Roberts Mountains allochthon: Stratigraphic comparison with lower Paleozoic outer continental margin strata of the northern Canadian Cordillera

Black shale, chert, turbidite sandstone, and basaltic lavas of Cambrian to Devonian age compose the outer continental margin of the northern Canadian Cordillera These deep-water rocks were deposited on miogeoctinal rocks of Late Proterozoic and Early Cambrian age following extension and subsidence of the continental margin. The stratigraphy of both the Roberts Mountains allochthon and the outer continental margin of the northern Canadian Cordillera record a strikingly similar history: Cambrian extension, Early Ordovician subsidence, Early to Late Ordovician extension, Silurian regression and elastic sedimentation, and Late Devonian extension. Starved-basin conditions persisted through much of Ordovician and Devonian time in both areas. On the basis of this correlation, the rocks of the Roberts Mountains allochthon are interpreted to have originated as part of the outer continental margin of western North America.