: 15:25h
AN: GP32A-08    [PDF]
TI: Paleomagnetic data from Late Cenozoic Fort Selkirk Lavas, Yukon,significance for secular variation and tectonics
AU: * Irving, T
EM: tirving@pgc-gsc.nrcan.gc.ca
AF: Pacific Geoscience Centre, 6000 West Saanich Road, North Saanich, BC V8L4B2 Canada
AU: Baker, J
EM: jubaker@nrcan.gc.ca
AF: Pacific Geoscience Centre, 6000 West Saanich Road, North Saanich, BC V8L4B2 Canada
AU: Barendregt, R W
EM: barendregt@uleth.ca
AF: University of Lethbridge, 4401 University Drive, Lethbridge, AB T1K 3M4 Canada
AU: Opdyke, N D
EM: drno@ufl.edu
AF: University of Florida, 137 Turlington Hall, Gainesville, FL 32611 United States
AB: Directions of magnetization in 33 basalt flows from Fort Selkirk, Yukon Canada, of Bruhnes, Matuyama and Gauss (1 flow only) age are well grouped. Normal and reversed magnetizations are present and it is likely therefore that secular variations have been covered. The very high accuracy within-lavas allows a good estimate of the dispersion of secular variation to be made. The circular standard deviation (theta63) of directions is 8.5deg at latitude 62.7deg N. The mean, regardless of sign, differs significantly from the geocentric axial dipole (GAD) field, indicating a 15ñ6deg counterclockwise rotation. Data from rocks of the same age range from the Western Cordillera of Canada and the NW USA agree well with the GAD. Recent seismic and GPS studies show that the dynamic crust in the Yukon is only 20 km thick and intensely mobile. Heat flow is high, allowing a ductile decollement for the tectonic float to transfer stress more than 1000 km inland to the currently seismic McKenzie Mountains from the indentor, the Yakutat block, which is colliding with North America. Yukon crust is moving NE and rotating counterclockwise with respect to North America as a result of this on-going collision. The geodetically determined general rotation is much less than that suggested by paleomagnetic deviation, indicating that Selkirk area may be moving seperately within the mosaic of the Yukon crust. The deviation from the GAD field is evidently tectonic not geomagnetic.
DE: 1522 Paleomagnetic secular variation
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1527 Paleomagnetism applied to geologic processes
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting