CHUKCHI AND BEYOND -- GEOPHYSICAL MODELS OF THE CHUKCHI BORDERLANDS AND ITS BOUNDARIES, AMERASIA BASIN OF THE ARCTIC OCEAN

The Chukchi borderlands, a relatively high-standing region of plateaus and ridges at the edge of the Alaska/Siberia continental shelf, are a continuing tectonic puzzle within the high Arctic. Potential field (gravity and magnetic) modeling, with new constraints from joint Canada-USA seismic/sonobuoy data, yield new geophysical characterization of the region with implications for its tectonic setting and history.

The Chukchi borderland consists of two previously unrecognized geophysical domains. The southern domain (includes the Chukchi Rise) consists of dense and magnetic crust with geophysical affinity to the adjacent Alaska/Chukotka crust. The northern Chukchi domain (includes the Chukchi Plateau) consists of less dense and generally non-magnetic crust. The geophysical domain boundary roughly follows a bathymetric saddle and is expressed by the magnetic potential (aka pseudogravity) anomaly filter that highlights deep magnetic character. The boundary between the two geophysical domains roughly parallels, but lies north of the adjacent Alaska Beaufort margin. These magnetic domains are cut by the N-S faults that are so conspicuous in the bathymetry of the Chukchi borderlands and they are also buried by the deep (> 15 km) North Chukchi Basin.

Geophysical models and modeled physical properties provide constraints for structural and tectonic models and reconstructions. Palinspastic restorations of Canada basin opening and formation of the Alpha/Mendeleev LIP can be tested by matching geophysical anomalies and domains. In particular, the northern Chukchi magnetic domain, a region of low magnetic potential, geophysically matches both similar (and relatively unique) domains on the Russian shelf west of the Kucherov terrace and with zones of low magnetic potential in the Pearya terrane north of Norway. Current understanding/interpretation of the age of the adjacent Russian shelf compared with Caledonian ages (on ~ 430 granitic rocks) obtained by dredging the northern Chukchi domain are inconsistent with association of N Chukchi with the Russian margin. We propose further consideration of possible links between the N Chukchi magnetic domain and the Pearya Caledonian terrane.