MAGNETOSTRATIGRAPHY OF THE LATE CRETACEOUS TO EOCENE SVERDRUP BASIN -IMPLICATIONS FOR HETEROCHRONEITY, DEFORMATION, AND ROTATIONS IN THE CANADIAN ARCTIC ARCHIPELAGO

The temporal and spatial patterns of sedimentation in the Sverdrup Bas in provide clues to how deformation in the Canadian Arctic accommodate d Late Cretaceous-Eocene relative motion between Greenland and North A merica. Although the sediments contain a rich assemblage of mammal and megafloral fossils, dating of the sequence has been controversial. So me work suggests a dramatic faunal and floral heterochroneity with spe cies appearing in the Arctic 2-18 m.y. prior to their appearance at lo wer latitudes. To obtain a chronostratigraphic framework for these sed iments, a 2.6-km section of the Eureka Sound Group and Kanguk Formatio n on western Axel Heiberg Island was sampled for magnetostratigraphy. After removal of a pervasive modern field overprint with thermal and a lternating field demagnetization, a characteristic remanent magnetizat ion (ChRM) is isolated. Despite high directional dispersion, the ChRMs form 11 distinct polarity intervals which can be correlated to chrons 34 to 24r. This correlation indicates that some of these sediments ar e similar to 10 m.y. younger than thought previously, reducing the nee d for large-scale heterochroneity. Sedimentation rates derived from th e magnetostratigraphy suggest that an increase in basin subsidence is recorded near the middle of the section sampled. A similar pattern has been reported from the Eureka Sound Group exposed on Ellesmere island . We interpret this increased sedimentation as a response to crustal f lexure caused by lithospheric loading during the middle Paleocene (C26 r). The loading may be related to a blind thrust system to the west of Axel Heiberg Island that marks compression between North America and Greenland driven by rapid seafloor spreading in the Labrador Sea. The new data, together with prior results, indicate that most of the Creta ceous Canadian Arctic archipelago has undergone a counterclockwise ver tical axis rotation. The new data are more consistent with this rotati on being related to events during chron 26r, rather than marking block rotations associated with the terminal Eocene phases of Eurekan defor mation.