Internal Deformation Within a Moving, Composite Super- terrane: Evidence from Southwest British Columbia

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A composite allochthonous super terrane now constitutes much of western Washington, British Columbia and southern Alaska. Paleomagnetic and paleobiologic data suggest that the western part of this terrane was assembled in equatorial latitudes and that during Late Cretaceous - early Tertiary time the composite terrane moved northward toward its present position along the western margin of North America. Several hypotheses concerning the tectonics of final emplacement will be tested in this study. These are that Late Jurassic to earliest Cretaceous deformation within the terrane was a response to sinistral oblique conver- gence, that early to mid-Cretaceous deformation was dominantly convergent and that the onset of dextral transcurrent deforma- tion began in late Cenomanian time. Strata of the Middle Jurassic to late Cretaceous Tyaughton basin should record these postulated events in faults of small displacement. This study will determine the paleo-stress by analysis of macro and micro structural data from younger units and subtracting results from successively older units. By this back-stripping, a history of paleostress will be obtained that will allow hypotheses to be tested.