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The Baja B.C. model has the Insular Superterrane and related entities of the Canadian Cordillera subject to >3000 km of northward displacement with respect to cratonic North America from ~90 to ~50 Ma. The Upper Cretaceous Nanaimo Group (on and about Vancouver Island, British Columbia) is a prime target to test the model paleomagnetically because of its locality and age. We have widely sampled the basin (67 sites from seven islands spread over 150 km, Santonian to Maastrichtian age). Most samples have low unblocking temperatures (<450°C) and coercivities (~10 mT) and strong present-field contamination, forcing us to reject three quarters of the collection. Beds are insufficiently tilted to provide a conclusive fold test, and we see evidence of relative vertical axis rotations. However, inclination-only analysis indicates pretilting remanence is preserved for many samples. Both polarities are observed, and reversals correlate well to paleontological data, proving that primary remanence is observed. The mean inclination, 55 ± 3°, is 13 ± 4° steeper than previously published results. Our new paleolatitude, 35.7 ± 2.6° is identical to that determined from the slightly older Silverquick and Powell Creek formations at Mount Tatlow, yet the inferred displacement is smaller (2300 ± 400 km versus 3000 ± 500 km) because North America was drifting southward starting around 90 Ma. The interpreted paleolatitude conflicts with sedimentologic and paleontologic evidence that the Nanaimo Basin was deposited near its present northern position.

Significant discrepancies exist between paleomagnetic and geologic estimates of the timing and magnitude of terrane displacement in the southern Canadian Cordillera. Lithostratigraphic, palynological, geochronologic, geochemical, and structural data, to which we add paleomagnetic data, demonstrate that Upper Cretaceous strata in Churn Creek are laterally equivalent facies of the Silverquick/Powell Creek (SPC) succession. These rocks therefore comprise a single overlap sequence linking the Insular and Intermontane Superterranes by Late Albian‐Cenomanian time (∼95 Ma), contradicting previous assertions based solely on paleomagnetic interpretation that major (∼2000 km) latitudinal displacement separated the two regions. The Churn Creek succession retains primary magnetic remanence, as demonstrated by positive fold, conglomerate and contact tests. The sediments do not hold the anisotropy signature of compaction‐shallowed inclinations. The mean inclination of all SPC sites, from both Mount Tatlow and Churn Creek, is 55.6° ± 2.3° (N = 36 sites), corresponding to a paleolatitude of 36.1° ± 2.4°. This reflects northward translation of the composite Insular/Intermontane Superterrane of 3050 ± 450 km between 85 and 50 Ma. The Silverquick/Powell Creek succession at Churn Creek unconformably overlies the northern end of the Spences Bridge Group, a late Early Cretaceous volcanic arc assemblage on the Intermontane Superterrane. Paleomagnetic data in the companion paper place it 1050 ± 450 km south of its current position between 100 and 105 Ma. Integration of these new data sets require that the Insular and Intermontane Superterranes formed a single, enormous crustal block that underwent complex, episodic south‐north translation between circa 105 and 50 Ma. The timing, rate, and vectors of translation are problematic in terms of geologic constraints along the continental margin.

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