Geologic mapping and petroleum exploration in northern Alaska and seismic surveys offshore suggest that 2 pulses of rifting created the Canada basin. Mississippian to Triassic miogeoclinal rocks in northern Alaska, derived from a now-displaced northerly source land, correlate with similar strata in the Canadian Arctic Islands. Underlying Ordovician and Silurian argillite and graywacke may correlate with the clastic succession in Heezen trough of the Arctic Islands. Closing Canada basin about a Mackenzie delta pole would rejoin these correlative rocks and recreate a unified pre-Jurassic Arctic paleogeography. Rifting began in earliest Jurassic time, creating a west-northwest-trending trough beneath the Beaufort Shelf and probably the southern Canada basin. The main rifting pulse, however, began in late Neocomian time, and the main post-rift progradational sedimentary prism off Alaska is Aptian or Albian and younger.

Apparently both late Neocomian and Laramide rifting thinned the crust beneath North Chukchi basin. Marked basinward thickening of Cretaceous strata records the earlier event, and extensional faulting and basinward thickening of Tertiary strata record the later one.

The high-standing, north-trending ridges and troughs of the Chukchi borderland, which trend into the North Chukchi basin from the north, may represent localized Laramide(?) crustal extension subparallel to that which created the Laramide(?) and Cenozoic Makarov and Eurasia basins of the Arctic Ocean. This model requires crustal shortening between the Chukchi borderland and Canada basin and transform faults north and south of the borderland. North of our seismic lines, the southern transform may be buried by Tertiary sediment of the North Chukchi basin.

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