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Cenozoic relative plate interactions along the Queen Charlotte margin, based on published models for the North America and northeast Pacific plates, are related to the tectonic and igneous history of the region. Plate motion models indicate convergence and subduction prior to the Eocene. Since that time, there has been transcurrent motion with varying small amounts of oblique extension or compression, assuming that the Pacific‐America‐Farallon triple junction was to the south of the region. A late Miocene or early Pliocene (about 4 Ma) to present period of oblique convergence is well resolved. The present Queen Charlotte fault zone along the west coast of the islands may have initiated more recently. Within the Cenozoic transcurrent regime, a period of oblique extension in the mid‐Tertiary (36–20 Ma) in one model is supported by a variety of volcanic and tectonic evidence. A small plate motion change at about 20 Ma may have resulted in the transfer of the Yakutat terrane from the North America plate to the Pacific plate and the resulting motion of the terrane northwestward to its present position along the margin of Alaska. The onset of Tertiary Masset volcanism that is extensive on the Queen Charlotte Islands corresponds within a few million years to the time of major plate reorganization at 43 Ma that has tectonic expression around the entire Pacific basin. The period of most extensive Masset volcanism and plutonism appears to correlate with the model oblique extension in the mid‐Tertiary for one model. The geochemistry and physical volcanology of the Masset volcanic s are indicative of an extension regime. The main syntectonic deposition in the Queen Charlotte Basin (Skonun Formation) as inferred from seismic reflection and well data also appears temporally correlated with this time interval of oblique extension. A variety of data, including plate models, dikes, normal faults, basin subsidence, crustal thickness from seismic refraction, and present and paleo‐heat flow, indicate mid‐Tertiary crustal extension of at least 20% in the Queen Charlotte region, with up to 150% (β up to 2.5) in the main Queen Charlotte Basin. Posttectonic basin subsidence and deposition may correlate with the model time interval of general transcurrent or oblique convergence motion from 20 to 4 Ma. More recent shortening deformation observed in outcrop and seismic sections of the northern parts of the basin may correlate with plate model oblique convergence from 4 Ma to the present. The latter convergence is associated with underthrusting that formed a trough or trench and an accretionary sedimentary prism off the west coast of the Queen Charlotte Islands and with inferred uplift and erosion of the western part of the islands.

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Slipstream Slump, a well-preserved 3 km wide sedimentary failure from the frontal ridge of the Cascadia accretionary wedge 85 km off Vancouver Island, Canada, was sampled during Canadian Coast Guard Ship (CCGS) John P. Tully cruise 2008007PGC along a transect of five piston cores. Shipboard sediment analysis and physical property logging revealed 12 turbidites interbedded with thick hemipelagic sediments overlying the slumped glacial diamict. Despite the different sedimentary setting, atop the abyssal plain fan, this record is similar in number and age to the sequence of turbidites sampled farther to the south from channel systems along the Cascadia Subduction Zone, with no extra turbidites present in this local record. Given the regional physiographic and tectonic setting, megathrust earthquake shaking is the most likely trigger for both the initial slumping and subsequent turbidity currents, with sediments sourced exclusively from the exposed slump face of the frontal ridge. Planktonic foraminifera picked from the resedimented diamict of the underlying main slump have a disordered cluster of 14C ages between 12.8 and 14.5 ka BP. For the post-slump stratigraphy, an event-free depth scale is defined by removing the turbidite sediment intervals and using the hemipelagic sediments. Nine 14C dates from the most foraminifera-rich intervals define a nearly constant hemipelagic sedimentation rate of 0.021 cm/year. The combined age model is defined using only planktonic foraminiferal dates and Bayesian analysis with a Poisson-process sedimentation model. The age model of ongoing hemipelagic sedimentation is strengthened by physical property correlations from Slipstream events to the turbidites for the Barkley Canyon site 40 km south. Additional modelling addressed the possibilities of seabed erosion or loss and basal erosion beneath turbidites. Neither of these approaches achieves a modern seabed age when applying the commonly used regional marine 14C reservoir age of 800 years (marine reservoir correction ΔR = 400 years). Rather, the top of the core appears to be 400 years in the future. A younger marine reservoir age of 400 years (ΔR = 0 years) brings the top to the present and produces better correlations with the nearby Effingham Inlet paleo-earthquake chronology based only on terrestrial carbon requiring no reservoir correction. The high-resolution dating and facies analysis of Slipstream Slump in this isolated slope basin setting demonstrates that this is also a useful type of sedimentary target for sampling the paleoseismic record in addition to the more studied turbidites from submarine canyon and channel systems. The first 10 turbidites at Slipstream Slump were deposited between 10.8 and 6.6 ka BP, after which the system became sediment starved and only two more turbidites were deposited. The recurrence interval for the inferred frequent early Holocene megathrust earthquakes is 460 ± 140 years, compatible with other estimates of paleoseismic megathrust earthquake occurrence rates along the subduction zone.