REGIONAL ELECTRICAL CONDUCTIVITY STRUCTURE OF THE SOUTHERN 
CANADIAN CORDILLERA AND ITS PHYSICAL INTERPRETATION 

Juanjo Ledo, Alan G. Jones
Geological Survey of Canada
615 Booth St., Ottawa, Ontario, K1A 0E9, Canada
ledo@cg.nrcan.gc.ca

The regional crustal structure of the southern Canadian Cordillera of 
western Canada is interpreted from the inversion of magnetotelluric 
data along five transects crossing the morphogeological belts. 
Decomposition of the data demonstrates that regional structures can be 
validly interpreted along the transects as two-dimensional, but with 
varying strike from profile to profile. The strike directions suggest 
a local clockwise rotation of crustal structures in the southern 
Intermontane and Omineca Belts, but not along the northern profiles in 
central British Columbia. Comparing the models from each profile 
allows us to obtain the regional-scale three-dimensional electrical 
crustal structure. The models show generally an upper resistive crust 
that contrasts with a more conductive lower crust. The conductivity in 
the Intermonate Belt is virtually the same along all profiles. In 
contrast, a strong along-strike variation in lower crustal 
conductivity is observed in the Omineca Belt, with much higher 
conductivities in the region of Eocene extension, and lower 
conductivities to the north in the unextended part of the Omineca. The 
joint interpretation of these magnetotelluric models with other 
geophysical data suggests that the presence of fluids in the lower 
crust can explain the observed data.