Cretaceous paleomagnetism of the Methow‐Pasayten Belt, Washington

Detailed demagnetization experiments isolated a characteristic remanent magnetization in ten stable sites from the upper Cretaceous Winthrop and Midnight Peak Formations in the Methow‐Pasayten belt of north‐central Washington. This remanence agrees best between opposite limbs of a fold (the Goat Peak syncline) when corrected for 46% of tilt. This is consistent with magnetization acquired during deformation. Synfolding magnetization may have been facilitated by a thermo‐chemical event associated with synkinematic intrusions along the axis of folding. The mean direction (D=12.0°, I=61.1°, Alpha‐95=4.8°) is highly discordant with respect to the expected direction for north‐central Washington. This discordance points to about 1,400 km of poleward transport and 48° of clockwise rotation between 93 and 45‐48 Ma.