CANADA BASIN, ARCTIC-OCEAN - EVIDENCE AGAINST A ROTATIONAL ORIGIN

The most widely accepted model for the opening of Canada Basin invokes 66 degrees of counterclockwise rotation of Arctic Alaska and Chukotka away from the Canadian Arctic in Early Cretaceous time. Late Paleozoi c structural trends and paleogeography have been used in support of th e rotation hypothesis. Recent refinements in the ages of Paleozoic tec tonic events in Arctic Alaska, Yukon, and the Canadian Arctic Islands provide new controls on correlations of late Paleozoic paleogeography and raise doubts about whether the Paleozoic tectonics of the Arctic A laska-Yukon region necessitate a rotational reconstruction of Arctic A laska against the Canadian Arctic Islands. A rotational restoration of Arctic Alaska requires the Alaskan and Canadian margins to be conjuga tes of comparable age and evolution. The rift-drift transition age for the Alaskan margin is most likely Hauterivian (Early Cretaceous), but for the Canadian Arctic margin it is most likely post-Albian (mid-Cre taceous). Crustal structure data from the Beaufort Sea, continental ma rgin in Canada define a rifted margin segmented by fracture zones whic h constrain the kinematics of ocean spreading to be northwestward, per pendicular to that required by the rotation hypothesis but subparallel to that suggested by seismic velocity anisotropy in the upper mantle. The Alaska-Chukotka rotation hypothesis also fails to account for up to 600 km of continental overlap upon restoration of 66 degrees of rot ation and the absence of any accommodating contractional structures in northern Yukon and adjacent Northwest Territories. Because the Alaska -Chukotka rotation hypothesis fails to account for much of the availab le data, serious doubt is cast on its viability. An existing multistag e tectonic model for the evolution of Canada and Makarov basins is sum marized as an example of a model which can account for the existing da ta.