BATHOZONAL TILT CORRECTIONS TO PALEOMAGNETIC DATA FROM MIDCRETACEOUS PLUTONIC ROCKS - EXAMPLES FROM THE OMINECA BELT, BRITISH-COLUMBIA

The Skelly Creek batholith (49.4°N, 116.6°W, 94-99 Ma) and Summit stock (49.1°N, 117.0°W, 102 Ma) are intruded into the southern Omineca Belt of southeastern British Columbia. Bathozonal mineral assemblages from contact aureoles of these plutons and others of the same age indicate that post emplacement tilting of the Purcell anticlinorium has probably not exceeded about 5°, whereas the Summit Stock has been tilted 24° down to the west. The Skelley Creek batholith has a mean direction of magnetization (D,I) with respect to present horizontal 349°,74° (13 sites, k = 53, α95 = 6°). The mean direction of magnetization of the Summit stock is 48°,72° (nine sites, k = 290, α95 = 3°), and after correction for a westerly dip of 24°, the mean direction becomes 318°,74°. Directions of the Skelly Creek batholith and tilt-corrected direction from the Summit stock are in agreement with the reference field for cratonic North America. Evidently, this part of the eastern Omineca Belt was close to the margin of ancestral North America in mid-Cretaceous time, essentially where it is today. -Authors