Rotation of Central and Southern Alaska in the Early Tertiary: Oroclinal Bending by Megakinking?

  • R. S. Coe
  • B. R. Globerman
  • G. A. Thrupp
Part of the NATO ASI Series book series (ASIC, volume 254)


Systematic counterclockwise rotations of paleomagnetic declinations relative to those expected from North American cratonic reference poles are exhibited by latest Cretaceous and early Tertiary volcanic rocks from the western two-thirds of central and southern Alaska. These data suggest that the entire region underwent a tectonic rotation of 44 ± 11° counterclockwise. The most probable rotation mechanism is one that resembles kink folding about a vertical axis, but on a gigantic scale, with the axial plane vertical and nearly coincident with the 148th meridian. The flexural slip required by such megakinking agrees with geological estimates of displacements on known faults. Moreover, this mechanism has the virtue of straightening the sharply bent part of the structural grain of Alaska without opening a huge sphenochasm. A plausible cause of the rotation is convergence between Eurasia and North America, which is predicted to have occurred at the correct time by several analyses of the marine magnetic anomalies in the North Atlantic and Arctic Oceans.


Late Cretaceous Lava Flow Secular Variation Canada Basin Paleomagnetic Result 
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Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • R. S. Coe
    • 1
  • B. R. Globerman
    • 1
  • G. A. Thrupp
    • 1
  1. 1.Earth SciencesUniversity of CaliforniaSanta CruzUSA

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