RECONCILING GEOLOGY, GEOCHRONOLOGY, AND PLATE MOTIONS IN THE AMERASIA BASIN

A growing Arctic geologic and geochronologic database highlights inadequacies in existing models of the opening of the Amerasia Basin. Using GPlates, we test several reconstructions against onshore geochronologic tie points, recently-revised timing of Arctic magmatism, and constraints from geophysical data. Sparse magnetic lineations, paleomagnetic data, and new detrital zircon data support rotation of Arctic Alaska from the Canadian Arctic Islands. However, recent studies link Chukotka to Siberia and Wrangel Island to Baltica, implying that the Arctic Alaska-Chukotka microplate (AACM) did not behave as a rigid plate during opening of the Amerasia Basin. These and other constraints suggest a multi-stage refinement of the prevailing rotational model with several attributes that better fit available data. In this model, Arctic Alaska and the Chukchi Borderland originate near the Canadian Arctic Islands and the Lomonosov Ridge and the Chukchi Borderland attains its present position by right-lateral strike-slip motion along the Northwind Escarpment during opening of the Canada Basin. The western (Russian) part of the AACM restores to the Eurasian portion of the Lomonosov Ridge, requiring significant right-lateral motion concomitant with syn-magmatic extension.