Provenance of the Incipient Passive Margin of NW Laurentia (Neoproterozoic): Detrital Zircon from Continental Slope and Basin Floor Deposits of the Windermere Supergroup, Southern Canadian Cordillera

Abstract The origin of the passive margin forming paleo-Pacific western edge ancestral North American continent (Laurentia) constrains breakup Rodinia and sets stage for Phanerozoic evolution Laurentia. Windermere Supergroup in southern Canadian Cordillera records rift-to-drift sedimentation form a prograding continental deposited between ~730 570 Ma. New U-Pb detrital zircon analysis from samples post-rift deposits shows that ultimate source area was shield NW Laurentia near uniformity age spectra are consistent with stable drainage system. No sediment detected. Detrital postrift slope proxy ca. 676-656 Ma igneous activity basin, likely related to breakup, set maximum depositional on eastern side basin at 652±9 These results previous interpretations. St. Mary-Moyie fault zone Canada-U.S. border most major transform boundary separating rifted north intracratonic rift basins south, resolving north-south variations along late Neoproterozoic approximately 650-600 For reconstructions, conjugate would have record rifting 650 followed by sedimentation.